Java Code Examples for org.apache.hadoop.hdfs.protocol.ExtendedBlock#getBlockId()

private static ExtendedBlock[][] generateBlocks(Suite s, long size
    ) throws IOException, InterruptedException, TimeoutException {
  final ExtendedBlock[][] blocks = new ExtendedBlock[s.clients.length][];
  for(int n = 0; n < s.clients.length; n++) {
    final long fileLen = size/s.replication;
    createFile(s, n, fileLen);

    final List<LocatedBlock> locatedBlocks = s.clients[n].getBlockLocations(
        FILE_NAME, 0, fileLen).getLocatedBlocks();

    final int numOfBlocks = locatedBlocks.size();
    blocks[n] = new ExtendedBlock[numOfBlocks];
    for(int i = 0; i < numOfBlocks; i++) {
      final ExtendedBlock b = locatedBlocks.get(i).getBlock();
      blocks[n][i] = new ExtendedBlock(b.getBlockPoolId(), b.getBlockId(),
          b.getNumBytes(), b.getGenerationStamp());
    }
  }
  return blocks;
}
 

private static ExtendedBlock[][] generateBlocks(Suite s, long size
    ) throws IOException, InterruptedException, TimeoutException {
  final ExtendedBlock[][] blocks = new ExtendedBlock[s.clients.length][];
  for(int n = 0; n < s.clients.length; n++) {
    final long fileLen = size/s.replication;
    createFile(s, n, fileLen);

    final List<LocatedBlock> locatedBlocks = s.clients[n].getBlockLocations(
        FILE_NAME, 0, fileLen).getLocatedBlocks();

    final int numOfBlocks = locatedBlocks.size();
    blocks[n] = new ExtendedBlock[numOfBlocks];
    for(int i = 0; i < numOfBlocks; i++) {
      final ExtendedBlock b = locatedBlocks.get(i).getBlock();
      blocks[n][i] = new ExtendedBlock(b.getBlockPoolId(), b.getBlockId(),
          b.getNumBytes(), b.getGenerationStamp());
    }
  }
  return blocks;
}
 

/** Generate a block token for a specified user */
public Token<BlockTokenIdentifier> generateToken(String userId,
    ExtendedBlock block, EnumSet<AccessMode> modes) throws IOException {
  BlockTokenIdentifier id = new BlockTokenIdentifier(userId, block
      .getBlockPoolId(), block.getBlockId(), modes);
  return new Token<BlockTokenIdentifier>(id, this);
}
 

static void checkSuccess(
    BlockOpResponseProto status, Peer peer,
    ExtendedBlock block, String file)
    throws IOException {
  String logInfo = "for OP_READ_BLOCK"
    + ", self=" + peer.getLocalAddressString()
    + ", remote=" + peer.getRemoteAddressString()
    + ", for file " + file
    + ", for pool " + block.getBlockPoolId()
    + " block " + block.getBlockId() + "_" + block.getGenerationStamp();
  DataTransferProtoUtil.checkBlockOpStatus(status, logInfo);
}
 

/**
 * Check if access should be allowed. userID is not checked if null. This
 * method doesn't check if token password is correct. It should be used only
 * when token password has already been verified (e.g., in the RPC layer).
 */
public void checkAccess(BlockTokenIdentifier id, String userId,
    ExtendedBlock block, AccessMode mode) throws InvalidToken {
  if (LOG.isDebugEnabled()) {
    LOG.debug("Checking access for user=" + userId + ", block=" + block
        + ", access mode=" + mode + " using " + id.toString());
  }
  if (userId != null && !userId.equals(id.getUserId())) {
    throw new InvalidToken("Block token with " + id.toString()
        + " doesn't belong to user " + userId);
  }
  if (!id.getBlockPoolId().equals(block.getBlockPoolId())) {
    throw new InvalidToken("Block token with " + id.toString()
        + " doesn't apply to block " + block);
  }
  if (id.getBlockId() != block.getBlockId()) {
    throw new InvalidToken("Block token with " + id.toString()
        + " doesn't apply to block " + block);
  }
  if (isExpired(id.getExpiryDate())) {
    throw new InvalidToken("Block token with " + id.toString()
        + " is expired.");
  }
  if (!id.getAccessModes().contains(mode)) {
    throw new InvalidToken("Block token with " + id.toString()
        + " doesn't have " + mode + " permission");
  }
}
 

