/**
 * 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.hdfs.server.namenode.FSImageFormat.renameReservedPathsOnUpgrade;
import static org.apache.hadoop.util.Time.now;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.EnumMap;
import java.util.EnumSet;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.XAttrSetFlag;
import org.apache.hadoop.hdfs.protocol.Block;
import org.apache.hadoop.hdfs.protocol.CacheDirectiveInfo;
import org.apache.hadoop.hdfs.protocol.HdfsConstants;
import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
import org.apache.hadoop.hdfs.protocol.LayoutVersion;
import org.apache.hadoop.hdfs.protocol.LocatedBlock;
import org.apache.hadoop.hdfs.server.blockmanagement.BlockInfo;
import org.apache.hadoop.hdfs.server.blockmanagement.BlockInfoUnderConstruction;
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.namenode.FSEditLogOp.AddBlockOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AddCacheDirectiveInfoOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AddCachePoolOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AddCloseOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AllocateBlockIdOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AllowSnapshotOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.BlockListUpdatingOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.CancelDelegationTokenOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.ClearNSQuotaOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.ConcatDeleteOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.CreateSnapshotOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.DeleteOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.DeleteSnapshotOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.DisallowSnapshotOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.GetDelegationTokenOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.MkdirOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.ModifyCacheDirectiveInfoOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.ModifyCachePoolOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.ReassignLeaseOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RemoveCacheDirectiveInfoOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RemoveCachePoolOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenameOldOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenameOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenameSnapshotOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenewDelegationTokenOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RollingUpgradeOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetAclOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetGenstampV1Op;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetGenstampV2Op;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetNSQuotaOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetOwnerOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetPermissionsOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetQuotaOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetReplicationOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetXAttrOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RemoveXAttrOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SymlinkOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.TimesOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.UpdateBlocksOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.UpdateMasterKeyOp;
import org.apache.hadoop.hdfs.server.namenode.INode.BlocksMapUpdateInfo;
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.snapshot.Snapshot;
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.Step;
import org.apache.hadoop.hdfs.util.ChunkedArrayList;
import org.apache.hadoop.hdfs.util.Holder;

import com.google.common.base.Joiner;
import com.google.common.base.Preconditions;

@InterfaceAudience.Private
@InterfaceStability.Evolving
public class FSEditLogLoader {
  static final Log LOG = LogFactory.getLog(FSEditLogLoader.class.getName());
  static final long REPLAY_TRANSACTION_LOG_INTERVAL = 1000; // 1sec

  private final FSNamesystem fsNamesys;
  private long lastAppliedTxId;
  /** Total number of end transactions loaded. */
  private int totalEdits = 0;
  
  public FSEditLogLoader(FSNamesystem fsNamesys, long lastAppliedTxId) {
    this.fsNamesys = fsNamesys;
    this.lastAppliedTxId = lastAppliedTxId;
  }
  
  long loadFSEdits(EditLogInputStream edits, long expectedStartingTxId)
      throws IOException {
    return loadFSEdits(edits, expectedStartingTxId, null, null);
  }

  /**
   * Load an edit log, and apply the changes to the in-memory structure
   * This is where we apply edits that we've been writing to disk all
   * along.
   */
  long loadFSEdits(EditLogInputStream edits, long expectedStartingTxId,
      StartupOption startOpt, MetaRecoveryContext recovery) throws IOException {
    StartupProgress prog = NameNode.getStartupProgress();
    Step step = createStartupProgressStep(edits);
    prog.beginStep(Phase.LOADING_EDITS, step);
    fsNamesys.writeLock();
    try {
      long startTime = now();
      FSImage.LOG.info("Start loading edits file " + edits.getName());
      long numEdits = loadEditRecords(edits, false, expectedStartingTxId,
          startOpt, recovery);
      FSImage.LOG.info("Edits file " + edits.getName() 
          + " of size " + edits.length() + " edits # " + numEdits 
          + " loaded in " + (now()-startTime)/1000 + " seconds");
      return numEdits;
    } finally {
      edits.close();
      fsNamesys.writeUnlock();
      prog.endStep(Phase.LOADING_EDITS, step);
    }
  }

  long loadEditRecords(EditLogInputStream in, boolean closeOnExit,
      long expectedStartingTxId, StartupOption startOpt,
      MetaRecoveryContext recovery) throws IOException {
    FSDirectory fsDir = fsNamesys.dir;

    EnumMap<FSEditLogOpCodes, Holder<Integer>> opCounts =
      new EnumMap<FSEditLogOpCodes, Holder<Integer>>(FSEditLogOpCodes.class);

    if (LOG.isTraceEnabled()) {
      LOG.trace("Acquiring write lock to replay edit log");
    }

    fsNamesys.writeLock();
    fsDir.writeLock();

    long recentOpcodeOffsets[] = new long[4];
    Arrays.fill(recentOpcodeOffsets, -1);
    
    long expectedTxId = expectedStartingTxId;
    long numEdits = 0;
    long lastTxId = in.getLastTxId();
    long numTxns = (lastTxId - expectedStartingTxId) + 1;
    StartupProgress prog = NameNode.getStartupProgress();
    Step step = createStartupProgressStep(in);
    prog.setTotal(Phase.LOADING_EDITS, step, numTxns);
    Counter counter = prog.getCounter(Phase.LOADING_EDITS, step);
    long lastLogTime = now();
    long lastInodeId = fsNamesys.getLastInodeId();
    
