/**
* 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.nio.ByteBuffer;
import java.util.AbstractMap;
import java.util.ArrayList;
import java.util.Collection;
import java.util.EnumSet;
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.Callable;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import org.apache.commons.io.IOUtils;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.fs.ByteBufferReadable;
import org.apache.hadoop.fs.ByteBufferUtil;
import org.apache.hadoop.fs.CanSetDropBehind;
import org.apache.hadoop.fs.CanSetReadahead;
import org.apache.hadoop.fs.ChecksumException;
import org.apache.hadoop.fs.FSInputStream;
import org.apache.hadoop.fs.HasEnhancedByteBufferAccess;
import org.apache.hadoop.fs.ReadOption;
import org.apache.hadoop.fs.UnresolvedLinkException;
import org.apache.hadoop.hdfs.client.ClientMmap;
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.protocol.datatransfer.InvalidEncryptionKeyException;
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.CachingStrategy;
import org.apache.hadoop.hdfs.server.datanode.ReplicaNotFoundException;
import org.apache.hadoop.io.ByteBufferPool;
import org.apache.hadoop.ipc.RPC;
import org.apache.hadoop.ipc.RemoteException;
import org.apache.hadoop.net.NetUtils;
import org.apache.hadoop.security.token.SecretManager.InvalidToken;
import org.apache.hadoop.security.token.Token;
import org.apache.hadoop.util.IdentityHashStore;
import com.google.common.annotations.VisibleForTesting;
/****************************************************************
* 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
implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
HasEnhancedByteBufferAccess {
@VisibleForTesting
static boolean tcpReadsDisabledForTesting = false;
private final DFSClient dfsClient;
private boolean closed = false;
private final String src;
private BlockReader blockReader = null;
private final 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;
private CachingStrategy cachingStrategy;
private final ReadStatistics readStatistics = new ReadStatistics();
/**
* Track the ByteBuffers that we have handed out to readers.
*
* The value type can be either ByteBufferPool or ClientMmap, depending on
* whether we this is a memory-mapped buffer or not.
*/
private final IdentityHashStore<ByteBuffer, Object>
extendedReadBuffers = new IdentityHashStore<ByteBuffer, Object>(0);
public static class ReadStatistics {
public ReadStatistics() {
this.totalBytesRead = 0;
this.totalLocalBytesRead = 0;
this.totalShortCircuitBytesRead = 0;
this.totalZeroCopyBytesRead = 0;
}
public ReadStatistics(ReadStatistics rhs) {
this.totalBytesRead = rhs.getTotalBytesRead();
this.totalLocalBytesRead = rhs.getTotalLocalBytesRead();
this.totalShortCircuitBytesRead = rhs.getTotalShortCircuitBytesRead();
this.totalZeroCopyBytesRead = rhs.getTotalZeroCopyBytesRead();
}
/**
* @return The total bytes read. This will always be at least as
* high as the other numbers, since it includes all of them.
*/
public long getTotalBytesRead() {
return totalBytesRead;
}
/**
* @return The total local bytes read. This will always be at least
* as high as totalShortCircuitBytesRead, since all short-circuit
* reads are also local.
*/
public long getTotalLocalBytesRead() {
return totalLocalBytesRead;
}
/**
* @return The total short-circuit local bytes read.
*/
public long getTotalShortCircuitBytesRead() {
return totalShortCircuitBytesRead;
}
/**
* @return The total number of zero-copy bytes read.
*/
public long getTotalZeroCopyBytesRead() {
return totalZeroCopyBytesRead;
}
/**
* @return The total number of bytes read which were not local.