/** Generate a block token for a specified user */
public Token<BlockTokenIdentifier> generateToken(String userId,
    ExtendedBlock block, EnumSet<AccessMode> modes) throws IOException {
  BlockTokenIdentifier id = new BlockTokenIdentifier(userId, block
      .getBlockPoolId(), block.getBlockId(), modes);
  return new Token<BlockTokenIdentifier>(id, this);
}
 

static void checkSuccess(
    BlockOpResponseProto status, Peer peer,
    ExtendedBlock block, String file)
    throws IOException {
  String logInfo = "for OP_READ_BLOCK"
    + ", self=" + peer.getLocalAddressString()
    + ", remote=" + peer.getRemoteAddressString()
    + ", for file " + file
    + ", for pool " + block.getBlockPoolId()
    + " block " + block.getBlockId() + "_" + block.getGenerationStamp();
  DataTransferProtoUtil.checkBlockOpStatus(status, logInfo);
}
 

/**
 * The following test first creates a file.
 * It verifies the block information from a datanode.
 * Then, it updates the block with new information and verifies again.
 * @param useDnHostname whether DNs should connect to other DNs by hostname
 */
private void checkBlockMetaDataInfo(boolean useDnHostname) throws Exception {
  MiniDFSCluster cluster = null;

  conf.setBoolean(DFSConfigKeys.DFS_DATANODE_USE_DN_HOSTNAME, useDnHostname);
  if (useDnHostname) {
    // Since the mini cluster only listens on the loopback we have to
    // ensure the hostname used to access DNs maps to the loopback. We
    // do this by telling the DN to advertise localhost as its hostname
    // instead of the default hostname.
    conf.set(DFSConfigKeys.DFS_DATANODE_HOST_NAME_KEY, "localhost");
  }

  try {
    cluster = new MiniDFSCluster.Builder(conf)
      .numDataNodes(3)
      .checkDataNodeHostConfig(true)
      .build();
    cluster.waitActive();

    //create a file
    DistributedFileSystem dfs = cluster.getFileSystem();
    String filestr = "/foo";
    Path filepath = new Path(filestr);
    DFSTestUtil.createFile(dfs, filepath, 1024L, (short)3, 0L);
    assertTrue(dfs.exists(filepath));

    //get block info
    LocatedBlock locatedblock = getLastLocatedBlock(
        DFSClientAdapter.getDFSClient(dfs).getNamenode(), filestr);
    DatanodeInfo[] datanodeinfo = locatedblock.getLocations();
    assertTrue(datanodeinfo.length > 0);

    //connect to a data node
    DataNode datanode = cluster.getDataNode(datanodeinfo[0].getIpcPort());
    InterDatanodeProtocol idp = DataNodeTestUtils.createInterDatanodeProtocolProxy(
        datanode, datanodeinfo[0], conf, useDnHostname);
    
    // Stop the block scanners.
    datanode.getBlockScanner().removeAllVolumeScanners();

    //verify BlockMetaDataInfo
    ExtendedBlock b = locatedblock.getBlock();
    InterDatanodeProtocol.LOG.info("b=" + b + ", " + b.getClass());
    checkMetaInfo(b, datanode);
    long recoveryId = b.getGenerationStamp() + 1;
    idp.initReplicaRecovery(
        new RecoveringBlock(b, locatedblock.getLocations(), recoveryId));

    //verify updateBlock
    ExtendedBlock newblock = new ExtendedBlock(b.getBlockPoolId(),
        b.getBlockId(), b.getNumBytes()/2, b.getGenerationStamp()+1);
    idp.updateReplicaUnderRecovery(b, recoveryId, b.getBlockId(),
        newblock.getNumBytes());
    checkMetaInfo(newblock, datanode);
    
    // Verify correct null response trying to init recovery for a missing block
    ExtendedBlock badBlock = new ExtendedBlock("fake-pool",
        b.getBlockId(), 0, 0);
    assertNull(idp.initReplicaRecovery(
        new RecoveringBlock(badBlock,
            locatedblock.getLocations(), recoveryId)));
  }
  finally {
    if (cluster != null) {cluster.shutdown();}
  }
}
 