    try {
      while (true) {
        try {
          FSEditLogOp op;
          try {
            op = in.readOp();
            if (op == null) {
              break;
            }
          } catch (Throwable e) {
            // Handle a problem with our input
            check203UpgradeFailure(in.getVersion(true), e);
            String errorMessage =
              formatEditLogReplayError(in, recentOpcodeOffsets, expectedTxId);
            FSImage.LOG.error(errorMessage, e);
            if (recovery == null) {
               // We will only try to skip over problematic opcodes when in
               // recovery mode.
              throw new EditLogInputException(errorMessage, e, numEdits);
            }
            MetaRecoveryContext.editLogLoaderPrompt(
                "We failed to read txId " + expectedTxId,
                recovery, "skipping the bad section in the log");
            in.resync();
            continue;
          }
          recentOpcodeOffsets[(int)(numEdits % recentOpcodeOffsets.length)] =
            in.getPosition();
          if (op.hasTransactionId()) {
            if (op.getTransactionId() > expectedTxId) { 
              MetaRecoveryContext.editLogLoaderPrompt("There appears " +
                  "to be a gap in the edit log.  We expected txid " +
                  expectedTxId + ", but got txid " +
                  op.getTransactionId() + ".", recovery, "ignoring missing " +
                  " transaction IDs");
            } else if (op.getTransactionId() < expectedTxId) { 
              MetaRecoveryContext.editLogLoaderPrompt("There appears " +
                  "to be an out-of-order edit in the edit log.  We " +
                  "expected txid " + expectedTxId + ", but got txid " +
                  op.getTransactionId() + ".", recovery,
                  "skipping the out-of-order edit");
              continue;
            }
          }
          try {
            if (LOG.isTraceEnabled()) {
              LOG.trace("op=" + op + ", startOpt=" + startOpt
                  + ", numEdits=" + numEdits + ", totalEdits=" + totalEdits);
            }
            long inodeId = applyEditLogOp(op, fsDir, startOpt,
                in.getVersion(true), lastInodeId);
            if (lastInodeId < inodeId) {
              lastInodeId = inodeId;
            }
          } catch (RollingUpgradeOp.RollbackException e) {
            throw e;
          } catch (Throwable e) {
            LOG.error("Encountered exception on operation " + op, e);
            if (recovery == null) {
              throw e instanceof IOException? (IOException)e: new IOException(e);
            }

            MetaRecoveryContext.editLogLoaderPrompt("Failed to " +
             "apply edit log operation " + op + ": error " +
             e.getMessage(), recovery, "applying edits");
          }
          // Now that the operation has been successfully decoded and
          // applied, update our bookkeeping.
          incrOpCount(op.opCode, opCounts, step, counter);
          if (op.hasTransactionId()) {
            lastAppliedTxId = op.getTransactionId();
            expectedTxId = lastAppliedTxId + 1;
          } else {
            expectedTxId = lastAppliedTxId = expectedStartingTxId;
          }
          // log progress
          if (op.hasTransactionId()) {
            long now = now();
            if (now - lastLogTime > REPLAY_TRANSACTION_LOG_INTERVAL) {
              long deltaTxId = lastAppliedTxId - expectedStartingTxId + 1;
              int percent = Math.round((float) deltaTxId / numTxns * 100);
              LOG.info("replaying edit log: " + deltaTxId + "/" + numTxns
                  + " transactions completed. (" + percent + "%)");
              lastLogTime = now;
            }
          }
          numEdits++;
          totalEdits++;
        } catch (RollingUpgradeOp.RollbackException e) {
          LOG.info("Stopped at OP_START_ROLLING_UPGRADE for rollback.");
          break;
        } catch (MetaRecoveryContext.RequestStopException e) {
          MetaRecoveryContext.LOG.warn("Stopped reading edit log at " +
              in.getPosition() + "/"  + in.length());
          break;
        }
      }
    } finally {
      fsNamesys.resetLastInodeId(lastInodeId);
      if(closeOnExit) {
        in.close();
      }
      fsDir.writeUnlock();
      fsNamesys.writeUnlock();

      if (LOG.isTraceEnabled()) {
        LOG.trace("replaying edit log finished");
      }

      if (FSImage.LOG.isDebugEnabled()) {
        dumpOpCounts(opCounts);
      }
    }
    return numEdits;
  }
  
  // allocate and update last allocated inode id
  private long getAndUpdateLastInodeId(long inodeIdFromOp, int logVersion,
      long lastInodeId) throws IOException {
    long inodeId = inodeIdFromOp;

    if (inodeId == INodeId.GRANDFATHER_INODE_ID) {
      if (NameNodeLayoutVersion.supports(
          LayoutVersion.Feature.ADD_INODE_ID, logVersion)) {
        throw new IOException("The layout version " + logVersion
            + " supports inodeId but gave bogus inodeId");
      }
      inodeId = fsNamesys.allocateNewInodeId();
    } else {
      // need to reset lastInodeId. fsnamesys gets lastInodeId firstly from
      // fsimage but editlog captures more recent inodeId allocations
      if (inodeId > lastInodeId) {
        fsNamesys.resetLastInodeId(inodeId);
      }
    }
    return inodeId;
  }

  @SuppressWarnings("deprecation")
  private long applyEditLogOp(FSEditLogOp op, FSDirectory fsDir,
      StartupOption startOpt, int logVersion, long lastInodeId) throws IOException {
    long inodeId = INodeId.GRANDFATHER_INODE_ID;
    if (LOG.isTraceEnabled()) {
      LOG.trace("replaying edit log: " + op);
    }
    final boolean toAddRetryCache = fsNamesys.hasRetryCache() && op.hasRpcIds();
    
    switch (op.opCode) {
    case OP_ADD: {
      AddCloseOp addCloseOp = (AddCloseOp)op;
      final String path =
          renameReservedPathsOnUpgrade(addCloseOp.path, logVersion);
      if (FSNamesystem.LOG.isDebugEnabled()) {
        FSNamesystem.LOG.debug(op.opCode + ": " + path +
            " numblocks : " + addCloseOp.blocks.length +
            " clientHolder " + addCloseOp.clientName +
            " clientMachine " + addCloseOp.clientMachine);
      }
      // There three cases here:
      // 1. OP_ADD to create a new file
      // 2. OP_ADD to update file blocks
      // 3. OP_ADD to open file for append