*/
public long getRemoteBytesRead() {
return totalBytesRead - totalLocalBytesRead;
}
void addRemoteBytes(long amt) {
this.totalBytesRead += amt;
}
void addLocalBytes(long amt) {
this.totalBytesRead += amt;
this.totalLocalBytesRead += amt;
}
void addShortCircuitBytes(long amt) {
this.totalBytesRead += amt;
this.totalLocalBytesRead += amt;
this.totalShortCircuitBytesRead += amt;
}
void addZeroCopyBytes(long amt) {
this.totalBytesRead += amt;
this.totalLocalBytesRead += amt;
this.totalShortCircuitBytesRead += amt;
this.totalZeroCopyBytesRead += amt;
}
private long totalBytesRead;
private long totalLocalBytesRead;
private long totalShortCircuitBytesRead;
private long totalZeroCopyBytesRead;
}
/**
* 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;
/* XXX Use of CocurrentHashMap is temp fix. Need to fix
* parallel accesses to DFSInputStream (through ptreads) properly */
private final ConcurrentHashMap<DatanodeInfo, DatanodeInfo> deadNodes =
new ConcurrentHashMap<DatanodeInfo, DatanodeInfo>();
private int buffersize = 1;
private final byte[] oneByteBuf = new byte[1]; // used for 'int read()'
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.cachingStrategy =
dfsClient.getDefaultReadCachingStrategy();
openInfo();
}
/**
* Grab the open-file info from namenode
*/
synchronized void openInfo() throws IOException, UnresolvedLinkException {
lastBlockBeingWrittenLength = fetchLocatedBlocksAndGetLastBlockLength();
int retriesForLastBlockLength = dfsClient.getConf().retryTimesForGetLastBlockLength;
while (retriesForLastBlockLength > 0) {
// Getting last block length as -1 is a special case. When cluster
// restarts, DNs may not report immediately. At this time partial block
// locations will not be available with NN for getting the length. Lets
// retry for 3 times to get the length.
if (lastBlockBeingWrittenLength == -1) {
DFSClient.LOG.warn("Last block locations not available. "
+ "Datanodes might not have reported blocks completely."
+ " Will retry for " + retriesForLastBlockLength + " times");
waitFor(dfsClient.getConf().retryIntervalForGetLastBlockLength);
lastBlockBeingWrittenLength = fetchLocatedBlocksAndGetLastBlockLength();
} else {
break;
}
retriesForLastBlockLength--;
}
if (retriesForLastBlockLength == 0) {
throw new IOException("Could not obtain the last block locations.");
}
}
private void waitFor(int waitTime) throws IOException {
try {
Thread.sleep(waitTime);
} catch (InterruptedException e) {
throw new IOException(
"Interrupted while getting the last block length.");
}
}
private long fetchLocatedBlocksAndGetLastBlockLength() throws IOException {
final LocatedBlocks newInfo = dfsClient.getLocatedBlocks(src, 0);
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;
long lastBlockBeingWrittenLength = 0;
if (!locatedBlocks.isLastBlockComplete()) {
final LocatedBlock last = locatedBlocks.getLastLocatedBlock();
if (last != null) {
if (last.getLocations().length == 0) {
if (last.getBlockSize() == 0) {
// if the length is zero, then no data has been written to
// datanode. So no need to wait for the locations.
return 0;
}
return -1;
}
final long len = readBlockLength(last);
last.getBlock().setNumBytes(len);
lastBlockBeingWrittenLength = len;
}
}
currentNode = null;
return lastBlockBeingWrittenLength;
}
/** Read the block length from one of the datanodes. */
private long readBlockLength(LocatedBlock locatedblock) throws IOException {
assert locatedblock != null : "LocatedBlock cannot be null";
int replicaNotFoundCount = locatedblock.getLocations().length;
for(DatanodeInfo datanode : locatedblock.getLocations()) {
ClientDatanodeProtocol cdp = null;
try {
cdp = DFSUtil.createClientDatanodeProtocolProxy(datanode,
dfsClient.getConfiguration(), dfsClient.getConf().socketTimeout,
dfsClient.getConf().connectToDnViaHostname, 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;
}
// Short circuit local reads are forbidden for files that are
// under construction. See HDFS-2757.
synchronized boolean shortCircuitForbidden() {
return locatedBlocks.isUnderConstruction();
}
/**
* 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.
*/
public 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
final LocatedBlocks newBlocks = dfsClient.getLocatedBlocks(src, offset);
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
final LocatedBlocks newBlocks = dfsClient.getLocatedBlocks(src, offset);
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.getLocatedBlocks(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) {
blockReader.close();
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
int refetchEncryptionKey = 1; // only need to get a new encryption key 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, null);
chosenNode = retval.info;
InetSocketAddress targetAddr = retval.addr;
try {
ExtendedBlock blk = targetBlock.getBlock();
Token<BlockTokenIdentifier> accessToken = targetBlock.getBlockToken();
blockReader = new BlockReaderFactory(dfsClient.getConf()).
setInetSocketAddress(targetAddr).
setRemotePeerFactory(dfsClient).
setDatanodeInfo(chosenNode).
setFileName(src).
setBlock(blk).