@Override // FsDatasetSpi
public synchronized ReplicaHandler createRbw(
    StorageType storageType, ExtendedBlock b, boolean allowLazyPersist)
    throws IOException {
  ReplicaInfo replicaInfo = volumeMap.get(b.getBlockPoolId(),
      b.getBlockId());
  if (replicaInfo != null) {
    throw new ReplicaAlreadyExistsException("Block " + b +
    " already exists in state " + replicaInfo.getState() +
    " and thus cannot be created.");
  }
  // create a new block
  FsVolumeReference ref;
  while (true) {
    try {
      if (allowLazyPersist) {
        // First try to place the block on a transient volume.
        ref = volumes.getNextTransientVolume(b.getNumBytes());
        datanode.getMetrics().incrRamDiskBlocksWrite();
      } else {
        ref = volumes.getNextVolume(storageType, b.getNumBytes());
      }
    } catch (DiskOutOfSpaceException de) {
      if (allowLazyPersist) {
        datanode.getMetrics().incrRamDiskBlocksWriteFallback();
        allowLazyPersist = false;
        continue;
      }
      throw de;
    }
    break;
  }
  FsVolumeImpl v = (FsVolumeImpl) ref.getVolume();
  // create an rbw file to hold block in the designated volume
  File f;
  try {
    f = v.createRbwFile(b.getBlockPoolId(), b.getLocalBlock());
  } catch (IOException e) {
    IOUtils.cleanup(null, ref);
    throw e;
  }

  ReplicaBeingWritten newReplicaInfo = new ReplicaBeingWritten(b.getBlockId(), 
      b.getGenerationStamp(), v, f.getParentFile(), b.getNumBytes());
  volumeMap.add(b.getBlockPoolId(), newReplicaInfo);
  return new ReplicaHandler(newReplicaInfo, ref);
}
 

@Override // FsDatasetSpi
public synchronized ReplicaInPipeline convertTemporaryToRbw(
    final ExtendedBlock b) throws IOException {
  final long blockId = b.getBlockId();
  final long expectedGs = b.getGenerationStamp();
  final long visible = b.getNumBytes();
  LOG.info("Convert " + b + " from Temporary to RBW, visible length="
      + visible);

  final ReplicaInPipeline temp;
  {
    // get replica
    final ReplicaInfo r = volumeMap.get(b.getBlockPoolId(), blockId);
    if (r == null) {
      throw new ReplicaNotFoundException(
          ReplicaNotFoundException.NON_EXISTENT_REPLICA + b);
    }
    // check the replica's state
    if (r.getState() != ReplicaState.TEMPORARY) {
      throw new ReplicaAlreadyExistsException(
          "r.getState() != ReplicaState.TEMPORARY, r=" + r);
    }
    temp = (ReplicaInPipeline)r;
  }
  // check generation stamp
  if (temp.getGenerationStamp() != expectedGs) {
    throw new ReplicaAlreadyExistsException(
        "temp.getGenerationStamp() != expectedGs = " + expectedGs
        + ", temp=" + temp);
  }

  // TODO: check writer?
  // set writer to the current thread
  // temp.setWriter(Thread.currentThread());

  // check length
  final long numBytes = temp.getNumBytes();
  if (numBytes < visible) {
    throw new IOException(numBytes + " = numBytes < visible = "
        + visible + ", temp=" + temp);
  }
  // check volume
  final FsVolumeImpl v = (FsVolumeImpl)temp.getVolume();
  if (v == null) {
    throw new IOException("r.getVolume() = null, temp="  + temp);
  }
  
  // move block files to the rbw directory
  BlockPoolSlice bpslice = v.getBlockPoolSlice(b.getBlockPoolId());
  final File dest = moveBlockFiles(b.getLocalBlock(), temp.getBlockFile(), 
      bpslice.getRbwDir());
  // create RBW
  final ReplicaBeingWritten rbw = new ReplicaBeingWritten(
      blockId, numBytes, expectedGs,
      v, dest.getParentFile(), Thread.currentThread(), 0);
  rbw.setBytesAcked(visible);
  // overwrite the RBW in the volume map
  volumeMap.add(b.getBlockPoolId(), rbw);
  return rbw;
}
 

@Override // FsDatasetSpi
public ReplicaHandler createTemporary(
    StorageType storageType, ExtendedBlock b) throws IOException {
  long startTimeMs = Time.monotonicNow();
  long writerStopTimeoutMs = datanode.getDnConf().getXceiverStopTimeout();
  ReplicaInfo lastFoundReplicaInfo = null;
  do {
    synchronized (this) {
      ReplicaInfo currentReplicaInfo =
          volumeMap.get(b.getBlockPoolId(), b.getBlockId());
      if (currentReplicaInfo == lastFoundReplicaInfo) {
        if (lastFoundReplicaInfo != null) {
          invalidate(b.getBlockPoolId(), new Block[] { lastFoundReplicaInfo });
        }
        FsVolumeReference ref =
            volumes.getNextVolume(storageType, b.getNumBytes());
        FsVolumeImpl v = (FsVolumeImpl) ref.getVolume();
        // create a temporary file to hold block in the designated volume
        File f;
        try {
          f = v.createTmpFile(b.getBlockPoolId(), b.getLocalBlock());
        } catch (IOException e) {
          IOUtils.cleanup(null, ref);
          throw e;
        }
        ReplicaInPipeline newReplicaInfo =
            new ReplicaInPipeline(b.getBlockId(), b.getGenerationStamp(), v,
                f.getParentFile(), 0);
        volumeMap.add(b.getBlockPoolId(), newReplicaInfo);
        return new ReplicaHandler(newReplicaInfo, ref);
      } else {
        if (!(currentReplicaInfo.getGenerationStamp() < b
            .getGenerationStamp() && currentReplicaInfo instanceof ReplicaInPipeline)) {
          throw new ReplicaAlreadyExistsException("Block " + b
              + " already exists in state " + currentReplicaInfo.getState()
              + " and thus cannot be created.");
        }
        lastFoundReplicaInfo = currentReplicaInfo;
      }
    }

