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HDFS-6735. A minor optimization to avoid pread() be blocked by read() inside the same DFSInputStream (Lars Hofhansl via stack)

This commit is contained in:
stack 2014-12-02 20:54:03 -08:00 committed by stack
parent 92ce6eda92
commit 7caa3bc98e
6 changed files with 217 additions and 155 deletions
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3
hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
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@ -422,6 +422,9 @@ Release 2.7.0 - UNRELEASED
HDFS-7446. HDFS inotify should have the ability to determine what txid it
has read up to (cmccabe)
HDFS-6735. A minor optimization to avoid pread() be blocked by read()
inside the same DFSInputStream (Lars Hofhansl via stack)
OPTIMIZATIONS
BUG FIXES

9
hadoop-hdfs-project/hadoop-hdfs/dev-support/findbugsExcludeFile.xml
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@ -207,4 +207,13 @@
<Bug pattern="NP_LOAD_OF_KNOWN_NULL_VALUE" />
</Match>
<!--
We use a separate lock to guard cachingStrategy in order to separate
locks for p-reads from seek + read invocations.
-->
<Match>
<Class name="org.apache.hadoop.hdfs.DFSInputStream" />
<Field name="cachingStrategy" />
<Bug pattern="IS2_INCONSISTENT_SYNC" />
</Match>
</FindBugsFilter>

98
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSInputStream.java
View File