setBlockToken(accessToken).
setStartOffset(offsetIntoBlock).
setVerifyChecksum(verifyChecksum).
setClientName(dfsClient.clientName).
setLength(blk.getNumBytes() - offsetIntoBlock).
setCachingStrategy(cachingStrategy).
setAllowShortCircuitLocalReads(!shortCircuitForbidden()).
setClientCacheContext(dfsClient.getClientContext()).
setUserGroupInformation(dfsClient.ugi).
setConfiguration(dfsClient.getConfiguration()).
build();
if(connectFailedOnce) {
DFSClient.LOG.info("Successfully connected to " + targetAddr +
" for " + blk);
}
return chosenNode;
} catch (IOException ex) {
if (ex instanceof InvalidEncryptionKeyException && refetchEncryptionKey > 0) {
DFSClient.LOG.info("Will fetch a new encryption key and retry, "
+ "encryption key was invalid when connecting to " + targetAddr
+ " : " + ex);
// The encryption key used is invalid.
refetchEncryptionKey--;
dfsClient.clearDataEncryptionKey();
} else if (refetchToken > 0 && tokenRefetchNeeded(ex, targetAddr)) {
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 (!extendedReadBuffers.isEmpty()) {
final StringBuilder builder = new StringBuilder();
extendedReadBuffers.visitAll(new IdentityHashStore.Visitor<ByteBuffer, Object>() {
private String prefix = "";
@Override
public void accept(ByteBuffer k, Object v) {
builder.append(prefix).append(k);
prefix = ", ";
}
});
DFSClient.LOG.warn("closing file " + src + ", but there are still " +
"unreleased ByteBuffers allocated by read(). " +
"Please release " + builder.toString() + ".");
}
if (blockReader != null) {
blockReader.close();
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);
}
/**
* Wraps different possible read implementations so that readBuffer can be
* strategy-agnostic.
*/
private interface ReaderStrategy {
public int doRead(BlockReader blockReader, int off, int len,
ReadStatistics readStatistics) throws ChecksumException, IOException;
}
private static void updateReadStatistics(ReadStatistics readStatistics,
int nRead, BlockReader blockReader) {
if (nRead <= 0) return;
if (blockReader.isShortCircuit()) {
readStatistics.addShortCircuitBytes(nRead);
} else if (blockReader.isLocal()) {
readStatistics.addLocalBytes(nRead);
} else {
readStatistics.addRemoteBytes(nRead);
}
}
/**
* Used to read bytes into a byte[]
*/
private static class ByteArrayStrategy implements ReaderStrategy {
final byte[] buf;
public ByteArrayStrategy(byte[] buf) {
this.buf = buf;
}
@Override
public int doRead(BlockReader blockReader, int off, int len,
ReadStatistics readStatistics) throws ChecksumException, IOException {
int nRead = blockReader.read(buf, off, len);
updateReadStatistics(readStatistics, nRead, blockReader);
return nRead;
}
}
/**
* Used to read bytes into a user-supplied ByteBuffer
*/
private static class ByteBufferStrategy implements ReaderStrategy {
final ByteBuffer buf;
ByteBufferStrategy(ByteBuffer buf) {
this.buf = buf;
}
@Override
public int doRead(BlockReader blockReader, int off, int len,
ReadStatistics readStatistics) throws ChecksumException, IOException {
int oldpos = buf.position();
int oldlimit = buf.limit();
boolean success = false;
try {
int ret = blockReader.read(buf);
success = true;
updateReadStatistics(readStatistics, ret, blockReader);
return ret;
} finally {
if (!success) {
// Reset to original state so that retries work correctly.
buf.position(oldpos);
buf.limit(oldlimit);
}
}
}
}
/* 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(ReaderStrategy reader, 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 reader.doRead(blockReader, off, len, readStatistics);
} catch ( ChecksumException ce ) {
DFSClient.LOG.warn("Found Checksum error for "
+ getCurrentBlock() + " from " + currentNode
+ " 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;
}
}
private int readWithStrategy(ReaderStrategy strategy, 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 {
// currentNode can be left as null if previous read had a checksum
// error on the same block. See HDFS-3067
if (pos > blockEnd || currentNode == null) {
currentNode = blockSeekTo(pos);
}
int realLen = (int) Math.min(len, (blockEnd - pos + 1L));
if (locatedBlocks.isLastBlockComplete()) {
realLen = (int) Math.min(realLen, locatedBlocks.getFileLength());
}
int result = readBuffer(strategy, 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;
}
/**
* Read the entire buffer.
