/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hdfs.server.namenode;

import static org.apache.hadoop.fs.CommonConfigurationKeysPublic.FS_TRASH_INTERVAL_DEFAULT;
import static org.apache.hadoop.fs.CommonConfigurationKeysPublic.FS_TRASH_INTERVAL_KEY;
import static org.apache.hadoop.fs.CommonConfigurationKeysPublic.IO_FILE_BUFFER_SIZE_DEFAULT;
import static org.apache.hadoop.fs.CommonConfigurationKeysPublic.IO_FILE_BUFFER_SIZE_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_BLOCK_SIZE_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_BLOCK_SIZE_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_BYTES_PER_CHECKSUM_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_BYTES_PER_CHECKSUM_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_CHECKSUM_TYPE_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_CHECKSUM_TYPE_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_CLIENT_WRITE_PACKET_SIZE_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_CLIENT_WRITE_PACKET_SIZE_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_ENCRYPT_DATA_TRANSFER_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_ENCRYPT_DATA_TRANSFER_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_HA_STANDBY_CHECKPOINTS_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_HA_STANDBY_CHECKPOINTS_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_ACCESSTIME_PRECISION_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_ACCESSTIME_PRECISION_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_AUDIT_LOGGERS_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_AUDIT_LOG_ASYNC_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_AUDIT_LOG_ASYNC_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_AUDIT_LOG_TOKEN_TRACKING_ID_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_AUDIT_LOG_TOKEN_TRACKING_ID_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_CHECKPOINT_TXNS_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_CHECKPOINT_TXNS_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_DEFAULT_AUDIT_LOGGER_NAME;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_DELEGATION_KEY_UPDATE_INTERVAL_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_DELEGATION_KEY_UPDATE_INTERVAL_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_DELEGATION_TOKEN_ALWAYS_USE_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_DELEGATION_TOKEN_ALWAYS_USE_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_DELEGATION_TOKEN_MAX_LIFETIME_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_DELEGATION_TOKEN_MAX_LIFETIME_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_DELEGATION_TOKEN_RENEW_INTERVAL_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_DELEGATION_TOKEN_RENEW_INTERVAL_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_EDITS_DIR_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_EDITS_DIR_REQUIRED_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_EDIT_LOG_AUTOROLL_CHECK_INTERVAL_MS;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_EDIT_LOG_AUTOROLL_CHECK_INTERVAL_MS_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_EDIT_LOG_AUTOROLL_MULTIPLIER_THRESHOLD;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_EDIT_LOG_AUTOROLL_MULTIPLIER_THRESHOLD_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_ENABLE_RETRY_CACHE_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_ENABLE_RETRY_CACHE_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_MAX_OBJECTS_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_MAX_OBJECTS_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_NAME_DIR_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_REPLICATION_MIN_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_REPLICATION_MIN_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_REPL_QUEUE_THRESHOLD_PCT_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_RESOURCE_CHECK_INTERVAL_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_RESOURCE_CHECK_INTERVAL_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_RETRY_CACHE_EXPIRYTIME_MILLIS_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_RETRY_CACHE_EXPIRYTIME_MILLIS_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_RETRY_CACHE_HEAP_PERCENT_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_RETRY_CACHE_HEAP_PERCENT_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_SAFEMODE_EXTENSION_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_SAFEMODE_MIN_DATANODES_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_SAFEMODE_MIN_DATANODES_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_SAFEMODE_THRESHOLD_PCT_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_SAFEMODE_THRESHOLD_PCT_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_SHARED_EDITS_DIR_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_PERMISSIONS_ENABLED_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_PERMISSIONS_ENABLED_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_PERMISSIONS_SUPERUSERGROUP_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_PERMISSIONS_SUPERUSERGROUP_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_REPLICATION_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_REPLICATION_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_SUPPORT_APPEND_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_SUPPORT_APPEND_KEY;
import static org.apache.hadoop.util.Time.now;

import java.io.BufferedWriter;
import java.io.ByteArrayInputStream;
import java.io.DataInput;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.URI;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Date;
import java.util.EnumSet;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

import javax.management.NotCompliantMBeanException;
import javax.management.ObjectName;
import javax.management.StandardMBean;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.commons.logging.impl.Log4JLogger;
import org.apache.hadoop.HadoopIllegalArgumentException;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.BatchedRemoteIterator.BatchedListEntries;
import org.apache.hadoop.fs.CacheFlag;
import org.apache.hadoop.fs.ContentSummary;
import org.apache.hadoop.fs.CreateFlag;
import org.apache.hadoop.fs.DirectoryListingStartAfterNotFoundException;
import org.apache.hadoop.fs.FileAlreadyExistsException;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.FsServerDefaults;
import org.apache.hadoop.fs.InvalidPathException;
import org.apache.hadoop.fs.Options;
import org.apache.hadoop.fs.Options.Rename;
import org.apache.hadoop.fs.ParentNotDirectoryException;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.fs.UnresolvedLinkException;
import org.apache.hadoop.fs.permission.AclEntry;
import org.apache.hadoop.fs.permission.AclStatus;
import org.apache.hadoop.fs.permission.FsAction;
import org.apache.hadoop.fs.permission.FsPermission;
import org.apache.hadoop.fs.permission.PermissionStatus;
import org.apache.hadoop.ha.HAServiceProtocol.HAServiceState;
import org.apache.hadoop.ha.ServiceFailedException;
import org.apache.hadoop.hdfs.DFSConfigKeys;
import org.apache.hadoop.hdfs.DFSUtil;
import org.apache.hadoop.hdfs.HAUtil;
import org.apache.hadoop.hdfs.HdfsConfiguration;
import org.apache.hadoop.hdfs.StorageType;
import org.apache.hadoop.hdfs.protocol.AlreadyBeingCreatedException;
import org.apache.hadoop.hdfs.protocol.Block;
import org.apache.hadoop.hdfs.protocol.CacheDirectiveEntry;
import org.apache.hadoop.hdfs.protocol.CacheDirectiveInfo;
import org.apache.hadoop.hdfs.protocol.CachePoolEntry;
import org.apache.hadoop.hdfs.protocol.CachePoolInfo;
import org.apache.hadoop.hdfs.protocol.ClientProtocol;
import org.apache.hadoop.hdfs.protocol.DatanodeID;
import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
import org.apache.hadoop.hdfs.protocol.DirectoryListing;
import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
import org.apache.hadoop.hdfs.protocol.HdfsConstants;
import org.apache.hadoop.hdfs.protocol.HdfsConstants.DatanodeReportType;
import org.apache.hadoop.hdfs.protocol.HdfsConstants.SafeModeAction;
import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
import org.apache.hadoop.hdfs.protocol.LocatedBlock;
import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
import org.apache.hadoop.hdfs.protocol.QuotaExceededException;
import org.apache.hadoop.hdfs.protocol.RecoveryInProgressException;
import org.apache.hadoop.hdfs.protocol.RollingUpgradeException;
import org.apache.hadoop.hdfs.protocol.RollingUpgradeInfo;
import org.apache.hadoop.hdfs.protocol.SnapshotDiffReport;
import org.apache.hadoop.hdfs.protocol.SnapshotDiffReport.DiffReportEntry;
import org.apache.hadoop.hdfs.protocol.SnapshottableDirectoryStatus;
import org.apache.hadoop.hdfs.protocol.datatransfer.ReplaceDatanodeOnFailure;
import org.apache.hadoop.hdfs.security.token.block.BlockTokenSecretManager;
import org.apache.hadoop.hdfs.security.token.block.BlockTokenSecretManager.AccessMode;
import org.apache.hadoop.hdfs.security.token.delegation.DelegationTokenIdentifier;
import org.apache.hadoop.hdfs.security.token.delegation.DelegationTokenSecretManager;
import org.apache.hadoop.hdfs.security.token.delegation.DelegationTokenSecretManager.SecretManagerState;
import org.apache.hadoop.hdfs.server.blockmanagement.BlockCollection;
import org.apache.hadoop.hdfs.server.blockmanagement.BlockInfo;
import org.apache.hadoop.hdfs.server.blockmanagement.BlockInfoUnderConstruction;
import org.apache.hadoop.hdfs.server.blockmanagement.BlockManager;
import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor;
import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeManager;
import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeStatistics;
import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeStorageInfo;
import org.apache.hadoop.hdfs.server.blockmanagement.OutOfV1GenerationStampsException;
import org.apache.hadoop.hdfs.server.common.GenerationStamp;
import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.BlockUCState;
import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.NamenodeRole;
import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.RollingUpgradeStartupOption;
import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.StartupOption;
import org.apache.hadoop.hdfs.server.common.Storage;
import org.apache.hadoop.hdfs.server.common.Storage.StorageDirType;
import org.apache.hadoop.hdfs.server.common.Storage.StorageDirectory;
import org.apache.hadoop.hdfs.server.common.Util;
import org.apache.hadoop.hdfs.server.namenode.FsImageProto.SecretManagerSection;
import org.apache.hadoop.hdfs.server.namenode.INode.BlocksMapUpdateInfo;
import org.apache.hadoop.hdfs.server.namenode.JournalSet.JournalAndStream;
import org.apache.hadoop.hdfs.server.namenode.LeaseManager.Lease;
import org.apache.hadoop.hdfs.server.namenode.NNStorage.NameNodeFile;
import org.apache.hadoop.hdfs.server.namenode.NameNode.OperationCategory;
import org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer;
import org.apache.hadoop.hdfs.server.namenode.ha.HAContext;
import org.apache.hadoop.hdfs.server.namenode.ha.StandbyCheckpointer;
import org.apache.hadoop.hdfs.server.namenode.metrics.FSNamesystemMBean;
import org.apache.hadoop.hdfs.server.namenode.metrics.NameNodeMetrics;
import org.apache.hadoop.hdfs.server.namenode.snapshot.INodeDirectorySnapshottable;
import org.apache.hadoop.hdfs.server.namenode.snapshot.INodeDirectorySnapshottable.SnapshotDiffInfo;
import org.apache.hadoop.hdfs.server.namenode.snapshot.Snapshot;
import org.apache.hadoop.hdfs.server.namenode.snapshot.SnapshotManager;
import org.apache.hadoop.hdfs.server.namenode.startupprogress.Phase;
import org.apache.hadoop.hdfs.server.namenode.startupprogress.StartupProgress;
import org.apache.hadoop.hdfs.server.namenode.startupprogress.StartupProgress.Counter;
import org.apache.hadoop.hdfs.server.namenode.startupprogress.Status;
import org.apache.hadoop.hdfs.server.namenode.startupprogress.Step;
import org.apache.hadoop.hdfs.server.namenode.startupprogress.StepType;
import org.apache.hadoop.hdfs.server.namenode.web.resources.NamenodeWebHdfsMethods;
import org.apache.hadoop.hdfs.server.protocol.DatanodeCommand;
import org.apache.hadoop.hdfs.server.protocol.DatanodeRegistration;
import org.apache.hadoop.hdfs.server.protocol.HeartbeatResponse;
import org.apache.hadoop.hdfs.server.protocol.NNHAStatusHeartbeat;
import org.apache.hadoop.hdfs.server.protocol.NamenodeCommand;
import org.apache.hadoop.hdfs.server.protocol.NamenodeRegistration;
import org.apache.hadoop.hdfs.server.protocol.NamespaceInfo;
import org.apache.hadoop.hdfs.server.protocol.StorageReceivedDeletedBlocks;
import org.apache.hadoop.hdfs.server.protocol.StorageReport;
import org.apache.hadoop.hdfs.util.ChunkedArrayList;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.ipc.RetriableException;
import org.apache.hadoop.ipc.RetryCache;
import org.apache.hadoop.ipc.RetryCache.CacheEntry;
import org.apache.hadoop.ipc.RetryCache.CacheEntryWithPayload;
import org.apache.hadoop.ipc.Server;
import org.apache.hadoop.ipc.StandbyException;
import org.apache.hadoop.metrics2.annotation.Metric;
import org.apache.hadoop.metrics2.annotation.Metrics;
import org.apache.hadoop.metrics2.lib.DefaultMetricsSystem;
import org.apache.hadoop.metrics2.util.MBeans;
import org.apache.hadoop.net.NetworkTopology;
import org.apache.hadoop.net.Node;
import org.apache.hadoop.security.AccessControlException;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.security.UserGroupInformation.AuthenticationMethod;
import org.apache.hadoop.security.token.SecretManager.InvalidToken;
import org.apache.hadoop.security.token.Token;
import org.apache.hadoop.security.token.TokenIdentifier;
import org.apache.hadoop.security.token.delegation.DelegationKey;
import org.apache.hadoop.util.Daemon;
import org.apache.hadoop.util.DataChecksum;
import org.apache.hadoop.util.StringUtils;
import org.apache.hadoop.util.Time;
import org.apache.hadoop.util.VersionInfo;
import org.apache.log4j.Appender;
import org.apache.log4j.AsyncAppender;
import org.apache.log4j.Logger;
import org.mortbay.util.ajax.JSON;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Charsets;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Lists;

/***************************************************
 * FSNamesystem does the actual bookkeeping work for the
 * DataNode.
 *
 * It tracks several important tables.
 *
 * 1)  valid fsname --> blocklist  (kept on disk, logged)
 * 2)  Set of all valid blocks (inverted #1)
 * 3)  block --> machinelist (kept in memory, rebuilt dynamically from reports)
 * 4)  machine --> blocklist (inverted #2)
 * 5)  LRU cache of updated-heartbeat machines
 ***************************************************/
@InterfaceAudience.Private
@Metrics(context="dfs")
public class FSNamesystem implements Namesystem, FSClusterStats,
    FSNamesystemMBean, NameNodeMXBean {
  public static final Log LOG = LogFactory.getLog(FSNamesystem.class);

  private static final ThreadLocal<StringBuilder> auditBuffer =
    new ThreadLocal<StringBuilder>() {
      @Override
      protected StringBuilder initialValue() {
        return new StringBuilder();
      }
  };

  @VisibleForTesting
  public boolean isAuditEnabled() {
    return !isDefaultAuditLogger || auditLog.isInfoEnabled();
  }

  private HdfsFileStatus getAuditFileInfo(String path, boolean resolveSymlink)
      throws IOException {
    return (isAuditEnabled() && isExternalInvocation())
        ? dir.getFileInfo(path, resolveSymlink) : null;
  }
  
  private void logAuditEvent(boolean succeeded, String cmd, String src)
      throws IOException {
    logAuditEvent(succeeded, cmd, src, null, null);
  }
  
  private void logAuditEvent(boolean succeeded, String cmd, String src,
      String dst, HdfsFileStatus stat) throws IOException {
    if (isAuditEnabled() && isExternalInvocation()) {
      logAuditEvent(succeeded, getRemoteUser(), getRemoteIp(),
                    cmd, src, dst, stat);
    }
  }

  private void logAuditEvent(boolean succeeded,
      UserGroupInformation ugi, InetAddress addr, String cmd, String src,
      String dst, HdfsFileStatus stat) {
    FileStatus status = null;
    if (stat != null) {
      Path symlink = stat.isSymlink() ? new Path(stat.getSymlink()) : null;
      Path path = dst != null ? new Path(dst) : new Path(src);
      status = new FileStatus(stat.getLen(), stat.isDir(),
          stat.getReplication(), stat.getBlockSize(), stat.getModificationTime(),
          stat.getAccessTime(), stat.getPermission(), stat.getOwner(),
          stat.getGroup(), symlink, path);
    }
    for (AuditLogger logger : auditLoggers) {
      if (logger instanceof HdfsAuditLogger) {
        HdfsAuditLogger hdfsLogger = (HdfsAuditLogger) logger;
        hdfsLogger.logAuditEvent(succeeded, ugi.toString(), addr, cmd, src, dst,
            status, ugi, dtSecretManager);
      } else {
        logger.logAuditEvent(succeeded, ugi.toString(), addr,
            cmd, src, dst, status);
      }
    }
  }

  /**
   * Logger for audit events, noting successful FSNamesystem operations. Emits
   * to FSNamesystem.audit at INFO. Each event causes a set of tab-separated
   * <code>key=value</code> pairs to be written for the following properties:
   * <code>
   * ugi=&lt;ugi in RPC&gt;
   * ip=&lt;remote IP&gt;
   * cmd=&lt;command&gt;
   * src=&lt;src path&gt;
   * dst=&lt;dst path (optional)&gt;
   * perm=&lt;permissions (optional)&gt;
   * </code>
   */
  public static final Log auditLog = LogFactory.getLog(
      FSNamesystem.class.getName() + ".audit");

  static final int DEFAULT_MAX_CORRUPT_FILEBLOCKS_RETURNED = 100;
  static int BLOCK_DELETION_INCREMENT = 1000;
  private final boolean isPermissionEnabled;
  private final UserGroupInformation fsOwner;
  private final String fsOwnerShortUserName;
  private final String supergroup;
  private final boolean standbyShouldCheckpoint;
  
  // Scan interval is not configurable.
  private static final long DELEGATION_TOKEN_REMOVER_SCAN_INTERVAL =
    TimeUnit.MILLISECONDS.convert(1, TimeUnit.HOURS);
  final DelegationTokenSecretManager dtSecretManager;
  private final boolean alwaysUseDelegationTokensForTests;

  private static final Step STEP_AWAITING_REPORTED_BLOCKS =
    new Step(StepType.AWAITING_REPORTED_BLOCKS);

  // Tracks whether the default audit logger is the only configured audit
  // logger; this allows isAuditEnabled() to return false in case the
  // underlying logger is disabled, and avoid some unnecessary work.
  private final boolean isDefaultAuditLogger;
  private final List<AuditLogger> auditLoggers;

  /** The namespace tree. */
  FSDirectory dir;
  private final BlockManager blockManager;
  private final SnapshotManager snapshotManager;
  private final CacheManager cacheManager;
  private final DatanodeStatistics datanodeStatistics;

  private RollingUpgradeInfo rollingUpgradeInfo = null;
  /**
   * A flag that indicates whether the checkpointer should checkpoint a rollback
   * fsimage. The edit log tailer sets this flag. The checkpoint will create a
   * rollback fsimage if the flag is true, and then change the flag to false.
   */
  private volatile boolean needRollbackFsImage;

  // Block pool ID used by this namenode
  private String blockPoolId;

  final LeaseManager leaseManager = new LeaseManager(this); 

  volatile Daemon smmthread = null;  // SafeModeMonitor thread
  
  Daemon nnrmthread = null; // NamenodeResourceMonitor thread

  Daemon nnEditLogRoller = null; // NameNodeEditLogRoller thread
  /**
   * When an active namenode will roll its own edit log, in # edits
   */
  private final long editLogRollerThreshold;
  /**
   * Check interval of an active namenode's edit log roller thread 
   */
  private final int editLogRollerInterval;

  private volatile boolean hasResourcesAvailable = false;
  private volatile boolean fsRunning = true;
  
  /** The start time of the namesystem. */
  private final long startTime = now();

  /** The interval of namenode checking for the disk space availability */
  private final long resourceRecheckInterval;

  // The actual resource checker instance.
  NameNodeResourceChecker nnResourceChecker;

  private final FsServerDefaults serverDefaults;
  private final boolean supportAppends;
  private final ReplaceDatanodeOnFailure dtpReplaceDatanodeOnFailure;

  private volatile SafeModeInfo safeMode;  // safe mode information

  private final long maxFsObjects;          // maximum number of fs objects

  private final long minBlockSize;         // minimum block size
  private final long maxBlocksPerFile;     // maximum # of blocks per file

  /**
   * The global generation stamp for legacy blocks with randomly
   * generated block IDs.
   */
  private final GenerationStamp generationStampV1 = new GenerationStamp();

  /**
   * The global generation stamp for this file system.
   */
  private final GenerationStamp generationStampV2 = new GenerationStamp();

  /**
   * The value of the generation stamp when the first switch to sequential
   * block IDs was made. Blocks with generation stamps below this value
   * have randomly allocated block IDs. Blocks with generation stamps above
   * this value had sequentially allocated block IDs. Read from the fsImage
   * (or initialized as an offset from the V1 (legacy) generation stamp on
   * upgrade).
   */
  private long generationStampV1Limit =
      GenerationStamp.GRANDFATHER_GENERATION_STAMP;

  /**
   * The global block ID space for this file system.
   */
  @VisibleForTesting
  private final SequentialBlockIdGenerator blockIdGenerator;

  // precision of access times.
  private final long accessTimePrecision;

  /** Lock to protect FSNamesystem. */
  private final FSNamesystemLock fsLock;

  /**
   * Used when this NN is in standby state to read from the shared edit log.
   */
  private EditLogTailer editLogTailer = null;

  /**
   * Used when this NN is in standby state to perform checkpoints.
   */
  private StandbyCheckpointer standbyCheckpointer;

  /**
   * Reference to the NN's HAContext object. This is only set once
   * {@link #startCommonServices(Configuration, HAContext)} is called. 
   */
  private HAContext haContext;

  private final boolean haEnabled;

  /** flag indicating whether replication queues have been initialized */
  boolean initializedReplQueues = false;

  /**
   * Whether the namenode is in the middle of starting the active service
   */
  private volatile boolean startingActiveService = false;
    
  private INodeId inodeId;
  
  private final RetryCache retryCache;

  private final AclConfigFlag aclConfigFlag;

  /**
   * Set the last allocated inode id when fsimage or editlog is loaded. 
   */
  public void resetLastInodeId(long newValue) throws IOException {
    try {
      inodeId.skipTo(newValue);
    } catch(IllegalStateException ise) {
      throw new IOException(ise);
    }
  }

  /** Should only be used for tests to reset to any value */
  void resetLastInodeIdWithoutChecking(long newValue) {
    inodeId.setCurrentValue(newValue);
  }
  
  /** @return the last inode ID. */
  public long getLastInodeId() {
    return inodeId.getCurrentValue();
  }

  /** Allocate a new inode ID. */
  public long allocateNewInodeId() {
    return inodeId.nextValue();
  }
  
  /**
   * Clear all loaded data
   */
  void clear() {
    dir.reset();
    dtSecretManager.reset();
    generationStampV1.setCurrentValue(GenerationStamp.LAST_RESERVED_STAMP);
    generationStampV2.setCurrentValue(GenerationStamp.LAST_RESERVED_STAMP);
    blockIdGenerator.setCurrentValue(
        SequentialBlockIdGenerator.LAST_RESERVED_BLOCK_ID);
    generationStampV1Limit = GenerationStamp.GRANDFATHER_GENERATION_STAMP;
    leaseManager.removeAllLeases();
    inodeId.setCurrentValue(INodeId.LAST_RESERVED_ID);
    snapshotManager.clearSnapshottableDirs();
    cacheManager.clear();
  }

  @VisibleForTesting
  LeaseManager getLeaseManager() {
    return leaseManager;
  }
  
  boolean isHaEnabled() {
    return haEnabled;
  }
  
  /**
   * Check the supplied configuration for correctness.
   * @param conf Supplies the configuration to validate.
   * @throws IOException if the configuration could not be queried.
   * @throws IllegalArgumentException if the configuration is invalid.
   */
  private static void checkConfiguration(Configuration conf)
      throws IOException {

    final Collection<URI> namespaceDirs =
        FSNamesystem.getNamespaceDirs(conf);
    final Collection<URI> editsDirs =
        FSNamesystem.getNamespaceEditsDirs(conf);
    final Collection<URI> requiredEditsDirs =
        FSNamesystem.getRequiredNamespaceEditsDirs(conf);
    final Collection<URI> sharedEditsDirs =
        FSNamesystem.getSharedEditsDirs(conf);

    for (URI u : requiredEditsDirs) {
      if (u.toString().compareTo(
              DFSConfigKeys.DFS_NAMENODE_EDITS_DIR_DEFAULT) == 0) {
        continue;
      }

      // Each required directory must also be in editsDirs or in
      // sharedEditsDirs.
      if (!editsDirs.contains(u) &&
          !sharedEditsDirs.contains(u)) {
        throw new IllegalArgumentException(
            "Required edits directory " + u.toString() + " not present in " +
            DFSConfigKeys.DFS_NAMENODE_EDITS_DIR_KEY + ". " +
            DFSConfigKeys.DFS_NAMENODE_EDITS_DIR_KEY + "=" +
            editsDirs.toString() + "; " +
            DFSConfigKeys.DFS_NAMENODE_EDITS_DIR_REQUIRED_KEY + "=" +
            requiredEditsDirs.toString() + ". " +
            DFSConfigKeys.DFS_NAMENODE_SHARED_EDITS_DIR_KEY + "=" +
            sharedEditsDirs.toString() + ".");
      }
    }

    if (namespaceDirs.size() == 1) {
      LOG.warn("Only one image storage directory ("
          + DFS_NAMENODE_NAME_DIR_KEY + ") configured. Beware of dataloss"
          + " due to lack of redundant storage directories!");
    }
    if (editsDirs.size() == 1) {
      LOG.warn("Only one namespace edits storage directory ("
          + DFS_NAMENODE_EDITS_DIR_KEY + ") configured. Beware of dataloss"
          + " due to lack of redundant storage directories!");
    }
  }

  /**
   * Instantiates an FSNamesystem loaded from the image and edits
   * directories specified in the passed Configuration.
   *
   * @param conf the Configuration which specifies the storage directories
   *             from which to load
   * @return an FSNamesystem which contains the loaded namespace
   * @throws IOException if loading fails
   */
  static FSNamesystem loadFromDisk(Configuration conf) throws IOException {

    checkConfiguration(conf);
    FSImage fsImage = new FSImage(conf,
        FSNamesystem.getNamespaceDirs(conf),
        FSNamesystem.getNamespaceEditsDirs(conf));
    FSNamesystem namesystem = new FSNamesystem(conf, fsImage, false);
    StartupOption startOpt = NameNode.getStartupOption(conf);
    if (startOpt == StartupOption.RECOVER) {
      namesystem.setSafeMode(SafeModeAction.SAFEMODE_ENTER);
    }

    long loadStart = now();
    try {
      namesystem.loadFSImage(startOpt);
    } catch (IOException ioe) {
      LOG.warn("Encountered exception loading fsimage", ioe);
      fsImage.close();
      throw ioe;
    }
    long timeTakenToLoadFSImage = now() - loadStart;
    LOG.info("Finished loading FSImage in " + timeTakenToLoadFSImage + " msecs");
    NameNodeMetrics nnMetrics = NameNode.getNameNodeMetrics();
    if (nnMetrics != null) {
      nnMetrics.setFsImageLoadTime((int) timeTakenToLoadFSImage);
    }
    return namesystem;
  }
  
  FSNamesystem(Configuration conf, FSImage fsImage) throws IOException {
    this(conf, fsImage, false);
  }
  
  /**
   * Create an FSNamesystem associated with the specified image.
   * 
   * Note that this does not load any data off of disk -- if you would
   * like that behavior, use {@link #loadFromDisk(Configuration)}
   *
   * @param conf configuration
   * @param fsImage The FSImage to associate with
   * @param ignoreRetryCache Whether or not should ignore the retry cache setup
   *                         step. For Secondary NN this should be set to true.
   * @throws IOException on bad configuration
   */
  FSNamesystem(Configuration conf, FSImage fsImage, boolean ignoreRetryCache)
      throws IOException {
    if (conf.getBoolean(DFS_NAMENODE_AUDIT_LOG_ASYNC_KEY,
                        DFS_NAMENODE_AUDIT_LOG_ASYNC_DEFAULT)) {
      LOG.info("Enabling async auditlog");
      enableAsyncAuditLog();
    }
    boolean fair = conf.getBoolean("dfs.namenode.fslock.fair", true);
    LOG.info("fsLock is fair:" + fair);
    fsLock = new FSNamesystemLock(fair);
    try {
      resourceRecheckInterval = conf.getLong(
          DFS_NAMENODE_RESOURCE_CHECK_INTERVAL_KEY,
          DFS_NAMENODE_RESOURCE_CHECK_INTERVAL_DEFAULT);

      this.blockManager = new BlockManager(this, this, conf);
      this.datanodeStatistics = blockManager.getDatanodeManager().getDatanodeStatistics();
      this.blockIdGenerator = new SequentialBlockIdGenerator(this.blockManager);

      this.fsOwner = UserGroupInformation.getCurrentUser();
      this.fsOwnerShortUserName = fsOwner.getShortUserName();
      this.supergroup = conf.get(DFS_PERMISSIONS_SUPERUSERGROUP_KEY, 
                                 DFS_PERMISSIONS_SUPERUSERGROUP_DEFAULT);
      this.isPermissionEnabled = conf.getBoolean(DFS_PERMISSIONS_ENABLED_KEY,
                                                 DFS_PERMISSIONS_ENABLED_DEFAULT);
      LOG.info("fsOwner             = " + fsOwner);
      LOG.info("supergroup          = " + supergroup);
      LOG.info("isPermissionEnabled = " + isPermissionEnabled);

      // block allocation has to be persisted in HA using a shared edits directory
      // so that the standby has up-to-date namespace information
      String nameserviceId = DFSUtil.getNamenodeNameServiceId(conf);
      this.haEnabled = HAUtil.isHAEnabled(conf, nameserviceId);  
      
      // Sanity check the HA-related config.
      if (nameserviceId != null) {
        LOG.info("Determined nameservice ID: " + nameserviceId);
      }
      LOG.info("HA Enabled: " + haEnabled);
      if (!haEnabled && HAUtil.usesSharedEditsDir(conf)) {
        LOG.warn("Configured NNs:\n" + DFSUtil.nnAddressesAsString(conf));
        throw new IOException("Invalid configuration: a shared edits dir " +
            "must not be specified if HA is not enabled.");
      }

      // Get the checksum type from config
      String checksumTypeStr = conf.get(DFS_CHECKSUM_TYPE_KEY, DFS_CHECKSUM_TYPE_DEFAULT);
      DataChecksum.Type checksumType;
      try {
         checksumType = DataChecksum.Type.valueOf(checksumTypeStr);
      } catch (IllegalArgumentException iae) {
         throw new IOException("Invalid checksum type in "
            + DFS_CHECKSUM_TYPE_KEY + ": " + checksumTypeStr);
      }

      this.serverDefaults = new FsServerDefaults(
          conf.getLongBytes(DFS_BLOCK_SIZE_KEY, DFS_BLOCK_SIZE_DEFAULT),
          conf.getInt(DFS_BYTES_PER_CHECKSUM_KEY, DFS_BYTES_PER_CHECKSUM_DEFAULT),
          conf.getInt(DFS_CLIENT_WRITE_PACKET_SIZE_KEY, DFS_CLIENT_WRITE_PACKET_SIZE_DEFAULT),
          (short) conf.getInt(DFS_REPLICATION_KEY, DFS_REPLICATION_DEFAULT),
          conf.getInt(IO_FILE_BUFFER_SIZE_KEY, IO_FILE_BUFFER_SIZE_DEFAULT),
          conf.getBoolean(DFS_ENCRYPT_DATA_TRANSFER_KEY, DFS_ENCRYPT_DATA_TRANSFER_DEFAULT),
          conf.getLong(FS_TRASH_INTERVAL_KEY, FS_TRASH_INTERVAL_DEFAULT),
          checksumType);
      
      this.maxFsObjects = conf.getLong(DFS_NAMENODE_MAX_OBJECTS_KEY, 
                                       DFS_NAMENODE_MAX_OBJECTS_DEFAULT);

      this.minBlockSize = conf.getLong(DFSConfigKeys.DFS_NAMENODE_MIN_BLOCK_SIZE_KEY,
          DFSConfigKeys.DFS_NAMENODE_MIN_BLOCK_SIZE_DEFAULT);
      this.maxBlocksPerFile = conf.getLong(DFSConfigKeys.DFS_NAMENODE_MAX_BLOCKS_PER_FILE_KEY,
          DFSConfigKeys.DFS_NAMENODE_MAX_BLOCKS_PER_FILE_DEFAULT);
      this.accessTimePrecision = conf.getLong(DFS_NAMENODE_ACCESSTIME_PRECISION_KEY,
          DFS_NAMENODE_ACCESSTIME_PRECISION_DEFAULT);
      this.supportAppends = conf.getBoolean(DFS_SUPPORT_APPEND_KEY, DFS_SUPPORT_APPEND_DEFAULT);
      LOG.info("Append Enabled: " + supportAppends);

      this.dtpReplaceDatanodeOnFailure = ReplaceDatanodeOnFailure.get(conf);
      
      this.standbyShouldCheckpoint = conf.getBoolean(
          DFS_HA_STANDBY_CHECKPOINTS_KEY, DFS_HA_STANDBY_CHECKPOINTS_DEFAULT);
      // # edit autoroll threshold is a multiple of the checkpoint threshold 
      this.editLogRollerThreshold = (long)
          (conf.getFloat(
              DFS_NAMENODE_EDIT_LOG_AUTOROLL_MULTIPLIER_THRESHOLD,
              DFS_NAMENODE_EDIT_LOG_AUTOROLL_MULTIPLIER_THRESHOLD_DEFAULT) *
          conf.getLong(
              DFS_NAMENODE_CHECKPOINT_TXNS_KEY,
              DFS_NAMENODE_CHECKPOINT_TXNS_DEFAULT));
      this.editLogRollerInterval = conf.getInt(
          DFS_NAMENODE_EDIT_LOG_AUTOROLL_CHECK_INTERVAL_MS,
          DFS_NAMENODE_EDIT_LOG_AUTOROLL_CHECK_INTERVAL_MS_DEFAULT);
      this.inodeId = new INodeId();
      
