/**
* 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;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.util.AbstractMap;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.fs.ChecksumException;
import org.apache.hadoop.fs.FSInputStream;
import org.apache.hadoop.fs.UnresolvedLinkException;
import org.apache.hadoop.hdfs.protocol.ClientDatanodeProtocol;
import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
import org.apache.hadoop.hdfs.protocol.LocatedBlock;
import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier;
import org.apache.hadoop.hdfs.security.token.block.InvalidBlockTokenException;
import org.apache.hadoop.hdfs.server.datanode.ReplicaNotFoundException;
import org.apache.hadoop.ipc.RPC;
import org.apache.hadoop.ipc.RemoteException;
import org.apache.hadoop.net.NetUtils;
import org.apache.hadoop.security.AccessControlException;
import org.apache.hadoop.security.token.Token;
/****************************************************************
* DFSInputStream provides bytes from a named file. It handles
* negotiation of the namenode and various datanodes as necessary.
****************************************************************/
@InterfaceAudience.Private
public class DFSInputStream extends FSInputStream {
private final SocketCache socketCache;
private final DFSClient dfsClient;
private boolean closed = false;
private final String src;
private long prefetchSize;
private BlockReader blockReader = null;
private boolean verifyChecksum;
private LocatedBlocks locatedBlocks = null;
private long lastBlockBeingWrittenLength = 0;
private DatanodeInfo currentNode = null;
private LocatedBlock currentLocatedBlock = null;
private long pos = 0;
private long blockEnd = -1;
/**
* This variable tracks the number of failures since the start of the
* most recent user-facing operation. That is to say, it should be reset
* whenever the user makes a call on this stream, and if at any point
* during the retry logic, the failure count exceeds a threshold,
* the errors will be thrown back to the operation.
*
* Specifically this counts the number of times the client has gone
* back to the namenode to get a new list of block locations, and is
* capped at maxBlockAcquireFailures
*/
private int failures = 0;
private int timeWindow;
/* XXX Use of CocurrentHashMap is temp fix. Need to fix
* parallel accesses to DFSInputStream (through ptreads) properly */
private ConcurrentHashMap<DatanodeInfo, DatanodeInfo> deadNodes =
new ConcurrentHashMap<DatanodeInfo, DatanodeInfo>();
private int buffersize = 1;
private byte[] oneByteBuf = new byte[1]; // used for 'int read()'
private int nCachedConnRetry;
void addToDeadNodes(DatanodeInfo dnInfo) {
deadNodes.put(dnInfo, dnInfo);
}
DFSInputStream(DFSClient dfsClient, String src, int buffersize, boolean verifyChecksum
) throws IOException, UnresolvedLinkException {
this.dfsClient = dfsClient;
this.verifyChecksum = verifyChecksum;
this.buffersize = buffersize;
this.src = src;
this.socketCache = dfsClient.socketCache;
prefetchSize = dfsClient.getConf().prefetchSize;
timeWindow = dfsClient.getConf().timeWindow;
nCachedConnRetry = dfsClient.getConf().nCachedConnRetry;
openInfo();
}
/**
* Grab the open-file info from namenode
*/
synchronized void openInfo() throws IOException, UnresolvedLinkException {
LocatedBlocks newInfo = DFSClient.callGetBlockLocations(dfsClient.namenode, src, 0, prefetchSize);
if (DFSClient.LOG.isDebugEnabled()) {
DFSClient.LOG.debug("newInfo = " + newInfo);
}
if (newInfo == null) {
throw new IOException("Cannot open filename " + src);
}
if (locatedBlocks != null) {
Iterator<LocatedBlock> oldIter = locatedBlocks.getLocatedBlocks().iterator();
Iterator<LocatedBlock> newIter = newInfo.getLocatedBlocks().iterator();
while (oldIter.hasNext() && newIter.hasNext()) {
if (! oldIter.next().getBlock().equals(newIter.next().getBlock())) {
throw new IOException("Blocklist for " + src + " has changed!");
}
}
}
locatedBlocks = newInfo;
lastBlockBeingWrittenLength = 0;
if (!locatedBlocks.isLastBlockComplete()) {
final LocatedBlock last = locatedBlocks.getLastLocatedBlock();
if (last != null) {
final long len = readBlockLength(last);
last.getBlock().setNumBytes(len);
lastBlockBeingWrittenLength = len;
}
}
currentNode = null;
}