*/
@Override
public synchronized int read(final byte buf[], int off, int len) throws IOException {
ReaderStrategy byteArrayReader = new ByteArrayStrategy(buf);
return readWithStrategy(byteArrayReader, off, len);
}
@Override
public synchronized int read(final ByteBuffer buf) throws IOException {
ReaderStrategy byteBufferReader = new ByteBufferStrategy(buf);
return readWithStrategy(byteBufferReader, 0, buf.remaining());
}
/**
* 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,
Collection<DatanodeInfo> ignoredNodes) throws IOException {
while (true) {
DatanodeInfo[] nodes = block.getLocations();
try {
return getBestNodeDNAddrPair(nodes, ignoredNodes);
} catch (IOException ie) {
String errMsg =
getBestNodeDNAddrPairErrorString(nodes, deadNodes, ignoredNodes);
String blockInfo = block.getBlock() + " file=" + src;
if (failures >= dfsClient.getMaxBlockAcquireFailures()) {
String description = "Could not obtain block: " + blockInfo;
DFSClient.LOG.warn(description + errMsg
+ ". Throwing a BlockMissingException");
throw new BlockMissingException(src, description,
block.getStartOffset());
}
if (nodes == null || nodes.length == 0) {
DFSClient.LOG.info("No node available for " + blockInfo);
}
DFSClient.LOG.info("Could not obtain " + block.getBlock()
+ " from any node: " + ie + errMsg
+ ". 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.
final int timeWindow = dfsClient.getConf().timeWindow;
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;
}
}
}
/**
* Get the best node.
* @param nodes Nodes to choose from.
* @param ignoredNodes Do not chose nodes in this array (may be null)
* @return The DNAddrPair of the best node.
* @throws IOException
*/
private DNAddrPair getBestNodeDNAddrPair(final DatanodeInfo[] nodes,
Collection<DatanodeInfo> ignoredNodes) throws IOException {
DatanodeInfo chosenNode = bestNode(nodes, deadNodes, ignoredNodes);
final String dnAddr =
chosenNode.getXferAddr(dfsClient.getConf().connectToDnViaHostname);
if (DFSClient.LOG.isDebugEnabled()) {
DFSClient.LOG.debug("Connecting to datanode " + dnAddr);
}
InetSocketAddress targetAddr = NetUtils.createSocketAddr(dnAddr);
return new DNAddrPair(chosenNode, targetAddr);
}
private static String getBestNodeDNAddrPairErrorString(
DatanodeInfo nodes[], AbstractMap<DatanodeInfo,
DatanodeInfo> deadNodes, Collection<DatanodeInfo> ignoredNodes) {
StringBuilder errMsgr = new StringBuilder(
" No live nodes contain current block ");
errMsgr.append("Block locations:");
for (DatanodeInfo datanode : nodes) {
errMsgr.append(" ");
errMsgr.append(datanode.toString());
}
errMsgr.append(" Dead nodes: ");
for (DatanodeInfo datanode : deadNodes.keySet()) {
errMsgr.append(" ");
errMsgr.append(datanode.toString());
}
if (ignoredNodes != null) {
errMsgr.append(" Ignored nodes: ");
for (DatanodeInfo datanode : ignoredNodes) {
errMsgr.append(" ");
errMsgr.append(datanode.toString());
}
}
return errMsgr.toString();
}
private void fetchBlockByteRange(LocatedBlock block, long start, long end,
byte[] buf, int offset,
Map<ExtendedBlock, Set<DatanodeInfo>> corruptedBlockMap)
throws IOException {
block = getBlockAt(block.getStartOffset(), false);
while (true) {
DNAddrPair addressPair = chooseDataNode(block, null);
try {
actualGetFromOneDataNode(addressPair, block, start, end, buf, offset,
corruptedBlockMap);
return;
} catch (IOException e) {
// Ignore. Already processed inside the function.
// Loop through to try the next node.