      // See if the file already exists (persistBlocks call)
      final INodesInPath iip = fsDir.getLastINodeInPath(path);
      final INodeFile oldFile = INodeFile.valueOf(
          iip.getINode(0), path, true);
      INodeFile newFile = oldFile;
      if (oldFile == null) { // this is OP_ADD on a new file (case 1)
        // versions > 0 support per file replication
        // get name and replication
        final short replication = fsNamesys.getBlockManager()
            .adjustReplication(addCloseOp.replication);
        assert addCloseOp.blocks.length == 0;

        // add to the file tree
        inodeId = getAndUpdateLastInodeId(addCloseOp.inodeId, logVersion,
            lastInodeId);
        newFile = fsDir.unprotectedAddFile(inodeId,
            path, addCloseOp.permissions, addCloseOp.aclEntries,
            replication, addCloseOp.mtime, addCloseOp.atime,
            addCloseOp.blockSize, true, addCloseOp.clientName,
            addCloseOp.clientMachine);
        fsNamesys.leaseManager.addLease(addCloseOp.clientName, path);

        // add the op into retry cache if necessary
        if (toAddRetryCache) {
          HdfsFileStatus stat = fsNamesys.dir.createFileStatus(
              HdfsFileStatus.EMPTY_NAME, newFile, Snapshot.CURRENT_STATE_ID);
          fsNamesys.addCacheEntryWithPayload(addCloseOp.rpcClientId,
              addCloseOp.rpcCallId, stat);
        }
      } else { // This is OP_ADD on an existing file
        if (!oldFile.isUnderConstruction()) {
          // This is case 3: a call to append() on an already-closed file.
          if (FSNamesystem.LOG.isDebugEnabled()) {
            FSNamesystem.LOG.debug("Reopening an already-closed file " +
                "for append");
          }
          LocatedBlock lb = fsNamesys.prepareFileForWrite(path,
              oldFile, addCloseOp.clientName, addCloseOp.clientMachine, null,
              false, iip.getLatestSnapshotId(), false);
          newFile = INodeFile.valueOf(fsDir.getINode(path),
              path, true);
          
          // add the op into retry cache is necessary
          if (toAddRetryCache) {
            fsNamesys.addCacheEntryWithPayload(addCloseOp.rpcClientId,
                addCloseOp.rpcCallId, lb);
          }
        }
      }
      // Fall-through for case 2.
      // Regardless of whether it's a new file or an updated file,
      // update the block list.
      
      // Update the salient file attributes.
      newFile.setAccessTime(addCloseOp.atime, Snapshot.CURRENT_STATE_ID);
      newFile.setModificationTime(addCloseOp.mtime, Snapshot.CURRENT_STATE_ID);
      updateBlocks(fsDir, addCloseOp, newFile);
      break;
    }
    case OP_CLOSE: {
      AddCloseOp addCloseOp = (AddCloseOp)op;
      final String path =
          renameReservedPathsOnUpgrade(addCloseOp.path, logVersion);
      if (FSNamesystem.LOG.isDebugEnabled()) {
        FSNamesystem.LOG.debug(op.opCode + ": " + path +
            " numblocks : " + addCloseOp.blocks.length +
            " clientHolder " + addCloseOp.clientName +
            " clientMachine " + addCloseOp.clientMachine);
      }

      final INodesInPath iip = fsDir.getLastINodeInPath(path);
      final INodeFile file = INodeFile.valueOf(iip.getINode(0), path);

      // Update the salient file attributes.
      file.setAccessTime(addCloseOp.atime, Snapshot.CURRENT_STATE_ID);
      file.setModificationTime(addCloseOp.mtime, Snapshot.CURRENT_STATE_ID);
      updateBlocks(fsDir, addCloseOp, file);

      // Now close the file
      if (!file.isUnderConstruction() &&
          logVersion <= LayoutVersion.BUGFIX_HDFS_2991_VERSION) {
        // There was a bug (HDFS-2991) in hadoop < 0.23.1 where OP_CLOSE
        // could show up twice in a row. But after that version, this
        // should be fixed, so we should treat it as an error.
        throw new IOException(
            "File is not under construction: " + path);
      }
      // One might expect that you could use removeLease(holder, path) here,
      // but OP_CLOSE doesn't serialize the holder. So, remove by path.
      if (file.isUnderConstruction()) {
        fsNamesys.leaseManager.removeLeaseWithPrefixPath(path);
        file.toCompleteFile(file.getModificationTime());
      }
      break;
    }
    case OP_UPDATE_BLOCKS: {
      UpdateBlocksOp updateOp = (UpdateBlocksOp)op;
      final String path =
          renameReservedPathsOnUpgrade(updateOp.path, logVersion);
      if (FSNamesystem.LOG.isDebugEnabled()) {
        FSNamesystem.LOG.debug(op.opCode + ": " + path +
            " numblocks : " + updateOp.blocks.length);
      }
      INodeFile oldFile = INodeFile.valueOf(fsDir.getINode(path),
          path);
      // Update in-memory data structures
      updateBlocks(fsDir, updateOp, oldFile);
      