/** Read the block length from one of the datanodes. */
private long readBlockLength(LocatedBlock locatedblock) throws IOException {
if (locatedblock == null || locatedblock.getLocations().length == 0) {
return 0;
}
int replicaNotFoundCount = locatedblock.getLocations().length;
for(DatanodeInfo datanode : locatedblock.getLocations()) {
ClientDatanodeProtocol cdp = null;
try {
cdp = DFSUtil.createClientDatanodeProtocolProxy(
datanode, dfsClient.conf, dfsClient.getConf().socketTimeout, locatedblock);
final long n = cdp.getReplicaVisibleLength(locatedblock.getBlock());
if (n >= 0) {
return n;
}
}
catch(IOException ioe) {
if (ioe instanceof RemoteException &&
(((RemoteException) ioe).unwrapRemoteException() instanceof
ReplicaNotFoundException)) {
// special case : replica might not be on the DN, treat as 0 length
replicaNotFoundCount--;
}
if (DFSClient.LOG.isDebugEnabled()) {
DFSClient.LOG.debug("Failed to getReplicaVisibleLength from datanode "
+ datanode + " for block " + locatedblock.getBlock(), ioe);
}
} finally {
if (cdp != null) {
RPC.stopProxy(cdp);
}
}
}
// Namenode told us about these locations, but none know about the replica
// means that we hit the race between pipeline creation start and end.
// we require all 3 because some other exception could have happened
// on a DN that has it. we want to report that error
if (replicaNotFoundCount == 0) {
return 0;
}
throw new IOException("Cannot obtain block length for " + locatedblock);
}
public synchronized long getFileLength() {
return locatedBlocks == null? 0:
locatedBlocks.getFileLength() + lastBlockBeingWrittenLength;
}
/**
* Returns the datanode from which the stream is currently reading.
*/
public DatanodeInfo getCurrentDatanode() {
return currentNode;
}
/**
* Returns the block containing the target position.
*/
synchronized public ExtendedBlock getCurrentBlock() {
if (currentLocatedBlock == null){
return null;
}
return currentLocatedBlock.getBlock();
}
/**
* Return collection of blocks that has already been located.
*/
synchronized List<LocatedBlock> getAllBlocks() throws IOException {
return getBlockRange(0, getFileLength());
}
/**
* Get block at the specified position.
* Fetch it from the namenode if not cached.
*
* @param offset
* @param updatePosition whether to update current position
* @return located block
* @throws IOException
*/
private synchronized LocatedBlock getBlockAt(long offset,
boolean updatePosition) throws IOException {
assert (locatedBlocks != null) : "locatedBlocks is null";
final LocatedBlock blk;
//check offset
if (offset < 0 || offset >= getFileLength()) {
throw new IOException("offset < 0 || offset > getFileLength(), offset="
+ offset
+ ", updatePosition=" + updatePosition
+ ", locatedBlocks=" + locatedBlocks);
}
else if (offset >= locatedBlocks.getFileLength()) {
// offset to the portion of the last block,
// which is not known to the name-node yet;
// getting the last block
blk = locatedBlocks.getLastLocatedBlock();
}
else {
// search cached blocks first
int targetBlockIdx = locatedBlocks.findBlock(offset);
if (targetBlockIdx < 0) { // block is not cached
targetBlockIdx = LocatedBlocks.getInsertIndex(targetBlockIdx);
// fetch more blocks
LocatedBlocks newBlocks;
newBlocks = DFSClient.callGetBlockLocations(dfsClient.namenode, src, offset, prefetchSize);
assert (newBlocks != null) : "Could not find target position " + offset;
locatedBlocks.insertRange(targetBlockIdx, newBlocks.getLocatedBlocks());
}
blk = locatedBlocks.get(targetBlockIdx);
}
// update current position
if (updatePosition) {
pos = offset;
blockEnd = blk.getStartOffset() + blk.getBlockSize() - 1;
currentLocatedBlock = blk;
}
return blk;
}
/** Fetch a block from namenode and cache it */
private synchronized void fetchBlockAt(long offset) throws IOException {
int targetBlockIdx = locatedBlocks.findBlock(offset);
if (targetBlockIdx < 0) { // block is not cached
targetBlockIdx = LocatedBlocks.getInsertIndex(targetBlockIdx);
}
// fetch blocks
LocatedBlocks newBlocks;
newBlocks = DFSClient.callGetBlockLocations(dfsClient.namenode, src, offset, prefetchSize);
if (newBlocks == null) {
throw new IOException("Could not find target position " + offset);
}
locatedBlocks.insertRange(targetBlockIdx, newBlocks.getLocatedBlocks());
}
/**
* Get blocks in the specified range.