@ -92,17 +92,32 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
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 FileEncryptionInfo fileEncryptionInfo = null;
// state by stateful read only:
// (protected by lock on this)
/////
private DatanodeInfo currentNode = null;
private LocatedBlock currentLocatedBlock = null;
private long pos = 0;
private long blockEnd = -1;
private BlockReader blockReader = null;
////
// state shared by stateful and positional read:
// (protected by lock on infoLock)
////
private LocatedBlocks locatedBlocks = null;
private long lastBlockBeingWrittenLength = 0;
private FileEncryptionInfo fileEncryptionInfo = null;
private CachingStrategy cachingStrategy;
////
private final ReadStatistics readStatistics = new ReadStatistics();
// lock for state shared between read and pread
// Note: Never acquire a lock on <this> with this lock held to avoid deadlocks
// (it's OK to acquire this lock when the lock on <this> is held)
private final Object infoLock = new Object();
/**
* Track the ByteBuffers that we have handed out to readers.
@ -226,15 +241,17 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
this.dfsClient = dfsClient;
this.verifyChecksum = verifyChecksum;
this.src = src;
this.cachingStrategy =
dfsClient.getDefaultReadCachingStrategy();
synchronized (infoLock) {
this.cachingStrategy = dfsClient.getDefaultReadCachingStrategy();
}
openInfo();
}
/**
* Grab the open-file info from namenode
*/
synchronized void openInfo() throws IOException, UnresolvedLinkException {
void openInfo() throws IOException, UnresolvedLinkException {
synchronized(infoLock) {
lastBlockBeingWrittenLength = fetchLocatedBlocksAndGetLastBlockLength();
int retriesForLastBlockLength = dfsClient.getConf().retryTimesForGetLastBlockLength;
while (retriesForLastBlockLength > 0) {
@ -257,6 +274,7 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
throw new IOException("Could not obtain the last block locations.");
}
}
}
private void waitFor(int waitTime) throws IOException {
try {
@ -306,7 +324,6 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
fileEncryptionInfo = locatedBlocks.getFileEncryptionInfo();
currentNode = null;
return lastBlockBeingWrittenLength;
}
@ -359,21 +376,25 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
throw new IOException("Cannot obtain block length for " + locatedblock);
}
public synchronized long getFileLength() {
public long getFileLength() {
synchronized(infoLock) {
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() {
boolean shortCircuitForbidden() {
synchronized(infoLock) {
return locatedBlocks.isUnderConstruction();
}
}
/**
* Returns the datanode from which the stream is currently reading.
*/
public DatanodeInfo getCurrentDatanode() {
public synchronized DatanodeInfo getCurrentDatanode() {
return currentNode;
}
@ -403,8 +424,9 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
* @return located block
* @throws IOException
*/
private synchronized LocatedBlock getBlockAt(long offset,
private LocatedBlock getBlockAt(long offset,
boolean updatePosition) throws IOException {
synchronized(infoLock) {
assert (locatedBlocks != null) : "locatedBlocks is null";
final LocatedBlock blk;
@ -437,15 +459,21 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
// update current position
if (updatePosition) {
// synchronized not strictly needed, since we only get here
// from synchronized caller methods
synchronized(this) {
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 {
private void fetchBlockAt(long offset) throws IOException {
synchronized(infoLock) {
int targetBlockIdx = locatedBlocks.findBlock(offset);
if (targetBlockIdx < 0) { // block is not cached
targetBlockIdx = LocatedBlocks.getInsertIndex(targetBlockIdx);
@ -457,6 +485,7 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
}
locatedBlocks.insertRange(targetBlockIdx, newBlocks.getLocatedBlocks());
}
}
/**
* Get blocks in the specified range.
@ -467,7 +496,7 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
* @return consequent segment of located blocks
* @throws IOException
*/
private synchronized List<LocatedBlock> getBlockRange(long offset,
private List<LocatedBlock> getBlockRange(long offset,
long length) throws IOException {
// getFileLength(): returns total file length
// locatedBlocks.getFileLength(): returns length of completed blocks
@ -475,7 +504,7 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
throw new IOException("Offset: " + offset +
" exceeds file length: " + getFileLength());
}
synchronized(infoLock) {
final List<LocatedBlock> blocks;
final long lengthOfCompleteBlk = locatedBlocks.getFileLength();
final boolean readOffsetWithinCompleteBlk = offset < lengthOfCompleteBlk;
@ -496,14 +525,16 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
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(
private List<LocatedBlock> getFinalizedBlockRange(
long offset, long length) throws IOException {
synchronized(infoLock) {
assert (locatedBlocks != null) : "locatedBlocks is null";
List<LocatedBlock> blockRange = new ArrayList<LocatedBlock>();
// search cached blocks first
@ -532,6 +563,7 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
}
return blockRange;
}
}
/**
* Open a DataInputStream to a DataNode so that it can be read from.
@ -573,6 +605,12 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
try {
ExtendedBlock blk = targetBlock.getBlock();
Token<BlockTokenIdentifier> accessToken = targetBlock.getBlockToken();
CachingStrategy curCachingStrategy;
boolean shortCircuitForbidden;
synchronized(infoLock) {
curCachingStrategy = cachingStrategy;
shortCircuitForbidden = shortCircuitForbidden();
}
blockReader = new BlockReaderFactory(dfsClient.getConf()).
setInetSocketAddress(targetAddr).
setRemotePeerFactory(dfsClient).
@ -585,8 +623,8 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
setVerifyChecksum(verifyChecksum).
setClientName(dfsClient.clientName).
setLength(blk.getNumBytes() - offsetIntoBlock).
setCachingStrategy(cachingStrategy).
setAllowShortCircuitLocalReads(!shortCircuitForbidden()).
setCachingStrategy(curCachingStrategy).
setAllowShortCircuitLocalReads(!shortCircuitForbidden).
setClientCacheContext(dfsClient.getClientContext()).
setUserGroupInformation(dfsClient.ugi).
setConfiguration(dfsClient.getConfiguration()).
@ -782,7 +820,7 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
}
}
private int readWithStrategy(ReaderStrategy strategy, int off, int len) throws IOException {
private synchronized int readWithStrategy(ReaderStrategy strategy, int off, int len) throws IOException {
dfsClient.checkOpen();
if (closed) {
throw new IOException("Stream closed");
@ -800,10 +838,12 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
currentNode = blockSeekTo(pos);
}
int realLen = (int) Math.min(len, (blockEnd - pos + 1L));
synchronized(infoLock) {
if (locatedBlocks.isLastBlockComplete()) {
realLen = (int) Math.min(realLen,
locatedBlocks.getFileLength() - pos);
}
}
int result = readBuffer(strategy, off, realLen, corruptedBlockMap);
if (result >= 0) {
@ -1055,8 +1095,8 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
// start of the loop.
CachingStrategy curCachingStrategy;
boolean allowShortCircuitLocalReads;
synchronized (this) {
block = getBlockAt(block.getStartOffset(), false);
synchronized(infoLock) {
curCachingStrategy = cachingStrategy;
allowShortCircuitLocalReads = !shortCircuitForbidden();
}
@ -1488,7 +1528,7 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
* 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)
private boolean seekToBlockSource(long targetPos)
throws IOException {
currentNode = blockSeekTo(targetPos);
return true;
@ -1575,11 +1615,13 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
return new ReadStatistics(readStatistics);
}
public synchronized FileEncryptionInfo getFileEncryptionInfo() {
public FileEncryptionInfo getFileEncryptionInfo() {
synchronized(infoLock) {
return fileEncryptionInfo;
}
}
private synchronized void closeCurrentBlockReader() {
private void closeCurrentBlockReader() {
if (blockReader == null) return;
// Close the current block reader so that the new caching settings can
// take effect immediately.
@ -1594,18 +1636,20 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
@Override
public synchronized void setReadahead(Long readahead)
throws IOException {
synchronized (infoLock) {
this.cachingStrategy =
new CachingStrategy.Builder(this.cachingStrategy).
setReadahead(readahead).build();
new CachingStrategy.Builder(this.cachingStrategy).setReadahead(readahead).build();
}
closeCurrentBlockReader();
}
@Override
public synchronized void setDropBehind(Boolean dropBehind)
throws IOException {
synchronized (infoLock) {
this.cachingStrategy =
new CachingStrategy.Builder(this.cachingStrategy).
setDropBehind(dropBehind).build();
new CachingStrategy.Builder(this.cachingStrategy).setDropBehind(dropBehind).build();
}
closeCurrentBlockReader();
}