    // Hang too long, just bail out. This is not supposed to happen.
    long writerStopMs = Time.monotonicNow() - startTimeMs;
    if (writerStopMs > writerStopTimeoutMs) {
      LOG.warn("Unable to stop existing writer for block " + b + " after " 
          + writerStopMs + " miniseconds.");
      throw new IOException("Unable to stop existing writer for block " + b
          + " after " + writerStopMs + " miniseconds.");
    }

    // Stop the previous writer
    ((ReplicaInPipeline) lastFoundReplicaInfo)
        .stopWriter(writerStopTimeoutMs);
  } while (true);
}
 

private BlockReaderLocalLegacy(DFSClient.Conf conf, String hdfsfile,
    ExtendedBlock block, Token<BlockTokenIdentifier> token, long startOffset,
    long length, BlockLocalPathInfo pathinfo, DataChecksum checksum,
    boolean verifyChecksum, FileInputStream dataIn, long firstChunkOffset,
    FileInputStream checksumIn) throws IOException {
  this.filename = hdfsfile;
  this.checksum = checksum;
  this.verifyChecksum = verifyChecksum;
  this.startOffset = Math.max(startOffset, 0);
  this.blockId = block.getBlockId();

  bytesPerChecksum = this.checksum.getBytesPerChecksum();
  checksumSize = this.checksum.getChecksumSize();

  this.dataIn = dataIn;
  this.checksumIn = checksumIn;
  this.offsetFromChunkBoundary = (int) (startOffset-firstChunkOffset);

  int chunksPerChecksumRead = getSlowReadBufferNumChunks(
      conf.shortCircuitBufferSize, bytesPerChecksum);
  slowReadBuff = bufferPool.getBuffer(bytesPerChecksum * chunksPerChecksumRead);
  checksumBuff = bufferPool.getBuffer(checksumSize * chunksPerChecksumRead);
  // Initially the buffers have nothing to read.
  slowReadBuff.flip();
  checksumBuff.flip();
  boolean success = false;
  try {
    // Skip both input streams to beginning of the chunk containing startOffset
    IOUtils.skipFully(dataIn, firstChunkOffset);
    if (checksumIn != null) {
      long checkSumOffset = (firstChunkOffset / bytesPerChecksum) * checksumSize;
      IOUtils.skipFully(checksumIn, checkSumOffset);
    }
    success = true;
  } finally {
    if (!success) {
      bufferPool.returnBuffer(slowReadBuff);
      bufferPool.returnBuffer(checksumBuff);
    }
  }
}
 

/**
 * The following test first creates a file.
 * It verifies the block information from a datanode.
 * Then, it updates the block with new information and verifies again.
 * @param useDnHostname whether DNs should connect to other DNs by hostname
 */
private void checkBlockMetaDataInfo(boolean useDnHostname) throws Exception {
  MiniDFSCluster cluster = null;

  conf.setBoolean(DFSConfigKeys.DFS_DATANODE_USE_DN_HOSTNAME, useDnHostname);
  if (useDnHostname) {
    // Since the mini cluster only listens on the loopback we have to
    // ensure the hostname used to access DNs maps to the loopback. We
    // do this by telling the DN to advertise localhost as its hostname
    // instead of the default hostname.
    conf.set(DFSConfigKeys.DFS_DATANODE_HOST_NAME_KEY, "localhost");
  }

  try {
    cluster = new MiniDFSCluster.Builder(conf)
      .numDataNodes(3)
      .checkDataNodeHostConfig(true)
      .build();
    cluster.waitActive();