}
}
}
private Callable<ByteBuffer> getFromOneDataNode(final DNAddrPair datanode,
final LocatedBlock block, final long start, final long end,
final ByteBuffer bb,
final Map<ExtendedBlock, Set<DatanodeInfo>> corruptedBlockMap,
final CountDownLatch latch) {
return new Callable<ByteBuffer>() {
@Override
public ByteBuffer call() throws Exception {
byte[] buf = bb.array();
int offset = bb.position();
actualGetFromOneDataNode(datanode, block, start, end, buf, offset,
corruptedBlockMap);
latch.countDown();
return bb;
}
};
}
private void actualGetFromOneDataNode(final DNAddrPair datanode,
LocatedBlock block, final long start, final long end, byte[] buf,
int offset, Map<ExtendedBlock, Set<DatanodeInfo>> corruptedBlockMap)
throws IOException {
DFSClientFaultInjector.get().startFetchFromDatanode();
int refetchToken = 1; // only need to get a new access token once
int refetchEncryptionKey = 1; // only need to get a new encryption key 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.
CachingStrategy curCachingStrategy;
boolean allowShortCircuitLocalReads;
synchronized (this) {
block = getBlockAt(block.getStartOffset(), false);
curCachingStrategy = cachingStrategy;
allowShortCircuitLocalReads = !shortCircuitForbidden();
}
DatanodeInfo chosenNode = datanode.info;
InetSocketAddress targetAddr = datanode.addr;
BlockReader reader = null;
try {
Token<BlockTokenIdentifier> blockToken = block.getBlockToken();
int len = (int) (end - start + 1);
reader = new BlockReaderFactory(dfsClient.getConf()).
setInetSocketAddress(targetAddr).
setRemotePeerFactory(dfsClient).
setDatanodeInfo(chosenNode).
setFileName(src).
setBlock(block.getBlock()).
setBlockToken(blockToken).
setStartOffset(start).
setVerifyChecksum(verifyChecksum).
setClientName(dfsClient.clientName).
setLength(len).
setCachingStrategy(curCachingStrategy).
setAllowShortCircuitLocalReads(allowShortCircuitLocalReads).
setClientCacheContext(dfsClient.getClientContext()).
setUserGroupInformation(dfsClient.ugi).
setConfiguration(dfsClient.getConfiguration()).
build();
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) {
String msg = "fetchBlockByteRange(). Got a checksum exception for "
+ src + " at " + block.getBlock() + ":" + e.getPos() + " from "
+ chosenNode;
DFSClient.LOG.warn(msg);
// we want to remember what we have tried
addIntoCorruptedBlockMap(block.getBlock(), chosenNode, corruptedBlockMap);
addToDeadNodes(chosenNode);
throw new IOException(msg);
} catch (IOException e) {
if (e instanceof InvalidEncryptionKeyException && refetchEncryptionKey > 0) {
DFSClient.LOG.info("Will fetch a new encryption key and retry, "
+ "encryption key was invalid when connecting to " + targetAddr
+ " : " + e);
// The encryption key used is invalid.
refetchEncryptionKey--;
dfsClient.clearDataEncryptionKey();
continue;
} else if (refetchToken > 0 && tokenRefetchNeeded(e, targetAddr)) {
refetchToken--;
try {
fetchBlockAt(block.getStartOffset());
} catch (IOException fbae) {
// ignore IOE, since we can retry it later in a loop
}
continue;
} else {
String msg = "Failed to connect to " + targetAddr + " for file "
+ src + " for block " + block.getBlock() + ":" + e;
DFSClient.LOG.warn("Connection failure: " + msg, e);
addToDeadNodes(chosenNode);
throw new IOException(msg);
}
} finally {
if (reader != null) {
reader.close();
}
}
}
}
/**
* Like {@link #fetchBlockByteRange(LocatedBlock, long, long, byte[],
* int, Map)} except we start up a second, parallel, 'hedged' read
* if the first read is taking longer than configured amount of
* time. We then wait on which ever read returns first.
*
* @param block
* @param start
* @param end
* @param buf
* @param offset
* @param corruptedBlockMap
* @throws IOException
*/
private void hedgedFetchBlockByteRange(LocatedBlock block, long start,
long end, byte[] buf, int offset,
Map<ExtendedBlock, Set<DatanodeInfo>> corruptedBlockMap)
throws IOException {
ArrayList<Future<ByteBuffer>> futures = null;
ArrayList<DatanodeInfo> ignored = new ArrayList<DatanodeInfo>();
ByteBuffer bb = null;
int len = (int) (end - start + 1);
block = getBlockAt(block.getStartOffset(), false);
// Latch shared by all outstanding reads. First to finish closes
CountDownLatch hasReceivedResult = new CountDownLatch(1);
while (true) {
DNAddrPair chosenNode = null;
Future<ByteBuffer> future = null;
// futures is null if there is no request already executing.