      // For testing purposes, allow the DT secret manager to be started regardless
      // of whether security is enabled.
      alwaysUseDelegationTokensForTests = conf.getBoolean(
          DFS_NAMENODE_DELEGATION_TOKEN_ALWAYS_USE_KEY,
          DFS_NAMENODE_DELEGATION_TOKEN_ALWAYS_USE_DEFAULT);

      this.dtSecretManager = createDelegationTokenSecretManager(conf);
      this.dir = new FSDirectory(fsImage, this, conf);
      this.snapshotManager = new SnapshotManager(dir);
      this.cacheManager = new CacheManager(this, conf, blockManager);
      this.safeMode = new SafeModeInfo(conf);
      this.auditLoggers = initAuditLoggers(conf);
      this.isDefaultAuditLogger = auditLoggers.size() == 1 &&
        auditLoggers.get(0) instanceof DefaultAuditLogger;
      this.retryCache = ignoreRetryCache ? null : initRetryCache(conf);
      this.aclConfigFlag = new AclConfigFlag(conf);
    } catch(IOException e) {
      LOG.error(getClass().getSimpleName() + " initialization failed.", e);
      close();
      throw e;
    } catch (RuntimeException re) {
      LOG.error(getClass().getSimpleName() + " initialization failed.", re);
      close();
      throw re;
    }
  }
  
  @VisibleForTesting
  public RetryCache getRetryCache() {
    return retryCache;
  }

  void lockRetryCache() {
    if (retryCache != null) {
      retryCache.lock();
    }
  }

  void unlockRetryCache() {
    if (retryCache != null) {
      retryCache.unlock();
    }
  }

  /** Whether or not retry cache is enabled */
  boolean hasRetryCache() {
    return retryCache != null;
  }
  
  void addCacheEntryWithPayload(byte[] clientId, int callId, Object payload) {
    if (retryCache != null) {
      retryCache.addCacheEntryWithPayload(clientId, callId, payload);
    }
  }
  
  void addCacheEntry(byte[] clientId, int callId) {
    if (retryCache != null) {
      retryCache.addCacheEntry(clientId, callId);
    }
  }

  @VisibleForTesting
  static RetryCache initRetryCache(Configuration conf) {
    boolean enable = conf.getBoolean(DFS_NAMENODE_ENABLE_RETRY_CACHE_KEY,
        DFS_NAMENODE_ENABLE_RETRY_CACHE_DEFAULT);
    LOG.info("Retry cache on namenode is " + (enable ? "enabled" : "disabled"));
    if (enable) {
      float heapPercent = conf.getFloat(
          DFS_NAMENODE_RETRY_CACHE_HEAP_PERCENT_KEY,
          DFS_NAMENODE_RETRY_CACHE_HEAP_PERCENT_DEFAULT);
      long entryExpiryMillis = conf.getLong(
          DFS_NAMENODE_RETRY_CACHE_EXPIRYTIME_MILLIS_KEY,
          DFS_NAMENODE_RETRY_CACHE_EXPIRYTIME_MILLIS_DEFAULT);
      LOG.info("Retry cache will use " + heapPercent
          + " of total heap and retry cache entry expiry time is "
          + entryExpiryMillis + " millis");
      long entryExpiryNanos = entryExpiryMillis * 1000 * 1000;
      return new RetryCache("NameNodeRetryCache", heapPercent,
          entryExpiryNanos);
    }
    return null;
  }

  private List<AuditLogger> initAuditLoggers(Configuration conf) {
    // Initialize the custom access loggers if configured.
    Collection<String> alClasses = conf.getStringCollection(DFS_NAMENODE_AUDIT_LOGGERS_KEY);
    List<AuditLogger> auditLoggers = Lists.newArrayList();
    if (alClasses != null && !alClasses.isEmpty()) {
      for (String className : alClasses) {
        try {
          AuditLogger logger;
          if (DFS_NAMENODE_DEFAULT_AUDIT_LOGGER_NAME.equals(className)) {
            logger = new DefaultAuditLogger();
          } else {
            logger = (AuditLogger) Class.forName(className).newInstance();
          }
          logger.initialize(conf);
          auditLoggers.add(logger);
        } catch (RuntimeException re) {
          throw re;
        } catch (Exception e) {
          throw new RuntimeException(e);
        }
      }
    }

    // Make sure there is at least one logger installed.
    if (auditLoggers.isEmpty()) {
      auditLoggers.add(new DefaultAuditLogger());
    }
    return Collections.unmodifiableList(auditLoggers);
  }

  private void loadFSImage(StartupOption startOpt) throws IOException {
    final FSImage fsImage = getFSImage();

    // format before starting up if requested
    if (startOpt == StartupOption.FORMAT) {
      
      fsImage.format(this, fsImage.getStorage().determineClusterId());// reuse current id

      startOpt = StartupOption.REGULAR;
    }
    boolean success = false;
    writeLock();
    try {
      // We shouldn't be calling saveNamespace if we've come up in standby state.
      MetaRecoveryContext recovery = startOpt.createRecoveryContext();
      final boolean staleImage
          = fsImage.recoverTransitionRead(startOpt, this, recovery);
      if (RollingUpgradeStartupOption.ROLLBACK.matches(startOpt)) {
        rollingUpgradeInfo = null;
      }
      final boolean needToSave = staleImage && !haEnabled && !isRollingUpgrade(); 
      LOG.info("Need to save fs image? " + needToSave
          + " (staleImage=" + staleImage + ", haEnabled=" + haEnabled
          + ", isRollingUpgrade=" + isRollingUpgrade() + ")");
      if (needToSave) {
        fsImage.saveNamespace(this);
      } else {
        // No need to save, so mark the phase done.
        StartupProgress prog = NameNode.getStartupProgress();
        prog.beginPhase(Phase.SAVING_CHECKPOINT);
        prog.endPhase(Phase.SAVING_CHECKPOINT);
      }
      // This will start a new log segment and write to the seen_txid file, so
      // we shouldn't do it when coming up in standby state
      if (!haEnabled || (haEnabled && startOpt == StartupOption.UPGRADE)) {
        fsImage.openEditLogForWrite();
      }
      success = true;
    } finally {
      if (!success) {
        fsImage.close();
      }
      writeUnlock();
    }
    dir.imageLoadComplete();
  }

  private void startSecretManager() {
    if (dtSecretManager != null) {
      try {
        dtSecretManager.startThreads();
      } catch (IOException e) {
        // Inability to start secret manager
        // can't be recovered from.
        throw new RuntimeException(e);
      }
    }
  }
  
  private void startSecretManagerIfNecessary() {
    boolean shouldRun = shouldUseDelegationTokens() &&
      !isInSafeMode() && getEditLog().isOpenForWrite();
    boolean running = dtSecretManager.isRunning();
    if (shouldRun && !running) {
      startSecretManager();
    }
  }

  private void stopSecretManager() {
    if (dtSecretManager != null) {
      dtSecretManager.stopThreads();
    }
  }
  
  /** 
   * Start services common to both active and standby states
   * @param haContext 
   * @throws IOException
   */
  void startCommonServices(Configuration conf, HAContext haContext) throws IOException {
    this.registerMBean(); // register the MBean for the FSNamesystemState
    writeLock();
    this.haContext = haContext;
    try {
      nnResourceChecker = new NameNodeResourceChecker(conf);
      checkAvailableResources();
      assert safeMode != null && !isPopulatingReplQueues();
      StartupProgress prog = NameNode.getStartupProgress();
      prog.beginPhase(Phase.SAFEMODE);
      prog.setTotal(Phase.SAFEMODE, STEP_AWAITING_REPORTED_BLOCKS,
        getCompleteBlocksTotal());
      setBlockTotal();
      blockManager.activate(conf);
    } finally {
      writeUnlock();
    }
    
    registerMXBean();
    DefaultMetricsSystem.instance().register(this);
  }
  
  /** 
   * Stop services common to both active and standby states
   * @throws IOException
   */
  void stopCommonServices() {
    writeLock();
    try {
      if (blockManager != null) blockManager.close();
    } finally {
      writeUnlock();
    }
    RetryCache.clear(retryCache);
  }
  
  /**
   * Start services required in active state
   * @throws IOException
   */
  void startActiveServices() throws IOException {
    startingActiveService = true;
    LOG.info("Starting services required for active state");
    writeLock();
    try {
      FSEditLog editLog = dir.fsImage.getEditLog();
      
      if (!editLog.isOpenForWrite()) {
        // During startup, we're already open for write during initialization.
        editLog.initJournalsForWrite();
        // May need to recover
        editLog.recoverUnclosedStreams();
        
        LOG.info("Catching up to latest edits from old active before " +
            "taking over writer role in edits logs");
        editLogTailer.catchupDuringFailover();
        
        blockManager.setPostponeBlocksFromFuture(false);
        blockManager.getDatanodeManager().markAllDatanodesStale();
        blockManager.clearQueues();
        blockManager.processAllPendingDNMessages();

        // Only need to re-process the queue, If not in SafeMode.
        if (!isInSafeMode()) {
          LOG.info("Reprocessing replication and invalidation queues");
          initializeReplQueues();
        }

        if (LOG.isDebugEnabled()) {
          LOG.debug("NameNode metadata after re-processing " +
              "replication and invalidation queues during failover:\n" +
              metaSaveAsString());
        }
        
        long nextTxId = dir.fsImage.getLastAppliedTxId() + 1;
        LOG.info("Will take over writing edit logs at txnid " + 
            nextTxId);
        editLog.setNextTxId(nextTxId);

        dir.fsImage.editLog.openForWrite();
      }
      
      if (haEnabled) {
        // Renew all of the leases before becoming active.
        // This is because, while we were in standby mode,
        // the leases weren't getting renewed on this NN.
        // Give them all a fresh start here.
        leaseManager.renewAllLeases();
      }
      leaseManager.startMonitor();
      startSecretManagerIfNecessary();

      //ResourceMonitor required only at ActiveNN. See HDFS-2914
      this.nnrmthread = new Daemon(new NameNodeResourceMonitor());
      nnrmthread.start();

      nnEditLogRoller = new Daemon(new NameNodeEditLogRoller(
          editLogRollerThreshold, editLogRollerInterval));
      nnEditLogRoller.start();

      cacheManager.startMonitorThread();
      blockManager.getDatanodeManager().setShouldSendCachingCommands(true);
    } finally {
      writeUnlock();
      startingActiveService = false;
    }
  }

  /**
   * Initialize replication queues.
   */
  private void initializeReplQueues() {
    LOG.info("initializing replication queues");
    blockManager.processMisReplicatedBlocks();
    initializedReplQueues = true;
  }

  private boolean inActiveState() {
    return haContext != null &&
        haContext.getState().getServiceState() == HAServiceState.ACTIVE;
  }

  /**
   * @return Whether the namenode is transitioning to active state and is in the
   *         middle of the {@link #startActiveServices()}
   */
  public boolean inTransitionToActive() {
    return haEnabled && inActiveState() && startingActiveService;
  }

  private boolean shouldUseDelegationTokens() {
    return UserGroupInformation.isSecurityEnabled() ||
      alwaysUseDelegationTokensForTests;
  }

  /** 
   * Stop services required in active state
   * @throws InterruptedException
   */
  void stopActiveServices() {
    LOG.info("Stopping services started for active state");
    writeLock();
    try {
      stopSecretManager();
      if (leaseManager != null) {
        leaseManager.stopMonitor();
      }
      if (nnrmthread != null) {
        ((NameNodeResourceMonitor) nnrmthread.getRunnable()).stopMonitor();
        nnrmthread.interrupt();
      }
      if (nnEditLogRoller != null) {
        ((NameNodeEditLogRoller)nnEditLogRoller.getRunnable()).stop();
        nnEditLogRoller.interrupt();
      }
      if (dir != null && dir.fsImage != null) {
        if (dir.fsImage.editLog != null) {
          dir.fsImage.editLog.close();
        }
        // Update the fsimage with the last txid that we wrote
        // so that the tailer starts from the right spot.
        dir.fsImage.updateLastAppliedTxIdFromWritten();
      }
      cacheManager.stopMonitorThread();
      cacheManager.clearDirectiveStats();
      blockManager.getDatanodeManager().clearPendingCachingCommands();
      blockManager.getDatanodeManager().setShouldSendCachingCommands(false);
      // Don't want to keep replication queues when not in Active.
      blockManager.clearQueues();
      initializedReplQueues = false;
    } finally {
      writeUnlock();
    }
  }
  
  /**
   * Start services required in standby state 
   * 
   * @throws IOException
   */
  void startStandbyServices(final Configuration conf) throws IOException {
    LOG.info("Starting services required for standby state");
    if (!dir.fsImage.editLog.isOpenForRead()) {
      // During startup, we're already open for read.
      dir.fsImage.editLog.initSharedJournalsForRead();
    }
    
    blockManager.setPostponeBlocksFromFuture(true);

    editLogTailer = new EditLogTailer(this, conf);
    editLogTailer.start();
    if (standbyShouldCheckpoint) {
      standbyCheckpointer = new StandbyCheckpointer(conf, this);
      standbyCheckpointer.start();
    }
  }

  /**
   * Called when the NN is in Standby state and the editlog tailer tails the
   * OP_ROLLING_UPGRADE_START.
   */
  void triggerRollbackCheckpoint() {
    setNeedRollbackFsImage(true);
    if (standbyCheckpointer != null) {
      standbyCheckpointer.triggerRollbackCheckpoint();
    }
  }

  /**
   * Called while the NN is in Standby state, but just about to be
   * asked to enter Active state. This cancels any checkpoints
   * currently being taken.
   */
  void prepareToStopStandbyServices() throws ServiceFailedException {
    if (standbyCheckpointer != null) {
      standbyCheckpointer.cancelAndPreventCheckpoints(
          "About to leave standby state");
    }
  }

  /** Stop services required in standby state */
  void stopStandbyServices() throws IOException {
    LOG.info("Stopping services started for standby state");
    if (standbyCheckpointer != null) {
      standbyCheckpointer.stop();
    }
    if (editLogTailer != null) {
      editLogTailer.stop();
    }
    if (dir != null && dir.fsImage != null && dir.fsImage.editLog != null) {
      dir.fsImage.editLog.close();
    }
  }
  
  @Override
  public void checkOperation(OperationCategory op) throws StandbyException {
    if (haContext != null) {
      // null in some unit tests
      haContext.checkOperation(op);
    }
  }
  
  /**
   * @throws RetriableException
   *           If 1) The NameNode is in SafeMode, 2) HA is enabled, and 3)
   *           NameNode is in active state
   * @throws SafeModeException
   *           Otherwise if NameNode is in SafeMode.
   */
  private void checkNameNodeSafeMode(String errorMsg)
      throws RetriableException, SafeModeException {
    if (isInSafeMode()) {
      SafeModeException se = new SafeModeException(errorMsg, safeMode);
      if (haEnabled && haContext != null
          && haContext.getState().getServiceState() == HAServiceState.ACTIVE
          && shouldRetrySafeMode(this.safeMode)) {
        throw new RetriableException(se);
      } else {
        throw se;
      }
    }
  }
  
  /**
   * We already know that the safemode is on. We will throw a RetriableException
   * if the safemode is not manual or caused by low resource.
   */
  private boolean shouldRetrySafeMode(SafeModeInfo safeMode) {
    if (safeMode == null) {
      return false;
    } else {
      return !safeMode.isManual() && !safeMode.areResourcesLow();
    }
  }
  
  public static Collection<URI> getNamespaceDirs(Configuration conf) {
    return getStorageDirs(conf, DFS_NAMENODE_NAME_DIR_KEY);
  }

  /**
   * Get all edits dirs which are required. If any shared edits dirs are
   * configured, these are also included in the set of required dirs.
   * 
   * @param conf the HDFS configuration.
   * @return all required dirs.
   */
  public static Collection<URI> getRequiredNamespaceEditsDirs(Configuration conf) {
    Set<URI> ret = new HashSet<URI>();
    ret.addAll(getStorageDirs(conf, DFS_NAMENODE_EDITS_DIR_REQUIRED_KEY));
    ret.addAll(getSharedEditsDirs(conf));
    return ret;
  }

  private static Collection<URI> getStorageDirs(Configuration conf,
                                                String propertyName) {
    Collection<String> dirNames = conf.getTrimmedStringCollection(propertyName);
    StartupOption startOpt = NameNode.getStartupOption(conf);
    if(startOpt == StartupOption.IMPORT) {
      // In case of IMPORT this will get rid of default directories 
      // but will retain directories specified in hdfs-site.xml
      // When importing image from a checkpoint, the name-node can
      // start with empty set of storage directories.
      Configuration cE = new HdfsConfiguration(false);
      cE.addResource("core-default.xml");
      cE.addResource("core-site.xml");
      cE.addResource("hdfs-default.xml");
      Collection<String> dirNames2 = cE.getTrimmedStringCollection(propertyName);
      dirNames.removeAll(dirNames2);
      if(dirNames.isEmpty())
        LOG.warn("!!! WARNING !!!" +
          "\n\tThe NameNode currently runs without persistent storage." +
          "\n\tAny changes to the file system meta-data may be lost." +
          "\n\tRecommended actions:" +
          "\n\t\t- shutdown and restart NameNode with configured \"" 
          + propertyName + "\" in hdfs-site.xml;" +
          "\n\t\t- use Backup Node as a persistent and up-to-date storage " +
          "of the file system meta-data.");
    } else if (dirNames.isEmpty()) {
      dirNames = Collections.singletonList(
          DFSConfigKeys.DFS_NAMENODE_EDITS_DIR_DEFAULT);
    }
    return Util.stringCollectionAsURIs(dirNames);
  }

  /**
   * Return an ordered list of edits directories to write to.
   * The list is ordered such that all shared edits directories
   * are ordered before non-shared directories, and any duplicates
   * are removed. The order they are specified in the configuration
   * is retained.
   * @return Collection of shared edits directories.
   * @throws IOException if multiple shared edits directories are configured
   */
  public static List<URI> getNamespaceEditsDirs(Configuration conf)
      throws IOException {
    return getNamespaceEditsDirs(conf, true);
  }
  
  public static List<URI> getNamespaceEditsDirs(Configuration conf,
      boolean includeShared)
      throws IOException {
    // Use a LinkedHashSet so that order is maintained while we de-dup
    // the entries.
    LinkedHashSet<URI> editsDirs = new LinkedHashSet<URI>();
    
    if (includeShared) {
      List<URI> sharedDirs = getSharedEditsDirs(conf);
  
      // Fail until multiple shared edits directories are supported (HDFS-2782)
      if (sharedDirs.size() > 1) {
        throw new IOException(
            "Multiple shared edits directories are not yet supported");
      }
  
      // First add the shared edits dirs. It's critical that the shared dirs
      // are added first, since JournalSet syncs them in the order they are listed,
      // and we need to make sure all edits are in place in the shared storage
      // before they are replicated locally. See HDFS-2874.
      for (URI dir : sharedDirs) {
        if (!editsDirs.add(dir)) {
          LOG.warn("Edits URI " + dir + " listed multiple times in " + 
              DFS_NAMENODE_SHARED_EDITS_DIR_KEY + ". Ignoring duplicates.");
        }
      }
    }    
    // Now add the non-shared dirs.
    for (URI dir : getStorageDirs(conf, DFS_NAMENODE_EDITS_DIR_KEY)) {
      if (!editsDirs.add(dir)) {
        LOG.warn("Edits URI " + dir + " listed multiple times in " + 
            DFS_NAMENODE_SHARED_EDITS_DIR_KEY + " and " +
            DFS_NAMENODE_EDITS_DIR_KEY + ". Ignoring duplicates.");
      }
    }

    if (editsDirs.isEmpty()) {
      // If this is the case, no edit dirs have been explicitly configured.
      // Image dirs are to be used for edits too.
      return Lists.newArrayList(getNamespaceDirs(conf));
    } else {
      return Lists.newArrayList(editsDirs);
    }
  }
  
  /**
   * Returns edit directories that are shared between primary and secondary.
   * @param conf
   * @return Collection of edit directories.
   */
  public static List<URI> getSharedEditsDirs(Configuration conf) {
    // don't use getStorageDirs here, because we want an empty default
    // rather than the dir in /tmp
    Collection<String> dirNames = conf.getTrimmedStringCollection(
        DFS_NAMENODE_SHARED_EDITS_DIR_KEY);
    return Util.stringCollectionAsURIs(dirNames);
  }

  @Override
  public void readLock() {
    this.fsLock.readLock().lock();
  }
  @Override
  public void longReadLockInterruptibly() throws InterruptedException {
    this.fsLock.longReadLock().lockInterruptibly();
    try {
      this.fsLock.readLock().lockInterruptibly();
    } catch (InterruptedException ie) {
      // In the event we're interrupted while getting the normal FSNS read lock,
      // release the long read lock.
      this.fsLock.longReadLock().unlock();
      throw ie;
    }
  }
  @Override
  public void longReadUnlock() {
    this.fsLock.readLock().unlock();
    this.fsLock.longReadLock().unlock();
  }
  @Override
  public void readUnlock() {
    this.fsLock.readLock().unlock();
  }
  @Override
  public void writeLock() {
    this.fsLock.longReadLock().lock();
    this.fsLock.writeLock().lock();
  }
  @Override
  public void writeLockInterruptibly() throws InterruptedException {
    this.fsLock.longReadLock().lockInterruptibly();
    try {
      this.fsLock.writeLock().lockInterruptibly();
    } catch (InterruptedException ie) {
      // In the event we're interrupted while getting the normal FSNS write
      // lock, release the long read lock.
      this.fsLock.longReadLock().unlock();
      throw ie;
    }
  }
  @Override
  public void writeUnlock() {
    this.fsLock.writeLock().unlock();
    this.fsLock.longReadLock().unlock();
  }
  @Override
  public boolean hasWriteLock() {
    return this.fsLock.isWriteLockedByCurrentThread();
  }
  @Override
  public boolean hasReadLock() {
    return this.fsLock.getReadHoldCount() > 0 || hasWriteLock();
  }

  public int getReadHoldCount() {
    return this.fsLock.getReadHoldCount();
  }

  public int getWriteHoldCount() {
    return this.fsLock.getWriteHoldCount();
  }

  NamespaceInfo getNamespaceInfo() {
    readLock();
    try {
      return unprotectedGetNamespaceInfo();
    } finally {
      readUnlock();
    }
  }

  /**
   * Version of @see #getNamespaceInfo() that is not protected by a lock.
   */
  NamespaceInfo unprotectedGetNamespaceInfo() {
    return new NamespaceInfo(dir.fsImage.getStorage().getNamespaceID(),
        getClusterId(), getBlockPoolId(),
        dir.fsImage.getStorage().getCTime());
  }

  /**
   * Close down this file system manager.
   * Causes heartbeat and lease daemons to stop; waits briefly for
   * them to finish, but a short timeout returns control back to caller.
   */
  void close() {
    fsRunning = false;
    try {
      stopCommonServices();
      if (smmthread != null) smmthread.interrupt();
    } finally {
      // using finally to ensure we also wait for lease daemon
      try {
        stopActiveServices();
        stopStandbyServices();
        if (dir != null) {
          dir.close();
        }
      } catch (IOException ie) {
        LOG.error("Error closing FSDirectory", ie);
        IOUtils.cleanup(LOG, dir);
      }
    }
  }

  @Override
  public boolean isRunning() {
    return fsRunning;
  }
  
  @Override
  public boolean isInStandbyState() {
    if (haContext == null || haContext.getState() == null) {
      // We're still starting up. In this case, if HA is
      // on for the cluster, we always start in standby. Otherwise
      // start in active.
      return haEnabled;
    }

    return HAServiceState.STANDBY == haContext.getState().getServiceState();
  }

  /**
   * Dump all metadata into specified file
   */
  void metaSave(String filename) throws IOException {
    checkSuperuserPrivilege();
    checkOperation(OperationCategory.UNCHECKED);
    writeLock();
    try {
      checkOperation(OperationCategory.UNCHECKED);
      File file = new File(System.getProperty("hadoop.log.dir"), filename);
      PrintWriter out = new PrintWriter(new BufferedWriter(
          new OutputStreamWriter(new FileOutputStream(file), Charsets.UTF_8)));
      metaSave(out);
      out.flush();
      out.close();
    } finally {
      writeUnlock();
    }
  }

  private void metaSave(PrintWriter out) {
    assert hasWriteLock();
    long totalInodes = this.dir.totalInodes();
    long totalBlocks = this.getBlocksTotal();
    out.println(totalInodes + " files and directories, " + totalBlocks
        + " blocks = " + (totalInodes + totalBlocks) + " total");

    blockManager.metaSave(out);
  }

  private String metaSaveAsString() {
    StringWriter sw = new StringWriter();
    PrintWriter pw = new PrintWriter(sw);
    metaSave(pw);
    pw.flush();
    return sw.toString();
  }
  

  long getDefaultBlockSize() {
    return serverDefaults.getBlockSize();
  }

  FsServerDefaults getServerDefaults() throws StandbyException {
    checkOperation(OperationCategory.READ);
    return serverDefaults;
  }

  long getAccessTimePrecision() {
    return accessTimePrecision;
  }

  private boolean isAccessTimeSupported() {
    return accessTimePrecision > 0;
  }

  /////////////////////////////////////////////////////////
  //
  // These methods are called by HadoopFS clients
  //
  /////////////////////////////////////////////////////////
  /**
   * Set permissions for an existing file.
   * @throws IOException
   */
  void setPermission(String src, FsPermission permission)
      throws AccessControlException, FileNotFoundException, SafeModeException,
      UnresolvedLinkException, IOException {
    try {
      setPermissionInt(src, permission);
    } catch (AccessControlException e) {
      logAuditEvent(false, "setPermission", src);
      throw e;
    }
  }

  private void setPermissionInt(String src, FsPermission permission)
      throws AccessControlException, FileNotFoundException, SafeModeException,
      UnresolvedLinkException, IOException {
    HdfsFileStatus resultingStat = null;
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot set permission for " + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      checkOwner(pc, src);
      dir.setPermission(src, permission);
      resultingStat = getAuditFileInfo(src, false);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    logAuditEvent(true, "setPermission", src, null, resultingStat);
  }

  /**
   * Set owner for an existing file.
   * @throws IOException
   */
  void setOwner(String src, String username, String group)
      throws AccessControlException, FileNotFoundException, SafeModeException,
      UnresolvedLinkException, IOException {
    try {
      setOwnerInt(src, username, group);
    } catch (AccessControlException e) {
      logAuditEvent(false, "setOwner", src);
      throw e;
    } 
  }

  private void setOwnerInt(String src, String username, String group)
      throws AccessControlException, FileNotFoundException, SafeModeException,
      UnresolvedLinkException, IOException {
    HdfsFileStatus resultingStat = null;
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot set owner for " + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      checkOwner(pc, src);
      if (!pc.isSuperUser()) {
        if (username != null && !pc.getUser().equals(username)) {
          throw new AccessControlException("Non-super user cannot change owner");
        }
        if (group != null && !pc.containsGroup(group)) {
          throw new AccessControlException("User does not belong to " + group);
        }
      }
      dir.setOwner(src, username, group);
      resultingStat = getAuditFileInfo(src, false);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    logAuditEvent(true, "setOwner", src, null, resultingStat);
  }

  /**
   * Get block locations within the specified range.
   * @see ClientProtocol#getBlockLocations(String, long, long)
   */
  LocatedBlocks getBlockLocations(String clientMachine, String src,
      long offset, long length) throws AccessControlException,
      FileNotFoundException, UnresolvedLinkException, IOException {
    LocatedBlocks blocks = getBlockLocations(src, offset, length, true, true,
        true);
    if (blocks != null) {
      blockManager.getDatanodeManager().sortLocatedBlocks(
          clientMachine, blocks.getLocatedBlocks());
      
      LocatedBlock lastBlock = blocks.getLastLocatedBlock();
      if (lastBlock != null) {
        ArrayList<LocatedBlock> lastBlockList = new ArrayList<LocatedBlock>();
        lastBlockList.add(lastBlock);
        blockManager.getDatanodeManager().sortLocatedBlocks(
                              clientMachine, lastBlockList);
      }
    }
    return blocks;
  }

  /**
   * Get block locations within the specified range.
   * @see ClientProtocol#getBlockLocations(String, long, long)
   * @throws FileNotFoundException, UnresolvedLinkException, IOException
   */
  LocatedBlocks getBlockLocations(String src, long offset, long length,
      boolean doAccessTime, boolean needBlockToken, boolean checkSafeMode)
      throws FileNotFoundException, UnresolvedLinkException, IOException {
    try {
      return getBlockLocationsInt(src, offset, length, doAccessTime,
                                  needBlockToken, checkSafeMode);
    } catch (AccessControlException e) {
      logAuditEvent(false, "open", src);
      throw e;
    }
  }

  private LocatedBlocks getBlockLocationsInt(String src, long offset,
      long length, boolean doAccessTime, boolean needBlockToken,
      boolean checkSafeMode)
      throws FileNotFoundException, UnresolvedLinkException, IOException {
    if (offset < 0) {
      throw new HadoopIllegalArgumentException(
          "Negative offset is not supported. File: " + src);
    }
    if (length < 0) {
      throw new HadoopIllegalArgumentException(
          "Negative length is not supported. File: " + src);
    }
    final LocatedBlocks ret = getBlockLocationsUpdateTimes(src,
        offset, length, doAccessTime, needBlockToken);  
    logAuditEvent(true, "open", src);
    if (checkSafeMode && isInSafeMode()) {
      for (LocatedBlock b : ret.getLocatedBlocks()) {
        // if safemode & no block locations yet then throw safemodeException
        if ((b.getLocations() == null) || (b.getLocations().length == 0)) {
          SafeModeException se = new SafeModeException(
              "Zero blocklocations for " + src, safeMode);
          if (haEnabled && haContext != null && 
              haContext.getState().getServiceState() == HAServiceState.ACTIVE) {
            throw new RetriableException(se);
          } else {
            throw se;
          }
        }
      }
    }
    return ret;
  }

  /*
   * Get block locations within the specified range, updating the
   * access times if necessary. 
   */
  private LocatedBlocks getBlockLocationsUpdateTimes(String src, long offset,
      long length, boolean doAccessTime, boolean needBlockToken)
      throws FileNotFoundException,
      UnresolvedLinkException, IOException {
    FSPermissionChecker pc = getPermissionChecker();
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    for (int attempt = 0; attempt < 2; attempt++) {
      boolean isReadOp = (attempt == 0);
      if (isReadOp) { // first attempt is with readlock
        checkOperation(OperationCategory.READ);
        readLock();
      }  else { // second attempt is with  write lock
        checkOperation(OperationCategory.WRITE);
        writeLock(); // writelock is needed to set accesstime
      }
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      try {
        if (isReadOp) {
          checkOperation(OperationCategory.READ);
        } else {
          checkOperation(OperationCategory.WRITE);
        }
        if (isPermissionEnabled) {
          checkPathAccess(pc, src, FsAction.READ);
        }