    //create a file
    DistributedFileSystem dfs = cluster.getFileSystem();
    String filestr = "/foo";
    Path filepath = new Path(filestr);
    DFSTestUtil.createFile(dfs, filepath, 1024L, (short)3, 0L);
    assertTrue(dfs.exists(filepath));

    //get block info
    LocatedBlock locatedblock = getLastLocatedBlock(
        DFSClientAdapter.getDFSClient(dfs).getNamenode(), filestr);
    DatanodeInfo[] datanodeinfo = locatedblock.getLocations();
    assertTrue(datanodeinfo.length > 0);

    //connect to a data node
    DataNode datanode = cluster.getDataNode(datanodeinfo[0].getIpcPort());
    InterDatanodeProtocol idp = DataNodeTestUtils.createInterDatanodeProtocolProxy(
        datanode, datanodeinfo[0], conf, useDnHostname);
    
    // Stop the block scanners.
    datanode.getBlockScanner().removeAllVolumeScanners();

    //verify BlockMetaDataInfo
    ExtendedBlock b = locatedblock.getBlock();
    InterDatanodeProtocol.LOG.info("b=" + b + ", " + b.getClass());
    checkMetaInfo(b, datanode);
    long recoveryId = b.getGenerationStamp() + 1;
    idp.initReplicaRecovery(
        new RecoveringBlock(b, locatedblock.getLocations(), recoveryId));

    //verify updateBlock
    ExtendedBlock newblock = new ExtendedBlock(b.getBlockPoolId(),
        b.getBlockId(), b.getNumBytes()/2, b.getGenerationStamp()+1);
    idp.updateReplicaUnderRecovery(b, recoveryId, b.getBlockId(),
        newblock.getNumBytes());
    checkMetaInfo(newblock, datanode);
    
    // Verify correct null response trying to init recovery for a missing block
    ExtendedBlock badBlock = new ExtendedBlock("fake-pool",
        b.getBlockId(), 0, 0);
    assertNull(idp.initReplicaRecovery(
        new RecoveringBlock(badBlock,
            locatedblock.getLocations(), recoveryId)));
  }
  finally {
    if (cluster != null) {cluster.shutdown();}
  }
}
 

/**
 * Create a new BlockReader specifically to satisfy a read.
 * This method also sends the OP_READ_BLOCK request.
 *
 * @param file  File location
 * @param block  The block object
 * @param blockToken  The block token for security
 * @param startOffset  The read offset, relative to block head
 * @param len  The number of bytes to read
 * @param bufferSize  The IO buffer size (not the client buffer size)
 * @param verifyChecksum  Whether to verify checksum
 * @param clientName  Client name
 * @return New BlockReader instance, or null on error.
 */
public static RemoteBlockReader newBlockReader(String file,
                                   ExtendedBlock block, 
                                   Token<BlockTokenIdentifier> blockToken,
                                   long startOffset, long len,
                                   int bufferSize, boolean verifyChecksum,
                                   String clientName, Peer peer,
                                   DatanodeID datanodeID,
                                   PeerCache peerCache,
                                   CachingStrategy cachingStrategy)
                                     throws IOException {
  // in and out will be closed when sock is closed (by the caller)
  final DataOutputStream out =
      new DataOutputStream(new BufferedOutputStream(peer.getOutputStream()));
  new Sender(out).readBlock(block, blockToken, clientName, startOffset, len,
      verifyChecksum, cachingStrategy);
  
  //
  // Get bytes in block, set streams
  //

  DataInputStream in = new DataInputStream(
      new BufferedInputStream(peer.getInputStream(), bufferSize));
  
  BlockOpResponseProto status = BlockOpResponseProto.parseFrom(
      PBHelper.vintPrefixed(in));
  RemoteBlockReader2.checkSuccess(status, peer, block, file);
  ReadOpChecksumInfoProto checksumInfo =
    status.getReadOpChecksumInfo();
  DataChecksum checksum = DataTransferProtoUtil.fromProto(
      checksumInfo.getChecksum());
  //Warning when we get CHECKSUM_NULL?
  
