/**
 * 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.util.Time.now;

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

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.hdfs.protocol.Block;
import org.apache.hadoop.hdfs.protocol.HdfsConstants;
import org.apache.hadoop.hdfs.protocol.LayoutVersion;
import org.apache.hadoop.hdfs.protocol.LayoutVersion.Feature;
import org.apache.hadoop.hdfs.server.blockmanagement.BlockInfo;
import org.apache.hadoop.hdfs.server.blockmanagement.BlockInfoUnderConstruction;
import org.apache.hadoop.hdfs.server.common.Storage;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AddCloseOp;
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.DeleteOp;
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.ReassignLeaseOp;
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.RenewDelegationTokenOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetGenstampOp;
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.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.LeaseManager.Lease;
import org.apache.hadoop.hdfs.util.Holder;

import com.google.common.base.Joiner;

@InterfaceAudience.Private
@InterfaceStability.Evolving
public class FSEditLogLoader {
  static final Log LOG = LogFactory.getLog(FSEditLogLoader.class.getName());
  static long REPLAY_TRANSACTION_LOG_INTERVAL = 1000; // 1sec
  private final FSNamesystem fsNamesys;
  private long lastAppliedTxId;
  
  public FSEditLogLoader(FSNamesystem fsNamesys, long lastAppliedTxId) {
    this.fsNamesys = fsNamesys;
    this.lastAppliedTxId = lastAppliedTxId;
  }
  
  /**
   * 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,
      MetaRecoveryContext recovery) throws IOException {
    fsNamesys.writeLock();
    try {
      long startTime = now();
      long numEdits = loadEditRecords(edits, false, 
                                 expectedStartingTxId, 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();
    }
  }

  long loadEditRecords(EditLogInputStream in, boolean closeOnExit,
                      long expectedStartingTxId, 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;
    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(), 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 {
            long inodeId = applyEditLogOp(op, fsDir, in.getVersion(), lastInodeId);
            if (lastInodeId < inodeId) {
              lastInodeId = inodeId;
            }
          } catch (Throwable e) {
            LOG.error("Encountered exception on operation " + op, 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);
          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++;
        } 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 (LayoutVersion.supports(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,
      int logVersion, long lastInodeId) throws IOException {
    long inodeId = INodeId.GRANDFATHER_INODE_ID;
    if (LOG.isTraceEnabled()) {
      LOG.trace("replaying edit log: " + op);
    }

    switch (op.opCode) {
    case OP_ADD: {
      AddCloseOp addCloseOp = (AddCloseOp)op;
      if (FSNamesystem.LOG.isDebugEnabled()) {
        FSNamesystem.LOG.debug(op.opCode + ": " + addCloseOp.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)
      INodeFile oldFile = getINodeFile(fsDir, addCloseOp.path);
      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 = (INodeFile) fsDir.unprotectedAddFile(inodeId,
            addCloseOp.path, addCloseOp.permissions, replication,
            addCloseOp.mtime, addCloseOp.atime, addCloseOp.blockSize, true,
            addCloseOp.clientName, addCloseOp.clientMachine);
        fsNamesys.leaseManager.addLease(addCloseOp.clientName, addCloseOp.path);

      } 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");
          }
          fsNamesys.prepareFileForWrite(addCloseOp.path, oldFile,
              addCloseOp.clientName, addCloseOp.clientMachine, null,
              false);
          newFile = getINodeFile(fsDir, addCloseOp.path);
        }
      }
      // 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);
      newFile.setModificationTimeForce(addCloseOp.mtime);
      updateBlocks(fsDir, addCloseOp, newFile);
      break;
    }
    case OP_CLOSE: {
      AddCloseOp addCloseOp = (AddCloseOp)op;
      
      if (FSNamesystem.LOG.isDebugEnabled()) {
        FSNamesystem.LOG.debug(op.opCode + ": " + addCloseOp.path +
            " numblocks : " + addCloseOp.blocks.length +
            " clientHolder " + addCloseOp.clientName +
            " clientMachine " + addCloseOp.clientMachine);
      }

      INodeFile oldFile = getINodeFile(fsDir, addCloseOp.path);
      if (oldFile == null) {
        throw new IOException("Operation trying to close non-existent file " +
            addCloseOp.path);
      }
      
      // Update the salient file attributes.
      oldFile.setAccessTime(addCloseOp.atime);
      oldFile.setModificationTimeForce(addCloseOp.mtime);
      updateBlocks(fsDir, addCloseOp, oldFile);

      // Now close the file
      if (!oldFile.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: " + addCloseOp.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 (oldFile.isUnderConstruction()) {
        INodeFileUnderConstruction ucFile = (INodeFileUnderConstruction) oldFile;
        fsNamesys.leaseManager.removeLeaseWithPrefixPath(addCloseOp.path);
        INodeFile newFile = ucFile.convertToInodeFile();
        fsDir.unprotectedReplaceNode(addCloseOp.path, ucFile, newFile);
      }
      break;
    }
    case OP_UPDATE_BLOCKS: {
      UpdateBlocksOp updateOp = (UpdateBlocksOp)op;
      if (FSNamesystem.LOG.isDebugEnabled()) {
        FSNamesystem.LOG.debug(op.opCode + ": " + updateOp.path +
            " numblocks : " + updateOp.blocks.length);
      }
      INodeFile oldFile = getINodeFile(fsDir, updateOp.path);
      if (oldFile == null) {
        throw new IOException(
            "Operation trying to update blocks in non-existent file " +
            updateOp.path);
      }
      