        // if the namenode is in safemode, then do not update access time
        if (isInSafeMode()) {
          doAccessTime = false;
        }

        final INodesInPath iip = dir.getLastINodeInPath(src);
        final INodeFile inode = INodeFile.valueOf(iip.getLastINode(), src);
        if (!iip.isSnapshot() //snapshots are readonly, so don't update atime.
            && doAccessTime && isAccessTimeSupported()) {
          final long now = now();
          if (now > inode.getAccessTime() + getAccessTimePrecision()) {
            // if we have to set access time but we only have the readlock, then
            // restart this entire operation with the writeLock.
            if (isReadOp) {
              continue;
            }
            dir.setTimes(src, inode, -1, now, false, iip.getLatestSnapshotId());
          }
        }
        final long fileSize = iip.isSnapshot() ?
            inode.computeFileSize(iip.getPathSnapshotId())
            : inode.computeFileSizeNotIncludingLastUcBlock();
        boolean isUc = inode.isUnderConstruction();
        if (iip.isSnapshot()) {
          // if src indicates a snapshot file, we need to make sure the returned
          // blocks do not exceed the size of the snapshot file.
          length = Math.min(length, fileSize - offset);
          isUc = false;
        }
        LocatedBlocks blocks =
          blockManager.createLocatedBlocks(inode.getBlocks(), fileSize,
            isUc, offset, length, needBlockToken, iip.isSnapshot());
        // Set caching information for the located blocks.
        for (LocatedBlock lb: blocks.getLocatedBlocks()) {
          cacheManager.setCachedLocations(lb);
        }
        return blocks;
      } finally {
        if (isReadOp) {
          readUnlock();
        } else {
          writeUnlock();
        }
      }
    }
    return null; // can never reach here
  }

  /**
   * Moves all the blocks from srcs and appends them to trg
   * To avoid rollbacks we will verify validitity of ALL of the args
   * before we start actual move.
   * 
   * This does not support ".inodes" relative path
   * @param target
   * @param srcs
   * @throws IOException
   */
  void concat(String target, String [] srcs) 
      throws IOException, UnresolvedLinkException {
    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return; // Return previous response
    }
    
    // Either there is no previous request in progres or it has failed
    if(FSNamesystem.LOG.isDebugEnabled()) {
      FSNamesystem.LOG.debug("concat " + Arrays.toString(srcs) +
          " to " + target);
    }
    
    boolean success = false;
    try {
      concatInt(target, srcs, cacheEntry != null);
      success = true;
    } catch (AccessControlException e) {
      logAuditEvent(false, "concat", Arrays.toString(srcs), target, null);
      throw e;
    } finally {
      RetryCache.setState(cacheEntry, success);
    }
  }

  private void concatInt(String target, String [] srcs, 
      boolean logRetryCache) throws IOException, UnresolvedLinkException {
    // verify args
    if(target.isEmpty()) {
      throw new IllegalArgumentException("Target file name is empty");
    }
    if(srcs == null || srcs.length == 0) {
      throw new IllegalArgumentException("No sources given");
    }
    
    // We require all files be in the same directory
    String trgParent = 
      target.substring(0, target.lastIndexOf(Path.SEPARATOR_CHAR));
    for (String s : srcs) {
      String srcParent = s.substring(0, s.lastIndexOf(Path.SEPARATOR_CHAR));
      if (!srcParent.equals(trgParent)) {
        throw new IllegalArgumentException(
           "Sources and target are not in the same directory");
      }
    }

    HdfsFileStatus resultingStat = null;
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot concat " + target);
      concatInternal(pc, target, srcs, logRetryCache);
      resultingStat = getAuditFileInfo(target, false);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    logAuditEvent(true, "concat", Arrays.toString(srcs), target, resultingStat);
  }

  /** See {@link #concat(String, String[])} */
  private void concatInternal(FSPermissionChecker pc, String target,
      String[] srcs, boolean logRetryCache) throws IOException,
      UnresolvedLinkException {
    assert hasWriteLock();

    // write permission for the target
    if (isPermissionEnabled) {
      checkPathAccess(pc, target, FsAction.WRITE);

      // and srcs
      for(String aSrc: srcs) {
        checkPathAccess(pc, aSrc, FsAction.READ); // read the file
        checkParentAccess(pc, aSrc, FsAction.WRITE); // for delete 
      }
    }

    // to make sure no two files are the same
    Set<INode> si = new HashSet<INode>();

    // we put the following prerequisite for the operation
    // replication and blocks sizes should be the same for ALL the blocks

    // check the target
    final INodeFile trgInode = INodeFile.valueOf(dir.getINode4Write(target),
        target);
    if(trgInode.isUnderConstruction()) {
      throw new HadoopIllegalArgumentException("concat: target file "
          + target + " is under construction");
    }
    // per design target shouldn't be empty and all the blocks same size
    if(trgInode.numBlocks() == 0) {
      throw new HadoopIllegalArgumentException("concat: target file "
          + target + " is empty");
    }
    if (trgInode.isWithSnapshot()) {
      throw new HadoopIllegalArgumentException("concat: target file "
          + target + " is in a snapshot");
    }

    long blockSize = trgInode.getPreferredBlockSize();

    // check the end block to be full
    final BlockInfo last = trgInode.getLastBlock();
    if(blockSize != last.getNumBytes()) {
      throw new HadoopIllegalArgumentException("The last block in " + target
          + " is not full; last block size = " + last.getNumBytes()
          + " but file block size = " + blockSize);
    }

    si.add(trgInode);
    final short repl = trgInode.getFileReplication();

    // now check the srcs
    boolean endSrc = false; // final src file doesn't have to have full end block
    for(int i=0; i<srcs.length; i++) {
      String src = srcs[i];
      if(i==srcs.length-1)
        endSrc=true;

      final INodeFile srcInode = INodeFile.valueOf(dir.getINode4Write(src), src);
      if(src.isEmpty() 
          || srcInode.isUnderConstruction()
          || srcInode.numBlocks() == 0) {
        throw new HadoopIllegalArgumentException("concat: source file " + src
            + " is invalid or empty or underConstruction");
      }

      // check replication and blocks size
      if(repl != srcInode.getBlockReplication()) {
        throw new HadoopIllegalArgumentException("concat: the soruce file "
            + src + " and the target file " + target
            + " should have the same replication: source replication is "
            + srcInode.getBlockReplication()
            + " but target replication is " + repl);
      }

      //boolean endBlock=false;
      // verify that all the blocks are of the same length as target
      // should be enough to check the end blocks
      final BlockInfo[] srcBlocks = srcInode.getBlocks();
      int idx = srcBlocks.length-1;
      if(endSrc)
        idx = srcBlocks.length-2; // end block of endSrc is OK not to be full
      if(idx >= 0 && srcBlocks[idx].getNumBytes() != blockSize) {
        throw new HadoopIllegalArgumentException("concat: the soruce file "
            + src + " and the target file " + target
            + " should have the same blocks sizes: target block size is "
            + blockSize + " but the size of source block " + idx + " is "
            + srcBlocks[idx].getNumBytes());
      }

      si.add(srcInode);
    }

    // make sure no two files are the same
    if(si.size() < srcs.length+1) { // trg + srcs
      // it means at least two files are the same
      throw new HadoopIllegalArgumentException(
          "concat: at least two of the source files are the same");
    }

    if(NameNode.stateChangeLog.isDebugEnabled()) {
      NameNode.stateChangeLog.debug("DIR* NameSystem.concat: " + 
          Arrays.toString(srcs) + " to " + target);
    }

    dir.concat(target,srcs, logRetryCache);
  }
  
  /**
   * stores the modification and access time for this inode. 
   * The access time is precise upto an hour. The transaction, if needed, is
   * written to the edits log but is not flushed.
   */
  void setTimes(String src, long mtime, long atime) 
      throws IOException, UnresolvedLinkException {
    if (!isAccessTimeSupported() && atime != -1) {
      throw new IOException("Access time for hdfs is not configured. " +
                            " Please set " + DFS_NAMENODE_ACCESSTIME_PRECISION_KEY + " configuration parameter.");
    }
    try {
      setTimesInt(src, mtime, atime);
    } catch (AccessControlException e) {
      logAuditEvent(false, "setTimes", src);
      throw e;
    }
  }

  private void setTimesInt(String src, long mtime, long atime) 
    throws IOException, UnresolvedLinkException {
    HdfsFileStatus resultingStat = null;
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot set times " + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);

      // Write access is required to set access and modification times
      if (isPermissionEnabled) {
        checkPathAccess(pc, src, FsAction.WRITE);
      }
      final INodesInPath iip = dir.getINodesInPath4Write(src);
      final INode inode = iip.getLastINode();
      if (inode != null) {
        dir.setTimes(src, inode, mtime, atime, true, iip.getLatestSnapshotId());
        resultingStat = getAuditFileInfo(src, false);
      } else {
        throw new FileNotFoundException("File/Directory " + src + " does not exist.");
      }
    } finally {
      writeUnlock();
    }
    logAuditEvent(true, "setTimes", src, null, resultingStat);
  }

  /**
   * Create a symbolic link.
   */
  @SuppressWarnings("deprecation")
  void createSymlink(String target, String link,
      PermissionStatus dirPerms, boolean createParent) 
      throws IOException, UnresolvedLinkException {
    if (!FileSystem.areSymlinksEnabled()) {
      throw new UnsupportedOperationException("Symlinks not supported");
    }
    if (!DFSUtil.isValidName(link)) {
      throw new InvalidPathException("Invalid link name: " + link);
    }
    if (FSDirectory.isReservedName(target)) {
      throw new InvalidPathException("Invalid target name: " + target);
    }
    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return; // Return previous response
    }
    boolean success = false;
    try {
      createSymlinkInt(target, link, dirPerms, createParent, cacheEntry != null);
      success = true;
    } catch (AccessControlException e) {
      logAuditEvent(false, "createSymlink", link, target, null);
      throw e;
    } finally {
      RetryCache.setState(cacheEntry, success);
    }
  }

  private void createSymlinkInt(String target, String link,
      PermissionStatus dirPerms, boolean createParent, boolean logRetryCache) 
      throws IOException, UnresolvedLinkException {
    if (NameNode.stateChangeLog.isDebugEnabled()) {
      NameNode.stateChangeLog.debug("DIR* NameSystem.createSymlink: target="
          + target + " link=" + link);
    }
    HdfsFileStatus resultingStat = null;
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(link);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot create symlink " + link);
      link = FSDirectory.resolvePath(link, pathComponents, dir);
      if (!createParent) {
        verifyParentDir(link);
      }
      if (!dir.isValidToCreate(link)) {
        throw new IOException("failed to create link " + link 
            +" either because the filename is invalid or the file exists");
      }
      if (isPermissionEnabled) {
        checkAncestorAccess(pc, link, FsAction.WRITE);
      }
      // validate that we have enough inodes.
      checkFsObjectLimit();

      // add symbolic link to namespace
      dir.addSymlink(link, target, dirPerms, createParent, logRetryCache);
      resultingStat = getAuditFileInfo(link, false);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    logAuditEvent(true, "createSymlink", link, target, resultingStat);
  }

  /**
   * Set replication for an existing file.
   * 
   * The NameNode sets new replication and schedules either replication of 
   * under-replicated data blocks or removal of the excessive block copies 
   * if the blocks are over-replicated.
   * 
   * @see ClientProtocol#setReplication(String, short)
   * @param src file name
   * @param replication new replication
   * @return true if successful; 
   *         false if file does not exist or is a directory
   */
  boolean setReplication(final String src, final short replication)
      throws IOException {
    try {
      return setReplicationInt(src, replication);
    } catch (AccessControlException e) {
      logAuditEvent(false, "setReplication", src);
      throw e;
    }
  }

  private boolean setReplicationInt(String src, final short replication)
      throws IOException {
    blockManager.verifyReplication(src, replication, null);
    final boolean isFile;
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot set replication for " + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      if (isPermissionEnabled) {
        checkPathAccess(pc, src, FsAction.WRITE);
      }

      final short[] blockRepls = new short[2]; // 0: old, 1: new
      final Block[] blocks = dir.setReplication(src, replication, blockRepls);
      isFile = blocks != null;
      if (isFile) {
        blockManager.setReplication(blockRepls[0], blockRepls[1], src, blocks);
      }
    } finally {
      writeUnlock();
    }

    getEditLog().logSync();
    if (isFile) {
      logAuditEvent(true, "setReplication", src);
    }
    return isFile;
  }

  long getPreferredBlockSize(String filename) 
      throws IOException, UnresolvedLinkException {
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.READ);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(filename);
    readLock();
    try {
      checkOperation(OperationCategory.READ);
      filename = FSDirectory.resolvePath(filename, pathComponents, dir);
      if (isPermissionEnabled) {
        checkTraverse(pc, filename);
      }
      return dir.getPreferredBlockSize(filename);
    } finally {
      readUnlock();
    }
  }

  /**
   * Verify that parent directory of src exists.
   */
  private void verifyParentDir(String src) throws FileNotFoundException,
      ParentNotDirectoryException, UnresolvedLinkException {
    assert hasReadLock();
    Path parent = new Path(src).getParent();
    if (parent != null) {
      final INode parentNode = dir.getINode(parent.toString());
      if (parentNode == null) {
        throw new FileNotFoundException("Parent directory doesn't exist: "
            + parent);
      } else if (!parentNode.isDirectory() && !parentNode.isSymlink()) {
        throw new ParentNotDirectoryException("Parent path is not a directory: "
            + parent);
      }
    }
  }
  
  /**
   * Create a new file entry in the namespace.
   * 
   * For description of parameters and exceptions thrown see
   * {@link ClientProtocol#create()}, except it returns valid file status upon
   * success
   * 
   * For retryCache handling details see -
   * {@link #getFileStatus(boolean, CacheEntryWithPayload)}
   * 
   */
  HdfsFileStatus startFile(String src, PermissionStatus permissions,
      String holder, String clientMachine, EnumSet<CreateFlag> flag,
      boolean createParent, short replication, long blockSize)
      throws AccessControlException, SafeModeException,
      FileAlreadyExistsException, UnresolvedLinkException,
      FileNotFoundException, ParentNotDirectoryException, IOException {
    HdfsFileStatus status = null;
    CacheEntryWithPayload cacheEntry = RetryCache.waitForCompletion(retryCache,
        null);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return (HdfsFileStatus) cacheEntry.getPayload();
    }
    
    try {
      status = startFileInt(src, permissions, holder, clientMachine, flag,
          createParent, replication, blockSize, cacheEntry != null);
    } catch (AccessControlException e) {
      logAuditEvent(false, "create", src);
      throw e;
    } finally {
      RetryCache.setState(cacheEntry, status != null, status);
    }
    return status;
  }

  private HdfsFileStatus startFileInt(String src, PermissionStatus permissions,
      String holder, String clientMachine, EnumSet<CreateFlag> flag,
      boolean createParent, short replication, long blockSize,
      boolean logRetryCache) throws AccessControlException, SafeModeException,
      FileAlreadyExistsException, UnresolvedLinkException,
      FileNotFoundException, ParentNotDirectoryException, IOException {
    if (NameNode.stateChangeLog.isDebugEnabled()) {
      NameNode.stateChangeLog.debug("DIR* NameSystem.startFile: src=" + src
          + ", holder=" + holder
          + ", clientMachine=" + clientMachine
          + ", createParent=" + createParent
          + ", replication=" + replication
          + ", createFlag=" + flag.toString());
    }
    if (!DFSUtil.isValidName(src)) {
      throw new InvalidPathException(src);
    }
    blockManager.verifyReplication(src, replication, clientMachine);

    boolean skipSync = false;
    HdfsFileStatus stat = null;
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    if (blockSize < minBlockSize) {
      throw new IOException("Specified block size is less than configured" +
          " minimum value (" + DFSConfigKeys.DFS_NAMENODE_MIN_BLOCK_SIZE_KEY
          + "): " + blockSize + " < " + minBlockSize);
    }
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    boolean create = flag.contains(CreateFlag.CREATE);
    boolean overwrite = flag.contains(CreateFlag.OVERWRITE);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot create file" + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      startFileInternal(pc, src, permissions, holder, clientMachine, create,
          overwrite, createParent, replication, blockSize, logRetryCache);
      stat = dir.getFileInfo(src, false);
    } catch (StandbyException se) {
      skipSync = true;
      throw se;
    } finally {
      writeUnlock();
      // There might be transactions logged while trying to recover the lease.
      // They need to be sync'ed even when an exception was thrown.
      if (!skipSync) {
        getEditLog().logSync();
      }
    } 
    logAuditEvent(true, "create", src, null, stat);
    return stat;
  }

  /**
   * Create a new file or overwrite an existing file<br>
   * 
   * Once the file is create the client then allocates a new block with the next
   * call using {@link NameNode#addBlock()}.
   * <p>
   * For description of parameters and exceptions thrown see
   * {@link ClientProtocol#create()}
   */
  private void startFileInternal(FSPermissionChecker pc, String src,
      PermissionStatus permissions, String holder, String clientMachine,
      boolean create, boolean overwrite, boolean createParent,
      short replication, long blockSize, boolean logRetryEntry)
      throws FileAlreadyExistsException, AccessControlException,
      UnresolvedLinkException, FileNotFoundException,
      ParentNotDirectoryException, IOException {
    assert hasWriteLock();
    // Verify that the destination does not exist as a directory already.
    final INodesInPath iip = dir.getINodesInPath4Write(src);
    final INode inode = iip.getLastINode();
    if (inode != null && inode.isDirectory()) {
      throw new FileAlreadyExistsException(src +
          " already exists as a directory");
    }
    final INodeFile myFile = INodeFile.valueOf(inode, src, true);
    if (isPermissionEnabled) {
      if (overwrite && myFile != null) {
        checkPathAccess(pc, src, FsAction.WRITE);
      } else {
        checkAncestorAccess(pc, src, FsAction.WRITE);
      }
    }

    if (!createParent) {
      verifyParentDir(src);
    }

    try {
      if (myFile == null) {
        if (!create) {
          throw new FileNotFoundException("Can't overwrite non-existent " +
              src + " for client " + clientMachine);
        }
      } else {
        if (overwrite) {
          try {
            deleteInt(src, true, false); // File exists - delete if overwrite
          } catch (AccessControlException e) {
            logAuditEvent(false, "delete", src);
            throw e;
          }
        } else {
          // If lease soft limit time is expired, recover the lease
          recoverLeaseInternal(myFile, src, holder, clientMachine, false);
          throw new FileAlreadyExistsException(src + " for client " +
              clientMachine + " already exists");
        }
      }

      checkFsObjectLimit();
      final DatanodeDescriptor clientNode = 
          blockManager.getDatanodeManager().getDatanodeByHost(clientMachine);

      INodeFile newNode = dir.addFile(src, permissions, replication, blockSize,
          holder, clientMachine, clientNode);
      if (newNode == null) {
        throw new IOException("Unable to add " + src +  " to namespace");
      }
      leaseManager.addLease(newNode.getFileUnderConstructionFeature()
          .getClientName(), src);

      // record file record in log, record new generation stamp
      getEditLog().logOpenFile(src, newNode, logRetryEntry);
      if (NameNode.stateChangeLog.isDebugEnabled()) {
        NameNode.stateChangeLog.debug("DIR* NameSystem.startFile: added " +
            src + " inode " + newNode.getId() + " " + holder);
      }
    } catch (IOException ie) {
      NameNode.stateChangeLog.warn("DIR* NameSystem.startFile: " + src + " " +
          ie.getMessage());
      throw ie;
    }
  }
  
  /**
   * Append to an existing file for append.
   * <p>
   * 
   * The method returns the last block of the file if this is a partial block,
   * which can still be used for writing more data. The client uses the returned
   * block locations to form the data pipeline for this block.<br>
   * The method returns null if the last block is full. The client then
   * allocates a new block with the next call using {@link NameNode#addBlock()}.
   * <p>
   * 
   * For description of parameters and exceptions thrown see
   * {@link ClientProtocol#append(String, String)}
   * 
   * @return the last block locations if the block is partial or null otherwise
   */
  private LocatedBlock appendFileInternal(FSPermissionChecker pc, String src,
      String holder, String clientMachine, boolean logRetryCache)
      throws AccessControlException, UnresolvedLinkException,
      FileNotFoundException, IOException {
    assert hasWriteLock();
    // Verify that the destination does not exist as a directory already.
    final INodesInPath iip = dir.getINodesInPath4Write(src);
    final INode inode = iip.getLastINode();
    if (inode != null && inode.isDirectory()) {
      throw new FileAlreadyExistsException("Cannot append to directory " + src
          + "; already exists as a directory.");
    }
    if (isPermissionEnabled) {
      checkPathAccess(pc, src, FsAction.WRITE);
    }

    try {
      if (inode == null) {
        throw new FileNotFoundException("failed to append to non-existent file "
          + src + " for client " + clientMachine);
      }
      INodeFile myFile = INodeFile.valueOf(inode, src, true);
      // Opening an existing file for write - may need to recover lease.
      recoverLeaseInternal(myFile, src, holder, clientMachine, false);
      
      // recoverLeaseInternal may create a new InodeFile via 
      // finalizeINodeFileUnderConstruction so we need to refresh 
      // the referenced file.  
      myFile = INodeFile.valueOf(dir.getINode(src), src, true);
      final BlockInfo lastBlock = myFile.getLastBlock();
      // Check that the block has at least minimum replication.
      if(lastBlock != null && lastBlock.isComplete() &&
          !getBlockManager().isSufficientlyReplicated(lastBlock)) {
        throw new IOException("append: lastBlock=" + lastBlock +
            " of src=" + src + " is not sufficiently replicated yet.");
      }
      final DatanodeDescriptor clientNode = 
          blockManager.getDatanodeManager().getDatanodeByHost(clientMachine);
      return prepareFileForWrite(src, myFile, holder, clientMachine, clientNode,
          true, iip.getLatestSnapshotId(), logRetryCache);
    } catch (IOException ie) {
      NameNode.stateChangeLog.warn("DIR* NameSystem.append: " +ie.getMessage());
      throw ie;
    }
  }
  
  /**
   * Replace current node with a INodeUnderConstruction.
   * Recreate in-memory lease record.
   * 
   * @param src path to the file
   * @param file existing file object
   * @param leaseHolder identifier of the lease holder on this file
   * @param clientMachine identifier of the client machine
   * @param clientNode if the client is collocated with a DN, that DN's descriptor
   * @param writeToEditLog whether to persist this change to the edit log
   * @param logRetryCache whether to record RPC ids in editlog for retry cache
   *                      rebuilding
   * @return the last block locations if the block is partial or null otherwise
   * @throws UnresolvedLinkException
   * @throws IOException
   */
  LocatedBlock prepareFileForWrite(String src, INodeFile file,
      String leaseHolder, String clientMachine, DatanodeDescriptor clientNode,
      boolean writeToEditLog, int latestSnapshot, boolean logRetryCache)
      throws IOException {
    file = file.recordModification(latestSnapshot);
    final INodeFile cons = file.toUnderConstruction(leaseHolder, clientMachine,
        clientNode);

    leaseManager.addLease(cons.getFileUnderConstructionFeature()
        .getClientName(), src);
    
    LocatedBlock ret = blockManager.convertLastBlockToUnderConstruction(cons);
    if (writeToEditLog) {
      getEditLog().logOpenFile(src, cons, logRetryCache);
    }
    return ret;
  }

  /**
   * Recover lease;
   * Immediately revoke the lease of the current lease holder and start lease
   * recovery so that the file can be forced to be closed.
   * 
   * @param src the path of the file to start lease recovery
   * @param holder the lease holder's name
   * @param clientMachine the client machine's name
   * @return true if the file is already closed
   * @throws IOException
   */
  boolean recoverLease(String src, String holder, String clientMachine)
      throws IOException {
    if (!DFSUtil.isValidName(src)) {
      throw new IOException("Invalid file name: " + src);
    }
  
    boolean skipSync = false;
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot recover the lease of " + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      final INodeFile inode = INodeFile.valueOf(dir.getINode(src), src);
      if (!inode.isUnderConstruction()) {
        return true;
      }
      if (isPermissionEnabled) {
        checkPathAccess(pc, src, FsAction.WRITE);
      }
  
      recoverLeaseInternal(inode, src, holder, clientMachine, true);
    } catch (StandbyException se) {
      skipSync = true;
      throw se;
    } finally {
      writeUnlock();
      // There might be transactions logged while trying to recover the lease.
      // They need to be sync'ed even when an exception was thrown.
      if (!skipSync) {
        getEditLog().logSync();
      }
    }
    return false;
  }

  private void recoverLeaseInternal(INodeFile fileInode, 
      String src, String holder, String clientMachine, boolean force)
      throws IOException {
    assert hasWriteLock();
    if (fileInode != null && fileInode.isUnderConstruction()) {
      //
      // If the file is under construction , then it must be in our
      // leases. Find the appropriate lease record.
      //
      Lease lease = leaseManager.getLease(holder);
      //
      // We found the lease for this file. And surprisingly the original
      // holder is trying to recreate this file. This should never occur.
      //
      if (!force && lease != null) {
        Lease leaseFile = leaseManager.getLeaseByPath(src);
        if ((leaseFile != null && leaseFile.equals(lease)) ||
            lease.getHolder().equals(holder)) { 
          throw new AlreadyBeingCreatedException(
            "failed to create file " + src + " for " + holder +
            " for client " + clientMachine +
            " because current leaseholder is trying to recreate file.");
        }
      }
      //
      // Find the original holder.
      //
      FileUnderConstructionFeature uc = fileInode.getFileUnderConstructionFeature();
      String clientName = uc.getClientName();
      lease = leaseManager.getLease(clientName);
      if (lease == null) {
        throw new AlreadyBeingCreatedException(
          "failed to create file " + src + " for " + holder +
          " for client " + clientMachine +
          " because pendingCreates is non-null but no leases found.");
      }
      if (force) {
        // close now: no need to wait for soft lease expiration and 
        // close only the file src
        LOG.info("recoverLease: " + lease + ", src=" + src +
          " from client " + clientName);
        internalReleaseLease(lease, src, holder);
      } else {
        assert lease.getHolder().equals(clientName) :
          "Current lease holder " + lease.getHolder() +
          " does not match file creator " + clientName;
        //
        // If the original holder has not renewed in the last SOFTLIMIT 
        // period, then start lease recovery.
        //
        if (lease.expiredSoftLimit()) {
          LOG.info("startFile: recover " + lease + ", src=" + src + " client "
              + clientName);
          boolean isClosed = internalReleaseLease(lease, src, null);
          if(!isClosed)
            throw new RecoveryInProgressException(
                "Failed to close file " + src +
                ". Lease recovery is in progress. Try again later.");
        } else {
          final BlockInfo lastBlock = fileInode.getLastBlock();
          if (lastBlock != null
              && lastBlock.getBlockUCState() == BlockUCState.UNDER_RECOVERY) {
            throw new RecoveryInProgressException("Recovery in progress, file ["
                + src + "], " + "lease owner [" + lease.getHolder() + "]");
          } else {
            throw new AlreadyBeingCreatedException("Failed to create file ["
                + src + "] for [" + holder + "] for client [" + clientMachine
                + "], because this file is already being created by ["
                + clientName + "] on ["
                + uc.getClientMachine() + "]");
          }
        }
      }
    }
  }

  /**
   * Append to an existing file in the namespace.
   */
  LocatedBlock appendFile(String src, String holder, String clientMachine)
      throws AccessControlException, SafeModeException,
      FileAlreadyExistsException, FileNotFoundException,
      ParentNotDirectoryException, IOException {
    LocatedBlock lb = null;
    CacheEntryWithPayload cacheEntry = RetryCache.waitForCompletion(retryCache,
        null);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return (LocatedBlock) cacheEntry.getPayload();
    }
      
    boolean success = false;
    try {
      lb = appendFileInt(src, holder, clientMachine, cacheEntry != null);
      success = true;
      return lb;
    } catch (AccessControlException e) {
      logAuditEvent(false, "append", src);
      throw e;
    } finally {
      RetryCache.setState(cacheEntry, success, lb);
    }
  }

  private LocatedBlock appendFileInt(String src, String holder,
      String clientMachine, boolean logRetryCache)
      throws AccessControlException, SafeModeException,
      FileAlreadyExistsException, FileNotFoundException,
      ParentNotDirectoryException, IOException {
    if (NameNode.stateChangeLog.isDebugEnabled()) {
      NameNode.stateChangeLog.debug("DIR* NameSystem.appendFile: src=" + src
          + ", holder=" + holder
          + ", clientMachine=" + clientMachine);
    }
    boolean skipSync = false;
    if (!supportAppends) {
      throw new UnsupportedOperationException(
          "Append is not enabled on this NameNode. Use the " +
          DFS_SUPPORT_APPEND_KEY + " configuration option to enable it.");
    }

    LocatedBlock lb = null;
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot append to file" + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      lb = appendFileInternal(pc, src, holder, clientMachine, logRetryCache);
    } catch (StandbyException se) {
      skipSync = true;
      throw se;
    } finally {
      writeUnlock();
      // There might be transactions logged while trying to recover the lease.
      // They need to be sync'ed even when an exception was thrown.
      if (!skipSync) {
        getEditLog().logSync();
      }
    }
    if (lb != null) {
      if (NameNode.stateChangeLog.isDebugEnabled()) {
        NameNode.stateChangeLog.debug("DIR* NameSystem.appendFile: file "
            +src+" for "+holder+" at "+clientMachine
            +" block " + lb.getBlock()
            +" block size " + lb.getBlock().getNumBytes());
      }
    }
    logAuditEvent(true, "append", src);
    return lb;
  }

  ExtendedBlock getExtendedBlock(Block blk) {
    return new ExtendedBlock(blockPoolId, blk);
  }
  
  void setBlockPoolId(String bpid) {
    blockPoolId = bpid;
    blockManager.setBlockPoolId(blockPoolId);
  }

  /**
   * The client would like to obtain an additional block for the indicated
   * filename (which is being written-to).  Return an array that consists
   * of the block, plus a set of machines.  The first on this list should
   * be where the client writes data.  Subsequent items in the list must
   * be provided in the connection to the first datanode.
   *
   * Make sure the previous blocks have been reported by datanodes and
   * are replicated.  Will return an empty 2-elt array if we want the
   * client to "try again later".
   */
  LocatedBlock getAdditionalBlock(String src, long fileId, String clientName,
      ExtendedBlock previous, Set<Node> excludedNodes, 
      List<String> favoredNodes)
      throws LeaseExpiredException, NotReplicatedYetException,
      QuotaExceededException, SafeModeException, UnresolvedLinkException,
      IOException {
    long blockSize;
    int replication;
    DatanodeDescriptor clientNode = null;

    if(NameNode.stateChangeLog.isDebugEnabled()) {
      NameNode.stateChangeLog.debug("BLOCK* NameSystem.getAdditionalBlock: "
          + src + " inodeId " +  fileId  + " for " + clientName);
    }

    // Part I. Analyze the state of the file with respect to the input data.
    checkOperation(OperationCategory.READ);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    readLock();
    try {
      checkOperation(OperationCategory.READ);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      LocatedBlock[] onRetryBlock = new LocatedBlock[1];
      final INode[] inodes = analyzeFileState(
          src, fileId, clientName, previous, onRetryBlock).getINodes();
      final INodeFile pendingFile = inodes[inodes.length - 1].asFile();

      if (onRetryBlock[0] != null && onRetryBlock[0].getLocations().length > 0) {
        // This is a retry. Just return the last block if having locations.
        return onRetryBlock[0];
      }
      if (pendingFile.getBlocks().length >= maxBlocksPerFile) {
        throw new IOException("File has reached the limit on maximum number of"
            + " blocks (" + DFSConfigKeys.DFS_NAMENODE_MAX_BLOCKS_PER_FILE_KEY
            + "): " + pendingFile.getBlocks().length + " >= "
            + maxBlocksPerFile);
      }
      blockSize = pendingFile.getPreferredBlockSize();
      clientNode = pendingFile.getFileUnderConstructionFeature().getClientNode();
      replication = pendingFile.getFileReplication();
    } finally {
      readUnlock();
    }

    // choose targets for the new block to be allocated.
    final DatanodeStorageInfo targets[] = getBlockManager().chooseTarget( 
        src, replication, clientNode, excludedNodes, blockSize, favoredNodes);

    // Part II.
    // Allocate a new block, add it to the INode and the BlocksMap. 
    Block newBlock = null;
    long offset;
    checkOperation(OperationCategory.WRITE);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      // Run the full analysis again, since things could have changed
      // while chooseTarget() was executing.
      LocatedBlock[] onRetryBlock = new LocatedBlock[1];
      INodesInPath inodesInPath =
          analyzeFileState(src, fileId, clientName, previous, onRetryBlock);
      final INode[] inodes = inodesInPath.getINodes();
      final INodeFile pendingFile = inodes[inodes.length - 1].asFile();

      if (onRetryBlock[0] != null) {
        if (onRetryBlock[0].getLocations().length > 0) {
          // This is a retry. Just return the last block if having locations.
          return onRetryBlock[0];
        } else {
          // add new chosen targets to already allocated block and return
          BlockInfo lastBlockInFile = pendingFile.getLastBlock();
          ((BlockInfoUnderConstruction) lastBlockInFile)
              .setExpectedLocations(targets);
          offset = pendingFile.computeFileSize();
          return makeLocatedBlock(lastBlockInFile, targets, offset);
        }
      }

      // commit the last block and complete it if it has minimum replicas
      commitOrCompleteLastBlock(pendingFile,
                                ExtendedBlock.getLocalBlock(previous));

      // allocate new block, record block locations in INode.
      newBlock = createNewBlock();
      saveAllocatedBlock(src, inodesInPath, newBlock, targets);

      dir.persistNewBlock(src, pendingFile);
      offset = pendingFile.computeFileSize();
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();

    // Return located block
    return makeLocatedBlock(newBlock, targets, offset);
  }

  INodesInPath analyzeFileState(String src,
                                long fileId,
                                String clientName,
                                ExtendedBlock previous,
                                LocatedBlock[] onRetryBlock)
          throws IOException  {
    assert hasReadLock();

    checkBlock(previous);
    onRetryBlock[0] = null;
    checkOperation(OperationCategory.WRITE);
    checkNameNodeSafeMode("Cannot add block to " + src);

    // have we exceeded the configured limit of fs objects.
    checkFsObjectLimit();

    Block previousBlock = ExtendedBlock.getLocalBlock(previous);
    final INodesInPath iip = dir.getINodesInPath4Write(src);
    final INodeFile pendingFile
        = checkLease(src, fileId, clientName, iip.getLastINode());
    BlockInfo lastBlockInFile = pendingFile.getLastBlock();
    if (!Block.matchingIdAndGenStamp(previousBlock, lastBlockInFile)) {
      // The block that the client claims is the current last block
      // doesn't match up with what we think is the last block. There are
      // four possibilities:
      // 1) This is the first block allocation of an append() pipeline
      //    which started appending exactly at a block boundary.
      //    In this case, the client isn't passed the previous block,
      //    so it makes the allocateBlock() call with previous=null.
      //    We can distinguish this since the last block of the file
      //    will be exactly a full block.
      // 2) This is a retry from a client that missed the response of a
      //    prior getAdditionalBlock() call, perhaps because of a network
      //    timeout, or because of an HA failover. In that case, we know
      //    by the fact that the client is re-issuing the RPC that it
      //    never began to write to the old block. Hence it is safe to
      //    to return the existing block.
      // 3) This is an entirely bogus request/bug -- we should error out
      //    rather than potentially appending a new block with an empty
      //    one in the middle, etc
      // 4) This is a retry from a client that timed out while
      //    the prior getAdditionalBlock() is still being processed,
      //    currently working on chooseTarget(). 
      //    There are no means to distinguish between the first and 
      //    the second attempts in Part I, because the first one hasn't
      //    changed the namesystem state yet.
      //    We run this analysis again in Part II where case 4 is impossible.