* Fetch them from the namenode if not cached. This function
* will not get a read request beyond the EOF.
* @param offset
* @param length
* @return consequent segment of located blocks
* @throws IOException
*/
private synchronized List<LocatedBlock> getBlockRange(long offset,
long length)
throws IOException {
// getFileLength(): returns total file length
// locatedBlocks.getFileLength(): returns length of completed blocks
if (offset >= getFileLength()) {
throw new IOException("Offset: " + offset +
" exceeds file length: " + getFileLength());
}
final List<LocatedBlock> blocks;
final long lengthOfCompleteBlk = locatedBlocks.getFileLength();
final boolean readOffsetWithinCompleteBlk = offset < lengthOfCompleteBlk;
final boolean readLengthPastCompleteBlk = offset + length > lengthOfCompleteBlk;
if (readOffsetWithinCompleteBlk) {
//get the blocks of finalized (completed) block range
blocks = getFinalizedBlockRange(offset,
Math.min(length, lengthOfCompleteBlk - offset));
} else {
blocks = new ArrayList<LocatedBlock>(1);
}
// get the blocks from incomplete block range
if (readLengthPastCompleteBlk) {
blocks.add(locatedBlocks.getLastLocatedBlock());
}
return blocks;
}
/**
* Get blocks in the specified range.
* Includes only the complete blocks.
* Fetch them from the namenode if not cached.
*/
private synchronized List<LocatedBlock> getFinalizedBlockRange(
long offset, long length) throws IOException {
assert (locatedBlocks != null) : "locatedBlocks is null";
List<LocatedBlock> blockRange = new ArrayList<LocatedBlock>();
// search cached blocks first
int blockIdx = locatedBlocks.findBlock(offset);
if (blockIdx < 0) { // block is not cached
blockIdx = LocatedBlocks.getInsertIndex(blockIdx);
}
long remaining = length;
long curOff = offset;
while(remaining > 0) {
LocatedBlock blk = null;
if(blockIdx < locatedBlocks.locatedBlockCount())
blk = locatedBlocks.get(blockIdx);
if (blk == null || curOff < blk.getStartOffset()) {
LocatedBlocks newBlocks;
newBlocks = DFSClient.callGetBlockLocations(dfsClient.namenode, src, curOff, remaining);
locatedBlocks.insertRange(blockIdx, newBlocks.getLocatedBlocks());
continue;
}
assert curOff >= blk.getStartOffset() : "Block not found";
blockRange.add(blk);
long bytesRead = blk.getStartOffset() + blk.getBlockSize() - curOff;
remaining -= bytesRead;
curOff += bytesRead;
blockIdx++;
}
return blockRange;
}
/**
* Open a DataInputStream to a DataNode so that it can be read from.
* We get block ID and the IDs of the destinations at startup, from the namenode.
*/
private synchronized DatanodeInfo blockSeekTo(long target) throws IOException {
if (target >= getFileLength()) {
throw new IOException("Attempted to read past end of file");
}
// Will be getting a new BlockReader.