      if (toAddRetryCache) {
        fsNamesys.addCacheEntry(updateOp.rpcClientId, updateOp.rpcCallId);
      }
      break;
    }
    case OP_ADD_BLOCK: {
      AddBlockOp addBlockOp = (AddBlockOp) op;
      String path = renameReservedPathsOnUpgrade(addBlockOp.getPath(), logVersion);
      if (FSNamesystem.LOG.isDebugEnabled()) {
        FSNamesystem.LOG.debug(op.opCode + ": " + path +
            " new block id : " + addBlockOp.getLastBlock().getBlockId());
      }
      INodeFile oldFile = INodeFile.valueOf(fsDir.getINode(path), path);
      // add the new block to the INodeFile
      addNewBlock(fsDir, addBlockOp, oldFile);
      break;
    }
    case OP_SET_REPLICATION: {
      SetReplicationOp setReplicationOp = (SetReplicationOp)op;
      short replication = fsNamesys.getBlockManager().adjustReplication(
          setReplicationOp.replication);
      fsDir.unprotectedSetReplication(
          renameReservedPathsOnUpgrade(setReplicationOp.path, logVersion),
                                      replication, null);
      break;
    }
    case OP_CONCAT_DELETE: {
      ConcatDeleteOp concatDeleteOp = (ConcatDeleteOp)op;
      String trg = renameReservedPathsOnUpgrade(concatDeleteOp.trg, logVersion);
      String[] srcs = new String[concatDeleteOp.srcs.length];
      for (int i=0; i<srcs.length; i++) {
        srcs[i] =
            renameReservedPathsOnUpgrade(concatDeleteOp.srcs[i], logVersion);
      }
      fsDir.unprotectedConcat(trg, srcs, concatDeleteOp.timestamp);
      
      if (toAddRetryCache) {
        fsNamesys.addCacheEntry(concatDeleteOp.rpcClientId,
            concatDeleteOp.rpcCallId);
      }
      break;
    }
    case OP_RENAME_OLD: {
      RenameOldOp renameOp = (RenameOldOp)op;
      final String src = renameReservedPathsOnUpgrade(renameOp.src, logVersion);
      final String dst = renameReservedPathsOnUpgrade(renameOp.dst, logVersion);
      fsDir.unprotectedRenameTo(src, dst,
                                renameOp.timestamp);
      
      if (toAddRetryCache) {
        fsNamesys.addCacheEntry(renameOp.rpcClientId, renameOp.rpcCallId);
      }
      break;
    }
    case OP_DELETE: {
      DeleteOp deleteOp = (DeleteOp)op;
      fsDir.unprotectedDelete(
          renameReservedPathsOnUpgrade(deleteOp.path, logVersion),
          deleteOp.timestamp);
      
      if (toAddRetryCache) {
        fsNamesys.addCacheEntry(deleteOp.rpcClientId, deleteOp.rpcCallId);
      }
      break;
    }
    case OP_MKDIR: {
      MkdirOp mkdirOp = (MkdirOp)op;
      inodeId = getAndUpdateLastInodeId(mkdirOp.inodeId, logVersion,
          lastInodeId);
      fsDir.unprotectedMkdir(inodeId,
          renameReservedPathsOnUpgrade(mkdirOp.path, logVersion),
          mkdirOp.permissions, mkdirOp.aclEntries, mkdirOp.timestamp);
      break;
    }
    case OP_SET_GENSTAMP_V1: {
      SetGenstampV1Op setGenstampV1Op = (SetGenstampV1Op)op;
      fsNamesys.setGenerationStampV1(setGenstampV1Op.genStampV1);
      break;
    }
    case OP_SET_PERMISSIONS: {
      SetPermissionsOp setPermissionsOp = (SetPermissionsOp)op;
      fsDir.unprotectedSetPermission(
          renameReservedPathsOnUpgrade(setPermissionsOp.src, logVersion),
          setPermissionsOp.permissions);
      break;
    }
    case OP_SET_OWNER: {
      SetOwnerOp setOwnerOp = (SetOwnerOp)op;
      fsDir.unprotectedSetOwner(
          renameReservedPathsOnUpgrade(setOwnerOp.src, logVersion),
          setOwnerOp.username, setOwnerOp.groupname);
      break;
    }
    case OP_SET_NS_QUOTA: {
      SetNSQuotaOp setNSQuotaOp = (SetNSQuotaOp)op;
      fsDir.unprotectedSetQuota(
          renameReservedPathsOnUpgrade(setNSQuotaOp.src, logVersion),
          setNSQuotaOp.nsQuota, HdfsConstants.QUOTA_DONT_SET);
      break;
    }
    case OP_CLEAR_NS_QUOTA: {
      ClearNSQuotaOp clearNSQuotaOp = (ClearNSQuotaOp)op;
      fsDir.unprotectedSetQuota(
          renameReservedPathsOnUpgrade(clearNSQuotaOp.src, logVersion),
          HdfsConstants.QUOTA_RESET, HdfsConstants.QUOTA_DONT_SET);
      break;
    }

    case OP_SET_QUOTA:
      SetQuotaOp setQuotaOp = (SetQuotaOp)op;
      fsDir.unprotectedSetQuota(
          renameReservedPathsOnUpgrade(setQuotaOp.src, logVersion),
          setQuotaOp.nsQuota, setQuotaOp.dsQuota);
      break;

    case OP_TIMES: {
      TimesOp timesOp = (TimesOp)op;

      fsDir.unprotectedSetTimes(
          renameReservedPathsOnUpgrade(timesOp.path, logVersion),
          timesOp.mtime, timesOp.atime, true);
      break;
    }
    case OP_SYMLINK: {
      SymlinkOp symlinkOp = (SymlinkOp)op;
      inodeId = getAndUpdateLastInodeId(symlinkOp.inodeId, logVersion,
          lastInodeId);
      fsDir.unprotectedAddSymlink(inodeId,
          renameReservedPathsOnUpgrade(symlinkOp.path, logVersion),
          symlinkOp.value, symlinkOp.mtime, symlinkOp.atime,
          symlinkOp.permissionStatus);
      
      if (toAddRetryCache) {
        fsNamesys.addCacheEntry(symlinkOp.rpcClientId, symlinkOp.rpcCallId);
      }
      break;
    }
    case OP_RENAME: {
      RenameOp renameOp = (RenameOp)op;
      fsDir.unprotectedRenameTo(
          renameReservedPathsOnUpgrade(renameOp.src, logVersion),
          renameReservedPathsOnUpgrade(renameOp.dst, logVersion),
          renameOp.timestamp, renameOp.options);
      