      BlockInfo penultimateBlock = pendingFile.getPenultimateBlock();
      if (previous == null &&
          lastBlockInFile != null &&
          lastBlockInFile.getNumBytes() == pendingFile.getPreferredBlockSize() &&
          lastBlockInFile.isComplete()) {
        // Case 1
        if (NameNode.stateChangeLog.isDebugEnabled()) {
           NameNode.stateChangeLog.debug(
               "BLOCK* NameSystem.allocateBlock: handling block allocation" +
               " writing to a file with a complete previous block: src=" +
               src + " lastBlock=" + lastBlockInFile);
        }
      } else if (Block.matchingIdAndGenStamp(penultimateBlock, previousBlock)) {
        if (lastBlockInFile.getNumBytes() != 0) {
          throw new IOException(
              "Request looked like a retry to allocate block " +
              lastBlockInFile + " but it already contains " +
              lastBlockInFile.getNumBytes() + " bytes");
        }

        // Case 2
        // Return the last block.
        NameNode.stateChangeLog.info("BLOCK* allocateBlock: " +
            "caught retry for allocation of a new block in " +
            src + ". Returning previously allocated block " + lastBlockInFile);
        long offset = pendingFile.computeFileSize();
        onRetryBlock[0] = makeLocatedBlock(lastBlockInFile,
            ((BlockInfoUnderConstruction)lastBlockInFile).getExpectedStorageLocations(),
            offset);
        return iip;
      } else {
        // Case 3
        throw new IOException("Cannot allocate block in " + src + ": " +
            "passed 'previous' block " + previous + " does not match actual " +
            "last block in file " + lastBlockInFile);
      }
    }

    // Check if the penultimate block is minimally replicated
    if (!checkFileProgress(pendingFile, false)) {
      throw new NotReplicatedYetException("Not replicated yet: " + src);
    }
    return iip;
  }

  LocatedBlock makeLocatedBlock(Block blk, DatanodeStorageInfo[] locs,
                                        long offset) throws IOException {
    LocatedBlock lBlk = new LocatedBlock(
        getExtendedBlock(blk), locs, offset, false);
    getBlockManager().setBlockToken(
        lBlk, BlockTokenSecretManager.AccessMode.WRITE);
    return lBlk;
  }

  /** @see NameNode#getAdditionalDatanode(String, ExtendedBlock, DatanodeInfo[], DatanodeInfo[], int, String) */
  LocatedBlock getAdditionalDatanode(String src, final ExtendedBlock blk,
      final DatanodeInfo[] existings, final String[] storageIDs,
      final Set<Node> excludes,
      final int numAdditionalNodes, final String clientName
      ) throws IOException {
    //check if the feature is enabled
    dtpReplaceDatanodeOnFailure.checkEnabled();

    final DatanodeDescriptor clientnode;
    final long preferredblocksize;
    final List<DatanodeStorageInfo> chosen;
    checkOperation(OperationCategory.READ);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    readLock();
    try {
      checkOperation(OperationCategory.READ);
      //check safe mode
      checkNameNodeSafeMode("Cannot add datanode; src=" + src + ", blk=" + blk);
      src = FSDirectory.resolvePath(src, pathComponents, dir);

      //check lease
      final INodeFile file = checkLease(src, clientName);
      clientnode = file.getFileUnderConstructionFeature().getClientNode();
      preferredblocksize = file.getPreferredBlockSize();

      //find datanode storages
      final DatanodeManager dm = blockManager.getDatanodeManager();
      chosen = Arrays.asList(dm.getDatanodeStorageInfos(existings, storageIDs));
    } finally {
      readUnlock();
    }

    // choose new datanodes.
    final DatanodeStorageInfo[] targets = blockManager.getBlockPlacementPolicy(
        ).chooseTarget(src, numAdditionalNodes, clientnode, chosen, true,
            // TODO: get storage type from the file
        excludes, preferredblocksize, StorageType.DEFAULT);
    final LocatedBlock lb = new LocatedBlock(blk, targets);
    blockManager.setBlockToken(lb, AccessMode.COPY);
    return lb;
  }

  /**
   * The client would like to let go of the given block
   */
  boolean abandonBlock(ExtendedBlock b, String src, String holder)
      throws LeaseExpiredException, FileNotFoundException,
      UnresolvedLinkException, IOException {
    if(NameNode.stateChangeLog.isDebugEnabled()) {
      NameNode.stateChangeLog.debug("BLOCK* NameSystem.abandonBlock: " + b
          + "of file " + src);
    }
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot abandon block " + b + " for fle" + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);

      //
      // Remove the block from the pending creates list
      //
      INodeFile file = checkLease(src, holder);
      boolean removed = dir.removeBlock(src, file,
          ExtendedBlock.getLocalBlock(b));
      if (!removed) {
        return true;
      }
      if(NameNode.stateChangeLog.isDebugEnabled()) {
        NameNode.stateChangeLog.debug("BLOCK* NameSystem.abandonBlock: "
                                      + b + " is removed from pendingCreates");
      }
      dir.persistBlocks(src, file, false);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();

    return true;
  }
  
  /** make sure that we still have the lease on this file. */
  private INodeFile checkLease(String src, String holder)
      throws LeaseExpiredException, UnresolvedLinkException,
      FileNotFoundException {
    return checkLease(src, INodeId.GRANDFATHER_INODE_ID, holder,
        dir.getINode(src));
  }
  
  private INodeFile checkLease(String src, long fileId, String holder,
      INode inode) throws LeaseExpiredException, FileNotFoundException {
    assert hasReadLock();
    if (inode == null || !inode.isFile()) {
      Lease lease = leaseManager.getLease(holder);
      throw new LeaseExpiredException(
          "No lease on " + src + ": File does not exist. "
          + (lease != null ? lease.toString()
              : "Holder " + holder + " does not have any open files."));
    }
    final INodeFile file = inode.asFile();
    if (!file.isUnderConstruction()) {
      Lease lease = leaseManager.getLease(holder);
      throw new LeaseExpiredException(
          "No lease on " + src + ": File is not open for writing. "
          + (lease != null ? lease.toString()
              : "Holder " + holder + " does not have any open files."));
    }
    String clientName = file.getFileUnderConstructionFeature().getClientName();
    if (holder != null && !clientName.equals(holder)) {
      throw new LeaseExpiredException("Lease mismatch on " + src + " owned by "
          + clientName + " but is accessed by " + holder);
    }
    INodeId.checkId(fileId, file);
    return file;
  }
 
  /**
   * Complete in-progress write to the given file.
   * @return true if successful, false if the client should continue to retry
   *         (e.g if not all blocks have reached minimum replication yet)
   * @throws IOException on error (eg lease mismatch, file not open, file deleted)
   */
  boolean completeFile(String src, String holder,
                       ExtendedBlock last, long fileId)
    throws SafeModeException, UnresolvedLinkException, IOException {
    if (NameNode.stateChangeLog.isDebugEnabled()) {
      NameNode.stateChangeLog.debug("DIR* NameSystem.completeFile: " +
          src + " for " + holder);
    }
    checkBlock(last);
    boolean success = false;
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot complete file " + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      success = completeFileInternal(src, holder,
        ExtendedBlock.getLocalBlock(last), fileId);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    if (success) {
      NameNode.stateChangeLog.info("DIR* completeFile: " + src
          + " is closed by " + holder);
    }
    return success;
  }

  private boolean completeFileInternal(String src, 
      String holder, Block last, long fileId) throws SafeModeException,
      UnresolvedLinkException, IOException {
    assert hasWriteLock();
    final INodesInPath iip = dir.getLastINodeInPath(src);
    final INodeFile pendingFile;
    try {
      pendingFile = checkLease(src, fileId, holder, iip.getINode(0));
    } catch (LeaseExpiredException lee) {
      final INode inode = dir.getINode(src);
      if (inode != null
          && inode.isFile()
          && !inode.asFile().isUnderConstruction()) {
        // This could be a retry RPC - i.e the client tried to close
        // the file, but missed the RPC response. Thus, it is trying
        // again to close the file. If the file still exists and
        // the client's view of the last block matches the actual
        // last block, then we'll treat it as a successful close.
        // See HDFS-3031.
        final Block realLastBlock = inode.asFile().getLastBlock();
        if (Block.matchingIdAndGenStamp(last, realLastBlock)) {
          NameNode.stateChangeLog.info("DIR* completeFile: " +
              "request from " + holder + " to complete " + src +
              " which is already closed. But, it appears to be an RPC " +
              "retry. Returning success");
          return true;
        }
      }
      throw lee;
    }
    // Check the state of the penultimate block. It should be completed
    // before attempting to complete the last one.
    if (!checkFileProgress(pendingFile, false)) {
      return false;
    }

    // commit the last block and complete it if it has minimum replicas
    commitOrCompleteLastBlock(pendingFile, last);

    if (!checkFileProgress(pendingFile, true)) {
      return false;
    }

    finalizeINodeFileUnderConstruction(src, pendingFile,
        iip.getLatestSnapshotId());
    return true;
  }

  /**
   * Save allocated block at the given pending filename
   * 
   * @param src path to the file
   * @param inodesInPath representing each of the components of src. 
   *                     The last INode is the INode for the file.
   * @throws QuotaExceededException If addition of block exceeds space quota
   */
  BlockInfo saveAllocatedBlock(String src, INodesInPath inodes,
      Block newBlock, DatanodeStorageInfo[] targets)
          throws IOException {
    assert hasWriteLock();
    BlockInfo b = dir.addBlock(src, inodes, newBlock, targets);
    NameNode.stateChangeLog.info("BLOCK* allocateBlock: " + src + ". "
        + getBlockPoolId() + " " + b);
    DatanodeStorageInfo.incrementBlocksScheduled(targets);
    return b;
  }

  /**
   * Create new block with a unique block id and a new generation stamp.
   */
  Block createNewBlock() throws IOException {
    assert hasWriteLock();
    Block b = new Block(nextBlockId(), 0, 0);
    // Increment the generation stamp for every new block.
    b.setGenerationStamp(nextGenerationStamp(false));
    return b;
  }

  /**
   * Check that the indicated file's blocks are present and
   * replicated.  If not, return false. If checkall is true, then check
   * all blocks, otherwise check only penultimate block.
   */
  boolean checkFileProgress(INodeFile v, boolean checkall) {
    readLock();
    try {
      if (checkall) {
        //
        // check all blocks of the file.
        //
        for (BlockInfo block: v.getBlocks()) {
          if (!block.isComplete()) {
            LOG.info("BLOCK* checkFileProgress: " + block
                + " has not reached minimal replication "
                + blockManager.minReplication);
            return false;
          }
        }
      } else {
        //
        // check the penultimate block of this file
        //
        BlockInfo b = v.getPenultimateBlock();
        if (b != null && !b.isComplete()) {
          LOG.warn("BLOCK* checkFileProgress: " + b
              + " has not reached minimal replication "
              + blockManager.minReplication);
          return false;
        }
      }
      return true;
    } finally {
      readUnlock();
    }
  }

  ////////////////////////////////////////////////////////////////
  // Here's how to handle block-copy failure during client write:
  // -- As usual, the client's write should result in a streaming
  // backup write to a k-machine sequence.
  // -- If one of the backup machines fails, no worries.  Fail silently.
  // -- Before client is allowed to close and finalize file, make sure
  // that the blocks are backed up.  Namenode may have to issue specific backup
  // commands to make up for earlier datanode failures.  Once all copies
  // are made, edit namespace and return to client.
  ////////////////////////////////////////////////////////////////

  /** 
   * Change the indicated filename. 
   * @deprecated Use {@link #renameTo(String, String, Options.Rename...)} instead.
   */
  @Deprecated
  boolean renameTo(String src, String dst) 
      throws IOException, UnresolvedLinkException {
    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return true; // Return previous response
    }
    boolean ret = false;
    try {
      ret = renameToInt(src, dst, cacheEntry != null);
    } catch (AccessControlException e) {
      logAuditEvent(false, "rename", src, dst, null);
      throw e;
    } finally {
      RetryCache.setState(cacheEntry, ret);
    }
    return ret;
  }

  private boolean renameToInt(String src, String dst, boolean logRetryCache) 
    throws IOException, UnresolvedLinkException {
    if (NameNode.stateChangeLog.isDebugEnabled()) {
      NameNode.stateChangeLog.debug("DIR* NameSystem.renameTo: " + src +
          " to " + dst);
    }
    if (!DFSUtil.isValidName(dst)) {
      throw new IOException("Invalid name: " + dst);
    }
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    byte[][] srcComponents = FSDirectory.getPathComponentsForReservedPath(src);
    byte[][] dstComponents = FSDirectory.getPathComponentsForReservedPath(dst);
    boolean status = false;
    HdfsFileStatus resultingStat = null;
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot rename " + src);
      src = FSDirectory.resolvePath(src, srcComponents, dir);
      dst = FSDirectory.resolvePath(dst, dstComponents, dir);
      checkOperation(OperationCategory.WRITE);
      status = renameToInternal(pc, src, dst, logRetryCache);
      if (status) {
        resultingStat = getAuditFileInfo(dst, false);
      }
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    if (status) {
      logAuditEvent(true, "rename", src, dst, resultingStat);
    }
    return status;
  }

  /** @deprecated See {@link #renameTo(String, String)} */
  @Deprecated
  private boolean renameToInternal(FSPermissionChecker pc, String src,
      String dst, boolean logRetryCache) throws IOException,
      UnresolvedLinkException {
    assert hasWriteLock();
    if (isPermissionEnabled) {
      //We should not be doing this.  This is move() not renameTo().
      //but for now,
      //NOTE: yes, this is bad!  it's assuming much lower level behavior
      //      of rewriting the dst
      String actualdst = dir.isDir(dst)?
          dst + Path.SEPARATOR + new Path(src).getName(): dst;
      // Rename does not operates on link targets
      // Do not resolveLink when checking permissions of src and dst
      // Check write access to parent of src
      checkPermission(pc, src, false, null, FsAction.WRITE, null, null, false);
      // Check write access to ancestor of dst
      checkPermission(pc, actualdst, false, FsAction.WRITE, null, null, null,
          false);
    }

    if (dir.renameTo(src, dst, logRetryCache)) {
      return true;
    }
    return false;
  }
  

  /** Rename src to dst */
  void renameTo(String src, String dst, Options.Rename... options)
      throws IOException, UnresolvedLinkException {
    if (NameNode.stateChangeLog.isDebugEnabled()) {
      NameNode.stateChangeLog.debug("DIR* NameSystem.renameTo: with options - "
          + src + " to " + dst);
    }
    if (!DFSUtil.isValidName(dst)) {
      throw new InvalidPathException("Invalid name: " + dst);
    }
    final FSPermissionChecker pc = getPermissionChecker();
    
    checkOperation(OperationCategory.WRITE);
    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return; // Return previous response
    }
    byte[][] srcComponents = FSDirectory.getPathComponentsForReservedPath(src);
    byte[][] dstComponents = FSDirectory.getPathComponentsForReservedPath(dst);
    HdfsFileStatus resultingStat = null;
    boolean success = false;
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot rename " + src);
      src = FSDirectory.resolvePath(src, srcComponents, dir);
      dst = FSDirectory.resolvePath(dst, dstComponents, dir);
      renameToInternal(pc, src, dst, cacheEntry != null, options);
      resultingStat = getAuditFileInfo(dst, false);
      success = true;
    } finally {
      writeUnlock();
      RetryCache.setState(cacheEntry, success);
    }
    getEditLog().logSync();
    if (resultingStat != null) {
      StringBuilder cmd = new StringBuilder("rename options=");
      for (Rename option : options) {
        cmd.append(option.value()).append(" ");
      }
      logAuditEvent(true, cmd.toString(), src, dst, resultingStat);
    }
  }

  private void renameToInternal(FSPermissionChecker pc, String src, String dst,
      boolean logRetryCache, Options.Rename... options) throws IOException {
    assert hasWriteLock();
    if (isPermissionEnabled) {
      // Rename does not operates on link targets
      // Do not resolveLink when checking permissions of src and dst
      // Check write access to parent of src
      checkPermission(pc, src, false, null, FsAction.WRITE, null, null, false);
      // Check write access to ancestor of dst
      checkPermission(pc, dst, false, FsAction.WRITE, null, null, null, false);
    }

    dir.renameTo(src, dst, logRetryCache, options);
  }
  
  /**
   * Remove the indicated file from namespace.
   * 
   * @see ClientProtocol#delete(String, boolean) for detailed description and 
   * description of exceptions
   */
  boolean delete(String src, boolean recursive)
      throws AccessControlException, SafeModeException,
      UnresolvedLinkException, IOException {
    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return true; // Return previous response
    }
    boolean ret = false;
    try {
      ret = deleteInt(src, recursive, cacheEntry != null);
    } catch (AccessControlException e) {
      logAuditEvent(false, "delete", src);
      throw e;
    } finally {
      RetryCache.setState(cacheEntry, ret);
    }
    return ret;
  }
      
  private boolean deleteInt(String src, boolean recursive, boolean logRetryCache)
      throws AccessControlException, SafeModeException,
      UnresolvedLinkException, IOException {
    if (NameNode.stateChangeLog.isDebugEnabled()) {
      NameNode.stateChangeLog.debug("DIR* NameSystem.delete: " + src);
    }
    boolean status = deleteInternal(src, recursive, true, logRetryCache);
    if (status) {
      logAuditEvent(true, "delete", src);
    }
    return status;
  }
    
  private FSPermissionChecker getPermissionChecker()
      throws AccessControlException {
    try {
      return new FSPermissionChecker(fsOwnerShortUserName, supergroup, getRemoteUser());
    } catch (IOException ioe) {
      throw new AccessControlException(ioe);
    }
  }
  
  /**
   * Remove a file/directory from the namespace.
   * <p>
   * For large directories, deletion is incremental. The blocks under
   * the directory are collected and deleted a small number at a time holding
   * the {@link FSNamesystem} lock.
   * <p>
   * For small directory or file the deletion is done in one shot.
   * 
   * @see ClientProtocol#delete(String, boolean) for description of exceptions
   */
  private boolean deleteInternal(String src, boolean recursive,
      boolean enforcePermission, boolean logRetryCache)
      throws AccessControlException, SafeModeException, UnresolvedLinkException,
             IOException {
    BlocksMapUpdateInfo collectedBlocks = new BlocksMapUpdateInfo();
    List<INode> removedINodes = new ChunkedArrayList<INode>();
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    boolean ret = false;
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot delete " + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      if (!recursive && dir.isNonEmptyDirectory(src)) {
        throw new IOException(src + " is non empty");
      }
      if (enforcePermission && isPermissionEnabled) {
        checkPermission(pc, src, false, null, FsAction.WRITE, null,
            FsAction.ALL, false);
      }
      // Unlink the target directory from directory tree
      if (!dir.delete(src, collectedBlocks, removedINodes, logRetryCache)) {
        return false;
      }
      ret = true;
    } finally {
      writeUnlock();
    }
    getEditLog().logSync(); 
    removeBlocks(collectedBlocks); // Incremental deletion of blocks
    collectedBlocks.clear();
    dir.writeLock();
    try {
      dir.removeFromInodeMap(removedINodes);
    } finally {
      dir.writeUnlock();
    }
    removedINodes.clear();
    if (NameNode.stateChangeLog.isDebugEnabled()) {
      NameNode.stateChangeLog.debug("DIR* Namesystem.delete: "
        + src +" is removed");
    }
    return ret;
  }

  /**
   * From the given list, incrementally remove the blocks from blockManager
   * Writelock is dropped and reacquired every BLOCK_DELETION_INCREMENT to
   * ensure that other waiters on the lock can get in. See HDFS-2938
   * 
   * @param blocks
   *          An instance of {@link BlocksMapUpdateInfo} which contains a list
   *          of blocks that need to be removed from blocksMap
   */
  void removeBlocks(BlocksMapUpdateInfo blocks) {
    List<Block> toDeleteList = blocks.getToDeleteList();
    Iterator<Block> iter = toDeleteList.iterator();
    while (iter.hasNext()) {
      writeLock();
      try {
        for (int i = 0; i < BLOCK_DELETION_INCREMENT && iter.hasNext(); i++) {
          blockManager.removeBlock(iter.next());
        }
      } finally {
        writeUnlock();
      }
    }
  }
  
  /**
   * Remove leases, inodes and blocks related to a given path
   * @param src The given path
   * @param blocks Containing the list of blocks to be deleted from blocksMap
   * @param removedINodes Containing the list of inodes to be removed from 
   *                      inodesMap
   */
  void removePathAndBlocks(String src, BlocksMapUpdateInfo blocks,
      List<INode> removedINodes) {
    assert hasWriteLock();
    leaseManager.removeLeaseWithPrefixPath(src);
    // remove inodes from inodesMap
    if (removedINodes != null) {
      dir.removeFromInodeMap(removedINodes);
      removedINodes.clear();
    }
    if (blocks == null) {
      return;
    }
    
    removeBlocksAndUpdateSafemodeTotal(blocks);
  }

  /**
   * Removes the blocks from blocksmap and updates the safemode blocks total
   * 
   * @param blocks
   *          An instance of {@link BlocksMapUpdateInfo} which contains a list
   *          of blocks that need to be removed from blocksMap
   */
  void removeBlocksAndUpdateSafemodeTotal(BlocksMapUpdateInfo blocks) {
    assert hasWriteLock();
    // In the case that we are a Standby tailing edits from the
    // active while in safe-mode, we need to track the total number
    // of blocks and safe blocks in the system.
    boolean trackBlockCounts = isSafeModeTrackingBlocks();
    int numRemovedComplete = 0, numRemovedSafe = 0;

    for (Block b : blocks.getToDeleteList()) {
      if (trackBlockCounts) {
        BlockInfo bi = getStoredBlock(b);
        if (bi.isComplete()) {
          numRemovedComplete++;
          if (bi.numNodes() >= blockManager.minReplication) {
            numRemovedSafe++;
          }
        }
      }
      blockManager.removeBlock(b);
    }
    if (trackBlockCounts) {
      if (LOG.isDebugEnabled()) {
        LOG.debug("Adjusting safe-mode totals for deletion."
            + "decreasing safeBlocks by " + numRemovedSafe
            + ", totalBlocks by " + numRemovedComplete);
      }
      adjustSafeModeBlockTotals(-numRemovedSafe, -numRemovedComplete);
    }
  }

  /**
   * @see SafeModeInfo#shouldIncrementallyTrackBlocks
   */
  private boolean isSafeModeTrackingBlocks() {
    if (!haEnabled) {
      // Never track blocks incrementally in non-HA code.
      return false;
    }
    SafeModeInfo sm = this.safeMode;
    return sm != null && sm.shouldIncrementallyTrackBlocks();
  }

  /**
   * Get the file info for a specific file.
   *
   * @param src The string representation of the path to the file
   * @param resolveLink whether to throw UnresolvedLinkException 
   *        if src refers to a symlink
   *
   * @throws AccessControlException if access is denied
   * @throws UnresolvedLinkException if a symlink is encountered.
   *
   * @return object containing information regarding the file
   *         or null if file not found
   * @throws StandbyException 
   */
  HdfsFileStatus getFileInfo(String src, boolean resolveLink) 
    throws AccessControlException, UnresolvedLinkException,
           StandbyException, IOException {
    if (!DFSUtil.isValidName(src)) {
      throw new InvalidPathException("Invalid file name: " + src);
    }
    HdfsFileStatus stat = null;
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.READ);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    readLock();
    try {
      checkOperation(OperationCategory.READ);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      if (isPermissionEnabled) {
        checkPermission(pc, src, false, null, null, null, null, resolveLink);
      }
      stat = dir.getFileInfo(src, resolveLink);
    } catch (AccessControlException e) {
      logAuditEvent(false, "getfileinfo", src);
      throw e;
    } finally {
      readUnlock();
    }
    logAuditEvent(true, "getfileinfo", src);
    return stat;
  }
  
  /**
   * Returns true if the file is closed
   */
  boolean isFileClosed(String src) 
      throws AccessControlException, UnresolvedLinkException,
      StandbyException, IOException {
    FSPermissionChecker pc = getPermissionChecker();  
    checkOperation(OperationCategory.READ);
    readLock();
    try {
      checkOperation(OperationCategory.READ);
      if (isPermissionEnabled) {
        checkTraverse(pc, src);
      }
      return !INodeFile.valueOf(dir.getINode(src), src).isUnderConstruction();
    } catch (AccessControlException e) {
      if (isAuditEnabled() && isExternalInvocation()) {
        logAuditEvent(false, "isFileClosed", src);
      }
      throw e;
    } finally {
      readUnlock();
    }
  }

  /**
   * Create all the necessary directories
   */
  boolean mkdirs(String src, PermissionStatus permissions,
      boolean createParent) throws IOException, UnresolvedLinkException {
    boolean ret = false;
    try {
      ret = mkdirsInt(src, permissions, createParent);
    } catch (AccessControlException e) {
      logAuditEvent(false, "mkdirs", src);
      throw e;
    }
    return ret;
  }

  private boolean mkdirsInt(String src, PermissionStatus permissions,
      boolean createParent) throws IOException, UnresolvedLinkException {
    if(NameNode.stateChangeLog.isDebugEnabled()) {
      NameNode.stateChangeLog.debug("DIR* NameSystem.mkdirs: " + src);
    }
    if (!DFSUtil.isValidName(src)) {
      throw new InvalidPathException(src);
    }
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    HdfsFileStatus resultingStat = null;
    boolean status = false;
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);   
      checkNameNodeSafeMode("Cannot create directory " + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      status = mkdirsInternal(pc, src, permissions, createParent);
      if (status) {
        resultingStat = dir.getFileInfo(src, false);
      }
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    if (status) {
      logAuditEvent(true, "mkdirs", src, null, resultingStat);
    }
    return status;
  }
    
  /**
   * Create all the necessary directories
   */
  private boolean mkdirsInternal(FSPermissionChecker pc, String src,
      PermissionStatus permissions, boolean createParent) 
      throws IOException, UnresolvedLinkException {
    assert hasWriteLock();
    if (isPermissionEnabled) {
      checkTraverse(pc, src);
    }
    if (dir.isDirMutable(src)) {
      // all the users of mkdirs() are used to expect 'true' even if
      // a new directory is not created.
      return true;
    }
    if (isPermissionEnabled) {
      checkAncestorAccess(pc, src, FsAction.WRITE);
    }
    if (!createParent) {
      verifyParentDir(src);
    }

    // validate that we have enough inodes. This is, at best, a 
    // heuristic because the mkdirs() operation might need to 
    // create multiple inodes.
    checkFsObjectLimit();

    if (!dir.mkdirs(src, permissions, false, now())) {
      throw new IOException("Failed to create directory: " + src);
    }
    return true;
  }

  /**
   * Get the content summary for a specific file/dir.
   *
   * @param src The string representation of the path to the file
   *
   * @throws AccessControlException if access is denied
   * @throws UnresolvedLinkException if a symlink is encountered.
   * @throws FileNotFoundException if no file exists
   * @throws StandbyException
   * @throws IOException for issues with writing to the audit log
   *
   * @return object containing information regarding the file
   *         or null if file not found
   */
  ContentSummary getContentSummary(String src) throws IOException {
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.READ);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    readLock();
    boolean success = true;
    try {
      checkOperation(OperationCategory.READ);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      if (isPermissionEnabled) {
        checkPermission(pc, src, false, null, null, null, FsAction.READ_EXECUTE);
      }
      return dir.getContentSummary(src);

    } catch (AccessControlException ace) {
      success = false;
      throw ace;
    } finally {
      readUnlock();
      logAuditEvent(success, "contentSummary", src);
    }
  }

  /**
   * Set the namespace quota and diskspace quota for a directory.
   * See {@link ClientProtocol#setQuota(String, long, long)} for the 
   * contract.
   * 
   * Note: This does not support ".inodes" relative path.
   */
  void setQuota(String path, long nsQuota, long dsQuota) 
      throws IOException, UnresolvedLinkException {
    checkSuperuserPrivilege();
    checkOperation(OperationCategory.WRITE);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot set quota on " + path);
      dir.setQuota(path, nsQuota, dsQuota);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
  }

  /** Persist all metadata about this file.
   * @param src The string representation of the path
   * @param clientName The string representation of the client
   * @param lastBlockLength The length of the last block 
   *                        under construction reported from client.
   * @throws IOException if path does not exist
   */
  void fsync(String src, String clientName, long lastBlockLength) 
      throws IOException, UnresolvedLinkException {
    NameNode.stateChangeLog.info("BLOCK* fsync: " + src + " for " + clientName);
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot fsync file " + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      INodeFile pendingFile  = checkLease(src, clientName);
      if (lastBlockLength > 0) {
        pendingFile.getFileUnderConstructionFeature().updateLengthOfLastBlock(
            pendingFile, lastBlockLength);
      }
      dir.persistBlocks(src, pendingFile, false);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
  }

  /**
   * Move a file that is being written to be immutable.
   * @param src The filename
   * @param lease The lease for the client creating the file
   * @param recoveryLeaseHolder reassign lease to this holder if the last block
   *        needs recovery; keep current holder if null.
   * @throws AlreadyBeingCreatedException if file is waiting to achieve minimal
   *         replication;<br>
   *         RecoveryInProgressException if lease recovery is in progress.<br>
   *         IOException in case of an error.
   * @return true  if file has been successfully finalized and closed or 
   *         false if block recovery has been initiated. Since the lease owner
   *         has been changed and logged, caller should call logSync().
   */
  boolean internalReleaseLease(Lease lease, String src, 
      String recoveryLeaseHolder) throws AlreadyBeingCreatedException, 
      IOException, UnresolvedLinkException {
    LOG.info("Recovering " + lease + ", src=" + src);
    assert !isInSafeMode();
    assert hasWriteLock();

    final INodesInPath iip = dir.getLastINodeInPath(src);
    final INodeFile pendingFile = iip.getINode(0).asFile();
    int nrBlocks = pendingFile.numBlocks();
    BlockInfo[] blocks = pendingFile.getBlocks();

    int nrCompleteBlocks;
    BlockInfo curBlock = null;
    for(nrCompleteBlocks = 0; nrCompleteBlocks < nrBlocks; nrCompleteBlocks++) {
      curBlock = blocks[nrCompleteBlocks];
      if(!curBlock.isComplete())
        break;
      assert blockManager.checkMinReplication(curBlock) :
              "A COMPLETE block is not minimally replicated in " + src;
    }