if (blockReader != null) {
closeBlockReader(blockReader);
blockReader = null;
}
//
// Connect to best DataNode for desired Block, with potential offset
//
DatanodeInfo chosenNode = null;
int refetchToken = 1; // only need to get a new access token once
boolean connectFailedOnce = false;
while (true) {
//
// Compute desired block
//
LocatedBlock targetBlock = getBlockAt(target, true);
assert (target==pos) : "Wrong postion " + pos + " expect " + target;
long offsetIntoBlock = target - targetBlock.getStartOffset();
DNAddrPair retval = chooseDataNode(targetBlock);
chosenNode = retval.info;
InetSocketAddress targetAddr = retval.addr;
try {
ExtendedBlock blk = targetBlock.getBlock();
Token<BlockTokenIdentifier> accessToken = targetBlock.getBlockToken();
blockReader = getBlockReader(targetAddr, chosenNode, src, blk,
accessToken, offsetIntoBlock, blk.getNumBytes() - offsetIntoBlock,
buffersize, verifyChecksum, dfsClient.clientName);
if(connectFailedOnce) {
DFSClient.LOG.info("Successfully connected to " + targetAddr +
" for block " + blk.getBlockId());
}
return chosenNode;
} catch (IOException ex) {
if (ex instanceof InvalidBlockTokenException && refetchToken > 0) {
DFSClient.LOG.info("Will fetch a new access token and retry, "
+ "access token was invalid when connecting to " + targetAddr
+ " : " + ex);
/*
* Get a new access token and retry. Retry is needed in 2 cases. 1)
* When both NN and DN re-started while DFSClient holding a cached
* access token. 2) In the case that NN fails to update its
* access key at pre-set interval (by a wide margin) and
* subsequently restarts. In this case, DN re-registers itself with
* NN and receives a new access key, but DN will delete the old
* access key from its memory since it's considered expired based on
* the estimated expiration date.
*/
refetchToken--;
fetchBlockAt(target);
} else {
connectFailedOnce = true;
DFSClient.LOG.warn("Failed to connect to " + targetAddr + " for block"
+ ", add to deadNodes and continue. " + ex, ex);
// Put chosen node into dead list, continue
addToDeadNodes(chosenNode);
}
}
}
}
/**
* Close it down!
*/
@Override
public synchronized void close() throws IOException {
if (closed) {
return;
}
dfsClient.checkOpen();
if (blockReader != null) {
closeBlockReader(blockReader);
blockReader = null;
}
super.close();
closed = true;
}
@Override
public synchronized int read() throws IOException {
int ret = read( oneByteBuf, 0, 1 );
return ( ret <= 0 ) ? -1 : (oneByteBuf[0] & 0xff);
}
/* This is a used by regular read() and handles ChecksumExceptions.
* name readBuffer() is chosen to imply similarity to readBuffer() in
* ChecksumFileSystem
*/
private synchronized int readBuffer(byte buf[], int off, int len,
Map<ExtendedBlock, Set<DatanodeInfo>> corruptedBlockMap)
throws IOException {
IOException ioe;
/* we retry current node only once. So this is set to true only here.
* Intention is to handle one common case of an error that is not a
* failure on datanode or client : when DataNode closes the connection
* since client is idle. If there are other cases of "non-errors" then
* then a datanode might be retried by setting this to true again.
*/
boolean retryCurrentNode = true;
while (true) {
// retry as many times as seekToNewSource allows.
try {
return blockReader.read(buf, off, len);
} catch ( ChecksumException ce ) {
DFSClient.LOG.warn("Found Checksum error for "
+ getCurrentBlock() + " from " + currentNode.getName()
+ " at " + ce.getPos());
ioe = ce;
retryCurrentNode = false;
// we want to remember which block replicas we have tried
addIntoCorruptedBlockMap(getCurrentBlock(), currentNode,
corruptedBlockMap);
} catch ( IOException e ) {
if (!retryCurrentNode) {
DFSClient.LOG.warn("Exception while reading from "
+ getCurrentBlock() + " of " + src + " from "
+ currentNode, e);
}
ioe = e;
}
boolean sourceFound = false;
if (retryCurrentNode) {
/* possibly retry the same node so that transient errors don't
* result in application level failures (e.g. Datanode could have
* closed the connection because the client is idle for too long).
*/
sourceFound = seekToBlockSource(pos);
} else {
addToDeadNodes(currentNode);
sourceFound = seekToNewSource(pos);
}
if (!sourceFound) {
throw ioe;
}
retryCurrentNode = false;
}
}
/**
* Read the entire buffer.