      if (toAddRetryCache) {
        fsNamesys.addCacheEntry(renameOp.rpcClientId, renameOp.rpcCallId);
      }
      break;
    }
    case OP_GET_DELEGATION_TOKEN: {
      GetDelegationTokenOp getDelegationTokenOp
        = (GetDelegationTokenOp)op;

      fsNamesys.getDelegationTokenSecretManager()
        .addPersistedDelegationToken(getDelegationTokenOp.token,
                                     getDelegationTokenOp.expiryTime);
      break;
    }
    case OP_RENEW_DELEGATION_TOKEN: {
      RenewDelegationTokenOp renewDelegationTokenOp
        = (RenewDelegationTokenOp)op;
      fsNamesys.getDelegationTokenSecretManager()
        .updatePersistedTokenRenewal(renewDelegationTokenOp.token,
                                     renewDelegationTokenOp.expiryTime);
      break;
    }
    case OP_CANCEL_DELEGATION_TOKEN: {
      CancelDelegationTokenOp cancelDelegationTokenOp
        = (CancelDelegationTokenOp)op;
      fsNamesys.getDelegationTokenSecretManager()
          .updatePersistedTokenCancellation(
              cancelDelegationTokenOp.token);
      break;
    }
    case OP_UPDATE_MASTER_KEY: {
      UpdateMasterKeyOp updateMasterKeyOp = (UpdateMasterKeyOp)op;
      fsNamesys.getDelegationTokenSecretManager()
        .updatePersistedMasterKey(updateMasterKeyOp.key);
      break;
    }
    case OP_REASSIGN_LEASE: {
      ReassignLeaseOp reassignLeaseOp = (ReassignLeaseOp)op;

      Lease lease = fsNamesys.leaseManager.getLease(
          reassignLeaseOp.leaseHolder);
      final String path =
          renameReservedPathsOnUpgrade(reassignLeaseOp.path, logVersion);
      INodeFile pendingFile = fsDir.getINode(path).asFile();
      Preconditions.checkState(pendingFile.isUnderConstruction());
      fsNamesys.reassignLeaseInternal(lease,
          path, reassignLeaseOp.newHolder, pendingFile);
      break;
    }
    case OP_START_LOG_SEGMENT:
    case OP_END_LOG_SEGMENT: {
      // no data in here currently.
      break;
    }
    case OP_CREATE_SNAPSHOT: {
      CreateSnapshotOp createSnapshotOp = (CreateSnapshotOp) op;
      final String snapshotRoot =
          renameReservedPathsOnUpgrade(createSnapshotOp.snapshotRoot,
              logVersion);
      String path = fsNamesys.getSnapshotManager().createSnapshot(
          snapshotRoot, createSnapshotOp.snapshotName);
      if (toAddRetryCache) {
        fsNamesys.addCacheEntryWithPayload(createSnapshotOp.rpcClientId,
            createSnapshotOp.rpcCallId, path);
      }
      break;
    }
    case OP_DELETE_SNAPSHOT: {
      DeleteSnapshotOp deleteSnapshotOp = (DeleteSnapshotOp) op;
      BlocksMapUpdateInfo collectedBlocks = new BlocksMapUpdateInfo();
      List<INode> removedINodes = new ChunkedArrayList<INode>();
      final String snapshotRoot =
          renameReservedPathsOnUpgrade(deleteSnapshotOp.snapshotRoot,
              logVersion);
      fsNamesys.getSnapshotManager().deleteSnapshot(
          snapshotRoot, deleteSnapshotOp.snapshotName,
          collectedBlocks, removedINodes);
      fsNamesys.removeBlocksAndUpdateSafemodeTotal(collectedBlocks);
      collectedBlocks.clear();
      fsNamesys.dir.removeFromInodeMap(removedINodes);
      removedINodes.clear();
      
      if (toAddRetryCache) {
        fsNamesys.addCacheEntry(deleteSnapshotOp.rpcClientId,
            deleteSnapshotOp.rpcCallId);
      }
      break;
    }
    case OP_RENAME_SNAPSHOT: {
      RenameSnapshotOp renameSnapshotOp = (RenameSnapshotOp) op;
      final String snapshotRoot =
          renameReservedPathsOnUpgrade(renameSnapshotOp.snapshotRoot,
              logVersion);
      fsNamesys.getSnapshotManager().renameSnapshot(
          snapshotRoot, renameSnapshotOp.snapshotOldName,
          renameSnapshotOp.snapshotNewName);
      