    // If there are no incomplete blocks associated with this file,
    // then reap lease immediately and close the file.
    if(nrCompleteBlocks == nrBlocks) {
      finalizeINodeFileUnderConstruction(src, pendingFile,
          iip.getLatestSnapshotId());
      NameNode.stateChangeLog.warn("BLOCK*"
        + " internalReleaseLease: All existing blocks are COMPLETE,"
        + " lease removed, file closed.");
      return true;  // closed!
    }

    // Only the last and the penultimate blocks may be in non COMPLETE state.
    // If the penultimate block is not COMPLETE, then it must be COMMITTED.
    if(nrCompleteBlocks < nrBlocks - 2 ||
       nrCompleteBlocks == nrBlocks - 2 &&
         curBlock != null &&
         curBlock.getBlockUCState() != BlockUCState.COMMITTED) {
      final String message = "DIR* NameSystem.internalReleaseLease: "
        + "attempt to release a create lock on "
        + src + " but file is already closed.";
      NameNode.stateChangeLog.warn(message);
      throw new IOException(message);
    }

    // The last block is not COMPLETE, and
    // that the penultimate block if exists is either COMPLETE or COMMITTED
    final BlockInfo lastBlock = pendingFile.getLastBlock();
    BlockUCState lastBlockState = lastBlock.getBlockUCState();
    BlockInfo penultimateBlock = pendingFile.getPenultimateBlock();
    boolean penultimateBlockMinReplication;
    BlockUCState penultimateBlockState;
    if (penultimateBlock == null) {
      penultimateBlockState = BlockUCState.COMPLETE;
      // If penultimate block doesn't exist then its minReplication is met
      penultimateBlockMinReplication = true;
    } else {
      penultimateBlockState = BlockUCState.COMMITTED;
      penultimateBlockMinReplication = 
        blockManager.checkMinReplication(penultimateBlock);
    }
    assert penultimateBlockState == BlockUCState.COMPLETE ||
           penultimateBlockState == BlockUCState.COMMITTED :
           "Unexpected state of penultimate block in " + src;

    switch(lastBlockState) {
    case COMPLETE:
      assert false : "Already checked that the last block is incomplete";
      break;
    case COMMITTED:
      // Close file if committed blocks are minimally replicated
      if(penultimateBlockMinReplication &&
          blockManager.checkMinReplication(lastBlock)) {
        finalizeINodeFileUnderConstruction(src, pendingFile,
            iip.getLatestSnapshotId());
        NameNode.stateChangeLog.warn("BLOCK*"
          + " internalReleaseLease: Committed blocks are minimally replicated,"
          + " lease removed, file closed.");
        return true;  // closed!
      }
      // Cannot close file right now, since some blocks 
      // are not yet minimally replicated.
      // This may potentially cause infinite loop in lease recovery
      // if there are no valid replicas on data-nodes.
      String message = "DIR* NameSystem.internalReleaseLease: " +
          "Failed to release lease for file " + src +
          ". Committed blocks are waiting to be minimally replicated." +
          " Try again later.";
      NameNode.stateChangeLog.warn(message);
      throw new AlreadyBeingCreatedException(message);
    case UNDER_CONSTRUCTION:
    case UNDER_RECOVERY:
      final BlockInfoUnderConstruction uc = (BlockInfoUnderConstruction)lastBlock;
      // setup the last block locations from the blockManager if not known
      if (uc.getNumExpectedLocations() == 0) {
        uc.setExpectedLocations(blockManager.getStorages(lastBlock));
      }

      if (uc.getNumExpectedLocations() == 0 && uc.getNumBytes() == 0) {
        // There is no datanode reported to this block.
        // may be client have crashed before writing data to pipeline.
        // This blocks doesn't need any recovery.
        // We can remove this block and close the file.
        pendingFile.removeLastBlock(lastBlock);
        finalizeINodeFileUnderConstruction(src, pendingFile,
            iip.getLatestSnapshotId());
        NameNode.stateChangeLog.warn("BLOCK* internalReleaseLease: "
            + "Removed empty last block and closed file.");
        return true;
      }
      // start recovery of the last block for this file
      long blockRecoveryId = nextGenerationStamp(isLegacyBlock(uc));
      lease = reassignLease(lease, src, recoveryLeaseHolder, pendingFile);
      uc.initializeBlockRecovery(blockRecoveryId);
      leaseManager.renewLease(lease);
      // Cannot close file right now, since the last block requires recovery.
      // This may potentially cause infinite loop in lease recovery
      // if there are no valid replicas on data-nodes.
      NameNode.stateChangeLog.warn(
                "DIR* NameSystem.internalReleaseLease: " +
                "File " + src + " has not been closed." +
               " Lease recovery is in progress. " +
                "RecoveryId = " + blockRecoveryId + " for block " + lastBlock);
      break;
    }
    return false;
  }

  private Lease reassignLease(Lease lease, String src, String newHolder,
      INodeFile pendingFile) {
    assert hasWriteLock();
    if(newHolder == null)
      return lease;
    // The following transaction is not synced. Make sure it's sync'ed later.
    logReassignLease(lease.getHolder(), src, newHolder);
    return reassignLeaseInternal(lease, src, newHolder, pendingFile);
  }
  
  Lease reassignLeaseInternal(Lease lease, String src, String newHolder,
      INodeFile pendingFile) {
    assert hasWriteLock();
    pendingFile.getFileUnderConstructionFeature().setClientName(newHolder);
    return leaseManager.reassignLease(lease, src, newHolder);
  }

  private void commitOrCompleteLastBlock(final INodeFile fileINode,
      final Block commitBlock) throws IOException {
    assert hasWriteLock();
    Preconditions.checkArgument(fileINode.isUnderConstruction());
    if (!blockManager.commitOrCompleteLastBlock(fileINode, commitBlock)) {
      return;
    }

    // Adjust disk space consumption if required
    final long diff = fileINode.getPreferredBlockSize() - commitBlock.getNumBytes();    
    if (diff > 0) {
      try {
        String path = fileINode.getFullPathName();
        dir.updateSpaceConsumed(path, 0, -diff*fileINode.getFileReplication());
      } catch (IOException e) {
        LOG.warn("Unexpected exception while updating disk space.", e);
      }
    }
  }

  private void finalizeINodeFileUnderConstruction(String src,
      INodeFile pendingFile, int latestSnapshot) throws IOException,
      UnresolvedLinkException {
    assert hasWriteLock();
    FileUnderConstructionFeature uc = pendingFile.getFileUnderConstructionFeature();
    Preconditions.checkArgument(uc != null);
    leaseManager.removeLease(uc.getClientName(), src);
    
    pendingFile = pendingFile.recordModification(latestSnapshot);

    // The file is no longer pending.
    // Create permanent INode, update blocks. No need to replace the inode here
    // since we just remove the uc feature from pendingFile
    final INodeFile newFile = pendingFile.toCompleteFile(now());

    // close file and persist block allocations for this file
    dir.closeFile(src, newFile);

    blockManager.checkReplication(newFile);
  }

  @VisibleForTesting
  BlockInfo getStoredBlock(Block block) {
    return blockManager.getStoredBlock(block);
  }
  
  @Override
  public boolean isInSnapshot(BlockInfoUnderConstruction blockUC) {
    assert hasReadLock();
    final BlockCollection bc = blockUC.getBlockCollection();
    if (bc == null || !(bc instanceof INodeFile)
        || !((INodeFile) bc).isUnderConstruction()) {
      return false;
    }

    INodeFile inodeUC = (INodeFile) bc;
    String fullName = inodeUC.getName();
    try {
      if (fullName != null && fullName.startsWith(Path.SEPARATOR)
          && dir.getINode(fullName) == inodeUC) {
        // If file exists in normal path then no need to look in snapshot
        return false;
      }
    } catch (UnresolvedLinkException e) {
      LOG.error("Error while resolving the link : " + fullName, e);
      return false;
    }
    /*
     * 1. if bc is an instance of INodeFileUnderConstructionWithSnapshot, and
     * bc is not in the current fsdirectory tree, bc must represent a snapshot
     * file. 
     * 2. if fullName is not an absolute path, bc cannot be existent in the 
     * current fsdirectory tree. 
     * 3. if bc is not the current node associated with fullName, bc must be a
     * snapshot inode.
     */
    return true;
  }

  void commitBlockSynchronization(ExtendedBlock lastblock,
      long newgenerationstamp, long newlength,
      boolean closeFile, boolean deleteblock, DatanodeID[] newtargets,
      String[] newtargetstorages)
      throws IOException, UnresolvedLinkException {
    LOG.info("commitBlockSynchronization(lastblock=" + lastblock
             + ", newgenerationstamp=" + newgenerationstamp
             + ", newlength=" + newlength
             + ", newtargets=" + Arrays.asList(newtargets)
             + ", closeFile=" + closeFile
             + ", deleteBlock=" + deleteblock
             + ")");
    checkOperation(OperationCategory.WRITE);
    String src = "";
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      // If a DN tries to commit to the standby, the recovery will
      // fail, and the next retry will succeed on the new NN.
  
      checkNameNodeSafeMode(
          "Cannot commitBlockSynchronization while in safe mode");
      final BlockInfo storedBlock = getStoredBlock(
          ExtendedBlock.getLocalBlock(lastblock));
      if (storedBlock == null) {
        if (deleteblock) {
          // This may be a retry attempt so ignore the failure
          // to locate the block.
          if (LOG.isDebugEnabled()) {
            LOG.debug("Block (=" + lastblock + ") not found");
          }
          return;
        } else {
          throw new IOException("Block (=" + lastblock + ") not found");
        }
      }
      INodeFile iFile = ((INode)storedBlock.getBlockCollection()).asFile();
      if (!iFile.isUnderConstruction() || storedBlock.isComplete()) {
        if (LOG.isDebugEnabled()) {
          LOG.debug("Unexpected block (=" + lastblock
                    + ") since the file (=" + iFile.getLocalName()
                    + ") is not under construction");
        }
        return;
      }

      long recoveryId =
        ((BlockInfoUnderConstruction)storedBlock).getBlockRecoveryId();
      if(recoveryId != newgenerationstamp) {
        throw new IOException("The recovery id " + newgenerationstamp
                              + " does not match current recovery id "
                              + recoveryId + " for block " + lastblock); 
      }

      if (deleteblock) {
        Block blockToDel = ExtendedBlock.getLocalBlock(lastblock);
        boolean remove = iFile.removeLastBlock(blockToDel);
        if (remove) {
          blockManager.removeBlockFromMap(storedBlock);
        }
      }
      else {
        // update last block
        storedBlock.setGenerationStamp(newgenerationstamp);
        storedBlock.setNumBytes(newlength);

        // find the DatanodeDescriptor objects
        // There should be no locations in the blockManager till now because the
        // file is underConstruction
        ArrayList<DatanodeDescriptor> trimmedTargets =
            new ArrayList<DatanodeDescriptor>(newtargets.length);
        ArrayList<String> trimmedStorages =
            new ArrayList<String>(newtargets.length);
        if (newtargets.length > 0) {
          for (int i = 0; i < newtargets.length; ++i) {
            // try to get targetNode
            DatanodeDescriptor targetNode =
                blockManager.getDatanodeManager().getDatanode(newtargets[i]);
            if (targetNode != null) {
              trimmedTargets.add(targetNode);
              trimmedStorages.add(newtargetstorages[i]);
            } else if (LOG.isDebugEnabled()) {
              LOG.debug("DatanodeDescriptor (=" + newtargets[i] + ") not found");
            }
          }
        }
        if ((closeFile) && !trimmedTargets.isEmpty()) {
          // the file is getting closed. Insert block locations into blockManager.
          // Otherwise fsck will report these blocks as MISSING, especially if the
          // blocksReceived from Datanodes take a long time to arrive.
          for (int i = 0; i < trimmedTargets.size(); i++) {
            trimmedTargets.get(i).addBlock(
              trimmedStorages.get(i), storedBlock);
          }
        }

        // add pipeline locations into the INodeUnderConstruction
        DatanodeStorageInfo[] trimmedStorageInfos =
            blockManager.getDatanodeManager().getDatanodeStorageInfos(
                trimmedTargets.toArray(new DatanodeID[trimmedTargets.size()]),
                trimmedStorages.toArray(new String[trimmedStorages.size()]));
        iFile.setLastBlock(storedBlock, trimmedStorageInfos);
      }

      if (closeFile) {
        src = closeFileCommitBlocks(iFile, storedBlock);
      } else {
        // If this commit does not want to close the file, persist blocks
        src = persistBlocks(iFile, false);
      }
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    if (closeFile) {
      LOG.info("commitBlockSynchronization(newblock=" + lastblock
          + ", file=" + src
          + ", newgenerationstamp=" + newgenerationstamp
          + ", newlength=" + newlength
          + ", newtargets=" + Arrays.asList(newtargets) + ") successful");
    } else {
      LOG.info("commitBlockSynchronization(" + lastblock + ") successful");
    }
  }

  /**
   *
   * @param pendingFile
   * @param storedBlock
   * @return Path of the file that was closed.
   * @throws IOException
   */
  @VisibleForTesting
  String closeFileCommitBlocks(INodeFile pendingFile, BlockInfo storedBlock)
      throws IOException {
    String src = pendingFile.getFullPathName();

    // commit the last block and complete it if it has minimum replicas
    commitOrCompleteLastBlock(pendingFile, storedBlock);

    //remove lease, close file
    finalizeINodeFileUnderConstruction(src, pendingFile,
        Snapshot.findLatestSnapshot(pendingFile, Snapshot.CURRENT_STATE_ID));

    return src;
  }

  /**
   * Persist the block list for the given file.
   *
   * @param pendingFile
   * @return Path to the given file.
   * @throws IOException
   */
  @VisibleForTesting
  String persistBlocks(INodeFile pendingFile, boolean logRetryCache)
      throws IOException {
    String src = pendingFile.getFullPathName();
    dir.persistBlocks(src, pendingFile, logRetryCache);
    return src;
  }

  /**
   * Renew the lease(s) held by the given client
   */
  void renewLease(String holder) throws IOException {
    checkOperation(OperationCategory.WRITE);
    readLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot renew lease for " + holder);
      leaseManager.renewLease(holder);
    } finally {
      readUnlock();
    }
  }

  /**
   * Get a partial listing of the indicated directory
   *
   * @param src the directory name
   * @param startAfter the name to start after
   * @param needLocation if blockLocations need to be returned
   * @return a partial listing starting after startAfter
   * 
   * @throws AccessControlException if access is denied
   * @throws UnresolvedLinkException if symbolic link is encountered
   * @throws IOException if other I/O error occurred
   */
  DirectoryListing getListing(String src, byte[] startAfter,
      boolean needLocation) 
      throws AccessControlException, UnresolvedLinkException, IOException {
    try {
      return getListingInt(src, startAfter, needLocation);
    } catch (AccessControlException e) {
      logAuditEvent(false, "listStatus", src);
      throw e;
    }
  }

  private DirectoryListing getListingInt(String src, byte[] startAfter,
      boolean needLocation) 
    throws AccessControlException, UnresolvedLinkException, IOException {
    DirectoryListing dl;
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.READ);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    String startAfterString = new String(startAfter);
    readLock();
    try {
      checkOperation(OperationCategory.READ);
      src = FSDirectory.resolvePath(src, pathComponents, dir);

      // Get file name when startAfter is an INodePath
      if (FSDirectory.isReservedName(startAfterString)) {
        byte[][] startAfterComponents = FSDirectory
            .getPathComponentsForReservedPath(startAfterString);
        try {
          String tmp = FSDirectory.resolvePath(src, startAfterComponents, dir);
          byte[][] regularPath = INode.getPathComponents(tmp);
          startAfter = regularPath[regularPath.length - 1];
        } catch (IOException e) {
          // Possibly the inode is deleted
          throw new DirectoryListingStartAfterNotFoundException(
              "Can't find startAfter " + startAfterString);
        }
      }
      
      if (isPermissionEnabled) {
        if (dir.isDir(src)) {
          checkPathAccess(pc, src, FsAction.READ_EXECUTE);
        } else {
          checkTraverse(pc, src);
        }
      }
      logAuditEvent(true, "listStatus", src);
      dl = dir.getListing(src, startAfter, needLocation);
    } finally {
      readUnlock();
    }
    return dl;
  }

  /////////////////////////////////////////////////////////
  //
  // These methods are called by datanodes
  //
  /////////////////////////////////////////////////////////
  /**
   * Register Datanode.
   * <p>
   * The purpose of registration is to identify whether the new datanode
   * serves a new data storage, and will report new data block copies,
   * which the namenode was not aware of; or the datanode is a replacement
   * node for the data storage that was previously served by a different
   * or the same (in terms of host:port) datanode.
   * The data storages are distinguished by their storageIDs. When a new
   * data storage is reported the namenode issues a new unique storageID.
   * <p>
   * Finally, the namenode returns its namespaceID as the registrationID
   * for the datanodes. 
   * namespaceID is a persistent attribute of the name space.
   * The registrationID is checked every time the datanode is communicating
   * with the namenode. 
   * Datanodes with inappropriate registrationID are rejected.
   * If the namenode stops, and then restarts it can restore its 
   * namespaceID and will continue serving the datanodes that has previously
   * registered with the namenode without restarting the whole cluster.
   * 
   * @see org.apache.hadoop.hdfs.server.datanode.DataNode
   */
  void registerDatanode(DatanodeRegistration nodeReg) throws IOException {
    writeLock();
    try {
      getBlockManager().getDatanodeManager().registerDatanode(nodeReg);
      checkSafeMode();
    } finally {
      writeUnlock();
    }
  }
  
  /**
   * Get registrationID for datanodes based on the namespaceID.
   * 
   * @see #registerDatanode(DatanodeRegistration)
   * @return registration ID
   */
  String getRegistrationID() {
    return Storage.getRegistrationID(dir.fsImage.getStorage());
  }

  /**
   * The given node has reported in.  This method should:
   * 1) Record the heartbeat, so the datanode isn't timed out
   * 2) Adjust usage stats for future block allocation
   * 
   * If a substantial amount of time passed since the last datanode 
   * heartbeat then request an immediate block report.  
   * 
   * @return an array of datanode commands 
   * @throws IOException
   */
  HeartbeatResponse handleHeartbeat(DatanodeRegistration nodeReg,
      StorageReport[] reports, long cacheCapacity, long cacheUsed,
      int xceiverCount, int xmitsInProgress, int failedVolumes)
        throws IOException {
    readLock();
    try {
      //get datanode commands
      final int maxTransfer = blockManager.getMaxReplicationStreams()
          - xmitsInProgress;
      DatanodeCommand[] cmds = blockManager.getDatanodeManager().handleHeartbeat(
          nodeReg, reports, blockPoolId, cacheCapacity, cacheUsed,
          xceiverCount, maxTransfer, failedVolumes);
      
      //create ha status
      final NNHAStatusHeartbeat haState = new NNHAStatusHeartbeat(
          haContext.getState().getServiceState(),
          getFSImage().getLastAppliedOrWrittenTxId());

      return new HeartbeatResponse(cmds, haState, rollingUpgradeInfo);
    } finally {
      readUnlock();
    }
  }

  /**
   * Returns whether or not there were available resources at the last check of
   * resources.
   *
   * @return true if there were sufficient resources available, false otherwise.
   */
  boolean nameNodeHasResourcesAvailable() {
    return hasResourcesAvailable;
  }

  /**
   * Perform resource checks and cache the results.
   * @throws IOException
   */
  void checkAvailableResources() {
    Preconditions.checkState(nnResourceChecker != null,
        "nnResourceChecker not initialized");
    hasResourcesAvailable = nnResourceChecker.hasAvailableDiskSpace();
  }

  /**
   * Periodically calls hasAvailableResources of NameNodeResourceChecker, and if
   * there are found to be insufficient resources available, causes the NN to
   * enter safe mode. If resources are later found to have returned to
   * acceptable levels, this daemon will cause the NN to exit safe mode.
   */
  class NameNodeResourceMonitor implements Runnable  {
    boolean shouldNNRmRun = true;
    @Override
    public void run () {
      try {
        while (fsRunning && shouldNNRmRun) {
          checkAvailableResources();
          if(!nameNodeHasResourcesAvailable()) {
            String lowResourcesMsg = "NameNode low on available disk space. ";
            if (!isInSafeMode()) {
              FSNamesystem.LOG.warn(lowResourcesMsg + "Entering safe mode.");
            } else {
              FSNamesystem.LOG.warn(lowResourcesMsg + "Already in safe mode.");
            }
            enterSafeMode(true);
          }
          try {
            Thread.sleep(resourceRecheckInterval);
          } catch (InterruptedException ie) {
            // Deliberately ignore
          }
        }
      } catch (Exception e) {
        FSNamesystem.LOG.error("Exception in NameNodeResourceMonitor: ", e);
      }
    }

    public void stopMonitor() {
      shouldNNRmRun = false;
    }
 }

  class NameNodeEditLogRoller implements Runnable {

    private boolean shouldRun = true;
    private final long rollThreshold;
    private final long sleepIntervalMs;

    public NameNodeEditLogRoller(long rollThreshold, int sleepIntervalMs) {
        this.rollThreshold = rollThreshold;
        this.sleepIntervalMs = sleepIntervalMs;
    }

    @Override
    public void run() {
      while (fsRunning && shouldRun) {
        try {
          FSEditLog editLog = getFSImage().getEditLog();
          long numEdits =
              editLog.getLastWrittenTxId() - editLog.getCurSegmentTxId();
          if (numEdits > rollThreshold) {
            FSNamesystem.LOG.info("NameNode rolling its own edit log because"
                + " number of edits in open segment exceeds threshold of "
                + rollThreshold);
            rollEditLog();
          }
          Thread.sleep(sleepIntervalMs);
        } catch (InterruptedException e) {
          FSNamesystem.LOG.info(NameNodeEditLogRoller.class.getSimpleName()
              + " was interrupted, exiting");
          break;
        } catch (Exception e) {
          FSNamesystem.LOG.error("Swallowing exception in "
              + NameNodeEditLogRoller.class.getSimpleName() + ":", e);
        }
      }
    }

    public void stop() {
      shouldRun = false;
    }
  }

  public FSImage getFSImage() {
    return dir.fsImage;
  }

  public FSEditLog getEditLog() {
    return getFSImage().getEditLog();
  }    

  private void checkBlock(ExtendedBlock block) throws IOException {
    if (block != null && !this.blockPoolId.equals(block.getBlockPoolId())) {
      throw new IOException("Unexpected BlockPoolId " + block.getBlockPoolId()
          + " - expected " + blockPoolId);
    }
  }

  @Metric({"MissingBlocks", "Number of missing blocks"})
  public long getMissingBlocksCount() {
    // not locking
    return blockManager.getMissingBlocksCount();
  }
  
  @Metric({"ExpiredHeartbeats", "Number of expired heartbeats"})
  public int getExpiredHeartbeats() {
    return datanodeStatistics.getExpiredHeartbeats();
  }
  
  @Metric({"TransactionsSinceLastCheckpoint",
      "Number of transactions since last checkpoint"})
  public long getTransactionsSinceLastCheckpoint() {
    return getEditLog().getLastWrittenTxId() -
        getFSImage().getStorage().getMostRecentCheckpointTxId();
  }
  
  @Metric({"TransactionsSinceLastLogRoll",
      "Number of transactions since last edit log roll"})
  public long getTransactionsSinceLastLogRoll() {
    if (isInStandbyState() || !getEditLog().isSegmentOpen()) {
      return 0;
    } else {
      return getEditLog().getLastWrittenTxId() -
        getEditLog().getCurSegmentTxId() + 1;
    }
  }
  
  @Metric({"LastWrittenTransactionId", "Transaction ID written to the edit log"})
  public long getLastWrittenTransactionId() {
    return getEditLog().getLastWrittenTxId();
  }
  
  @Metric({"LastCheckpointTime",
      "Time in milliseconds since the epoch of the last checkpoint"})
  public long getLastCheckpointTime() {
    return getFSImage().getStorage().getMostRecentCheckpointTime();
  }

  /** @see ClientProtocol#getStats() */
  long[] getStats() {
    final long[] stats = datanodeStatistics.getStats();
    stats[ClientProtocol.GET_STATS_UNDER_REPLICATED_IDX] = getUnderReplicatedBlocks();
    stats[ClientProtocol.GET_STATS_CORRUPT_BLOCKS_IDX] = getCorruptReplicaBlocks();
    stats[ClientProtocol.GET_STATS_MISSING_BLOCKS_IDX] = getMissingBlocksCount();
    return stats;
  }

  @Override // FSNamesystemMBean
  @Metric({"CapacityTotal",
      "Total raw capacity of data nodes in bytes"})
  public long getCapacityTotal() {
    return datanodeStatistics.getCapacityTotal();
  }

  @Metric({"CapacityTotalGB",
      "Total raw capacity of data nodes in GB"})
  public float getCapacityTotalGB() {
    return DFSUtil.roundBytesToGB(getCapacityTotal());
  }

  @Override // FSNamesystemMBean
  @Metric({"CapacityUsed",
      "Total used capacity across all data nodes in bytes"})
  public long getCapacityUsed() {
    return datanodeStatistics.getCapacityUsed();
  }

  @Metric({"CapacityUsedGB",
      "Total used capacity across all data nodes in GB"})
  public float getCapacityUsedGB() {
    return DFSUtil.roundBytesToGB(getCapacityUsed());
  }

  @Override // FSNamesystemMBean
  @Metric({"CapacityRemaining", "Remaining capacity in bytes"})
  public long getCapacityRemaining() {
    return datanodeStatistics.getCapacityRemaining();
  }

  @Metric({"CapacityRemainingGB", "Remaining capacity in GB"})
  public float getCapacityRemainingGB() {
    return DFSUtil.roundBytesToGB(getCapacityRemaining());
  }

  @Metric({"CapacityUsedNonDFS",
      "Total space used by data nodes for non DFS purposes in bytes"})
  public long getCapacityUsedNonDFS() {
    return datanodeStatistics.getCapacityUsedNonDFS();
  }

  /**
   * Total number of connections.
   */
  @Override // FSNamesystemMBean
  @Metric
  public int getTotalLoad() {
    return datanodeStatistics.getXceiverCount();
  }
  
  @Metric({ "SnapshottableDirectories", "Number of snapshottable directories" })
  public int getNumSnapshottableDirs() {
    return this.snapshotManager.getNumSnapshottableDirs();
  }

  @Metric({ "Snapshots", "The number of snapshots" })
  public int getNumSnapshots() {
    return this.snapshotManager.getNumSnapshots();
  }

  @Override
  public String getSnapshotStats() {
    Map<String, Object> info = new HashMap<String, Object>();
    info.put("SnapshottableDirectories", this.getNumSnapshottableDirs());
    info.put("Snapshots", this.getNumSnapshots());
    return JSON.toString(info);
  }

  int getNumberOfDatanodes(DatanodeReportType type) {
    readLock();
    try {
      return getBlockManager().getDatanodeManager().getDatanodeListForReport(
          type).size(); 
    } finally {
      readUnlock();
    }
  }

  DatanodeInfo[] datanodeReport(final DatanodeReportType type
      ) throws AccessControlException, StandbyException {
    checkSuperuserPrivilege();
    checkOperation(OperationCategory.UNCHECKED);
    readLock();
    try {
      checkOperation(OperationCategory.UNCHECKED);
      final DatanodeManager dm = getBlockManager().getDatanodeManager();      
      final List<DatanodeDescriptor> results = dm.getDatanodeListForReport(type);

      DatanodeInfo[] arr = new DatanodeInfo[results.size()];
      for (int i=0; i<arr.length; i++) {
        arr[i] = new DatanodeInfo(results.get(i));
      }
      return arr;
    } finally {
      readUnlock();
    }
  }

  /**
   * Save namespace image.
   * This will save current namespace into fsimage file and empty edits file.
   * Requires superuser privilege and safe mode.
   * 
   * @throws AccessControlException if superuser privilege is violated.
   * @throws IOException if 
   */
  void saveNamespace() throws AccessControlException, IOException {
    checkOperation(OperationCategory.UNCHECKED);
    checkSuperuserPrivilege();
    
    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return; // Return previous response
    }
    boolean success = false;
    readLock();
    try {
      checkOperation(OperationCategory.UNCHECKED);

      if (!isInSafeMode()) {
        throw new IOException("Safe mode should be turned ON "
            + "in order to create namespace image.");
      }
      getFSImage().saveNamespace(this);
      success = true;
    } finally {
      readUnlock();
      RetryCache.setState(cacheEntry, success);
    }
    LOG.info("New namespace image has been created");
  }
  
  /**
   * Enables/Disables/Checks restoring failed storage replicas if the storage becomes available again.
   * Requires superuser privilege.
   * 
   * @throws AccessControlException if superuser privilege is violated.
   */
  boolean restoreFailedStorage(String arg) throws AccessControlException,
      StandbyException {
    checkSuperuserPrivilege();
    checkOperation(OperationCategory.UNCHECKED);
    writeLock();
    try {
      checkOperation(OperationCategory.UNCHECKED);
      
      // if it is disabled - enable it and vice versa.
      if(arg.equals("check"))
        return getFSImage().getStorage().getRestoreFailedStorage();
      
      boolean val = arg.equals("true");  // false if not
      getFSImage().getStorage().setRestoreFailedStorage(val);
      
      return val;
    } finally {
      writeUnlock();
    }
  }

  Date getStartTime() {
    return new Date(startTime); 
  }
    
  void finalizeUpgrade() throws IOException {
    checkSuperuserPrivilege();
    checkOperation(OperationCategory.UNCHECKED);
    writeLock();
    try {
      checkOperation(OperationCategory.UNCHECKED);
      getFSImage().finalizeUpgrade(this.isHaEnabled() && inActiveState());
    } finally {
      writeUnlock();
    }
  }

  void refreshNodes() throws IOException {
    checkOperation(OperationCategory.UNCHECKED);
    checkSuperuserPrivilege();
    getBlockManager().getDatanodeManager().refreshNodes(new HdfsConfiguration());
  }

  void setBalancerBandwidth(long bandwidth) throws IOException {
    checkOperation(OperationCategory.UNCHECKED);
    checkSuperuserPrivilege();
    getBlockManager().getDatanodeManager().setBalancerBandwidth(bandwidth);
  }

  /**
   * SafeModeInfo contains information related to the safe mode.
   * <p>
   * An instance of {@link SafeModeInfo} is created when the name node
   * enters safe mode.
   * <p>
   * During name node startup {@link SafeModeInfo} counts the number of
   * <em>safe blocks</em>, those that have at least the minimal number of
   * replicas, and calculates the ratio of safe blocks to the total number
   * of blocks in the system, which is the size of blocks in
   * {@link FSNamesystem#blockManager}. When the ratio reaches the
   * {@link #threshold} it starts the SafeModeMonitor daemon in order
   * to monitor whether the safe mode {@link #extension} is passed.
   * Then it leaves safe mode and destroys itself.
   * <p>
   * If safe mode is turned on manually then the number of safe blocks is
   * not tracked because the name node is not intended to leave safe mode
   * automatically in the case.
   *
   * @see ClientProtocol#setSafeMode(HdfsConstants.SafeModeAction, boolean)
   */
  public class SafeModeInfo {
    // configuration fields
    /** Safe mode threshold condition %.*/
    private final double threshold;
    /** Safe mode minimum number of datanodes alive */
    private final int datanodeThreshold;
    /** Safe mode extension after the threshold. */
    private int extension;
    /** Min replication required by safe mode. */
    private final int safeReplication;
    /** threshold for populating needed replication queues */
    private final double replQueueThreshold;
    // internal fields
    /** Time when threshold was reached.
     * <br> -1 safe mode is off
     * <br> 0 safe mode is on, and threshold is not reached yet
     * <br> >0 safe mode is on, but we are in extension period 
     */
    private long reached = -1;  
    /** Total number of blocks. */
    int blockTotal; 
    /** Number of safe blocks. */
    int blockSafe;
    /** Number of blocks needed to satisfy safe mode threshold condition */
    private int blockThreshold;
    /** Number of blocks needed before populating replication queues */
    private int blockReplQueueThreshold;
    /** time of the last status printout */
    private long lastStatusReport = 0;
    /** Was safemode entered automatically because available resources were low. */
    private boolean resourcesLow = false;
    /** Should safemode adjust its block totals as blocks come in */
    private boolean shouldIncrementallyTrackBlocks = false;
    /** counter for tracking startup progress of reported blocks */
    private Counter awaitingReportedBlocksCounter;
    