  // Read the first chunk offset.
  long firstChunkOffset = checksumInfo.getChunkOffset();
  
  if ( firstChunkOffset < 0 || firstChunkOffset > startOffset ||
      firstChunkOffset <= (startOffset - checksum.getBytesPerChecksum())) {
    throw new IOException("BlockReader: error in first chunk offset (" +
                          firstChunkOffset + ") startOffset is " + 
                          startOffset + " for file " + file);
  }

  return new RemoteBlockReader(file, block.getBlockPoolId(), block.getBlockId(),
      in, checksum, verifyChecksum, startOffset, firstChunkOffset, len,
      peer, datanodeID, peerCache);
}
 

/**
 * Create a new BlockReader specifically to satisfy a read.
 * This method also sends the OP_READ_BLOCK request.
 *
 * @param file  File location
 * @param block  The block object
 * @param blockToken  The block token for security
 * @param startOffset  The read offset, relative to block head
 * @param len  The number of bytes to read
 * @param verifyChecksum  Whether to verify checksum
 * @param clientName  Client name
 * @param peer  The Peer to use
 * @param datanodeID  The DatanodeID this peer is connected to
 * @return New BlockReader instance, or null on error.
 */
public static BlockReader newBlockReader(String file,
                                   ExtendedBlock block,
                                   Token<BlockTokenIdentifier> blockToken,
                                   long startOffset, long len,
                                   boolean verifyChecksum,
                                   String clientName,
                                   Peer peer, DatanodeID datanodeID,
                                   PeerCache peerCache,
                                   CachingStrategy cachingStrategy) throws IOException {
  // in and out will be closed when sock is closed (by the caller)
  final DataOutputStream out = new DataOutputStream(new BufferedOutputStream(
        peer.getOutputStream()));
  new Sender(out).readBlock(block, blockToken, clientName, startOffset, len,
      verifyChecksum, cachingStrategy);

  //
  // Get bytes in block
  //
  DataInputStream in = new DataInputStream(peer.getInputStream());

  BlockOpResponseProto status = BlockOpResponseProto.parseFrom(
      PBHelper.vintPrefixed(in));
  checkSuccess(status, peer, block, file);
  ReadOpChecksumInfoProto checksumInfo =
    status.getReadOpChecksumInfo();
  DataChecksum checksum = DataTransferProtoUtil.fromProto(
      checksumInfo.getChecksum());
  //Warning when we get CHECKSUM_NULL?

  // Read the first chunk offset.
  long firstChunkOffset = checksumInfo.getChunkOffset();

  if ( firstChunkOffset < 0 || firstChunkOffset > startOffset ||
      firstChunkOffset <= (startOffset - checksum.getBytesPerChecksum())) {
    throw new IOException("BlockReader: error in first chunk offset (" +
                          firstChunkOffset + ") startOffset is " +
                          startOffset + " for file " + file);
  }

  return new RemoteBlockReader2(file, block.getBlockPoolId(), block.getBlockId(),
      checksum, verifyChecksum, startOffset, firstChunkOffset, len, peer,
      datanodeID, peerCache);
}
 

/**
 * Create a new BlockReader specifically to satisfy a read.
 * This method also sends the OP_READ_BLOCK request.
 *
 * @param file  File location
 * @param block  The block object
 * @param blockToken  The block token for security
 * @param startOffset  The read offset, relative to block head
 * @param len  The number of bytes to read
 * @param verifyChecksum  Whether to verify checksum
 * @param clientName  Client name
 * @param peer  The Peer to use
 * @param datanodeID  The DatanodeID this peer is connected to
 * @return New BlockReader instance, or null on error.
 */
public static BlockReader newBlockReader(String file,
                                   ExtendedBlock block,
                                   Token<BlockTokenIdentifier> blockToken,
                                   long startOffset, long len,
                                   boolean verifyChecksum,
                                   String clientName,
                                   Peer peer, DatanodeID datanodeID,
                                   PeerCache peerCache,
                                   CachingStrategy cachingStrategy) throws IOException {
  // in and out will be closed when sock is closed (by the caller)
  final DataOutputStream out = new DataOutputStream(new BufferedOutputStream(
        peer.getOutputStream()));
  new Sender(out).readBlock(block, blockToken, clientName, startOffset, len,
      verifyChecksum, cachingStrategy);

  //
  // Get bytes in block
  //
  DataInputStream in = new DataInputStream(peer.getInputStream());

  BlockOpResponseProto status = BlockOpResponseProto.parseFrom(
      PBHelper.vintPrefixed(in));
  checkSuccess(status, peer, block, file);
  ReadOpChecksumInfoProto checksumInfo =
    status.getReadOpChecksumInfo();
  DataChecksum checksum = DataTransferProtoUtil.fromProto(
      checksumInfo.getChecksum());
  //Warning when we get CHECKSUM_NULL?