      if (toAddRetryCache) {
        fsNamesys.addCacheEntry(renameSnapshotOp.rpcClientId,
            renameSnapshotOp.rpcCallId);
      }
      break;
    }
    case OP_ALLOW_SNAPSHOT: {
      AllowSnapshotOp allowSnapshotOp = (AllowSnapshotOp) op;
      final String snapshotRoot =
          renameReservedPathsOnUpgrade(allowSnapshotOp.snapshotRoot, logVersion);
      fsNamesys.getSnapshotManager().setSnapshottable(
          snapshotRoot, false);
      break;
    }
    case OP_DISALLOW_SNAPSHOT: {
      DisallowSnapshotOp disallowSnapshotOp = (DisallowSnapshotOp) op;
      final String snapshotRoot =
          renameReservedPathsOnUpgrade(disallowSnapshotOp.snapshotRoot,
              logVersion);
      fsNamesys.getSnapshotManager().resetSnapshottable(
          snapshotRoot);
      break;
    }
    case OP_SET_GENSTAMP_V2: {
      SetGenstampV2Op setGenstampV2Op = (SetGenstampV2Op) op;
      fsNamesys.setGenerationStampV2(setGenstampV2Op.genStampV2);
      break;
    }
    case OP_ALLOCATE_BLOCK_ID: {
      AllocateBlockIdOp allocateBlockIdOp = (AllocateBlockIdOp) op;
      fsNamesys.setLastAllocatedBlockId(allocateBlockIdOp.blockId);
      break;
    }
    case OP_ROLLING_UPGRADE_START: {
      if (startOpt == StartupOption.ROLLINGUPGRADE) {
        final RollingUpgradeStartupOption rollingUpgradeOpt
            = startOpt.getRollingUpgradeStartupOption(); 
        if (rollingUpgradeOpt == RollingUpgradeStartupOption.ROLLBACK) {
          throw new RollingUpgradeOp.RollbackException();
        } else if (rollingUpgradeOpt == RollingUpgradeStartupOption.DOWNGRADE) {
          //ignore upgrade marker
          break;
        }
      }
      // start rolling upgrade
      final long startTime = ((RollingUpgradeOp) op).getTime();
      fsNamesys.startRollingUpgradeInternal(startTime);
      fsNamesys.triggerRollbackCheckpoint();
      break;
    }
    case OP_ROLLING_UPGRADE_FINALIZE: {
      final long finalizeTime = ((RollingUpgradeOp) op).getTime();
      fsNamesys.finalizeRollingUpgradeInternal(finalizeTime);
      fsNamesys.getFSImage().renameCheckpoint(NameNodeFile.IMAGE_ROLLBACK,
          NameNodeFile.IMAGE);
      break;
    }
    case OP_ADD_CACHE_DIRECTIVE: {
      AddCacheDirectiveInfoOp addOp = (AddCacheDirectiveInfoOp) op;
      CacheDirectiveInfo result = fsNamesys.
          getCacheManager().addDirectiveFromEditLog(addOp.directive);
      if (toAddRetryCache) {
        Long id = result.getId();
        fsNamesys.addCacheEntryWithPayload(op.rpcClientId, op.rpcCallId, id);
      }
      break;
    }
    case OP_MODIFY_CACHE_DIRECTIVE: {
      ModifyCacheDirectiveInfoOp modifyOp =
          (ModifyCacheDirectiveInfoOp) op;
      fsNamesys.getCacheManager().modifyDirectiveFromEditLog(
          modifyOp.directive);
      if (toAddRetryCache) {
        fsNamesys.addCacheEntry(op.rpcClientId, op.rpcCallId);
      }
      break;
    }
    case OP_REMOVE_CACHE_DIRECTIVE: {
      RemoveCacheDirectiveInfoOp removeOp =
          (RemoveCacheDirectiveInfoOp) op;
      fsNamesys.getCacheManager().removeDirective(removeOp.id, null);
      if (toAddRetryCache) {
        fsNamesys.addCacheEntry(op.rpcClientId, op.rpcCallId);
      }
      break;
    }
    case OP_ADD_CACHE_POOL: {
      AddCachePoolOp addOp = (AddCachePoolOp) op;
      fsNamesys.getCacheManager().addCachePool(addOp.info);
      if (toAddRetryCache) {
        fsNamesys.addCacheEntry(op.rpcClientId, op.rpcCallId);
      }
      break;
    }
    case OP_MODIFY_CACHE_POOL: {
      ModifyCachePoolOp modifyOp = (ModifyCachePoolOp) op;
      fsNamesys.getCacheManager().modifyCachePool(modifyOp.info);
      if (toAddRetryCache) {
        fsNamesys.addCacheEntry(op.rpcClientId, op.rpcCallId);
      }
      break;
    }
    case OP_REMOVE_CACHE_POOL: {
      RemoveCachePoolOp removeOp = (RemoveCachePoolOp) op;
      fsNamesys.getCacheManager().removeCachePool(removeOp.poolName);
      if (toAddRetryCache) {
        fsNamesys.addCacheEntry(op.rpcClientId, op.rpcCallId);
      }
      break;
    }
    case OP_SET_ACL: {
      SetAclOp setAclOp = (SetAclOp) op;
      fsDir.unprotectedSetAcl(setAclOp.src, setAclOp.aclEntries);
      break;
    }
    case OP_SET_XATTR: {
      SetXAttrOp setXAttrOp = (SetXAttrOp) op;
      fsDir.unprotectedSetXAttr(setXAttrOp.src, setXAttrOp.xAttr, 
          EnumSet.of(XAttrSetFlag.CREATE, XAttrSetFlag.REPLACE));
      if (toAddRetryCache) {
        fsNamesys.addCacheEntry(setXAttrOp.rpcClientId, setXAttrOp.rpcCallId);
      }
      break;
    }
    case OP_REMOVE_XATTR: {
      RemoveXAttrOp removeXAttrOp = (RemoveXAttrOp) op;
      fsDir.unprotectedRemoveXAttr(removeXAttrOp.src, removeXAttrOp.xAttr);
      break;
    }
    default:
      throw new IOException("Invalid operation read " + op.opCode);
    }
    return inodeId;
  }
  
  private static String formatEditLogReplayError(EditLogInputStream in,
      long recentOpcodeOffsets[], long txid) {
    StringBuilder sb = new StringBuilder();
    sb.append("Error replaying edit log at offset " + in.getPosition());
    sb.append(".  Expected transaction ID was ").append(txid);
    if (recentOpcodeOffsets[0] != -1) {
      Arrays.sort(recentOpcodeOffsets);
      sb.append("\nRecent opcode offsets:");
      for (long offset : recentOpcodeOffsets) {
        if (offset != -1) {
          sb.append(' ').append(offset);
        }
      }
    }
    return sb.toString();
  }