*/
@Override
public synchronized int read(byte buf[], int off, int len) throws IOException {
dfsClient.checkOpen();
if (closed) {
throw new IOException("Stream closed");
}
Map<ExtendedBlock,Set<DatanodeInfo>> corruptedBlockMap
= new HashMap<ExtendedBlock, Set<DatanodeInfo>>();
failures = 0;
if (pos < getFileLength()) {
int retries = 2;
while (retries > 0) {
try {
if (pos > blockEnd) {
currentNode = blockSeekTo(pos);
}
int realLen = (int) Math.min((long) len, (blockEnd - pos + 1L));
int result = readBuffer(buf, off, realLen, corruptedBlockMap);
if (result >= 0) {
pos += result;
} else {
// got a EOS from reader though we expect more data on it.
throw new IOException("Unexpected EOS from the reader");
}
if (dfsClient.stats != null && result != -1) {
dfsClient.stats.incrementBytesRead(result);
}
return result;
} catch (ChecksumException ce) {
throw ce;
} catch (IOException e) {
if (retries == 1) {
DFSClient.LOG.warn("DFS Read", e);
}
blockEnd = -1;
if (currentNode != null) { addToDeadNodes(currentNode); }
if (--retries == 0) {
throw e;
}
} finally {
// Check if need to report block replicas corruption either read
// was successful or ChecksumException occured.
reportCheckSumFailure(corruptedBlockMap,
currentLocatedBlock.getLocations().length);
}
}
}
return -1;
}
/**
* Add corrupted block replica into map.
* @param corruptedBlockMap
*/
private void addIntoCorruptedBlockMap(ExtendedBlock blk, DatanodeInfo node,
Map<ExtendedBlock, Set<DatanodeInfo>> corruptedBlockMap) {
Set<DatanodeInfo> dnSet = null;
if((corruptedBlockMap.containsKey(blk))) {
dnSet = corruptedBlockMap.get(blk);
}else {
dnSet = new HashSet<DatanodeInfo>();
}
if (!dnSet.contains(node)) {
dnSet.add(node);
corruptedBlockMap.put(blk, dnSet);
}
}
private DNAddrPair chooseDataNode(LocatedBlock block)
throws IOException {
while (true) {
DatanodeInfo[] nodes = block.getLocations();
try {
DatanodeInfo chosenNode = bestNode(nodes, deadNodes);
InetSocketAddress targetAddr =
NetUtils.createSocketAddr(chosenNode.getName());
return new DNAddrPair(chosenNode, targetAddr);
} catch (IOException ie) {
String blockInfo = block.getBlock() + " file=" + src;
if (failures >= dfsClient.getMaxBlockAcquireFailures()) {
throw new BlockMissingException(src, "Could not obtain block: " + blockInfo,
block.getStartOffset());
}
if (nodes == null || nodes.length == 0) {
DFSClient.LOG.info("No node available for block: " + blockInfo);
}
DFSClient.LOG.info("Could not obtain block " + block.getBlock()
+ " from any node: " + ie
+ ". Will get new block locations from namenode and retry...");
try {
// Introducing a random factor to the wait time before another retry.
// The wait time is dependent on # of failures and a random factor.
// At the first time of getting a BlockMissingException, the wait time
// is a random number between 0..3000 ms. If the first retry
// still fails, we will wait 3000 ms grace period before the 2nd retry.
// Also at the second retry, the waiting window is expanded to 6000 ms
// alleviating the request rate from the server. Similarly the 3rd retry
// will wait 6000ms grace period before retry and the waiting window is
// expanded to 9000ms.
double waitTime = timeWindow * failures + // grace period for the last round of attempt
timeWindow * (failures + 1) * DFSUtil.getRandom().nextDouble(); // expanding time window for each failure
DFSClient.LOG.warn("DFS chooseDataNode: got # " + (failures + 1) + " IOException, will wait for " + waitTime + " msec.");
Thread.sleep((long)waitTime);
} catch (InterruptedException iex) {
}
deadNodes.clear(); //2nd option is to remove only nodes[blockId]
openInfo();
block = getBlockAt(block.getStartOffset(), false);
failures++;
continue;
}
}
}
private void fetchBlockByteRange(LocatedBlock block, long start, long end,
byte[] buf, int offset,
Map<ExtendedBlock, Set<DatanodeInfo>> corruptedBlockMap)
throws IOException {
//
// Connect to best DataNode for desired Block, with potential offset
//
int refetchToken = 1; // only need to get a new access token once
while (true) {
// cached block locations may have been updated by chooseDataNode()
// or fetchBlockAt(). Always get the latest list of locations at the
// start of the loop.