  // Read the first chunk offset.
  long firstChunkOffset = checksumInfo.getChunkOffset();

  if ( firstChunkOffset < 0 || firstChunkOffset > startOffset ||
      firstChunkOffset <= (startOffset - checksum.getBytesPerChecksum())) {
    throw new IOException("BlockReader: error in first chunk offset (" +
                          firstChunkOffset + ") startOffset is " +
                          startOffset + " for file " + file);
  }

  return new RemoteBlockReader2(file, block.getBlockPoolId(), block.getBlockId(),
      checksum, verifyChecksum, startOffset, firstChunkOffset, len, peer,
      datanodeID, peerCache);
}
 

/**
 * Create a new BlockReader specifically to satisfy a read.
 * This method also sends the OP_READ_BLOCK request.
 *
 * @param file  File location
 * @param block  The block object
 * @param blockToken  The block token for security
 * @param startOffset  The read offset, relative to block head
 * @param len  The number of bytes to read
 * @param bufferSize  The IO buffer size (not the client buffer size)
 * @param verifyChecksum  Whether to verify checksum
 * @param clientName  Client name
 * @return New BlockReader instance, or null on error.
 */
public static RemoteBlockReader newBlockReader(String file,
                                   ExtendedBlock block, 
                                   Token<BlockTokenIdentifier> blockToken,
                                   long startOffset, long len,
                                   int bufferSize, boolean verifyChecksum,
                                   String clientName, Peer peer,
                                   DatanodeID datanodeID,
                                   PeerCache peerCache,
                                   CachingStrategy cachingStrategy)
                                     throws IOException {
  // in and out will be closed when sock is closed (by the caller)
  final DataOutputStream out =
      new DataOutputStream(new BufferedOutputStream(peer.getOutputStream()));
  new Sender(out).readBlock(block, blockToken, clientName, startOffset, len,
      verifyChecksum, cachingStrategy);
  
  //
  // Get bytes in block, set streams
  //

  DataInputStream in = new DataInputStream(
      new BufferedInputStream(peer.getInputStream(), bufferSize));
  
  BlockOpResponseProto status = BlockOpResponseProto.parseFrom(
      PBHelper.vintPrefixed(in));
  RemoteBlockReader2.checkSuccess(status, peer, block, file);
  ReadOpChecksumInfoProto checksumInfo =
    status.getReadOpChecksumInfo();
  DataChecksum checksum = DataTransferProtoUtil.fromProto(
      checksumInfo.getChecksum());
  //Warning when we get CHECKSUM_NULL?
  
  // Read the first chunk offset.
  long firstChunkOffset = checksumInfo.getChunkOffset();
  
  if ( firstChunkOffset < 0 || firstChunkOffset > startOffset ||
      firstChunkOffset <= (startOffset - checksum.getBytesPerChecksum())) {
    throw new IOException("BlockReader: error in first chunk offset (" +
                          firstChunkOffset + ") startOffset is " + 
                          startOffset + " for file " + file);
  }

  return new RemoteBlockReader(file, block.getBlockPoolId(), block.getBlockId(),
      in, checksum, verifyChecksum, startOffset, firstChunkOffset, len,
      peer, datanodeID, peerCache);
}
 

private BlockReaderLocalLegacy(DFSClient.Conf conf, String hdfsfile,
    ExtendedBlock block, Token<BlockTokenIdentifier> token, long startOffset,
    long length, BlockLocalPathInfo pathinfo, DataChecksum checksum,
    boolean verifyChecksum, FileInputStream dataIn, long firstChunkOffset,
    FileInputStream checksumIn) throws IOException {
  this.filename = hdfsfile;
  this.checksum = checksum;
  this.verifyChecksum = verifyChecksum;
  this.startOffset = Math.max(startOffset, 0);
  this.blockId = block.getBlockId();

  bytesPerChecksum = this.checksum.getBytesPerChecksum();
  checksumSize = this.checksum.getChecksumSize();

  this.dataIn = dataIn;
  this.checksumIn = checksumIn;
  this.offsetFromChunkBoundary = (int) (startOffset-firstChunkOffset);

  int chunksPerChecksumRead = getSlowReadBufferNumChunks(
      conf.shortCircuitBufferSize, bytesPerChecksum);
  slowReadBuff = bufferPool.getBuffer(bytesPerChecksum * chunksPerChecksumRead);
  checksumBuff = bufferPool.getBuffer(checksumSize * chunksPerChecksumRead);
  // Initially the buffers have nothing to read.
  slowReadBuff.flip();
  checksumBuff.flip();
  boolean success = false;
  try {
    // Skip both input streams to beginning of the chunk containing startOffset
    IOUtils.skipFully(dataIn, firstChunkOffset);
    if (checksumIn != null) {
      long checkSumOffset = (firstChunkOffset / bytesPerChecksum) * checksumSize;
      IOUtils.skipFully(checksumIn, checkSumOffset);
    }
    success = true;
  } finally {
    if (!success) {
      bufferPool.returnBuffer(slowReadBuff);
      bufferPool.returnBuffer(checksumBuff);
    }
  }
}
 