if (futures == null) {
// chooseDataNode is a commitment. If no node, we go to
// the NN to reget block locations. Only go here on first read.
chosenNode = chooseDataNode(block, ignored);
bb = ByteBuffer.wrap(buf, offset, len);
future = getHedgedReadFuture(chosenNode, block, start, end, bb,
corruptedBlockMap, hasReceivedResult);
try {
future.get(dfsClient.getHedgedReadTimeout(), TimeUnit.MILLISECONDS);
return;
} catch (TimeoutException e) {
if (DFSClient.LOG.isDebugEnabled()) {
DFSClient.LOG.debug("Waited " + dfsClient.getHedgedReadTimeout() +
"ms to read from " + chosenNode.info + "; spawning hedged read");
}
// Ignore this node on next go around.
ignored.add(chosenNode.info);
dfsClient.getHedgedReadMetrics().incHedgedReadOps();
futures = new ArrayList<Future<ByteBuffer>>();
futures.add(future);
continue; // no need to refresh block locations
} catch (InterruptedException e) {
// Ignore
} catch (ExecutionException e) {
// Ignore already logged in the call.
}
} else {
// We are starting up a 'hedged' read. We have a read already
// ongoing. Call getBestNodeDNAddrPair instead of chooseDataNode.
// If no nodes to do hedged reads against, pass.
try {
chosenNode = getBestNodeDNAddrPair(block.getLocations(), ignored);
bb = ByteBuffer.allocate(len);
future = getHedgedReadFuture(chosenNode, block, start, end, bb,
corruptedBlockMap, hasReceivedResult);
futures.add(future);
} catch (IOException ioe) {
if (DFSClient.LOG.isDebugEnabled()) {
DFSClient.LOG.debug("Failed getting node for hedged read: " +
ioe.getMessage());
}
}
// if not succeeded. Submit callables for each datanode in a loop, wait
// for a fixed interval and get the result from the fastest one.
try {
ByteBuffer result = getFirstToComplete(futures, hasReceivedResult);
// cancel the rest.
cancelAll(futures);
if (result.array() != buf) { // compare the array pointers
dfsClient.getHedgedReadMetrics().incHedgedReadWins();
System.arraycopy(result.array(), result.position(), buf, offset,
len);
} else {
dfsClient.getHedgedReadMetrics().incHedgedReadOps();
}
return;
} catch (InterruptedException ie) {
// Ignore
} catch (ExecutionException e) {
// exception already handled in the call method. getFirstToComplete
// will remove the failing future from the list. nothing more to do.
}
// We got here if exception. Ignore this node on next go around IFF
// we found a chosenNode to hedge read against.
if (chosenNode != null && chosenNode.info != null) {
ignored.add(chosenNode.info);
}
}
// executed if we get an error from a data node
block = getBlockAt(block.getStartOffset(), false);
}
}
private Future<ByteBuffer> getHedgedReadFuture(final DNAddrPair chosenNode,
final LocatedBlock block, long start,
final long end, final ByteBuffer bb,
final Map<ExtendedBlock, Set<DatanodeInfo>> corruptedBlockMap,
final CountDownLatch hasReceivedResult) {
Callable<ByteBuffer> getFromDataNodeCallable =
getFromOneDataNode(chosenNode, block, start, end, bb,
corruptedBlockMap, hasReceivedResult);
return dfsClient.getHedgedReadsThreadPool().submit(getFromDataNodeCallable);
}
private ByteBuffer getFirstToComplete(ArrayList<Future<ByteBuffer>> futures,
CountDownLatch latch) throws ExecutionException, InterruptedException {
latch.await();
for (Future<ByteBuffer> future : futures) {
if (future.isDone()) {
try {
return future.get();
} catch (ExecutionException e) {
// already logged in the Callable
futures.remove(future);
throw e;
}
}
}
throw new InterruptedException("latch has counted down to zero but no"
+ "result available yet, for safety try to request another one from"
+ "outside loop, this should be rare");
}
private void cancelAll(List<Future<ByteBuffer>> futures) {
for (Future<ByteBuffer> future : futures) {
// Unfortunately, hdfs reads do not take kindly to interruption.