  /**
   * Add a new block into the given INodeFile
   */
  private void addNewBlock(FSDirectory fsDir, AddBlockOp op, INodeFile file)
      throws IOException {
    BlockInfo[] oldBlocks = file.getBlocks();
    Block pBlock = op.getPenultimateBlock();
    Block newBlock= op.getLastBlock();
    
    if (pBlock != null) { // the penultimate block is not null
      Preconditions.checkState(oldBlocks != null && oldBlocks.length > 0);
      // compare pBlock with the last block of oldBlocks
      Block oldLastBlock = oldBlocks[oldBlocks.length - 1];
      if (oldLastBlock.getBlockId() != pBlock.getBlockId()
          || oldLastBlock.getGenerationStamp() != pBlock.getGenerationStamp()) {
        throw new IOException(
            "Mismatched block IDs or generation stamps for the old last block of file "
                + op.getPath() + ", the old last block is " + oldLastBlock
                + ", and the block read from editlog is " + pBlock);
      }
      
      oldLastBlock.setNumBytes(pBlock.getNumBytes());
      if (oldLastBlock instanceof BlockInfoUnderConstruction) {
        fsNamesys.getBlockManager().forceCompleteBlock(file,
            (BlockInfoUnderConstruction) oldLastBlock);
        fsNamesys.getBlockManager().processQueuedMessagesForBlock(pBlock);
      }
    } else { // the penultimate block is null
      Preconditions.checkState(oldBlocks == null || oldBlocks.length == 0);
    }
    // add the new block
    BlockInfo newBI = new BlockInfoUnderConstruction(
          newBlock, file.getBlockReplication());
    fsNamesys.getBlockManager().addBlockCollection(newBI, file);
    file.addBlock(newBI);
    fsNamesys.getBlockManager().processQueuedMessagesForBlock(newBlock);
  }
  
  /**
   * Update in-memory data structures with new block information.
   * @throws IOException
   */
  private void updateBlocks(FSDirectory fsDir, BlockListUpdatingOp op,
      INodeFile file) throws IOException {
    // Update its block list
    BlockInfo[] oldBlocks = file.getBlocks();
    Block[] newBlocks = op.getBlocks();
    String path = op.getPath();
    
    // Are we only updating the last block's gen stamp.
    boolean isGenStampUpdate = oldBlocks.length == newBlocks.length;
    
    // First, update blocks in common
    for (int i = 0; i < oldBlocks.length && i < newBlocks.length; i++) {
      BlockInfo oldBlock = oldBlocks[i];
      Block newBlock = newBlocks[i];
      
      boolean isLastBlock = i == newBlocks.length - 1;
      if (oldBlock.getBlockId() != newBlock.getBlockId() ||
          (oldBlock.getGenerationStamp() != newBlock.getGenerationStamp() && 
              !(isGenStampUpdate && isLastBlock))) {
        throw new IOException("Mismatched block IDs or generation stamps, " +
            "attempting to replace block " + oldBlock + " with " + newBlock +
            " as block # " + i + "/" + newBlocks.length + " of " +
            path);
      }
      
      oldBlock.setNumBytes(newBlock.getNumBytes());
      boolean changeMade =
        oldBlock.getGenerationStamp() != newBlock.getGenerationStamp();
      oldBlock.setGenerationStamp(newBlock.getGenerationStamp());
      
      if (oldBlock instanceof BlockInfoUnderConstruction &&
          (!isLastBlock || op.shouldCompleteLastBlock())) {
        changeMade = true;
        fsNamesys.getBlockManager().forceCompleteBlock(file,
            (BlockInfoUnderConstruction) oldBlock);
      }
      if (changeMade) {
        // The state or gen-stamp of the block has changed. So, we may be
        // able to process some messages from datanodes that we previously
        // were unable to process.
        fsNamesys.getBlockManager().processQueuedMessagesForBlock(newBlock);
      }
    }
    
    if (newBlocks.length < oldBlocks.length) {
      // We're removing a block from the file, e.g. abandonBlock(...)
      if (!file.isUnderConstruction()) {
        throw new IOException("Trying to remove a block from file " +
            path + " which is not under construction.");
      }
      if (newBlocks.length != oldBlocks.length - 1) {
        throw new IOException("Trying to remove more than one block from file "
            + path);
      }
      Block oldBlock = oldBlocks[oldBlocks.length - 1];
      boolean removed = fsDir.unprotectedRemoveBlock(path, file, oldBlock);
      if (!removed && !(op instanceof UpdateBlocksOp)) {
        throw new IOException("Trying to delete non-existant block " + oldBlock);
      }
    } else if (newBlocks.length > oldBlocks.length) {
      // We're adding blocks
      for (int i = oldBlocks.length; i < newBlocks.length; i++) {
        Block newBlock = newBlocks[i];
        BlockInfo newBI;
        if (!op.shouldCompleteLastBlock()) {
          // TODO: shouldn't this only be true for the last block?
          // what about an old-version fsync() where fsync isn't called
          // until several blocks in?
          newBI = new BlockInfoUnderConstruction(
              newBlock, file.getBlockReplication());
        } else {
          // OP_CLOSE should add finalized blocks. This code path
          // is only executed when loading edits written by prior
          // versions of Hadoop. Current versions always log
          // OP_ADD operations as each block is allocated.
          newBI = new BlockInfo(newBlock, file.getBlockReplication());
        }
        fsNamesys.getBlockManager().addBlockCollection(newBI, file);
        file.addBlock(newBI);
        fsNamesys.getBlockManager().processQueuedMessagesForBlock(newBlock);
      }
    }
  }

  private static void dumpOpCounts(
      EnumMap<FSEditLogOpCodes, Holder<Integer>> opCounts) {
    StringBuilder sb = new StringBuilder();
    sb.append("Summary of operations loaded from edit log:\n  ");
    Joiner.on("\n  ").withKeyValueSeparator("=").appendTo(sb, opCounts);
    FSImage.LOG.debug(sb.toString());
  }

  private void incrOpCount(FSEditLogOpCodes opCode,
      EnumMap<FSEditLogOpCodes, Holder<Integer>> opCounts, Step step,
      Counter counter) {
    Holder<Integer> holder = opCounts.get(opCode);
    if (holder == null) {
      holder = new Holder<Integer>(1);
      opCounts.put(opCode, holder);
    } else {
      holder.held++;
    }
    counter.increment();
  }