block = getBlockAt(block.getStartOffset(), false);
DNAddrPair retval = chooseDataNode(block);
DatanodeInfo chosenNode = retval.info;
InetSocketAddress targetAddr = retval.addr;
BlockReader reader = null;
try {
Token<BlockTokenIdentifier> blockToken = block.getBlockToken();
int len = (int) (end - start + 1);
reader = getBlockReader(targetAddr, chosenNode, src, block.getBlock(),
blockToken, start, len, buffersize, verifyChecksum,
dfsClient.clientName);
int nread = reader.readAll(buf, offset, len);
if (nread != len) {
throw new IOException("truncated return from reader.read(): " +
"excpected " + len + ", got " + nread);
}
return;
} catch (ChecksumException e) {
DFSClient.LOG.warn("fetchBlockByteRange(). Got a checksum exception for " +
src + " at " + block.getBlock() + ":" +
e.getPos() + " from " + chosenNode.getName());
// we want to remember what we have tried
addIntoCorruptedBlockMap(block.getBlock(), chosenNode, corruptedBlockMap);
} catch (AccessControlException ex) {
DFSClient.LOG.warn("Short circuit access failed ", ex);
dfsClient.disableShortCircuit();
continue;
} catch (IOException e) {
if (e instanceof InvalidBlockTokenException && refetchToken > 0) {
DFSClient.LOG.info("Will get a new access token and retry, "
+ "access token was invalid when connecting to " + targetAddr
+ " : " + e);
refetchToken--;
fetchBlockAt(block.getStartOffset());
continue;
} else {
DFSClient.LOG.warn("Failed to connect to " + targetAddr +
" for file " + src + " for block " + block.getBlock() + ":" + e);
if (DFSClient.LOG.isDebugEnabled()) {
DFSClient.LOG.debug("Connection failure ", e);
}
}
} finally {
if (reader != null) {
closeBlockReader(reader);
}
}
// Put chosen node into dead list, continue
addToDeadNodes(chosenNode);
}
}
/**
* Close the given BlockReader and cache its socket.
*/
private void closeBlockReader(BlockReader reader) throws IOException {
if (reader.hasSentStatusCode()) {
Socket oldSock = reader.takeSocket();
socketCache.put(oldSock);
}
reader.close();
}
/**
* Retrieve a BlockReader suitable for reading.
* This method will reuse the cached connection to the DN if appropriate.
* Otherwise, it will create a new connection.
*
* @param dnAddr Address of the datanode
* @param chosenNode Chosen datanode information
* @param file File location
* @param block The Block object
* @param blockToken The access 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
*/
protected BlockReader getBlockReader(InetSocketAddress dnAddr,
DatanodeInfo chosenNode,
String file,
ExtendedBlock block,
Token<BlockTokenIdentifier> blockToken,
long startOffset,
long len,
int bufferSize,
boolean verifyChecksum,
String clientName)
throws IOException {
if (dfsClient.shouldTryShortCircuitRead(dnAddr)) {
return DFSClient.getLocalBlockReader(dfsClient.conf, src, block,
blockToken, chosenNode, dfsClient.hdfsTimeout, startOffset);
}
IOException err = null;
boolean fromCache = true;
// Allow retry since there is no way of knowing whether the cached socket
// is good until we actually use it.
for (int retries = 0; retries <= nCachedConnRetry && fromCache; ++retries) {
Socket sock = socketCache.get(dnAddr);
if (sock == null) {
fromCache = false;
sock = dfsClient.socketFactory.createSocket();
// TCP_NODELAY is crucial here because of bad interactions between
// Nagle's Algorithm and Delayed ACKs. With connection keepalive
// between the client and DN, the conversation looks like:
// 1. Client -> DN: Read block X
// 2. DN -> Client: data for block X
// 3. Client -> DN: Status OK (successful read)
// 4. Client -> DN: Read block Y
// The fact that step #3 and #4 are both in the client->DN direction
// triggers Nagling. If the DN is using delayed ACKs, this results
// in a delay of 40ms or more.
