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HDFS-10182. Hedged read might overwrite user's buf. Contributed by zhouyingchao. 

(cherry picked from commit d8383c687c)
This commit is contained in:
Walter Su 2016-03-28 15:44:25 +08:00
parent 17dbf82f54
commit ec459e3966
1 changed files with 7 additions and 9 deletions
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10
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSInputStream.java
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@ -1249,7 +1249,7 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
// 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);
bb = ByteBuffer.allocate(len);
Callable<ByteBuffer> getFromDataNodeCallable = getFromOneDataNode(
chosenNode, block, start, end, bb, corruptedBlockMap,
hedgedReadId++);
@ -1260,7 +1260,9 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
Future<ByteBuffer> future = hedgedService.poll(
dfsClient.getHedgedReadTimeout(), TimeUnit.MILLISECONDS);
if (future != null) {
future.get();
ByteBuffer result = future.get();
System.arraycopy(result.array(), result.position(), buf, offset,
len);
return;
}
if (DFSClient.LOG.isDebugEnabled()) {
@ -1306,13 +1308,9 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
ByteBuffer result = getFirstToComplete(hedgedService, futures);
// 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 and retry