// Threads return a variety of interrupted-type exceptions but
// also complaints about invalid pbs -- likely because read
// is interrupted before gets whole pb. Also verbose WARN
// logging. So, for now, do not interrupt running read.
future.cancel(false);
}
}
/**
* Should the block access token be refetched on an exception
*
* @param ex Exception received
* @param targetAddr Target datanode address from where exception was received
* @return true if block access token has expired or invalid and it should be
* refetched
*/
private static boolean tokenRefetchNeeded(IOException ex,
InetSocketAddress targetAddr) {
/*
* 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.
*/
if (ex instanceof InvalidBlockTokenException || ex instanceof InvalidToken) {
DFSClient.LOG.info("Access token was invalid when connecting to "
+ targetAddr + " : " + ex);
return true;
}
return false;
}
/**
* 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 {
if (dfsClient.isHedgedReadsEnabled()) {
hedgedFetchBlockByteRange(blk, targetStart, targetStart + bytesToRead
- 1, buffer, offset, corruptedBlockMap);
} else {
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 (targetPos < 0) {
throw new IOException("Cannot seek to negative offset");
}
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 <= blockReader.available()) {
try {
pos += blockReader.skip(diff);
if (pos == targetPos) {
done = true;
} else {
// The range was already checked. If the block reader returns
// something unexpected instead of throwing an exception, it is
// most likely a bug.
String errMsg = "BlockReader failed to seek to " +
targetPos + ". Instead, it seeked to " + pos + ".";
DFSClient.LOG.warn(errMsg);
throw new IOException(errMsg);
}
} 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.getDatanodeUuid().equals(newNode.getDatanodeUuid())) {
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,
Collection<DatanodeInfo> ignoredNodes) throws IOException {
if (nodes != null) {
for (int i = 0; i < nodes.length; i++) {
if (!deadNodes.containsKey(nodes[i])
&& (ignoredNodes == null || !ignoredNodes.contains(nodes[i]))) {
return nodes[i];
}
}
}
throw new IOException("No live nodes contain current block");
}
/** Utility class to encapsulate data node info and its address. */
static class DNAddrPair {
final DatanodeInfo info;
final InetSocketAddress addr;
DNAddrPair(DatanodeInfo info, InetSocketAddress addr) {
this.info = info;
this.addr = addr;
}
}
/**
* Get statistics about the reads which this DFSInputStream has done.
*/
public synchronized ReadStatistics getReadStatistics() {
return new ReadStatistics(readStatistics);
}
private synchronized void closeCurrentBlockReader() {
if (blockReader == null) return;
// Close the current block reader so that the new caching settings can
// take effect immediately.
try {
blockReader.close();
} catch (IOException e) {
DFSClient.LOG.error("error closing blockReader", e);
}
blockReader = null;
}
@Override
public synchronized void setReadahead(Long readahead)
throws IOException {
this.cachingStrategy =
new CachingStrategy.Builder(this.cachingStrategy).
setReadahead(readahead).build();
closeCurrentBlockReader();
}
@Override
public synchronized void setDropBehind(Boolean dropBehind)
throws IOException {
this.cachingStrategy =
new CachingStrategy.Builder(this.cachingStrategy).
setDropBehind(dropBehind).build();
closeCurrentBlockReader();
}
/**
* The immutable empty buffer we return when we reach EOF when doing a
* zero-copy read.
*/
private static final ByteBuffer EMPTY_BUFFER =
ByteBuffer.allocateDirect(0).asReadOnlyBuffer();
@Override
public synchronized ByteBuffer read(ByteBufferPool bufferPool,
int maxLength, EnumSet<ReadOption> opts)
throws IOException, UnsupportedOperationException {
if (maxLength == 0) {
return EMPTY_BUFFER;
} else if (maxLength < 0) {
throw new IllegalArgumentException("can't read a negative " +
"number of bytes.");
}
if ((blockReader == null) || (blockEnd == -1)) {
if (pos >= getFileLength()) {
return null;
}
/*
* If we don't have a blockReader, or the one we have has no more bytes
* left to read, we call seekToBlockSource to get a new blockReader and
* recalculate blockEnd. Note that we assume we're not at EOF here
* (we check this above).