//
// TCP_NODELAY disables nagling and thus avoids this performance
// disaster.
sock.setTcpNoDelay(true);
NetUtils.connect(sock, dnAddr, dfsClient.getConf().socketTimeout);
sock.setSoTimeout(dfsClient.getConf().socketTimeout);
}
try {
// The OP_READ_BLOCK request is sent as we make the BlockReader
BlockReader reader =
BlockReaderFactory.newBlockReader(dfsClient.getConf(),
sock, file, block,
blockToken,
startOffset, len,
bufferSize, verifyChecksum,
clientName);
return reader;
} catch (IOException ex) {
// Our socket is no good.
DFSClient.LOG.debug("Error making BlockReader. Closing stale " + sock, ex);
sock.close();
err = ex;
}
}
throw err;
}
/**
* Read bytes starting from the specified position.
*
* @param position start read from this position
* @param buffer read buffer
* @param offset offset into buffer
* @param length number of bytes to read
*
* @return actual number of bytes read
*/
@Override
public int read(long position, byte[] buffer, int offset, int length)
throws IOException {
// sanity checks
dfsClient.checkOpen();
if (closed) {
throw new IOException("Stream closed");
}
failures = 0;
long filelen = getFileLength();
if ((position < 0) || (position >= filelen)) {
return -1;
}
int realLen = length;
if ((position + length) > filelen) {
realLen = (int)(filelen - position);
}
// determine the block and byte range within the block
// corresponding to position and realLen
List<LocatedBlock> blockRange = getBlockRange(position, realLen);
int remaining = realLen;
Map<ExtendedBlock,Set<DatanodeInfo>> corruptedBlockMap
= new HashMap<ExtendedBlock, Set<DatanodeInfo>>();
for (LocatedBlock blk : blockRange) {
long targetStart = position - blk.getStartOffset();
long bytesToRead = Math.min(remaining, blk.getBlockSize() - targetStart);
try {
fetchBlockByteRange(blk, targetStart,
targetStart + bytesToRead - 1, buffer, offset, corruptedBlockMap);
} finally {
// Check and report if any block replicas are corrupted.
// BlockMissingException may be caught if all block replicas are
// corrupted.
reportCheckSumFailure(corruptedBlockMap, blk.getLocations().length);
}
remaining -= bytesToRead;
position += bytesToRead;
offset += bytesToRead;
}
assert remaining == 0 : "Wrong number of bytes read.";
if (dfsClient.stats != null) {
dfsClient.stats.incrementBytesRead(realLen);
}
return realLen;
}
/**
* DFSInputStream reports checksum failure.
* Case I : client has tried multiple data nodes and at least one of the
* attempts has succeeded. We report the other failures as corrupted block to
* namenode.
* Case II: client has tried out all data nodes, but all failed. We
* only report if the total number of replica is 1. We do not
* report otherwise since this maybe due to the client is a handicapped client
* (who can not read).