    /**
     * Creates SafeModeInfo when the name node enters
     * automatic safe mode at startup.
     *  
     * @param conf configuration
     */
    private SafeModeInfo(Configuration conf) {
      this.threshold = conf.getFloat(DFS_NAMENODE_SAFEMODE_THRESHOLD_PCT_KEY,
          DFS_NAMENODE_SAFEMODE_THRESHOLD_PCT_DEFAULT);
      if(threshold > 1.0) {
        LOG.warn("The threshold value should't be greater than 1, threshold: " + threshold);
      }
      this.datanodeThreshold = conf.getInt(
        DFS_NAMENODE_SAFEMODE_MIN_DATANODES_KEY,
        DFS_NAMENODE_SAFEMODE_MIN_DATANODES_DEFAULT);
      this.extension = conf.getInt(DFS_NAMENODE_SAFEMODE_EXTENSION_KEY, 0);
      this.safeReplication = conf.getInt(DFS_NAMENODE_REPLICATION_MIN_KEY, 
                                         DFS_NAMENODE_REPLICATION_MIN_DEFAULT);
      
      LOG.info(DFS_NAMENODE_SAFEMODE_THRESHOLD_PCT_KEY + " = " + threshold);
      LOG.info(DFS_NAMENODE_SAFEMODE_MIN_DATANODES_KEY + " = " + datanodeThreshold);
      LOG.info(DFS_NAMENODE_SAFEMODE_EXTENSION_KEY + "     = " + extension);

      // default to safe mode threshold (i.e., don't populate queues before leaving safe mode)
      this.replQueueThreshold = 
        conf.getFloat(DFS_NAMENODE_REPL_QUEUE_THRESHOLD_PCT_KEY,
                      (float) threshold);
      this.blockTotal = 0; 
      this.blockSafe = 0;
    }

    /**
     * In the HA case, the StandbyNode can be in safemode while the namespace
     * is modified by the edit log tailer. In this case, the number of total
     * blocks changes as edits are processed (eg blocks are added and deleted).
     * However, we don't want to do the incremental tracking during the
     * startup-time loading process -- only once the initial total has been
     * set after the image has been loaded.
     */
    private boolean shouldIncrementallyTrackBlocks() {
      return shouldIncrementallyTrackBlocks;
    }

    /**
     * Creates SafeModeInfo when safe mode is entered manually, or because
     * available resources are low.
     *
     * The {@link #threshold} is set to 1.5 so that it could never be reached.
     * {@link #blockTotal} is set to -1 to indicate that safe mode is manual.
     * 
     * @see SafeModeInfo
     */
    private SafeModeInfo(boolean resourcesLow) {
      this.threshold = 1.5f;  // this threshold can never be reached
      this.datanodeThreshold = Integer.MAX_VALUE;
      this.extension = Integer.MAX_VALUE;
      this.safeReplication = Short.MAX_VALUE + 1; // more than maxReplication
      this.replQueueThreshold = 1.5f; // can never be reached
      this.blockTotal = -1;
      this.blockSafe = -1;
      this.resourcesLow = resourcesLow;
      enter();
      reportStatus("STATE* Safe mode is ON.", true);
    }
      
    /**
     * Check if safe mode is on.
     * @return true if in safe mode
     */
    private synchronized boolean isOn() {
      doConsistencyCheck();
      return this.reached >= 0;
    }
      
    /**
     * Enter safe mode.
     */
    private void enter() {
      this.reached = 0;
    }
      
    /**
     * Leave safe mode.
     * <p>
     * Check for invalid, under- & over-replicated blocks in the end of startup.
     */
    private synchronized void leave() {
      // if not done yet, initialize replication queues.
      // In the standby, do not populate repl queues
      if (!isPopulatingReplQueues() && shouldPopulateReplQueues()) {
        initializeReplQueues();
      }
      long timeInSafemode = now() - startTime;
      NameNode.stateChangeLog.info("STATE* Leaving safe mode after " 
                                    + timeInSafemode/1000 + " secs");
      NameNode.getNameNodeMetrics().setSafeModeTime((int) timeInSafemode);

      //Log the following only once (when transitioning from ON -> OFF)
      if (reached >= 0) {
        NameNode.stateChangeLog.info("STATE* Safe mode is OFF"); 
      }
      reached = -1;
      safeMode = null;
      final NetworkTopology nt = blockManager.getDatanodeManager().getNetworkTopology();
      NameNode.stateChangeLog.info("STATE* Network topology has "
          + nt.getNumOfRacks() + " racks and "
          + nt.getNumOfLeaves() + " datanodes");
      NameNode.stateChangeLog.info("STATE* UnderReplicatedBlocks has "
          + blockManager.numOfUnderReplicatedBlocks() + " blocks");

      startSecretManagerIfNecessary();

      // If startup has not yet completed, end safemode phase.
      StartupProgress prog = NameNode.getStartupProgress();
      if (prog.getStatus(Phase.SAFEMODE) != Status.COMPLETE) {
        prog.endStep(Phase.SAFEMODE, STEP_AWAITING_REPORTED_BLOCKS);
        prog.endPhase(Phase.SAFEMODE);
      }
    }

    /**
     * Check whether we have reached the threshold for 
     * initializing replication queues.
     */
    private synchronized boolean canInitializeReplQueues() {
      return shouldPopulateReplQueues()
          && blockSafe >= blockReplQueueThreshold;
    }
      
    /** 
     * Safe mode can be turned off iff 
     * the threshold is reached and 
     * the extension time have passed.
     * @return true if can leave or false otherwise.
     */
    private synchronized boolean canLeave() {
      if (reached == 0) {
        return false;
      }

      if (now() - reached < extension) {
        reportStatus("STATE* Safe mode ON, in safe mode extension.", false);
        return false;
      }

      if (needEnter()) {
        reportStatus("STATE* Safe mode ON, thresholds not met.", false);
        return false;
      }

      return true;
    }
      
    /** 
     * There is no need to enter safe mode 
     * if DFS is empty or {@link #threshold} == 0
     */
    private boolean needEnter() {
      return (threshold != 0 && blockSafe < blockThreshold) ||
        (datanodeThreshold != 0 && getNumLiveDataNodes() < datanodeThreshold) ||
        (!nameNodeHasResourcesAvailable());
    }
      
    /**
     * Check and trigger safe mode if needed. 
     */
    private void checkMode() {
      // Have to have write-lock since leaving safemode initializes
      // repl queues, which requires write lock
      assert hasWriteLock();
      // if smmthread is already running, the block threshold must have been 
      // reached before, there is no need to enter the safe mode again
      if (smmthread == null && needEnter()) {
        enter();
        // check if we are ready to initialize replication queues
        if (canInitializeReplQueues() && !isPopulatingReplQueues()
            && !haEnabled) {
          initializeReplQueues();
        }
        reportStatus("STATE* Safe mode ON.", false);
        return;
      }
      // the threshold is reached or was reached before
      if (!isOn() ||                           // safe mode is off
          extension <= 0 || threshold <= 0) {  // don't need to wait
        this.leave(); // leave safe mode
        return;
      }
      if (reached > 0) {  // threshold has already been reached before
        reportStatus("STATE* Safe mode ON.", false);
        return;
      }
      // start monitor
      reached = now();
      if (smmthread == null) {
        smmthread = new Daemon(new SafeModeMonitor());
        smmthread.start();
        reportStatus("STATE* Safe mode extension entered.", true);
      }

      // check if we are ready to initialize replication queues
      if (canInitializeReplQueues() && !isPopulatingReplQueues() && !haEnabled) {
        initializeReplQueues();
      }
    }
      
    /**
     * Set total number of blocks.
     */
    private synchronized void setBlockTotal(int total) {
      this.blockTotal = total;
      this.blockThreshold = (int) (blockTotal * threshold);
      this.blockReplQueueThreshold = 
        (int) (blockTotal * replQueueThreshold);
      if (haEnabled) {
        // After we initialize the block count, any further namespace
        // modifications done while in safe mode need to keep track
        // of the number of total blocks in the system.
        this.shouldIncrementallyTrackBlocks = true;
      }
      if(blockSafe < 0)
        this.blockSafe = 0;
      checkMode();
    }
      
    /**
     * Increment number of safe blocks if current block has 
     * reached minimal replication.
     * @param replication current replication 
     */
    private synchronized void incrementSafeBlockCount(short replication) {
      if (replication == safeReplication) {
        this.blockSafe++;

        // Report startup progress only if we haven't completed startup yet.
        StartupProgress prog = NameNode.getStartupProgress();
        if (prog.getStatus(Phase.SAFEMODE) != Status.COMPLETE) {
          if (this.awaitingReportedBlocksCounter == null) {
            this.awaitingReportedBlocksCounter = prog.getCounter(Phase.SAFEMODE,
              STEP_AWAITING_REPORTED_BLOCKS);
          }
          this.awaitingReportedBlocksCounter.increment();
        }

        checkMode();
      }
    }
      
    /**
     * Decrement number of safe blocks if current block has 
     * fallen below minimal replication.
     * @param replication current replication 
     */
    private synchronized void decrementSafeBlockCount(short replication) {
      if (replication == safeReplication-1) {
        this.blockSafe--;
        //blockSafe is set to -1 in manual / low resources safemode
        assert blockSafe >= 0 || isManual() || areResourcesLow();
        checkMode();
      }
    }

    /**
     * Check if safe mode was entered manually
     */
    private boolean isManual() {
      return extension == Integer.MAX_VALUE;
    }

    /**
     * Set manual safe mode.
     */
    private synchronized void setManual() {
      extension = Integer.MAX_VALUE;
    }

    /**
     * Check if safe mode was entered due to resources being low.
     */
    private boolean areResourcesLow() {
      return resourcesLow;
    }

    /**
     * Set that resources are low for this instance of safe mode.
     */
    private void setResourcesLow() {
      resourcesLow = true;
    }

    /**
     * A tip on how safe mode is to be turned off: manually or automatically.
     */
    String getTurnOffTip() {
      if(!isOn()) {
        return "Safe mode is OFF.";
      }

      //Manual OR low-resource safemode. (Admin intervention required)
      String adminMsg = "It was turned on manually. ";
      if (areResourcesLow()) {
        adminMsg = "Resources are low on NN. Please add or free up more "
          + "resources then turn off safe mode manually. NOTE:  If you turn off"
          + " safe mode before adding resources, "
          + "the NN will immediately return to safe mode. ";
      }
      if (isManual() || areResourcesLow()) {
        return adminMsg
          + "Use \"hdfs dfsadmin -safemode leave\" to turn safe mode off.";
      }

      boolean thresholdsMet = true;
      int numLive = getNumLiveDataNodes();
      String msg = "";
      if (blockSafe < blockThreshold) {
        msg += String.format(
          "The reported blocks %d needs additional %d"
          + " blocks to reach the threshold %.4f of total blocks %d.\n",
          blockSafe, (blockThreshold - blockSafe) + 1, threshold, blockTotal);
        thresholdsMet = false;
      } else {
        msg += String.format("The reported blocks %d has reached the threshold"
            + " %.4f of total blocks %d. ", blockSafe, threshold, blockTotal);
      }
      if (numLive < datanodeThreshold) {
        msg += String.format(
          "The number of live datanodes %d needs an additional %d live "
          + "datanodes to reach the minimum number %d.\n",
          numLive, (datanodeThreshold - numLive), datanodeThreshold);
        thresholdsMet = false;
      } else {
        msg += String.format("The number of live datanodes %d has reached "
            + "the minimum number %d. ",
            numLive, datanodeThreshold);
      }
      msg += (reached > 0) ? "In safe mode extension. " : "";
      msg += "Safe mode will be turned off automatically ";

      if (!thresholdsMet) {
        msg += "once the thresholds have been reached.";
      } else if (reached + extension - now() > 0) {
        msg += ("in " + (reached + extension - now()) / 1000 + " seconds.");
      } else {
        msg += "soon.";
      }

      return msg;
    }

    /**
     * Print status every 20 seconds.
     */
    private void reportStatus(String msg, boolean rightNow) {
      long curTime = now();
      if(!rightNow && (curTime - lastStatusReport < 20 * 1000))
        return;
      NameNode.stateChangeLog.info(msg + " \n" + getTurnOffTip());
      lastStatusReport = curTime;
    }

    @Override
    public String toString() {
      String resText = "Current safe blocks = " 
        + blockSafe 
        + ". Target blocks = " + blockThreshold + " for threshold = %" + threshold
        + ". Minimal replication = " + safeReplication + ".";
      if (reached > 0) 
        resText += " Threshold was reached " + new Date(reached) + ".";
      return resText;
    }
      
    /**
     * Checks consistency of the class state.
     * This is costly so only runs if asserts are enabled.
     */
    private void doConsistencyCheck() {
      boolean assertsOn = false;
      assert assertsOn = true; // set to true if asserts are on
      if (!assertsOn) return;
      
      if (blockTotal == -1 && blockSafe == -1) {
        return; // manual safe mode
      }
      int activeBlocks = blockManager.getActiveBlockCount();
      if ((blockTotal != activeBlocks) &&
          !(blockSafe >= 0 && blockSafe <= blockTotal)) {
        throw new AssertionError(
            " SafeMode: Inconsistent filesystem state: "
        + "SafeMode data: blockTotal=" + blockTotal
        + " blockSafe=" + blockSafe + "; "
        + "BlockManager data: active="  + activeBlocks);
      }
    }

    private synchronized void adjustBlockTotals(int deltaSafe, int deltaTotal) {
      if (!shouldIncrementallyTrackBlocks) {
        return;
      }
      assert haEnabled;
      
      if (LOG.isDebugEnabled()) {
        LOG.debug("Adjusting block totals from " +
            blockSafe + "/" + blockTotal + " to " +
            (blockSafe + deltaSafe) + "/" + (blockTotal + deltaTotal));
      }
      assert blockSafe + deltaSafe >= 0 : "Can't reduce blockSafe " +
        blockSafe + " by " + deltaSafe + ": would be negative";
      assert blockTotal + deltaTotal >= 0 : "Can't reduce blockTotal " +
        blockTotal + " by " + deltaTotal + ": would be negative";
      
      blockSafe += deltaSafe;
      setBlockTotal(blockTotal + deltaTotal);
    }
  }
    
  /**
   * Periodically check whether it is time to leave safe mode.
   * This thread starts when the threshold level is reached.
   *
   */
  class SafeModeMonitor implements Runnable {
    /** interval in msec for checking safe mode: {@value} */
    private static final long recheckInterval = 1000;
      
    /**
     */
    @Override
    public void run() {
      while (fsRunning) {
        writeLock();
        try {
          if (safeMode == null) { // Not in safe mode.
            break;
          }
          if (safeMode.canLeave()) {
            // Leave safe mode.
            safeMode.leave();
            smmthread = null;
            break;
          }
        } finally {
          writeUnlock();
        }

        try {
          Thread.sleep(recheckInterval);
        } catch (InterruptedException ie) {
          // Ignored
        }
      }
      if (!fsRunning) {
        LOG.info("NameNode is being shutdown, exit SafeModeMonitor thread");
      }
    }
  }
    
  boolean setSafeMode(SafeModeAction action) throws IOException {
    if (action != SafeModeAction.SAFEMODE_GET) {
      checkSuperuserPrivilege();
      switch(action) {
      case SAFEMODE_LEAVE: // leave safe mode
        leaveSafeMode();
        break;
      case SAFEMODE_ENTER: // enter safe mode
        enterSafeMode(false);
        break;
      default:
        LOG.error("Unexpected safe mode action");
      }
    }
    return isInSafeMode();
  }

  @Override
  public void checkSafeMode() {
    // safeMode is volatile, and may be set to null at any time
    SafeModeInfo safeMode = this.safeMode;
    if (safeMode != null) {
      safeMode.checkMode();
    }
  }

  @Override
  public boolean isInSafeMode() {
    // safeMode is volatile, and may be set to null at any time
    SafeModeInfo safeMode = this.safeMode;
    if (safeMode == null)
      return false;
    return safeMode.isOn();
  }

  @Override
  public boolean isInStartupSafeMode() {
    // safeMode is volatile, and may be set to null at any time
    SafeModeInfo safeMode = this.safeMode;
    if (safeMode == null)
      return false;
    // If the NN is in safemode, and not due to manual / low resources, we
    // assume it must be because of startup. If the NN had low resources during
    // startup, we assume it came out of startup safemode and it is now in low
    // resources safemode
    return !safeMode.isManual() && !safeMode.areResourcesLow()
      && safeMode.isOn();
  }

  /**
   * Check if replication queues are to be populated
   * @return true when node is HAState.Active and not in the very first safemode
   */
  @Override
  public boolean isPopulatingReplQueues() {
    if (!shouldPopulateReplQueues()) {
      return false;
    }
    return initializedReplQueues;
  }

  private boolean shouldPopulateReplQueues() {
    if(haContext == null || haContext.getState() == null)
      return false;
    return haContext.getState().shouldPopulateReplQueues();
  }

  @Override
  public void incrementSafeBlockCount(int replication) {
    // safeMode is volatile, and may be set to null at any time
    SafeModeInfo safeMode = this.safeMode;
    if (safeMode == null)
      return;
    safeMode.incrementSafeBlockCount((short)replication);
  }

  @Override
  public void decrementSafeBlockCount(Block b) {
    // safeMode is volatile, and may be set to null at any time
    SafeModeInfo safeMode = this.safeMode;
    if (safeMode == null) // mostly true
      return;
    BlockInfo storedBlock = getStoredBlock(b);
    if (storedBlock.isComplete()) {
      safeMode.decrementSafeBlockCount((short)blockManager.countNodes(b).liveReplicas());
    }
  }
  
  /**
   * Adjust the total number of blocks safe and expected during safe mode.
   * If safe mode is not currently on, this is a no-op.
   * @param deltaSafe the change in number of safe blocks
   * @param deltaTotal the change i nnumber of total blocks expected
   */
  @Override
  public void adjustSafeModeBlockTotals(int deltaSafe, int deltaTotal) {
    // safeMode is volatile, and may be set to null at any time
    SafeModeInfo safeMode = this.safeMode;
    if (safeMode == null)
      return;
    safeMode.adjustBlockTotals(deltaSafe, deltaTotal);
  }

  /**
   * Set the total number of blocks in the system. 
   */
  public void setBlockTotal() {
    // safeMode is volatile, and may be set to null at any time
    SafeModeInfo safeMode = this.safeMode;
    if (safeMode == null)
      return;
    safeMode.setBlockTotal((int)getCompleteBlocksTotal());
  }

  /**
   * Get the total number of blocks in the system. 
   */
  @Override // FSNamesystemMBean
  @Metric
  public long getBlocksTotal() {
    return blockManager.getTotalBlocks();
  }

  /**
   * Get the total number of COMPLETE blocks in the system.
   * For safe mode only complete blocks are counted.
   */
  private long getCompleteBlocksTotal() {
    // Calculate number of blocks under construction
    long numUCBlocks = 0;
    readLock();
    try {
      for (Lease lease : leaseManager.getSortedLeases()) {
        for (String path : lease.getPaths()) {
          final INodeFile cons;
          try {
            cons = dir.getINode(path).asFile();
            Preconditions.checkState(cons.isUnderConstruction());
          } catch (UnresolvedLinkException e) {
            throw new AssertionError("Lease files should reside on this FS");
          }
          BlockInfo[] blocks = cons.getBlocks();
          if(blocks == null)
            continue;
          for(BlockInfo b : blocks) {
            if(!b.isComplete())
              numUCBlocks++;
          }
        }
      }
      LOG.info("Number of blocks under construction: " + numUCBlocks);
      return getBlocksTotal() - numUCBlocks;
    } finally {
      readUnlock();
    }
  }

  /**
   * Enter safe mode. If resourcesLow is false, then we assume it is manual
   * @throws IOException
   */
  void enterSafeMode(boolean resourcesLow) throws IOException {
    writeLock();
    try {
      // Stop the secret manager, since rolling the master key would
      // try to write to the edit log
      stopSecretManager();

      // Ensure that any concurrent operations have been fully synced
      // before entering safe mode. This ensures that the FSImage
      // is entirely stable on disk as soon as we're in safe mode.
      boolean isEditlogOpenForWrite = getEditLog().isOpenForWrite();
      // Before Editlog is in OpenForWrite mode, editLogStream will be null. So,
      // logSyncAll call can be called only when Edlitlog is in OpenForWrite mode
      if (isEditlogOpenForWrite) {
        getEditLog().logSyncAll();
      }
      if (!isInSafeMode()) {
        safeMode = new SafeModeInfo(resourcesLow);
        return;
      }
      if (resourcesLow) {
        safeMode.setResourcesLow();
      } else {
        safeMode.setManual();
      }
      if (isEditlogOpenForWrite) {
        getEditLog().logSyncAll();
      }
      NameNode.stateChangeLog.info("STATE* Safe mode is ON"
          + safeMode.getTurnOffTip());
    } finally {
      writeUnlock();
    }
  }

  /**
   * Leave safe mode.
   * @throws IOException
   */
  void leaveSafeMode() {
    writeLock();
    try {
      if (!isInSafeMode()) {
        NameNode.stateChangeLog.info("STATE* Safe mode is already OFF"); 
        return;
      }
      safeMode.leave();
    } finally {
      writeUnlock();
    }
  }
    
  String getSafeModeTip() {
    readLock();
    try {
      if (!isInSafeMode()) {
        return "";
      }
      return safeMode.getTurnOffTip();
    } finally {
      readUnlock();
    }
  }

  CheckpointSignature rollEditLog() throws IOException {
    checkSuperuserPrivilege();
    checkOperation(OperationCategory.JOURNAL);
    writeLock();
    try {
      checkOperation(OperationCategory.JOURNAL);
      checkNameNodeSafeMode("Log not rolled");
      if (Server.isRpcInvocation()) {
        LOG.info("Roll Edit Log from " + Server.getRemoteAddress());
      }
      return getFSImage().rollEditLog();
    } finally {
      writeUnlock();
    }
  }

  NamenodeCommand startCheckpoint(NamenodeRegistration backupNode,
      NamenodeRegistration activeNamenode) throws IOException {
    checkOperation(OperationCategory.CHECKPOINT);
    CacheEntryWithPayload cacheEntry = RetryCache.waitForCompletion(retryCache,
        null);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return (NamenodeCommand) cacheEntry.getPayload();
    }
    writeLock();
    NamenodeCommand cmd = null;
    try {
      checkOperation(OperationCategory.CHECKPOINT);
      checkNameNodeSafeMode("Checkpoint not started");
      
      LOG.info("Start checkpoint for " + backupNode.getAddress());
      cmd = getFSImage().startCheckpoint(backupNode, activeNamenode);
      getEditLog().logSync();
      return cmd;
    } finally {
      writeUnlock();
      RetryCache.setState(cacheEntry, cmd != null, cmd);
    }
  }

  public void processIncrementalBlockReport(final DatanodeID nodeID,
      final String poolId, final StorageReceivedDeletedBlocks srdb)
      throws IOException {
    writeLock();
    try {
      blockManager.processIncrementalBlockReport(nodeID, srdb);
    } finally {
      writeUnlock();
    }
  }
  
  void endCheckpoint(NamenodeRegistration registration,
                            CheckpointSignature sig) throws IOException {
    checkOperation(OperationCategory.CHECKPOINT);
    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return; // Return previous response
    }
    boolean success = false;
    readLock();
    try {
      checkOperation(OperationCategory.CHECKPOINT);

      checkNameNodeSafeMode("Checkpoint not ended");
      LOG.info("End checkpoint for " + registration.getAddress());
      getFSImage().endCheckpoint(sig);
      success = true;
    } finally {
      readUnlock();
      RetryCache.setState(cacheEntry, success);
    }
  }

  PermissionStatus createFsOwnerPermissions(FsPermission permission) {
    return new PermissionStatus(fsOwner.getShortUserName(), supergroup, permission);
  }

  private void checkOwner(FSPermissionChecker pc, String path)
      throws AccessControlException, UnresolvedLinkException {
    checkPermission(pc, path, true, null, null, null, null);
  }

  private void checkPathAccess(FSPermissionChecker pc,
      String path, FsAction access) throws AccessControlException,
      UnresolvedLinkException {
    checkPermission(pc, path, false, null, null, access, null);
  }

  private void checkParentAccess(FSPermissionChecker pc,
      String path, FsAction access) throws AccessControlException,
      UnresolvedLinkException {
    checkPermission(pc, path, false, null, access, null, null);
  }

  private void checkAncestorAccess(FSPermissionChecker pc,
      String path, FsAction access) throws AccessControlException,
      UnresolvedLinkException {
    checkPermission(pc, path, false, access, null, null, null);
  }

  private void checkTraverse(FSPermissionChecker pc, String path)
      throws AccessControlException, UnresolvedLinkException {
    checkPermission(pc, path, false, null, null, null, null);
  }

  @Override
  public void checkSuperuserPrivilege()
      throws AccessControlException {
    if (isPermissionEnabled) {
      FSPermissionChecker pc = getPermissionChecker();
      pc.checkSuperuserPrivilege();
    }
  }

  /**
   * Check whether current user have permissions to access the path. For more
   * details of the parameters, see
   * {@link FSPermissionChecker#checkPermission()}.
   */
  private void checkPermission(FSPermissionChecker pc,
      String path, boolean doCheckOwner, FsAction ancestorAccess,
      FsAction parentAccess, FsAction access, FsAction subAccess)
      throws AccessControlException, UnresolvedLinkException {
        checkPermission(pc, path, doCheckOwner, ancestorAccess,
            parentAccess, access, subAccess, true);
  }

  /**
   * Check whether current user have permissions to access the path. For more
   * details of the parameters, see
   * {@link FSPermissionChecker#checkPermission()}.
   */
  private void checkPermission(FSPermissionChecker pc,
      String path, boolean doCheckOwner, FsAction ancestorAccess,
      FsAction parentAccess, FsAction access, FsAction subAccess,
      boolean resolveLink)
      throws AccessControlException, UnresolvedLinkException {
    if (!pc.isSuperUser()) {
      dir.waitForReady();
      readLock();
      try {
        pc.checkPermission(path, dir.rootDir, doCheckOwner, ancestorAccess,
            parentAccess, access, subAccess, resolveLink);
      } finally {
        readUnlock();
      }
    }
  }
  
  /**
   * Check to see if we have exceeded the limit on the number
   * of inodes.
   */
  void checkFsObjectLimit() throws IOException {
    if (maxFsObjects != 0 &&
        maxFsObjects <= dir.totalInodes() + getBlocksTotal()) {
      throw new IOException("Exceeded the configured number of objects " +
                             maxFsObjects + " in the filesystem.");
    }
  }

  /**
   * Get the total number of objects in the system. 
   */
  @Override // FSNamesystemMBean
  public long getMaxObjects() {
    return maxFsObjects;
  }

  @Override // FSNamesystemMBean
  @Metric
  public long getFilesTotal() {
    readLock();
    try {
      return this.dir.totalInodes();
    } finally {
      readUnlock();
    }
  }

  @Override // FSNamesystemMBean
  @Metric
  public long getPendingReplicationBlocks() {
    return blockManager.getPendingReplicationBlocksCount();
  }

  @Override // FSNamesystemMBean
  @Metric
  public long getUnderReplicatedBlocks() {
    return blockManager.getUnderReplicatedBlocksCount();
  }

  /** Returns number of blocks with corrupt replicas */
  @Metric({"CorruptBlocks", "Number of blocks with corrupt replicas"})
  public long getCorruptReplicaBlocks() {
    return blockManager.getCorruptReplicaBlocksCount();
  }

  @Override // FSNamesystemMBean
  @Metric
  public long getScheduledReplicationBlocks() {
    return blockManager.getScheduledReplicationBlocksCount();
  }

  @Override
  @Metric
  public long getPendingDeletionBlocks() {
    return blockManager.getPendingDeletionBlocksCount();
  }

  @Metric
  public long getExcessBlocks() {
    return blockManager.getExcessBlocksCount();
  }
  
  // HA-only metric
  @Metric
  public long getPostponedMisreplicatedBlocks() {
    return blockManager.getPostponedMisreplicatedBlocksCount();
  }

  // HA-only metric
  @Metric
  public int getPendingDataNodeMessageCount() {
    return blockManager.getPendingDataNodeMessageCount();
  }
  
  // HA-only metric
  @Metric
  public String getHAState() {
    return haContext.getState().toString();
  }

  // HA-only metric
  @Metric
  public long getMillisSinceLastLoadedEdits() {
    if (isInStandbyState() && editLogTailer != null) {
      return now() - editLogTailer.getLastLoadTimestamp();
    } else {
      return 0;
    }
  }
  
  @Metric
  public int getBlockCapacity() {
    return blockManager.getCapacity();
  }

  @Override // FSNamesystemMBean
  public String getFSState() {
    return isInSafeMode() ? "safeMode" : "Operational";
  }
  
  private ObjectName mbeanName;
  private ObjectName mxbeanName;

  /**
   * Register the FSNamesystem MBean using the name
   *        "hadoop:service=NameNode,name=FSNamesystemState"
   */
  private void registerMBean() {
    // We can only implement one MXBean interface, so we keep the old one.
    try {
      StandardMBean bean = new StandardMBean(this, FSNamesystemMBean.class);
      mbeanName = MBeans.register("NameNode", "FSNamesystemState", bean);
    } catch (NotCompliantMBeanException e) {
      throw new RuntimeException("Bad MBean setup", e);
    }

    LOG.info("Registered FSNamesystemState MBean");
  }

  /**
   * shutdown FSNamesystem
   */
  void shutdown() {
    if (mbeanName != null) {
      MBeans.unregister(mbeanName);
      mbeanName = null;
    }
    if (mxbeanName != null) {
      MBeans.unregister(mxbeanName);
      mxbeanName = null;
    }
    if (dir != null) {
      dir.shutdown();
    }
    if (blockManager != null) {
      blockManager.shutdown();
    }
  }
  

  @Override // FSNamesystemMBean
  public int getNumLiveDataNodes() {
    return getBlockManager().getDatanodeManager().getNumLiveDataNodes();
  }

  @Override // FSNamesystemMBean
  public int getNumDeadDataNodes() {
    return getBlockManager().getDatanodeManager().getNumDeadDataNodes();
  }
  
  @Override // FSNamesystemMBean
  public int getNumDecomLiveDataNodes() {
    final List<DatanodeDescriptor> live = new ArrayList<DatanodeDescriptor>();
    getBlockManager().getDatanodeManager().fetchDatanodes(live, null, true);
    int liveDecommissioned = 0;
    for (DatanodeDescriptor node : live) {
      liveDecommissioned += node.isDecommissioned() ? 1 : 0;
    }
    return liveDecommissioned;
  }

  @Override // FSNamesystemMBean
  public int getNumDecomDeadDataNodes() {
    final List<DatanodeDescriptor> dead = new ArrayList<DatanodeDescriptor>();
    getBlockManager().getDatanodeManager().fetchDatanodes(null, dead, true);
    int deadDecommissioned = 0;
    for (DatanodeDescriptor node : dead) {
      deadDecommissioned += node.isDecommissioned() ? 1 : 0;
    }
    return deadDecommissioned;
  }

  @Override // FSNamesystemMBean
  public int getNumDecommissioningDataNodes() {
    return getBlockManager().getDatanodeManager().getDecommissioningNodes()
        .size();
  }

  @Override // FSNamesystemMBean
  @Metric({"StaleDataNodes", 
    "Number of datanodes marked stale due to delayed heartbeat"})
  public int getNumStaleDataNodes() {
    return getBlockManager().getDatanodeManager().getNumStaleNodes();
  }

  /**
   * Sets the current generation stamp for legacy blocks
   */
  void setGenerationStampV1(long stamp) {
    generationStampV1.setCurrentValue(stamp);
  }

  /**
   * Gets the current generation stamp for legacy blocks
   */
  long getGenerationStampV1() {
    return generationStampV1.getCurrentValue();
  }