*/
if ((!seekToBlockSource(pos)) || (blockReader == null)) {
throw new IOException("failed to allocate new BlockReader " +
"at position " + pos);
}
}
ByteBuffer buffer = null;
if (dfsClient.getConf().shortCircuitMmapEnabled) {
buffer = tryReadZeroCopy(maxLength, opts);
}
if (buffer != null) {
return buffer;
}
buffer = ByteBufferUtil.fallbackRead(this, bufferPool, maxLength);
if (buffer != null) {
extendedReadBuffers.put(buffer, bufferPool);
}
return buffer;
}
private synchronized ByteBuffer tryReadZeroCopy(int maxLength,
EnumSet<ReadOption> opts) throws IOException {
// Copy 'pos' and 'blockEnd' to local variables to make it easier for the
// JVM to optimize this function.
final long curPos = pos;
final long curEnd = blockEnd;
final long blockStartInFile = currentLocatedBlock.getStartOffset();
final long blockPos = curPos - blockStartInFile;
// Shorten this read if the end of the block is nearby.
long length63;
if ((curPos + maxLength) <= (curEnd + 1)) {
length63 = maxLength;
} else {
length63 = 1 + curEnd - curPos;
if (length63 <= 0) {
if (DFSClient.LOG.isDebugEnabled()) {
DFSClient.LOG.debug("Unable to perform a zero-copy read from offset " +
curPos + " of " + src + "; " + length63 + " bytes left in block. " +
"blockPos=" + blockPos + "; curPos=" + curPos +
"; curEnd=" + curEnd);
}
return null;
}
if (DFSClient.LOG.isDebugEnabled()) {
DFSClient.LOG.debug("Reducing read length from " + maxLength +
" to " + length63 + " to avoid going more than one byte " +
"past the end of the block. blockPos=" + blockPos +
"; curPos=" + curPos + "; curEnd=" + curEnd);
}
}
// Make sure that don't go beyond 31-bit offsets in the MappedByteBuffer.
int length;
if (blockPos + length63 <= Integer.MAX_VALUE) {
length = (int)length63;
} else {
long length31 = Integer.MAX_VALUE - blockPos;
if (length31 <= 0) {
// Java ByteBuffers can't be longer than 2 GB, because they use
// 4-byte signed integers to represent capacity, etc.
// So we can't mmap the parts of the block higher than the 2 GB offset.
// FIXME: we could work around this with multiple memory maps.
// See HDFS-5101.
if (DFSClient.LOG.isDebugEnabled()) {
DFSClient.LOG.debug("Unable to perform a zero-copy read from offset " +
curPos + " of " + src + "; 31-bit MappedByteBuffer limit " +
"exceeded. blockPos=" + blockPos + ", curEnd=" + curEnd);
}
return null;
}
length = (int)length31;
if (DFSClient.LOG.isDebugEnabled()) {
DFSClient.LOG.debug("Reducing read length from " + maxLength +
" to " + length + " to avoid 31-bit limit. " +
"blockPos=" + blockPos + "; curPos=" + curPos +
"; curEnd=" + curEnd);
}
}
final ClientMmap clientMmap = blockReader.getClientMmap(opts);
if (clientMmap == null) {
if (DFSClient.LOG.isDebugEnabled()) {
DFSClient.LOG.debug("unable to perform a zero-copy read from offset " +
curPos + " of " + src + "; BlockReader#getClientMmap returned " +
"null.");
}
return null;
}
boolean success = false;
ByteBuffer buffer;
try {
seek(curPos + length);
buffer = clientMmap.getMappedByteBuffer().asReadOnlyBuffer();
buffer.position((int)blockPos);
buffer.limit((int)(blockPos + length));
extendedReadBuffers.put(buffer, clientMmap);
readStatistics.addZeroCopyBytes(length);
if (DFSClient.LOG.isDebugEnabled()) {
DFSClient.LOG.debug("readZeroCopy read " + length +
" bytes from offset " + curPos + " via the zero-copy read " +
"path. blockEnd = " + blockEnd);
}
success = true;
} finally {
if (!success) {
IOUtils.closeQuietly(clientMmap);
}
}
return buffer;
}
@Override
public synchronized void releaseBuffer(ByteBuffer buffer) {
if (buffer == EMPTY_BUFFER) return;
Object val = extendedReadBuffers.remove(buffer);
if (val == null) {
throw new IllegalArgumentException("tried to release a buffer " +
"that was not created by this stream, " + buffer);
}
if (val instanceof ClientMmap) {
IOUtils.closeQuietly((ClientMmap)val);
} else if (val instanceof ByteBufferPool) {
((ByteBufferPool)val).putBuffer(buffer);
}
}
}