* @param corruptedBlockMap, map of corrupted blocks
* @param dataNodeCount, number of data nodes who contains the block replicas
*/
private void reportCheckSumFailure(
Map<ExtendedBlock, Set<DatanodeInfo>> corruptedBlockMap,
int dataNodeCount) {
if (corruptedBlockMap.isEmpty()) {
return;
}
Iterator<Entry<ExtendedBlock, Set<DatanodeInfo>>> it = corruptedBlockMap
.entrySet().iterator();
Entry<ExtendedBlock, Set<DatanodeInfo>> entry = it.next();
ExtendedBlock blk = entry.getKey();
Set<DatanodeInfo> dnSet = entry.getValue();
if (((dnSet.size() < dataNodeCount) && (dnSet.size() > 0))
|| ((dataNodeCount == 1) && (dnSet.size() == dataNodeCount))) {
DatanodeInfo[] locs = new DatanodeInfo[dnSet.size()];
int i = 0;
for (DatanodeInfo dn:dnSet) {
locs[i++] = dn;
}
LocatedBlock [] lblocks = { new LocatedBlock(blk, locs) };
dfsClient.reportChecksumFailure(src, lblocks);
}
corruptedBlockMap.clear();
}
@Override
public long skip(long n) throws IOException {
if ( n > 0 ) {
long curPos = getPos();
long fileLen = getFileLength();
if( n+curPos > fileLen ) {
n = fileLen - curPos;
}
seek(curPos+n);
return n;
}
return n < 0 ? -1 : 0;
}
/**
* Seek to a new arbitrary location
*/
@Override
public synchronized void seek(long targetPos) throws IOException {
if (targetPos > getFileLength()) {
throw new IOException("Cannot seek after EOF");
}
if (closed) {
throw new IOException("Stream is closed!");
}
boolean done = false;
if (pos <= targetPos && targetPos <= blockEnd) {
//
// If this seek is to a positive position in the current
// block, and this piece of data might already be lying in
// the TCP buffer, then just eat up the intervening data.
//
int diff = (int)(targetPos - pos);
if (diff <= DFSClient.TCP_WINDOW_SIZE) {
try {
pos += blockReader.skip(diff);
if (pos == targetPos) {
done = true;
}
} catch (IOException e) {//make following read to retry
if(DFSClient.LOG.isDebugEnabled()) {
DFSClient.LOG.debug("Exception while seek to " + targetPos
+ " from " + getCurrentBlock() + " of " + src + " from "
+ currentNode, e);
}
}
}
}
if (!done) {
pos = targetPos;
blockEnd = -1;
}
}
/**
* Same as {@link #seekToNewSource(long)} except that it does not exclude
* the current datanode and might connect to the same node.
*/
private synchronized boolean seekToBlockSource(long targetPos)
throws IOException {
currentNode = blockSeekTo(targetPos);
return true;
}
/**
* Seek to given position on a node other than the current node. If
* a node other than the current node is found, then returns true.
* If another node could not be found, then returns false.
*/
@Override
public synchronized boolean seekToNewSource(long targetPos) throws IOException {
boolean markedDead = deadNodes.containsKey(currentNode);
addToDeadNodes(currentNode);
DatanodeInfo oldNode = currentNode;
DatanodeInfo newNode = blockSeekTo(targetPos);
if (!markedDead) {
/* remove it from deadNodes. blockSeekTo could have cleared
* deadNodes and added currentNode again. Thats ok. */
deadNodes.remove(oldNode);
}
if (!oldNode.getStorageID().equals(newNode.getStorageID())) {
currentNode = newNode;
return true;
} else {
return false;
}
}
/**
*/
@Override
public synchronized long getPos() throws IOException {
return pos;
}
/** Return the size of the remaining available bytes
* if the size is less than or equal to {@link Integer#MAX_VALUE},
* otherwise, return {@link Integer#MAX_VALUE}.
*/
@Override
public synchronized int available() throws IOException {
if (closed) {
throw new IOException("Stream closed");
}
final long remaining = getFileLength() - pos;
return remaining <= Integer.MAX_VALUE? (int)remaining: Integer.MAX_VALUE;
}
/**
* We definitely don't support marks
*/
@Override
public boolean markSupported() {
return false;
}
@Override
public void mark(int readLimit) {
}
@Override
public void reset() throws IOException {
throw new IOException("Mark/reset not supported");
}
/**
* Pick the best node from which to stream the data.
* Entries in <i>nodes</i> are already in the priority order
*/
static DatanodeInfo bestNode(DatanodeInfo nodes[],
AbstractMap<DatanodeInfo, DatanodeInfo> deadNodes)
throws IOException {
if (nodes != null) {
for (int i = 0; i < nodes.length; i++) {
if (!deadNodes.containsKey(nodes[i])) {
return nodes[i];
}
}
}
throw new IOException("No live nodes contain current block");
}
/** Utility class to encapsulate data node info and its ip address. */
static class DNAddrPair {
DatanodeInfo info;
InetSocketAddress addr;
DNAddrPair(DatanodeInfo info, InetSocketAddress addr) {
this.info = info;
this.addr = addr;
}
}
}