      // Update in-memory data structures
      updateBlocks(fsDir, updateOp, oldFile);
      break;
    }
      
    case OP_SET_REPLICATION: {
      SetReplicationOp setReplicationOp = (SetReplicationOp)op;
      short replication = fsNamesys.getBlockManager().adjustReplication(
          setReplicationOp.replication);
      fsDir.unprotectedSetReplication(setReplicationOp.path,
                                      replication, null);
      break;
    }
    case OP_CONCAT_DELETE: {
      ConcatDeleteOp concatDeleteOp = (ConcatDeleteOp)op;
      fsDir.unprotectedConcat(concatDeleteOp.trg, concatDeleteOp.srcs,
          concatDeleteOp.timestamp);
      break;
    }
    case OP_RENAME_OLD: {
      RenameOldOp renameOp = (RenameOldOp)op;
      fsDir.unprotectedRenameTo(renameOp.src, renameOp.dst,
                                renameOp.timestamp);
      break;
    }
    case OP_DELETE: {
      DeleteOp deleteOp = (DeleteOp)op;
      fsDir.unprotectedDelete(deleteOp.path, deleteOp.timestamp);
      break;
    }
    case OP_MKDIR: {
      MkdirOp mkdirOp = (MkdirOp)op;
      inodeId = getAndUpdateLastInodeId(mkdirOp.inodeId, logVersion,
          lastInodeId);
      fsDir.unprotectedMkdir(inodeId, mkdirOp.path, mkdirOp.permissions,
                             mkdirOp.timestamp);
      break;
    }
    case OP_SET_GENSTAMP: {
      SetGenstampOp setGenstampOp = (SetGenstampOp)op;
      fsNamesys.setGenerationStamp(setGenstampOp.genStamp);
      break;
    }
    case OP_SET_PERMISSIONS: {
      SetPermissionsOp setPermissionsOp = (SetPermissionsOp)op;
      fsDir.unprotectedSetPermission(setPermissionsOp.src,
                                     setPermissionsOp.permissions);
      break;
    }
    case OP_SET_OWNER: {
      SetOwnerOp setOwnerOp = (SetOwnerOp)op;
      fsDir.unprotectedSetOwner(setOwnerOp.src, setOwnerOp.username,
                                setOwnerOp.groupname);
      break;
    }
    case OP_SET_NS_QUOTA: {
      SetNSQuotaOp setNSQuotaOp = (SetNSQuotaOp)op;
      fsDir.unprotectedSetQuota(setNSQuotaOp.src,
                                setNSQuotaOp.nsQuota,
                                HdfsConstants.QUOTA_DONT_SET);
      break;
    }
    case OP_CLEAR_NS_QUOTA: {
      ClearNSQuotaOp clearNSQuotaOp = (ClearNSQuotaOp)op;
      fsDir.unprotectedSetQuota(clearNSQuotaOp.src,
                                HdfsConstants.QUOTA_RESET,
                                HdfsConstants.QUOTA_DONT_SET);
      break;
    }

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

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

      fsDir.unprotectedSetTimes(timesOp.path,
                                timesOp.mtime,
                                timesOp.atime, true);
      break;
    }
    case OP_SYMLINK: {
      SymlinkOp symlinkOp = (SymlinkOp)op;
      inodeId = getAndUpdateLastInodeId(symlinkOp.inodeId, logVersion,
          lastInodeId);
      fsDir.unprotectedAddSymlink(inodeId, symlinkOp.path,
                                  symlinkOp.value, symlinkOp.mtime, 
                                  symlinkOp.atime, symlinkOp.permissionStatus);
      break;
    }
    case OP_RENAME: {
      RenameOp renameOp = (RenameOp)op;
      fsDir.unprotectedRenameTo(renameOp.src, renameOp.dst,
                                renameOp.timestamp, renameOp.options);
      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);
      INodeFileUnderConstruction pendingFile =
          INodeFileUnderConstruction.valueOf( 
              fsDir.getINode(reassignLeaseOp.path), reassignLeaseOp.path);
      fsNamesys.reassignLeaseInternal(lease,
          reassignLeaseOp.path, reassignLeaseOp.newHolder, pendingFile);
      break;
    }
    case OP_START_LOG_SEGMENT:
    case OP_END_LOG_SEGMENT: {
      // no data in here currently.
      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();
  }
  
  private static INodeFile getINodeFile(FSDirectory fsDir, String path)
      throws IOException {
    INode inode = fsDir.getINode(path);
    if (inode != null) {
      if (!(inode instanceof INodeFile)) {
        throw new IOException("Operation trying to get non-file " + path);
      }
    }
    return (INodeFile)inode;
  }
  
  /**
   * 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(
            (INodeFileUnderConstruction)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);
      }
      fsDir.unprotectedRemoveBlock(path,
          (INodeFileUnderConstruction)file, oldBlocks[oldBlocks.length - 1]);
    } 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) {
    Holder<Integer> holder = opCounts.get(opCode);
    if (holder == null) {
      holder = new Holder<Integer>(1);
      opCounts.put(opCode, holder);
    } else {
      holder.held++;
    }
  }

  /**
   * 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.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.
   *
   * @throws IOException if the stream cannot be read due to an IO error (eg
   *                     if the log does not exist)
   */
  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 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;
  }
}