@Override // FsDatasetSpi
public ReplicaHandler createTemporary(
    StorageType storageType, ExtendedBlock b) throws IOException {
  long startTimeMs = Time.monotonicNow();
  long writerStopTimeoutMs = datanode.getDnConf().getXceiverStopTimeout();
  ReplicaInfo lastFoundReplicaInfo = null;
  do {
    synchronized (this) {
      ReplicaInfo currentReplicaInfo =
          volumeMap.get(b.getBlockPoolId(), b.getBlockId());
      if (currentReplicaInfo == lastFoundReplicaInfo) {
        if (lastFoundReplicaInfo != null) {
          invalidate(b.getBlockPoolId(), new Block[] { lastFoundReplicaInfo });
        }
        FsVolumeReference ref =
            volumes.getNextVolume(storageType, b.getNumBytes());
        FsVolumeImpl v = (FsVolumeImpl) ref.getVolume();
        // create a temporary file to hold block in the designated volume
        File f;
        try {
          f = v.createTmpFile(b.getBlockPoolId(), b.getLocalBlock());
        } catch (IOException e) {
          IOUtils.cleanup(null, ref);
          throw e;
        }
        ReplicaInPipeline newReplicaInfo =
            new ReplicaInPipeline(b.getBlockId(), b.getGenerationStamp(), v,
                f.getParentFile(), 0);
        volumeMap.add(b.getBlockPoolId(), newReplicaInfo);
        return new ReplicaHandler(newReplicaInfo, ref);
      } else {
        if (!(currentReplicaInfo.getGenerationStamp() < b
            .getGenerationStamp() && currentReplicaInfo instanceof ReplicaInPipeline)) {
          throw new ReplicaAlreadyExistsException("Block " + b
              + " already exists in state " + currentReplicaInfo.getState()
              + " and thus cannot be created.");
        }
        lastFoundReplicaInfo = currentReplicaInfo;
      }
    }

    // Hang too long, just bail out. This is not supposed to happen.
    long writerStopMs = Time.monotonicNow() - startTimeMs;
    if (writerStopMs > writerStopTimeoutMs) {
      LOG.warn("Unable to stop existing writer for block " + b + " after " 
          + writerStopMs + " miniseconds.");
      throw new IOException("Unable to stop existing writer for block " + b
          + " after " + writerStopMs + " miniseconds.");
    }

    // Stop the previous writer
    ((ReplicaInPipeline) lastFoundReplicaInfo)
        .stopWriter(writerStopTimeoutMs);
  } while (true);
}
 

@Override // FsDatasetSpi
public synchronized ReplicaHandler createRbw(
    StorageType storageType, ExtendedBlock b, boolean allowLazyPersist)
    throws IOException {
  ReplicaInfo replicaInfo = volumeMap.get(b.getBlockPoolId(),
      b.getBlockId());
  if (replicaInfo != null) {
    throw new ReplicaAlreadyExistsException("Block " + b +
    " already exists in state " + replicaInfo.getState() +
    " and thus cannot be created.");
  }
  // create a new block
  FsVolumeReference ref;
  while (true) {
    try {
      if (allowLazyPersist) {
        // First try to place the block on a transient volume.
        ref = volumes.getNextTransientVolume(b.getNumBytes());
        datanode.getMetrics().incrRamDiskBlocksWrite();
      } else {
        ref = volumes.getNextVolume(storageType, b.getNumBytes());
      }
    } catch (DiskOutOfSpaceException de) {
      if (allowLazyPersist) {
        datanode.getMetrics().incrRamDiskBlocksWriteFallback();
        allowLazyPersist = false;
        continue;
      }
      throw de;
    }
    break;
  }
  FsVolumeImpl v = (FsVolumeImpl) ref.getVolume();
  // create an rbw file to hold block in the designated volume
  File f;
  try {
    f = v.createRbwFile(b.getBlockPoolId(), b.getLocalBlock());
  } catch (IOException e) {
    IOUtils.cleanup(null, ref);
    throw e;
  }

  ReplicaBeingWritten newReplicaInfo = new ReplicaBeingWritten(b.getBlockId(), 
      b.getGenerationStamp(), v, f.getParentFile(), b.getNumBytes());
  volumeMap.add(b.getBlockPoolId(), newReplicaInfo);
  return new ReplicaHandler(newReplicaInfo, ref);
}