9
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/LocatedBlocks.java
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@ -34,14 +34,17 @@ public class LocatedBlocks {
private final long fileLength;
private final List<LocatedBlock> blocks; // array of blocks with prioritized locations
private final boolean underConstruction;
private LocatedBlock lastLocatedBlock = null;
private boolean isLastBlockComplete = false;
private FileEncryptionInfo fileEncryptionInfo = null;
private final LocatedBlock lastLocatedBlock;
private final boolean isLastBlockComplete;
private final FileEncryptionInfo fileEncryptionInfo;
public LocatedBlocks() {
fileLength = 0;
blocks = null;
underConstruction = false;
lastLocatedBlock = null;
isLastBlockComplete = false;
fileEncryptionInfo = null;
}
public LocatedBlocks(long flength, boolean isUnderConstuction,

19
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/shortcircuit/ShortCircuitCache.java
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@ -400,7 +400,7 @@ public class ShortCircuitCache implements Closeable {
lock.lock();
try {
Preconditions.checkArgument(replica.refCount > 0,
"can't ref " + replica + " because its refCount reached " +
"can't ref %s because its refCount reached %d", replica,
replica.refCount);
Long evictableTimeNs = replica.getEvictableTimeNs();
replica.refCount++;
@ -456,14 +456,13 @@ public class ShortCircuitCache implements Closeable {
if (newRefCount == 0) {
// Close replica, since there are no remaining references to it.
Preconditions.checkArgument(replica.purged,
"Replica " + replica + " reached a refCount of 0 without " +
"being purged");
"Replica %s reached a refCount of 0 without being purged", replica);
replica.close();
} else if (newRefCount == 1) {
Preconditions.checkState(null == replica.getEvictableTimeNs(),
"Replica " + replica + " had a refCount higher than 1, " +
"but was still evictable (evictableTimeNs = " +
replica.getEvictableTimeNs() + ")");
"Replica %s had a refCount higher than 1, " +
"but was still evictable (evictableTimeNs = %d)",
replica, replica.getEvictableTimeNs());
if (!replica.purged) {
// Add the replica to the end of an eviction list.
// Eviction lists are sorted by time.
@ -478,8 +477,8 @@ public class ShortCircuitCache implements Closeable {
}
} else {
Preconditions.checkArgument(replica.refCount >= 0,
"replica's refCount went negative (refCount = " +
replica.refCount + " for " + replica + ")");
"replica's refCount went negative (refCount = %d" +
" for %s)", replica.refCount, replica);
}
if (LOG.isTraceEnabled()) {
LOG.trace(this + ": unref replica " + replica +
@ -602,7 +601,7 @@ public class ShortCircuitCache implements Closeable {
Preconditions.checkNotNull(evictableTimeNs);
ShortCircuitReplica removed = map.remove(evictableTimeNs);
Preconditions.checkState(removed == replica,
"failed to make " + replica + " unevictable");
"failed to make %s unevictable", replica);
replica.setEvictableTimeNs(null);
}
@ -859,7 +858,7 @@ public class ShortCircuitCache implements Closeable {
Condition cond = (Condition)replica.mmapData;
cond.awaitUninterruptibly();
} else {
Preconditions.checkState(false, "invalid mmapData type " +
Preconditions.checkState(false, "invalid mmapData type %s",
replica.mmapData.getClass().getName());
}
}

8
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/shortcircuit/ShortCircuitReplica.java
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@ -243,19 +243,23 @@ public class ShortCircuitReplica {
String suffix = "";
Preconditions.checkState(refCount == 0,
"tried to close replica with refCount " + refCount + ": " + this);
"tried to close replica with refCount %d: %s", refCount, this);
refCount = -1;
Preconditions.checkState(purged,
"tried to close unpurged replica " + this);
"tried to close unpurged replica %s", this);
if (hasMmap()) {
munmap();
if (LOG.isTraceEnabled()) {
suffix += " munmapped.";
}
}
IOUtils.cleanup(LOG, dataStream, metaStream);
if (slot != null) {
cache.scheduleSlotReleaser(slot);
if (LOG.isTraceEnabled()) {
suffix += " scheduling " + slot + " for later release.";
}
}
if (LOG.isTraceEnabled()) {
LOG.trace("closed " + this + suffix);
}