  /**
   * Throw appropriate exception during upgrade from 203, when editlog loading
   * could fail due to opcode conflicts.
   */
  private void check203UpgradeFailure(int logVersion, Throwable e)
      throws IOException {
    // 0.20.203 version version has conflicting opcodes with the later releases.
    // The editlog must be emptied by restarting the namenode, before proceeding
    // with the upgrade.
    if (Storage.is203LayoutVersion(logVersion)
        && logVersion != HdfsConstants.NAMENODE_LAYOUT_VERSION) {
      String msg = "During upgrade failed to load the editlog version "
          + logVersion + " from release 0.20.203. Please go back to the old "
          + " release and restart the namenode. This empties the editlog "
          + " and saves the namespace. Resume the upgrade after this step.";
      throw new IOException(msg, e);
    }
  }
  
  /**
   * Find the last valid transaction ID in the stream.
   * If there are invalid or corrupt transactions in the middle of the stream,
   * validateEditLog will skip over them.
   * This reads through the stream but does not close it.
   */
  static EditLogValidation validateEditLog(EditLogInputStream in) {
    long lastPos = 0;
    long lastTxId = HdfsConstants.INVALID_TXID;
    long numValid = 0;
    FSEditLogOp op = null;
    while (true) {
      lastPos = in.getPosition();
      try {
        if ((op = in.readOp()) == null) {
          break;
        }
      } catch (Throwable t) {
        FSImage.LOG.warn("Caught exception after reading " + numValid +
            " ops from " + in + " while determining its valid length." +
            "Position was " + lastPos, t);
        in.resync();
        FSImage.LOG.warn("After resync, position is " + in.getPosition());
        continue;
      }
      if (lastTxId == HdfsConstants.INVALID_TXID
          || op.getTransactionId() > lastTxId) {
        lastTxId = op.getTransactionId();
      }
      numValid++;
    }
    return new EditLogValidation(lastPos, lastTxId, false);
  }

  static EditLogValidation scanEditLog(EditLogInputStream in) {
    long lastPos = 0;
    long lastTxId = HdfsConstants.INVALID_TXID;
    long numValid = 0;
    FSEditLogOp op = null;
    while (true) {
      lastPos = in.getPosition();
      try {
        if ((op = in.readOp()) == null) { // TODO
          break;
        }
      } catch (Throwable t) {
        FSImage.LOG.warn("Caught exception after reading " + numValid +
            " ops from " + in + " while determining its valid length." +
            "Position was " + lastPos, t);
        in.resync();
        FSImage.LOG.warn("After resync, position is " + in.getPosition());
        continue;
      }
      if (lastTxId == HdfsConstants.INVALID_TXID
          || op.getTransactionId() > lastTxId) {
        lastTxId = op.getTransactionId();
      }
      numValid++;
    }
    return new EditLogValidation(lastPos, lastTxId, false);
  }

  static class EditLogValidation {
    private final long validLength;
    private final long endTxId;
    private final boolean hasCorruptHeader;

    EditLogValidation(long validLength, long endTxId,
        boolean hasCorruptHeader) {
      this.validLength = validLength;
      this.endTxId = endTxId;
      this.hasCorruptHeader = hasCorruptHeader;
    }

    long getValidLength() { return validLength; }

    long getEndTxId() { return endTxId; }

    boolean hasCorruptHeader() { return hasCorruptHeader; }
  }

  /**
   * Stream wrapper that keeps track of the current stream position.
   * 
   * This stream also allows us to set a limit on how many bytes we can read
   * without getting an exception.
   */
  public static class PositionTrackingInputStream extends FilterInputStream
      implements StreamLimiter {
    private long curPos = 0;
    private long markPos = -1;
    private long limitPos = Long.MAX_VALUE;

    public PositionTrackingInputStream(InputStream is) {
      super(is);
    }

    private void checkLimit(long amt) throws IOException {
      long extra = (curPos + amt) - limitPos;
      if (extra > 0) {
        throw new IOException("Tried to read " + amt + " byte(s) past " +
            "the limit at offset " + limitPos);
      }
    }
    
    @Override
    public int read() throws IOException {
      checkLimit(1);
      int ret = super.read();
      if (ret != -1) curPos++;
      return ret;
    }

    @Override
    public int read(byte[] data) throws IOException {
      checkLimit(data.length);
      int ret = super.read(data);
      if (ret > 0) curPos += ret;
      return ret;
    }

    @Override
    public int read(byte[] data, int offset, int length) throws IOException {
      checkLimit(length);
      int ret = super.read(data, offset, length);
      if (ret > 0) curPos += ret;
      return ret;
    }

    @Override
    public void setLimit(long limit) {
      limitPos = curPos + limit;
    }

    @Override
    public void clearLimit() {
      limitPos = Long.MAX_VALUE;
    }

    @Override
    public void mark(int limit) {
      super.mark(limit);
      markPos = curPos;
    }

    @Override
    public void reset() throws IOException {
      if (markPos == -1) {
        throw new IOException("Not marked!");
      }
      super.reset();
      curPos = markPos;
      markPos = -1;
    }

    public long getPos() {
      return curPos;
    }
    
    @Override
    public long skip(long amt) throws IOException {
      long extra = (curPos + amt) - limitPos;
      if (extra > 0) {
        throw new IOException("Tried to skip " + extra + " bytes past " +
            "the limit at offset " + limitPos);
      }
      long ret = super.skip(amt);
      curPos += ret;
      return ret;
    }
  }

  public long getLastAppliedTxId() {
    return lastAppliedTxId;
  }

  /**
   * Creates a Step used for updating startup progress, populated with
   * information from the given edits.  The step always includes the log's name.
   * If the log has a known length, then the length is included in the step too.
   * 
   * @param edits EditLogInputStream to use for populating step
   * @return Step populated with information from edits
   * @throws IOException thrown if there is an I/O error
   */
  private static Step createStartupProgressStep(EditLogInputStream edits)
      throws IOException {
    long length = edits.length();
    String name = edits.getCurrentStreamName();
    return length != -1 ? new Step(name, length) : new Step(name);
  }
}