  /**
   * Gets the current generation stamp for this filesystem
   */
  void setGenerationStampV2(long stamp) {
    generationStampV2.setCurrentValue(stamp);
  }

  /**
   * Gets the current generation stamp for this filesystem
   */
  long getGenerationStampV2() {
    return generationStampV2.getCurrentValue();
  }

  /**
   * Upgrades the generation stamp for the filesystem
   * by reserving a sufficient range for all existing blocks.
   * Should be invoked only during the first upgrade to
   * sequential block IDs.
   */
  long upgradeGenerationStampToV2() {
    Preconditions.checkState(generationStampV2.getCurrentValue() ==
        GenerationStamp.LAST_RESERVED_STAMP);

    generationStampV2.skipTo(
        generationStampV1.getCurrentValue() +
        HdfsConstants.RESERVED_GENERATION_STAMPS_V1);

    generationStampV1Limit = generationStampV2.getCurrentValue();
    return generationStampV2.getCurrentValue();
  }

  /**
   * Sets the generation stamp that delineates random and sequentially
   * allocated block IDs.
   * @param stamp
   */
  void setGenerationStampV1Limit(long stamp) {
    Preconditions.checkState(generationStampV1Limit ==
                             GenerationStamp.GRANDFATHER_GENERATION_STAMP);
    generationStampV1Limit = stamp;
  }

  /**
   * Gets the value of the generation stamp that delineates sequential
   * and random block IDs.
   */
  long getGenerationStampAtblockIdSwitch() {
    return generationStampV1Limit;
  }

  @VisibleForTesting
  SequentialBlockIdGenerator getBlockIdGenerator() {
    return blockIdGenerator;
  }

  /**
   * Sets the maximum allocated block ID for this filesystem. This is
   * the basis for allocating new block IDs.
   */
  void setLastAllocatedBlockId(long blockId) {
    blockIdGenerator.skipTo(blockId);
  }

  /**
   * Gets the maximum sequentially allocated block ID for this filesystem
   */
  long getLastAllocatedBlockId() {
    return blockIdGenerator.getCurrentValue();
  }

  /**
   * Increments, logs and then returns the stamp
   */
  long nextGenerationStamp(boolean legacyBlock)
      throws IOException, SafeModeException {
    assert hasWriteLock();
    checkNameNodeSafeMode("Cannot get next generation stamp");

    long gs;
    if (legacyBlock) {
      gs = getNextGenerationStampV1();
      getEditLog().logGenerationStampV1(gs);
    } else {
      gs = getNextGenerationStampV2();
      getEditLog().logGenerationStampV2(gs);
    }

    // NB: callers sync the log
    return gs;
  }

  @VisibleForTesting
  long getNextGenerationStampV1() throws IOException {
    long genStampV1 = generationStampV1.nextValue();

    if (genStampV1 >= generationStampV1Limit) {
      // We ran out of generation stamps for legacy blocks. In practice, it
      // is extremely unlikely as we reserved 1T v1 generation stamps. The
      // result is that we can no longer append to the legacy blocks that
      // were created before the upgrade to sequential block IDs.
      throw new OutOfV1GenerationStampsException();
    }

    return genStampV1;
  }

  @VisibleForTesting
  long getNextGenerationStampV2() {
    return generationStampV2.nextValue();
  }

  long getGenerationStampV1Limit() {
    return generationStampV1Limit;
  }

  /**
   * Determine whether the block ID was randomly generated (legacy) or
   * sequentially generated. The generation stamp value is used to
   * make the distinction.
   * @param block
   * @return true if the block ID was randomly generated, false otherwise.
   */
  boolean isLegacyBlock(Block block) {
    return block.getGenerationStamp() < getGenerationStampV1Limit();
  }

  /**
   * Increments, logs and then returns the block ID
   */
  private long nextBlockId() throws IOException {
    assert hasWriteLock();
    checkNameNodeSafeMode("Cannot get next block ID");
    final long blockId = blockIdGenerator.nextValue();
    getEditLog().logAllocateBlockId(blockId);
    // NB: callers sync the log
    return blockId;
  }

  private INodeFile checkUCBlock(ExtendedBlock block,
      String clientName) throws IOException {
    assert hasWriteLock();
    checkNameNodeSafeMode("Cannot get a new generation stamp and an "
        + "access token for block " + block);
    
    // check stored block state
    BlockInfo storedBlock = getStoredBlock(ExtendedBlock.getLocalBlock(block));
    if (storedBlock == null || 
        storedBlock.getBlockUCState() != BlockUCState.UNDER_CONSTRUCTION) {
        throw new IOException(block + 
            " does not exist or is not under Construction" + storedBlock);
    }
    
    // check file inode
    final INodeFile file = ((INode)storedBlock.getBlockCollection()).asFile();
    if (file == null || !file.isUnderConstruction()) {
      throw new IOException("The file " + storedBlock + 
          " belonged to does not exist or it is not under construction.");
    }
    
    // check lease
    if (clientName == null
        || !clientName.equals(file.getFileUnderConstructionFeature()
            .getClientName())) {
      throw new LeaseExpiredException("Lease mismatch: " + block + 
          " is accessed by a non lease holder " + clientName); 
    }

    return file;
  }
  
  /**
   * Client is reporting some bad block locations.
   */
  void reportBadBlocks(LocatedBlock[] blocks) throws IOException {
    checkOperation(OperationCategory.WRITE);
    NameNode.stateChangeLog.info("*DIR* reportBadBlocks");
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      for (int i = 0; i < blocks.length; i++) {
        ExtendedBlock blk = blocks[i].getBlock();
        DatanodeInfo[] nodes = blocks[i].getLocations();
        String[] storageIDs = blocks[i].getStorageIDs();
        for (int j = 0; j < nodes.length; j++) {
          blockManager.findAndMarkBlockAsCorrupt(blk, nodes[j],
              storageIDs == null ? null: storageIDs[j], 
              "client machine reported it");
        }
      }
    } finally {
      writeUnlock();
    }
  }

  /**
   * Get a new generation stamp together with an access token for 
   * a block under construction
   * 
   * This method is called for recovering a failed pipeline or setting up
   * a pipeline to append to a block.
   * 
   * @param block a block
   * @param clientName the name of a client
   * @return a located block with a new generation stamp and an access token
   * @throws IOException if any error occurs
   */
  LocatedBlock updateBlockForPipeline(ExtendedBlock block, 
      String clientName) throws IOException {
    LocatedBlock locatedBlock;
    checkOperation(OperationCategory.WRITE);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);

      // check vadility of parameters
      checkUCBlock(block, clientName);
  
      // get a new generation stamp and an access token
      block.setGenerationStamp(
          nextGenerationStamp(isLegacyBlock(block.getLocalBlock())));
      locatedBlock = new LocatedBlock(block, new DatanodeInfo[0]);
      blockManager.setBlockToken(locatedBlock, AccessMode.WRITE);
    } finally {
      writeUnlock();
    }
    // Ensure we record the new generation stamp
    getEditLog().logSync();
    return locatedBlock;
  }
  
  /**
   * Update a pipeline for a block under construction
   * 
   * @param clientName the name of the client
   * @param oldBlock and old block
   * @param newBlock a new block with a new generation stamp and length
   * @param newNodes datanodes in the pipeline
   * @throws IOException if any error occurs
   */
  void updatePipeline(String clientName, ExtendedBlock oldBlock, 
      ExtendedBlock newBlock, DatanodeID[] newNodes, String[] newStorageIDs)
      throws IOException {
    checkOperation(OperationCategory.WRITE);
    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return; // Return previous response
    }
    LOG.info("updatePipeline(block=" + oldBlock
             + ", newGenerationStamp=" + newBlock.getGenerationStamp()
             + ", newLength=" + newBlock.getNumBytes()
             + ", newNodes=" + Arrays.asList(newNodes)
             + ", clientName=" + clientName
             + ")");
    writeLock();
    boolean success = false;
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Pipeline not updated");
      assert newBlock.getBlockId()==oldBlock.getBlockId() : newBlock + " and "
        + oldBlock + " has different block identifier";
      updatePipelineInternal(clientName, oldBlock, newBlock, newNodes,
          newStorageIDs, cacheEntry != null);
      success = true;
    } finally {
      writeUnlock();
      RetryCache.setState(cacheEntry, success);
    }
    getEditLog().logSync();
    LOG.info("updatePipeline(" + oldBlock + ") successfully to " + newBlock);
  }

  /** @see #updatePipeline(String, ExtendedBlock, ExtendedBlock, DatanodeID[]) */
  private void updatePipelineInternal(String clientName, ExtendedBlock oldBlock, 
      ExtendedBlock newBlock, DatanodeID[] newNodes, String[] newStorageIDs,
      boolean logRetryCache)
      throws IOException {
    assert hasWriteLock();
    // check the vadility of the block and lease holder name
    final INodeFile pendingFile = checkUCBlock(oldBlock, clientName);
    final BlockInfoUnderConstruction blockinfo
        = (BlockInfoUnderConstruction)pendingFile.getLastBlock();

    // check new GS & length: this is not expected
    if (newBlock.getGenerationStamp() <= blockinfo.getGenerationStamp() ||
        newBlock.getNumBytes() < blockinfo.getNumBytes()) {
      String msg = "Update " + oldBlock + " (len = " + 
        blockinfo.getNumBytes() + ") to an older state: " + newBlock + 
        " (len = " + newBlock.getNumBytes() +")";
      LOG.warn(msg);
      throw new IOException(msg);
    }

    // Update old block with the new generation stamp and new length
    blockinfo.setNumBytes(newBlock.getNumBytes());
    blockinfo.setGenerationStampAndVerifyReplicas(newBlock.getGenerationStamp());

    // find the DatanodeDescriptor objects
    final DatanodeStorageInfo[] storages = blockManager.getDatanodeManager()
        .getDatanodeStorageInfos(newNodes, newStorageIDs);
    blockinfo.setExpectedLocations(storages);

    String src = pendingFile.getFullPathName();
    dir.persistBlocks(src, pendingFile, logRetryCache);
  }

  // rename was successful. If any part of the renamed subtree had
  // files that were being written to, update with new filename.
  void unprotectedChangeLease(String src, String dst) {
    assert hasWriteLock();
    leaseManager.changeLease(src, dst);
  }

  /**
   * @return all the under-construction files in the lease map
   */
  Map<String, INodeFile> getFilesUnderConstruction() {
    synchronized (leaseManager) {
      return leaseManager.getINodesUnderConstruction();
    }
  }

  /**
   * Register a Backup name-node, verifying that it belongs
   * to the correct namespace, and adding it to the set of
   * active journals if necessary.
   * 
   * @param bnReg registration of the new BackupNode
   * @param nnReg registration of this NameNode
   * @throws IOException if the namespace IDs do not match
   */
  void registerBackupNode(NamenodeRegistration bnReg,
      NamenodeRegistration nnReg) throws IOException {
    writeLock();
    try {
      if(getFSImage().getStorage().getNamespaceID() 
         != bnReg.getNamespaceID())
        throw new IOException("Incompatible namespaceIDs: "
            + " Namenode namespaceID = "
            + getFSImage().getStorage().getNamespaceID() + "; "
            + bnReg.getRole() +
            " node namespaceID = " + bnReg.getNamespaceID());
      if (bnReg.getRole() == NamenodeRole.BACKUP) {
        getFSImage().getEditLog().registerBackupNode(
            bnReg, nnReg);
      }
    } finally {
      writeUnlock();
    }
  }

  /**
   * Release (unregister) backup node.
   * <p>
   * Find and remove the backup stream corresponding to the node.
   * @param registration
   * @throws IOException
   */
  void releaseBackupNode(NamenodeRegistration registration)
    throws IOException {
    checkOperation(OperationCategory.WRITE);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      if(getFSImage().getStorage().getNamespaceID()
         != registration.getNamespaceID())
        throw new IOException("Incompatible namespaceIDs: "
            + " Namenode namespaceID = "
            + getFSImage().getStorage().getNamespaceID() + "; "
            + registration.getRole() +
            " node namespaceID = " + registration.getNamespaceID());
      getEditLog().releaseBackupStream(registration);
    } finally {
      writeUnlock();
    }
  }

  static class CorruptFileBlockInfo {
    final String path;
    final Block block;
    
    public CorruptFileBlockInfo(String p, Block b) {
      path = p;
      block = b;
    }
    
    @Override
    public String toString() {
      return block.getBlockName() + "\t" + path;
    }
  }
  /**
   * @param path Restrict corrupt files to this portion of namespace.
   * @param startBlockAfter Support for continuation; the set of files we return
   *  back is ordered by blockid; startBlockAfter tells where to start from
   * @return a list in which each entry describes a corrupt file/block
   * @throws AccessControlException
   * @throws IOException
   */
  Collection<CorruptFileBlockInfo> listCorruptFileBlocks(String path,
  String[] cookieTab) throws IOException {
    checkSuperuserPrivilege();
    checkOperation(OperationCategory.READ);
    readLock();
    try {
      checkOperation(OperationCategory.READ);
      if (!isPopulatingReplQueues()) {
        throw new IOException("Cannot run listCorruptFileBlocks because " +
                              "replication queues have not been initialized.");
      }
      // print a limited # of corrupt files per call
      int count = 0;
      ArrayList<CorruptFileBlockInfo> corruptFiles = new ArrayList<CorruptFileBlockInfo>();

      final Iterator<Block> blkIterator = blockManager.getCorruptReplicaBlockIterator();

      if (cookieTab == null) {
        cookieTab = new String[] { null };
      }
      int skip = getIntCookie(cookieTab[0]);
      for (int i = 0; i < skip && blkIterator.hasNext(); i++) {
        blkIterator.next();
      }

      while (blkIterator.hasNext()) {
        Block blk = blkIterator.next();
        final INode inode = (INode)blockManager.getBlockCollection(blk);
        skip++;
        if (inode != null && blockManager.countNodes(blk).liveReplicas() == 0) {
          String src = FSDirectory.getFullPathName(inode);
          if (src.startsWith(path)){
            corruptFiles.add(new CorruptFileBlockInfo(src, blk));
            count++;
            if (count >= DEFAULT_MAX_CORRUPT_FILEBLOCKS_RETURNED)
              break;
          }
        }
      }
      cookieTab[0] = String.valueOf(skip);
      LOG.info("list corrupt file blocks returned: " + count);
      return corruptFiles;
    } finally {
      readUnlock();
    }
  }

  /**
   * Convert string cookie to integer.
   */
  private static int getIntCookie(String cookie){
    int c;
    if(cookie == null){
      c = 0;
    } else {
      try{
        c = Integer.parseInt(cookie);
      }catch (NumberFormatException e) {
        c = 0;
      }
    }
    c = Math.max(0, c);
    return c;
  }

  /**
   * Create delegation token secret manager
   */
  private DelegationTokenSecretManager createDelegationTokenSecretManager(
      Configuration conf) {
    return new DelegationTokenSecretManager(conf.getLong(
        DFS_NAMENODE_DELEGATION_KEY_UPDATE_INTERVAL_KEY,
        DFS_NAMENODE_DELEGATION_KEY_UPDATE_INTERVAL_DEFAULT),
        conf.getLong(DFS_NAMENODE_DELEGATION_TOKEN_MAX_LIFETIME_KEY,
            DFS_NAMENODE_DELEGATION_TOKEN_MAX_LIFETIME_DEFAULT),
        conf.getLong(DFS_NAMENODE_DELEGATION_TOKEN_RENEW_INTERVAL_KEY,
            DFS_NAMENODE_DELEGATION_TOKEN_RENEW_INTERVAL_DEFAULT),
        DELEGATION_TOKEN_REMOVER_SCAN_INTERVAL,
        conf.getBoolean(DFS_NAMENODE_AUDIT_LOG_TOKEN_TRACKING_ID_KEY,
            DFS_NAMENODE_AUDIT_LOG_TOKEN_TRACKING_ID_DEFAULT),
        this);
  }

  /**
   * Returns the DelegationTokenSecretManager instance in the namesystem.
   * @return delegation token secret manager object
   */
  DelegationTokenSecretManager getDelegationTokenSecretManager() {
    return dtSecretManager;
  }

  /**
   * @param renewer
   * @return Token<DelegationTokenIdentifier>
   * @throws IOException
   */
  Token<DelegationTokenIdentifier> getDelegationToken(Text renewer)
      throws IOException {
    Token<DelegationTokenIdentifier> token;
    checkOperation(OperationCategory.WRITE);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot issue delegation token");
      if (!isAllowedDelegationTokenOp()) {
        throw new IOException(
          "Delegation Token can be issued only with kerberos or web authentication");
      }
      if (dtSecretManager == null || !dtSecretManager.isRunning()) {
        LOG.warn("trying to get DT with no secret manager running");
        return null;
      }

      UserGroupInformation ugi = getRemoteUser();
      String user = ugi.getUserName();
      Text owner = new Text(user);
      Text realUser = null;
      if (ugi.getRealUser() != null) {
        realUser = new Text(ugi.getRealUser().getUserName());
      }
      DelegationTokenIdentifier dtId = new DelegationTokenIdentifier(owner,
        renewer, realUser);
      token = new Token<DelegationTokenIdentifier>(
        dtId, dtSecretManager);
      long expiryTime = dtSecretManager.getTokenExpiryTime(dtId);
      getEditLog().logGetDelegationToken(dtId, expiryTime);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    return token;
  }

  /**
   * 
   * @param token
   * @return New expiryTime of the token
   * @throws InvalidToken
   * @throws IOException
   */
  long renewDelegationToken(Token<DelegationTokenIdentifier> token)
      throws InvalidToken, IOException {
    long expiryTime;
    checkOperation(OperationCategory.WRITE);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);

      checkNameNodeSafeMode("Cannot renew delegation token");
      if (!isAllowedDelegationTokenOp()) {
        throw new IOException(
            "Delegation Token can be renewed only with kerberos or web authentication");
      }
      String renewer = getRemoteUser().getShortUserName();
      expiryTime = dtSecretManager.renewToken(token, renewer);
      DelegationTokenIdentifier id = new DelegationTokenIdentifier();
      ByteArrayInputStream buf = new ByteArrayInputStream(token.getIdentifier());
      DataInputStream in = new DataInputStream(buf);
      id.readFields(in);
      getEditLog().logRenewDelegationToken(id, expiryTime);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    return expiryTime;
  }

  /**
   * 
   * @param token
   * @throws IOException
   */
  void cancelDelegationToken(Token<DelegationTokenIdentifier> token)
      throws IOException {
    checkOperation(OperationCategory.WRITE);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);

      checkNameNodeSafeMode("Cannot cancel delegation token");
      String canceller = getRemoteUser().getUserName();
      DelegationTokenIdentifier id = dtSecretManager
        .cancelToken(token, canceller);
      getEditLog().logCancelDelegationToken(id);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
  }

  SecretManagerState saveSecretManagerState() {
    return dtSecretManager.saveSecretManagerState();
  }

  /**
   * @param in load the state of secret manager from input stream
   */
  void loadSecretManagerStateCompat(DataInput in) throws IOException {
    dtSecretManager.loadSecretManagerStateCompat(in);
  }

  void loadSecretManagerState(SecretManagerSection s,
      List<SecretManagerSection.DelegationKey> keys,
      List<SecretManagerSection.PersistToken> tokens) throws IOException {
    dtSecretManager.loadSecretManagerState(new SecretManagerState(s, keys, tokens));
  }

  /**
   * Log the updateMasterKey operation to edit logs
   * 
   * @param key new delegation key.
   */
  public void logUpdateMasterKey(DelegationKey key) {
    
    assert !isInSafeMode() :
      "this should never be called while in safemode, since we stop " +
      "the DT manager before entering safemode!";
    // No need to hold FSN lock since we don't access any internal
    // structures, and this is stopped before the FSN shuts itself
    // down, etc.
    getEditLog().logUpdateMasterKey(key);
    getEditLog().logSync();
  }
  
  /**
   * Log the cancellation of expired tokens to edit logs
   * 
   * @param id token identifier to cancel
   */
  public void logExpireDelegationToken(DelegationTokenIdentifier id) {
    assert !isInSafeMode() :
      "this should never be called while in safemode, since we stop " +
      "the DT manager before entering safemode!";
    // No need to hold FSN lock since we don't access any internal
    // structures, and this is stopped before the FSN shuts itself
    // down, etc.
    getEditLog().logCancelDelegationToken(id);
  }  
  
  private void logReassignLease(String leaseHolder, String src,
      String newHolder) {
    assert hasWriteLock();
    getEditLog().logReassignLease(leaseHolder, src, newHolder);
  }
  
  /**
   * 
   * @return true if delegation token operation is allowed
   */
  private boolean isAllowedDelegationTokenOp() throws IOException {
    AuthenticationMethod authMethod = getConnectionAuthenticationMethod();
    if (UserGroupInformation.isSecurityEnabled()
        && (authMethod != AuthenticationMethod.KERBEROS)
        && (authMethod != AuthenticationMethod.KERBEROS_SSL)
        && (authMethod != AuthenticationMethod.CERTIFICATE)) {
      return false;
    }
    return true;
  }
  
  /**
   * Returns authentication method used to establish the connection
   * @return AuthenticationMethod used to establish connection
   * @throws IOException
   */
  private AuthenticationMethod getConnectionAuthenticationMethod()
      throws IOException {
    UserGroupInformation ugi = getRemoteUser();
    AuthenticationMethod authMethod = ugi.getAuthenticationMethod();
    if (authMethod == AuthenticationMethod.PROXY) {
      authMethod = ugi.getRealUser().getAuthenticationMethod();
    }
    return authMethod;
  }
  
  /**
   * Client invoked methods are invoked over RPC and will be in 
   * RPC call context even if the client exits.
   */
  private boolean isExternalInvocation() {
    return Server.isRpcInvocation() || NamenodeWebHdfsMethods.isWebHdfsInvocation();
  }

  private static InetAddress getRemoteIp() {
    InetAddress ip = Server.getRemoteIp();
    if (ip != null) {
      return ip;
    }
    return NamenodeWebHdfsMethods.getRemoteIp();
  }
  
  // optimize ugi lookup for RPC operations to avoid a trip through
  // UGI.getCurrentUser which is synch'ed
  private static UserGroupInformation getRemoteUser() throws IOException {
    return NameNode.getRemoteUser();
  }
  
  /**
   * Log fsck event in the audit log 
   */
  void logFsckEvent(String src, InetAddress remoteAddress) throws IOException {
    if (isAuditEnabled()) {
      logAuditEvent(true, getRemoteUser(),
                    remoteAddress,
                    "fsck", src, null, null);
    }
  }
  /**
   * Register NameNodeMXBean
   */
  private void registerMXBean() {
    mxbeanName = MBeans.register("NameNode", "NameNodeInfo", this);
  }

  /**
   * Class representing Namenode information for JMX interfaces
   */
  @Override // NameNodeMXBean
  public String getVersion() {
    return VersionInfo.getVersion() + ", r" + VersionInfo.getRevision();
  }

  @Override // NameNodeMXBean
  public long getUsed() {
    return this.getCapacityUsed();
  }

  @Override // NameNodeMXBean
  public long getFree() {
    return this.getCapacityRemaining();
  }

  @Override // NameNodeMXBean
  public long getTotal() {
    return this.getCapacityTotal();
  }

  @Override // NameNodeMXBean
  public String getSafemode() {
    if (!this.isInSafeMode())
      return "";
    return "Safe mode is ON. " + this.getSafeModeTip();
  }

  @Override // NameNodeMXBean
  public boolean isUpgradeFinalized() {
    return this.getFSImage().isUpgradeFinalized();
  }

  @Override // NameNodeMXBean
  public long getNonDfsUsedSpace() {
    return datanodeStatistics.getCapacityUsedNonDFS();
  }

  @Override // NameNodeMXBean
  public float getPercentUsed() {
    return datanodeStatistics.getCapacityUsedPercent();
  }

  @Override // NameNodeMXBean
  public long getBlockPoolUsedSpace() {
    return datanodeStatistics.getBlockPoolUsed();
  }

  @Override // NameNodeMXBean
  public float getPercentBlockPoolUsed() {
    return datanodeStatistics.getPercentBlockPoolUsed();
  }

  @Override // NameNodeMXBean
  public float getPercentRemaining() {
    return datanodeStatistics.getCapacityRemainingPercent();
  }

  @Override // NameNodeMXBean
  public long getCacheCapacity() {
    return datanodeStatistics.getCacheCapacity();
  }

  @Override // NameNodeMXBean
  public long getCacheUsed() {
    return datanodeStatistics.getCacheUsed();
  }

  @Override // NameNodeMXBean
  public long getTotalBlocks() {
    return getBlocksTotal();
  }

  @Override // NameNodeMXBean
  @Metric
  public long getTotalFiles() {
    return getFilesTotal();
  }

  @Override // NameNodeMXBean
  public long getNumberOfMissingBlocks() {
    return getMissingBlocksCount();
  }
  
  @Override // NameNodeMXBean
  public int getThreads() {
    return ManagementFactory.getThreadMXBean().getThreadCount();
  }

  /**
   * Returned information is a JSON representation of map with host name as the
   * key and value is a map of live node attribute keys to its values
   */
  @Override // NameNodeMXBean
  public String getLiveNodes() {
    final Map<String, Map<String,Object>> info = 
      new HashMap<String, Map<String,Object>>();
    final List<DatanodeDescriptor> live = new ArrayList<DatanodeDescriptor>();
    blockManager.getDatanodeManager().fetchDatanodes(live, null, true);
    for (DatanodeDescriptor node : live) {
      Map<String, Object> innerinfo = ImmutableMap.<String, Object>builder()
          .put("infoAddr", node.getInfoAddr())
          .put("infoSecureAddr", node.getInfoSecureAddr())
          .put("xferaddr", node.getXferAddr())
          .put("lastContact", getLastContact(node))
          .put("usedSpace", getDfsUsed(node))
          .put("adminState", node.getAdminState().toString())
          .put("nonDfsUsedSpace", node.getNonDfsUsed())
          .put("capacity", node.getCapacity())
          .put("numBlocks", node.numBlocks())
          .put("version", node.getSoftwareVersion())
          .put("used", node.getDfsUsed())
          .put("remaining", node.getRemaining())
          .put("blockScheduled", node.getBlocksScheduled())
          .put("blockPoolUsed", node.getBlockPoolUsed())
          .put("blockPoolUsedPercent", node.getBlockPoolUsedPercent())
          .put("volfails", node.getVolumeFailures())
          .build();

      info.put(node.getHostName(), innerinfo);
    }
    return JSON.toString(info);
  }

  /**
   * Returned information is a JSON representation of map with host name as the
   * key and value is a map of dead node attribute keys to its values
   */
  @Override // NameNodeMXBean
  public String getDeadNodes() {
    final Map<String, Map<String, Object>> info = 
      new HashMap<String, Map<String, Object>>();
    final List<DatanodeDescriptor> dead = new ArrayList<DatanodeDescriptor>();
    blockManager.getDatanodeManager().fetchDatanodes(null, dead, true);
    for (DatanodeDescriptor node : dead) {
      Map<String, Object> innerinfo = ImmutableMap.<String, Object>builder()
          .put("lastContact", getLastContact(node))
          .put("decommissioned", node.isDecommissioned())
          .put("xferaddr", node.getXferAddr())
          .build();
      info.put(node.getHostName(), innerinfo);
    }
    return JSON.toString(info);
  }

  /**
   * Returned information is a JSON representation of map with host name as the
   * key and value is a map of decomisioning node attribute keys to its values
   */
  @Override // NameNodeMXBean
  public String getDecomNodes() {
    final Map<String, Map<String, Object>> info = 
      new HashMap<String, Map<String, Object>>();
    final List<DatanodeDescriptor> decomNodeList = blockManager.getDatanodeManager(
        ).getDecommissioningNodes();
    for (DatanodeDescriptor node : decomNodeList) {
      Map<String, Object> innerinfo = ImmutableMap
          .<String, Object> builder()
          .put("xferaddr", node.getXferAddr())
          .put("underReplicatedBlocks",
              node.decommissioningStatus.getUnderReplicatedBlocks())
          .put("decommissionOnlyReplicas",
              node.decommissioningStatus.getDecommissionOnlyReplicas())
          .put("underReplicateInOpenFiles",
              node.decommissioningStatus.getUnderReplicatedInOpenFiles())
          .build();
      info.put(node.getHostName(), innerinfo);
    }
    return JSON.toString(info);
  }

  private long getLastContact(DatanodeDescriptor alivenode) {
    return (Time.now() - alivenode.getLastUpdate())/1000;
  }

  private long getDfsUsed(DatanodeDescriptor alivenode) {
    return alivenode.getDfsUsed();
  }

  @Override  // NameNodeMXBean
  public String getClusterId() {
    return dir.fsImage.getStorage().getClusterID();
  }
  
  @Override  // NameNodeMXBean
  public String getBlockPoolId() {
    return blockPoolId;
  }
  
  @Override  // NameNodeMXBean
  public String getNameDirStatuses() {
    Map<String, Map<File, StorageDirType>> statusMap =
      new HashMap<String, Map<File, StorageDirType>>();
    
    Map<File, StorageDirType> activeDirs = new HashMap<File, StorageDirType>();
    for (Iterator<StorageDirectory> it
        = getFSImage().getStorage().dirIterator(); it.hasNext();) {
      StorageDirectory st = it.next();
      activeDirs.put(st.getRoot(), st.getStorageDirType());
    }
    statusMap.put("active", activeDirs);
    
    List<Storage.StorageDirectory> removedStorageDirs
        = getFSImage().getStorage().getRemovedStorageDirs();
    Map<File, StorageDirType> failedDirs = new HashMap<File, StorageDirType>();
    for (StorageDirectory st : removedStorageDirs) {
      failedDirs.put(st.getRoot(), st.getStorageDirType());
    }
    statusMap.put("failed", failedDirs);
    
    return JSON.toString(statusMap);
  }

  @Override // NameNodeMXBean
  public String getNodeUsage() {
    float median = 0;
    float max = 0;
    float min = 0;
    float dev = 0;

    final Map<String, Map<String,Object>> info =
        new HashMap<String, Map<String,Object>>();
    final List<DatanodeDescriptor> live = new ArrayList<DatanodeDescriptor>();
    blockManager.getDatanodeManager().fetchDatanodes(live, null, true);

    if (live.size() > 0) {
      float totalDfsUsed = 0;
      float[] usages = new float[live.size()];
      int i = 0;
      for (DatanodeDescriptor dn : live) {
        usages[i++] = dn.getDfsUsedPercent();
        totalDfsUsed += dn.getDfsUsedPercent();
      }
      totalDfsUsed /= live.size();
      Arrays.sort(usages);
      median = usages[usages.length / 2];
      max = usages[usages.length - 1];
      min = usages[0];

      for (i = 0; i < usages.length; i++) {
        dev += (usages[i] - totalDfsUsed) * (usages[i] - totalDfsUsed);
      }
      dev = (float) Math.sqrt(dev / usages.length);
    }

    final Map<String, Object> innerInfo = new HashMap<String, Object>();
    innerInfo.put("min", StringUtils.format("%.2f%%", min));
    innerInfo.put("median", StringUtils.format("%.2f%%", median));
    innerInfo.put("max", StringUtils.format("%.2f%%", max));
    innerInfo.put("stdDev", StringUtils.format("%.2f%%", dev));
    info.put("nodeUsage", innerInfo);

    return JSON.toString(info);
  }

  @Override  // NameNodeMXBean
  public String getNameJournalStatus() {
    List<Map<String, String>> jasList = new ArrayList<Map<String, String>>();
    FSEditLog log = getFSImage().getEditLog();
    if (log != null) {
      boolean openForWrite = log.isOpenForWrite();
      for (JournalAndStream jas : log.getJournals()) {
        final Map<String, String> jasMap = new HashMap<String, String>();
        String manager = jas.getManager().toString();

        jasMap.put("required", String.valueOf(jas.isRequired()));
        jasMap.put("disabled", String.valueOf(jas.isDisabled()));
        jasMap.put("manager", manager);

        if (jas.isDisabled()) {
          jasMap.put("stream", "Failed");
        } else if (openForWrite) {
          EditLogOutputStream elos = jas.getCurrentStream();
          if (elos != null) {
            jasMap.put("stream", elos.generateReport());
          } else {
            jasMap.put("stream", "not currently writing");
          }
        } else {
          jasMap.put("stream", "open for read");
        }
        jasList.add(jasMap);
      }
    }
    return JSON.toString(jasList);
  }

  @Override // NameNodeMxBean
  public String getJournalTransactionInfo() {
    Map<String, String> txnIdMap = new HashMap<String, String>();
    txnIdMap.put("LastAppliedOrWrittenTxId",
        Long.toString(this.getFSImage().getLastAppliedOrWrittenTxId()));
    txnIdMap.put("MostRecentCheckpointTxId",
        Long.toString(this.getFSImage().getMostRecentCheckpointTxId()));
    return JSON.toString(txnIdMap);
  }
  
  @Override  // NameNodeMXBean
  public String getNNStarted() {
    return getStartTime().toString();
  }

  @Override  // NameNodeMXBean
  public String getCompileInfo() {
    return VersionInfo.getDate() + " by " + VersionInfo.getUser() +
        " from " + VersionInfo.getBranch();
  }

  /** @return the block manager. */
  public BlockManager getBlockManager() {
    return blockManager;
  }
  /** @return the FSDirectory. */
  public FSDirectory getFSDirectory() {
    return dir;
  }
  /** @return the cache manager. */
  public CacheManager getCacheManager() {
    return cacheManager;
  }

  @Override  // NameNodeMXBean
  public String getCorruptFiles() {
    List<String> list = new ArrayList<String>();
    Collection<FSNamesystem.CorruptFileBlockInfo> corruptFileBlocks;
    try {
      corruptFileBlocks = listCorruptFileBlocks("/", null);
      int corruptFileCount = corruptFileBlocks.size();
      if (corruptFileCount != 0) {
        for (FSNamesystem.CorruptFileBlockInfo c : corruptFileBlocks) {
          list.add(c.toString());
        }
      }
    } catch (IOException e) {
      LOG.warn("Get corrupt file blocks returned error: " + e.getMessage());
    }
    return JSON.toString(list);
  }

  @Override  //NameNodeMXBean
  public int getDistinctVersionCount() {
    return blockManager.getDatanodeManager().getDatanodesSoftwareVersions()
      .size();
  }

  @Override  //NameNodeMXBean
  public Map<String, Integer> getDistinctVersions() {
    return blockManager.getDatanodeManager().getDatanodesSoftwareVersions();
  }

  @Override  //NameNodeMXBean
  public String getSoftwareVersion() {
    return VersionInfo.getVersion();
  }

  /**
   * Verifies that the given identifier and password are valid and match.
   * @param identifier Token identifier.
   * @param password Password in the token.
   */
  public synchronized void verifyToken(DelegationTokenIdentifier identifier,
      byte[] password) throws InvalidToken, RetriableException {
    try {
      getDelegationTokenSecretManager().verifyToken(identifier, password);
    } catch (InvalidToken it) {
      if (inTransitionToActive()) {
        throw new RetriableException(it);
      }
      throw it;
    }
  }
  
  @Override
  public boolean isGenStampInFuture(Block block) {
    if (isLegacyBlock(block)) {
      return block.getGenerationStamp() > getGenerationStampV1();
    } else {
      return block.getGenerationStamp() > getGenerationStampV2();
    }
  }

  @VisibleForTesting
  public EditLogTailer getEditLogTailer() {
    return editLogTailer;
  }
  
  @VisibleForTesting
  public void setEditLogTailerForTests(EditLogTailer tailer) {
    this.editLogTailer = tailer;
  }
  
  @VisibleForTesting
  void setFsLockForTests(ReentrantReadWriteLock lock) {
    this.fsLock.coarseLock = lock;
  }
  
  @VisibleForTesting
  public ReentrantReadWriteLock getFsLockForTests() {
    return fsLock.coarseLock;
  }
  
  @VisibleForTesting
  public ReentrantLock getLongReadLockForTests() {
    return fsLock.longReadLock;
  }

  @VisibleForTesting
  public SafeModeInfo getSafeModeInfoForTests() {
    return safeMode;
  }
  
  @VisibleForTesting
  public void setNNResourceChecker(NameNodeResourceChecker nnResourceChecker) {
    this.nnResourceChecker = nnResourceChecker;
  }

  @Override
  public boolean isAvoidingStaleDataNodesForWrite() {
    return this.blockManager.getDatanodeManager()
        .shouldAvoidStaleDataNodesForWrite();
  }

  @Override // FSClusterStats
  public int getNumDatanodesInService() {
    return getNumLiveDataNodes() - getNumDecomLiveDataNodes();
  }

  public SnapshotManager getSnapshotManager() {
    return snapshotManager;
  }
  
  /** Allow snapshot on a directroy. */
  void allowSnapshot(String path) throws SafeModeException, IOException {
    checkOperation(OperationCategory.WRITE);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot allow snapshot for " + path);
      checkSuperuserPrivilege();

      dir.writeLock();
      try {
        snapshotManager.setSnapshottable(path, true);
      } finally {
        dir.writeUnlock();
      }
      getEditLog().logAllowSnapshot(path);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();

    if (auditLog.isInfoEnabled() && isExternalInvocation()) {
      logAuditEvent(true, "allowSnapshot", path, null, null);
    }
  }
  
  /** Disallow snapshot on a directory. */
  void disallowSnapshot(String path) throws SafeModeException, IOException {
    checkOperation(OperationCategory.WRITE);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot disallow snapshot for " + path);
      checkSuperuserPrivilege();

      dir.writeLock();
      try {
        snapshotManager.resetSnapshottable(path);
      } finally {
        dir.writeUnlock();
      }
      getEditLog().logDisallowSnapshot(path);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    
    if (auditLog.isInfoEnabled() && isExternalInvocation()) {
      logAuditEvent(true, "disallowSnapshot", path, null, null);
    }
  }
  
  /**
   * Create a snapshot
   * @param snapshotRoot The directory path where the snapshot is taken
   * @param snapshotName The name of the snapshot
   */
  String createSnapshot(String snapshotRoot, String snapshotName)
      throws SafeModeException, IOException {
    checkOperation(OperationCategory.WRITE);
    final FSPermissionChecker pc = getPermissionChecker();
    CacheEntryWithPayload cacheEntry = RetryCache.waitForCompletion(retryCache,
        null);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return (String) cacheEntry.getPayload();
    }
    String snapshotPath = null;
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot create snapshot for " + snapshotRoot);
      if (isPermissionEnabled) {
        checkOwner(pc, snapshotRoot);
      }

      if (snapshotName == null || snapshotName.isEmpty()) {
        snapshotName = Snapshot.generateDefaultSnapshotName();
      }
      if(snapshotName != null){
        if (!DFSUtil.isValidNameForComponent(snapshotName)) {
            throw new InvalidPathException("Invalid snapshot name: "
                + snapshotName);
        }
      }
      dir.verifySnapshotName(snapshotName, snapshotRoot);
      dir.writeLock();
      try {
        snapshotPath = snapshotManager.createSnapshot(snapshotRoot, snapshotName);
      } finally {
        dir.writeUnlock();
      }
      getEditLog().logCreateSnapshot(snapshotRoot, snapshotName,
          cacheEntry != null);
    } finally {
      writeUnlock();
      RetryCache.setState(cacheEntry, snapshotPath != null, snapshotPath);
    }
    getEditLog().logSync();
    
    if (auditLog.isInfoEnabled() && isExternalInvocation()) {
      logAuditEvent(true, "createSnapshot", snapshotRoot, snapshotPath, null);
    }
    return snapshotPath;
  }
  
  /**
   * Rename a snapshot
   * @param path The directory path where the snapshot was taken
   * @param snapshotOldName Old snapshot name
   * @param snapshotNewName New snapshot name
   * @throws SafeModeException
   * @throws IOException 
   */
  void renameSnapshot(String path, String snapshotOldName,
      String snapshotNewName) throws SafeModeException, IOException {
    checkOperation(OperationCategory.WRITE);
    final FSPermissionChecker pc = getPermissionChecker();
    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return; // Return previous response
    }
    writeLock();
    boolean success = false;
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot rename snapshot for " + path);
      if (isPermissionEnabled) {
        checkOwner(pc, path);
      }
      dir.verifySnapshotName(snapshotNewName, path);
      
      snapshotManager.renameSnapshot(path, snapshotOldName, snapshotNewName);
      getEditLog().logRenameSnapshot(path, snapshotOldName, snapshotNewName,
          cacheEntry != null);
      success = true;
    } finally {
      writeUnlock();
      RetryCache.setState(cacheEntry, success);
    }
    getEditLog().logSync();
    
    if (auditLog.isInfoEnabled() && isExternalInvocation()) {
      String oldSnapshotRoot = Snapshot.getSnapshotPath(path, snapshotOldName);
      String newSnapshotRoot = Snapshot.getSnapshotPath(path, snapshotNewName);
      logAuditEvent(true, "renameSnapshot", oldSnapshotRoot, newSnapshotRoot, null);
    }
  }
  
  /**
   * Get the list of snapshottable directories that are owned 
   * by the current user. Return all the snapshottable directories if the 
   * current user is a super user.
   * @return The list of all the current snapshottable directories
   * @throws IOException
   */
  public SnapshottableDirectoryStatus[] getSnapshottableDirListing()
      throws IOException {
    SnapshottableDirectoryStatus[] status = null;
    checkOperation(OperationCategory.READ);
    final FSPermissionChecker checker = getPermissionChecker();
    readLock();
    try {
      checkOperation(OperationCategory.READ);
      final String user = checker.isSuperUser()? null : checker.getUser();
      status = snapshotManager.getSnapshottableDirListing(user);
    } finally {
      readUnlock();
    }
    if (auditLog.isInfoEnabled() && isExternalInvocation()) {
      logAuditEvent(true, "listSnapshottableDirectory", null, null, null);
    }
    return status;
  }
  
  /**
   * Get the difference between two snapshots (or between a snapshot and the
   * current status) of a snapshottable directory.
   * 
   * @param path The full path of the snapshottable directory.
   * @param fromSnapshot Name of the snapshot to calculate the diff from. Null
   *          or empty string indicates the current tree.
   * @param toSnapshot Name of the snapshot to calculated the diff to. Null or
   *          empty string indicates the current tree.
   * @return A report about the difference between {@code fromSnapshot} and 
   *         {@code toSnapshot}. Modified/deleted/created/renamed files and 
   *         directories belonging to the snapshottable directories are listed 
   *         and labeled as M/-/+/R respectively. 
   * @throws IOException
   */
  SnapshotDiffReport getSnapshotDiffReport(String path,
      String fromSnapshot, String toSnapshot) throws IOException {
    SnapshotDiffInfo diffs = null;
    checkOperation(OperationCategory.READ);
    final FSPermissionChecker pc = getPermissionChecker();
    readLock();
    try {
      checkOperation(OperationCategory.READ);
      if (isPermissionEnabled) {
        checkSubtreeReadPermission(pc, path, fromSnapshot);
        checkSubtreeReadPermission(pc, path, toSnapshot);
      }
      diffs = snapshotManager.diff(path, fromSnapshot, toSnapshot);
    } finally {
      readUnlock();
    }
    
    if (auditLog.isInfoEnabled() && isExternalInvocation()) {
      logAuditEvent(true, "computeSnapshotDiff", null, null, null);
    }
    return diffs != null ? diffs.generateReport() : new SnapshotDiffReport(
        path, fromSnapshot, toSnapshot,
        Collections.<DiffReportEntry> emptyList());
  }
  
  private void checkSubtreeReadPermission(final FSPermissionChecker pc,
      final String snapshottablePath, final String snapshot)
          throws AccessControlException, UnresolvedLinkException {
    final String fromPath = snapshot == null?
        snapshottablePath: Snapshot.getSnapshotPath(snapshottablePath, snapshot);
    checkPermission(pc, fromPath, false, null, null, FsAction.READ, FsAction.READ);
  }
  
  /**
   * Delete a snapshot of a snapshottable directory
   * @param snapshotRoot The snapshottable directory
   * @param snapshotName The name of the to-be-deleted snapshot
   * @throws SafeModeException
   * @throws IOException
   */
  void deleteSnapshot(String snapshotRoot, String snapshotName)
      throws SafeModeException, IOException {
    checkOperation(OperationCategory.WRITE);
    final FSPermissionChecker pc = getPermissionChecker();
    
    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return; // Return previous response
    }
    boolean success = false;
    BlocksMapUpdateInfo collectedBlocks = new BlocksMapUpdateInfo();
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot delete snapshot for " + snapshotRoot);
      if (isPermissionEnabled) {
        checkOwner(pc, snapshotRoot);
      }

      List<INode> removedINodes = new ChunkedArrayList<INode>();
      dir.writeLock();
      try {
        snapshotManager.deleteSnapshot(snapshotRoot, snapshotName,
            collectedBlocks, removedINodes);
        dir.removeFromInodeMap(removedINodes);
      } finally {
        dir.writeUnlock();
      }
      removedINodes.clear();
      getEditLog().logDeleteSnapshot(snapshotRoot, snapshotName,
          cacheEntry != null);
      success = true;
    } finally {
      writeUnlock();
      RetryCache.setState(cacheEntry, success);
    }
    getEditLog().logSync();

    removeBlocks(collectedBlocks);
    collectedBlocks.clear();

    if (auditLog.isInfoEnabled() && isExternalInvocation()) {
      String rootPath = Snapshot.getSnapshotPath(snapshotRoot, snapshotName);
      logAuditEvent(true, "deleteSnapshot", rootPath, null, null);
    }
  }

  /**
   * Remove a list of INodeDirectorySnapshottable from the SnapshotManager
   * @param toRemove the list of INodeDirectorySnapshottable to be removed
   */
  void removeSnapshottableDirs(List<INodeDirectorySnapshottable> toRemove) {
    if (snapshotManager != null) {
      snapshotManager.removeSnapshottable(toRemove);
    }
  }

  RollingUpgradeInfo queryRollingUpgrade() throws IOException {
    checkSuperuserPrivilege();
    checkOperation(OperationCategory.READ);
    readLock();
    try {
      if (rollingUpgradeInfo != null) {
        boolean hasRollbackImage = this.getFSImage().hasRollbackFSImage();
        rollingUpgradeInfo.setCreatedRollbackImages(hasRollbackImage);
      }
      return rollingUpgradeInfo;
    } finally {
      readUnlock();
    }
  }

  RollingUpgradeInfo startRollingUpgrade() throws IOException {
    checkSuperuserPrivilege();
    checkOperation(OperationCategory.WRITE);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      long startTime = now();
      if (!haEnabled) { // for non-HA, we require NN to be in safemode
        startRollingUpgradeInternalForNonHA(startTime);
      } else { // for HA, NN cannot be in safemode
        checkNameNodeSafeMode("Failed to start rolling upgrade");
        startRollingUpgradeInternal(startTime);
      }

      getEditLog().logStartRollingUpgrade(rollingUpgradeInfo.getStartTime());
      if (haEnabled) {
        // roll the edit log to make sure the standby NameNode can tail
        getFSImage().rollEditLog();
      }
    } finally {
      writeUnlock();
    }

    getEditLog().logSync();
    if (auditLog.isInfoEnabled() && isExternalInvocation()) {
      logAuditEvent(true, "startRollingUpgrade", null, null, null);
    }
    return rollingUpgradeInfo;
  }

  /**
   * Update internal state to indicate that a rolling upgrade is in progress.
   * @param startTime
   */
  void startRollingUpgradeInternal(long startTime)
      throws IOException {
    checkRollingUpgrade("start rolling upgrade");
    getFSImage().checkUpgrade(this);
    setRollingUpgradeInfo(false, startTime);
  }

  /**
   * Update internal state to indicate that a rolling upgrade is in progress for
   * non-HA setup. This requires the namesystem is in SafeMode and after doing a
   * checkpoint for rollback the namesystem will quit the safemode automatically 
   */
  private void startRollingUpgradeInternalForNonHA(long startTime)
      throws IOException {
    Preconditions.checkState(!haEnabled);
    if (!isInSafeMode()) {
      throw new IOException("Safe mode should be turned ON "
          + "in order to create namespace image.");
    }
    checkRollingUpgrade("start rolling upgrade");
    getFSImage().checkUpgrade(this);
    // in non-HA setup, we do an extra ckpt to generate a rollback image
    getFSImage().saveNamespace(this, NameNodeFile.IMAGE_ROLLBACK, null);
    LOG.info("Successfully saved namespace for preparing rolling upgrade.");

    // leave SafeMode automatically
    setSafeMode(SafeModeAction.SAFEMODE_LEAVE);
    setRollingUpgradeInfo(true, startTime);
  }

  void setRollingUpgradeInfo(boolean createdRollbackImages, long startTime) {
    rollingUpgradeInfo = new RollingUpgradeInfo(blockPoolId,
        createdRollbackImages, startTime, 0L);
  }

  public void setCreatedRollbackImages(boolean created) {
    if (rollingUpgradeInfo != null) {
      rollingUpgradeInfo.setCreatedRollbackImages(created);
    }
  }

  public RollingUpgradeInfo getRollingUpgradeInfo() {
    return rollingUpgradeInfo;
  }

  public boolean isNeedRollbackFsImage() {
    return needRollbackFsImage;
  }

  public void setNeedRollbackFsImage(boolean needRollbackFsImage) {
    this.needRollbackFsImage = needRollbackFsImage;
  }

  @Override  // NameNodeMXBean
  public RollingUpgradeInfo.Bean getRollingUpgradeStatus() {
    readLock();
    try {
      RollingUpgradeInfo upgradeInfo = getRollingUpgradeInfo();
      if (upgradeInfo != null) {
        return new RollingUpgradeInfo.Bean(upgradeInfo);
      }
      return null;
    } finally {
      readUnlock();
    }
  }

  /** Is rolling upgrade in progress? */
  public boolean isRollingUpgrade() {
    return rollingUpgradeInfo != null;
  }

  void checkRollingUpgrade(String action) throws RollingUpgradeException {
    if (isRollingUpgrade()) {
      throw new RollingUpgradeException("Failed to " + action
          + " since a rolling upgrade is already in progress."
          + " Existing rolling upgrade info:\n" + rollingUpgradeInfo);
    }
  }

  RollingUpgradeInfo finalizeRollingUpgrade() throws IOException {
    checkSuperuserPrivilege();
    checkOperation(OperationCategory.WRITE);
    writeLock();
    final RollingUpgradeInfo returnInfo;
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Failed to finalize rolling upgrade");

      returnInfo = finalizeRollingUpgradeInternal(now());
      getEditLog().logFinalizeRollingUpgrade(returnInfo.getFinalizeTime());
      getFSImage().saveNamespace(this);
      getFSImage().renameCheckpoint(NameNodeFile.IMAGE_ROLLBACK,
          NameNodeFile.IMAGE);
    } finally {
      writeUnlock();
    }

    // getEditLog().logSync() is not needed since it does saveNamespace 

    if (auditLog.isInfoEnabled() && isExternalInvocation()) {
      logAuditEvent(true, "finalizeRollingUpgrade", null, null, null);
    }
    return returnInfo;
  }

  RollingUpgradeInfo finalizeRollingUpgradeInternal(long finalizeTime)
      throws RollingUpgradeException {
    if (!isRollingUpgrade()) {
      throw new RollingUpgradeException(
          "Failed to finalize rolling upgrade since there is no rolling upgrade in progress.");
    }

    final long startTime = rollingUpgradeInfo.getStartTime();
    rollingUpgradeInfo = null;
    return new RollingUpgradeInfo(blockPoolId, false, startTime, finalizeTime);
  }

  long addCacheDirective(CacheDirectiveInfo directive, EnumSet<CacheFlag> flags)
      throws IOException {
    checkOperation(OperationCategory.WRITE);
    final FSPermissionChecker pc = isPermissionEnabled ?
        getPermissionChecker() : null;
    CacheEntryWithPayload cacheEntry =
        RetryCache.waitForCompletion(retryCache, null);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return (Long) cacheEntry.getPayload();
    }
    boolean success = false;
    if (!flags.contains(CacheFlag.FORCE)) {
      cacheManager.waitForRescanIfNeeded();
    }
    writeLock();
    Long result = null;
    try {
      checkOperation(OperationCategory.WRITE);
      if (isInSafeMode()) {
        throw new SafeModeException(
            "Cannot add cache directive", safeMode);
      }
      if (directive.getId() != null) {
        throw new IOException("addDirective: you cannot specify an ID " +
            "for this operation.");
      }
      CacheDirectiveInfo effectiveDirective = 
          cacheManager.addDirective(directive, pc, flags);
      getEditLog().logAddCacheDirectiveInfo(effectiveDirective,
          cacheEntry != null);
      result = effectiveDirective.getId();
      success = true;
    } finally {
      writeUnlock();
      if (success) {
        getEditLog().logSync();
      }
      if (isAuditEnabled() && isExternalInvocation()) {
        logAuditEvent(success, "addCacheDirective", null, null, null);
      }
      RetryCache.setState(cacheEntry, success, result);
    }
    return result;
  }

  void modifyCacheDirective(CacheDirectiveInfo directive,
      EnumSet<CacheFlag> flags) throws IOException {
    checkOperation(OperationCategory.WRITE);
    final FSPermissionChecker pc = isPermissionEnabled ?
        getPermissionChecker() : null;
    boolean success = false;
    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return;
    }
    if (!flags.contains(CacheFlag.FORCE)) {
      cacheManager.waitForRescanIfNeeded();
    }
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      if (isInSafeMode()) {
        throw new SafeModeException(
            "Cannot add cache directive", safeMode);
      }
      cacheManager.modifyDirective(directive, pc, flags);
      getEditLog().logModifyCacheDirectiveInfo(directive,
          cacheEntry != null);
      success = true;
    } finally {
      writeUnlock();
      if (success) {
        getEditLog().logSync();
      }
      if (isAuditEnabled() && isExternalInvocation()) {
        logAuditEvent(success, "modifyCacheDirective", null, null, null);
      }
      RetryCache.setState(cacheEntry, success);
    }
  }

  void removeCacheDirective(Long id) throws IOException {
    checkOperation(OperationCategory.WRITE);
    final FSPermissionChecker pc = isPermissionEnabled ?
        getPermissionChecker() : null;
    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return;
    }
    boolean success = false;
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      if (isInSafeMode()) {
        throw new SafeModeException(
            "Cannot remove cache directives", safeMode);
      }
      cacheManager.removeDirective(id, pc);
      getEditLog().logRemoveCacheDirectiveInfo(id, cacheEntry != null);
      success = true;
    } finally {
      writeUnlock();
      if (isAuditEnabled() && isExternalInvocation()) {
        logAuditEvent(success, "removeCacheDirective", null, null,
            null);
      }
      RetryCache.setState(cacheEntry, success);
    }
    getEditLog().logSync();
  }

  BatchedListEntries<CacheDirectiveEntry> listCacheDirectives(
      long startId, CacheDirectiveInfo filter) throws IOException {
    checkOperation(OperationCategory.READ);
    final FSPermissionChecker pc = isPermissionEnabled ?
        getPermissionChecker() : null;
    BatchedListEntries<CacheDirectiveEntry> results;
    cacheManager.waitForRescanIfNeeded();
    readLock();
    boolean success = false;
    try {
      checkOperation(OperationCategory.READ);
      results =
          cacheManager.listCacheDirectives(startId, filter, pc);
      success = true;
    } finally {
      readUnlock();
      if (isAuditEnabled() && isExternalInvocation()) {
        logAuditEvent(success, "listCacheDirectives", null, null,
            null);
      }
    }
    return results;
  }

  public void addCachePool(CachePoolInfo req) throws IOException {
    checkOperation(OperationCategory.WRITE);
    final FSPermissionChecker pc = isPermissionEnabled ?
        getPermissionChecker() : null;
    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return; // Return previous response
    }
    writeLock();
    boolean success = false;
    try {
      checkOperation(OperationCategory.WRITE);
      if (isInSafeMode()) {
        throw new SafeModeException(
            "Cannot add cache pool " + req.getPoolName(), safeMode);
      }
      if (pc != null) {
        pc.checkSuperuserPrivilege();
      }
      CachePoolInfo info = cacheManager.addCachePool(req);
      getEditLog().logAddCachePool(info, cacheEntry != null);
      success = true;
    } finally {
      writeUnlock();
      if (isAuditEnabled() && isExternalInvocation()) {
        logAuditEvent(success, "addCachePool", req.getPoolName(), null, null);
      }
      RetryCache.setState(cacheEntry, success);
    }
    
    getEditLog().logSync();
  }

  public void modifyCachePool(CachePoolInfo req) throws IOException {
    checkOperation(OperationCategory.WRITE);
    final FSPermissionChecker pc =
        isPermissionEnabled ? getPermissionChecker() : null;
    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return; // Return previous response
    }
    writeLock();
    boolean success = false;
    try {
      checkOperation(OperationCategory.WRITE);
      if (isInSafeMode()) {
        throw new SafeModeException(
            "Cannot modify cache pool " + req.getPoolName(), safeMode);
      }
      if (pc != null) {
        pc.checkSuperuserPrivilege();
      }
      cacheManager.modifyCachePool(req);
      getEditLog().logModifyCachePool(req, cacheEntry != null);
      success = true;
    } finally {
      writeUnlock();
      if (isAuditEnabled() && isExternalInvocation()) {
        logAuditEvent(success, "modifyCachePool", req.getPoolName(), null, null);
      }
      RetryCache.setState(cacheEntry, success);
    }

    getEditLog().logSync();
  }

  public void removeCachePool(String cachePoolName) throws IOException {
    checkOperation(OperationCategory.WRITE);
    final FSPermissionChecker pc =
        isPermissionEnabled ? getPermissionChecker() : null;
    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
    if (cacheEntry != null && cacheEntry.isSuccess()) {
      return; // Return previous response
    }
    writeLock();
    boolean success = false;
    try {
      checkOperation(OperationCategory.WRITE);
      if (isInSafeMode()) {
        throw new SafeModeException(
            "Cannot remove cache pool " + cachePoolName, safeMode);
      }
      if (pc != null) {
        pc.checkSuperuserPrivilege();
      }
      cacheManager.removeCachePool(cachePoolName);
      getEditLog().logRemoveCachePool(cachePoolName, cacheEntry != null);
      success = true;
    } finally {
      writeUnlock();
      if (isAuditEnabled() && isExternalInvocation()) {
        logAuditEvent(success, "removeCachePool", cachePoolName, null, null);
      }
      RetryCache.setState(cacheEntry, success);
    }
    
    getEditLog().logSync();
  }

  public BatchedListEntries<CachePoolEntry> listCachePools(String prevKey)
      throws IOException {
    final FSPermissionChecker pc =
        isPermissionEnabled ? getPermissionChecker() : null;
    BatchedListEntries<CachePoolEntry> results;
    checkOperation(OperationCategory.READ);
    boolean success = false;
    cacheManager.waitForRescanIfNeeded();
    readLock();
    try {
      checkOperation(OperationCategory.READ);
      results = cacheManager.listCachePools(pc, prevKey);
      success = true;
    } finally {
      readUnlock();
      if (isAuditEnabled() && isExternalInvocation()) {
        logAuditEvent(success, "listCachePools", null, null, null);
      }
    }
    return results;
  }

  void modifyAclEntries(String src, List<AclEntry> aclSpec) throws IOException {
    aclConfigFlag.checkForApiCall();
    HdfsFileStatus resultingStat = null;
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot modify ACL entries on " + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      checkOwner(pc, src);
      dir.modifyAclEntries(src, aclSpec);
      resultingStat = getAuditFileInfo(src, false);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    logAuditEvent(true, "modifyAclEntries", src, null, resultingStat);
  }

  void removeAclEntries(String src, List<AclEntry> aclSpec) throws IOException {
    aclConfigFlag.checkForApiCall();
    HdfsFileStatus resultingStat = null;
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot remove ACL entries on " + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      checkOwner(pc, src);
      dir.removeAclEntries(src, aclSpec);
      resultingStat = getAuditFileInfo(src, false);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    logAuditEvent(true, "removeAclEntries", src, null, resultingStat);
  }

  void removeDefaultAcl(String src) throws IOException {
    aclConfigFlag.checkForApiCall();
    HdfsFileStatus resultingStat = null;
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot remove default ACL entries on " + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      checkOwner(pc, src);
      dir.removeDefaultAcl(src);
      resultingStat = getAuditFileInfo(src, false);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    logAuditEvent(true, "removeDefaultAcl", src, null, resultingStat);
  }

  void removeAcl(String src) throws IOException {
    aclConfigFlag.checkForApiCall();
    HdfsFileStatus resultingStat = null;
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot remove ACL on " + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      checkOwner(pc, src);
      dir.removeAcl(src);
      resultingStat = getAuditFileInfo(src, false);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    logAuditEvent(true, "removeAcl", src, null, resultingStat);
  }

  void setAcl(String src, List<AclEntry> aclSpec) throws IOException {
    aclConfigFlag.checkForApiCall();
    HdfsFileStatus resultingStat = null;
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.WRITE);
    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
    writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot set ACL on " + src);
      src = FSDirectory.resolvePath(src, pathComponents, dir);
      checkOwner(pc, src);
      dir.setAcl(src, aclSpec);
      resultingStat = getAuditFileInfo(src, false);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    logAuditEvent(true, "setAcl", src, null, resultingStat);
  }

  AclStatus getAclStatus(String src) throws IOException {
    aclConfigFlag.checkForApiCall();
    FSPermissionChecker pc = getPermissionChecker();
    checkOperation(OperationCategory.READ);
    readLock();
    try {
      checkOperation(OperationCategory.READ);
      if (isPermissionEnabled) {
        checkPermission(pc, src, false, null, null, null, null);
      }
      return dir.getAclStatus(src);
    } finally {
      readUnlock();
    }
  }

  /**
   * Default AuditLogger implementation; used when no access logger is
   * defined in the config file. It can also be explicitly listed in the
   * config file.
   */
  private static class DefaultAuditLogger extends HdfsAuditLogger {

    private boolean logTokenTrackingId;

    @Override
    public void initialize(Configuration conf) {
      logTokenTrackingId = conf.getBoolean(
          DFSConfigKeys.DFS_NAMENODE_AUDIT_LOG_TOKEN_TRACKING_ID_KEY,
          DFSConfigKeys.DFS_NAMENODE_AUDIT_LOG_TOKEN_TRACKING_ID_DEFAULT);
    }

    @Override
    public void logAuditEvent(boolean succeeded, String userName,
        InetAddress addr, String cmd, String src, String dst,
        FileStatus status, UserGroupInformation ugi,
        DelegationTokenSecretManager dtSecretManager) {
      if (auditLog.isInfoEnabled()) {
        final StringBuilder sb = auditBuffer.get();
        sb.setLength(0);
        sb.append("allowed=").append(succeeded).append("\t");
        sb.append("ugi=").append(userName).append("\t");
        sb.append("ip=").append(addr).append("\t");
        sb.append("cmd=").append(cmd).append("\t");
        sb.append("src=").append(src).append("\t");
        sb.append("dst=").append(dst).append("\t");
        if (null == status) {
          sb.append("perm=null");
        } else {
          sb.append("perm=");
          sb.append(status.getOwner()).append(":");
          sb.append(status.getGroup()).append(":");
          sb.append(status.getPermission());
        }
        if (logTokenTrackingId) {
          sb.append("\t").append("trackingId=");
          String trackingId = null;
          if (ugi != null && dtSecretManager != null
              && ugi.getAuthenticationMethod() == AuthenticationMethod.TOKEN) {
            for (TokenIdentifier tid: ugi.getTokenIdentifiers()) {
              if (tid instanceof DelegationTokenIdentifier) {
                DelegationTokenIdentifier dtid =
                    (DelegationTokenIdentifier)tid;
                trackingId = dtSecretManager.getTokenTrackingId(dtid);
                break;
              }
            }
          }
          sb.append(trackingId);
        }
        logAuditMessage(sb.toString());
      }
    }

    public void logAuditMessage(String message) {
      auditLog.info(message);
    }
  }

  private static void enableAsyncAuditLog() {
    if (!(auditLog instanceof Log4JLogger)) {
      LOG.warn("Log4j is required to enable async auditlog");
      return;
    }
    Logger logger = ((Log4JLogger)auditLog).getLogger();
    @SuppressWarnings("unchecked")
    List<Appender> appenders = Collections.list(logger.getAllAppenders());
    // failsafe against trying to async it more than once
    if (!appenders.isEmpty() && !(appenders.get(0) instanceof AsyncAppender)) {
      AsyncAppender asyncAppender = new AsyncAppender();
      // change logger to have an async appender containing all the
      // previously configured appenders
      for (Appender appender : appenders) {
        logger.removeAppender(appender);
        asyncAppender.addAppender(appender);
      }
      logger.addAppender(asyncAppender);        
    }
  }

}