HDFS-10182. Hedged read might overwrite user's buf. Contributed by zhouyingchao.
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115be193df
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d8383c687c
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@ -1279,7 +1279,7 @@ public class DFSInputStream extends FSInputStream
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// chooseDataNode is a commitment. If no node, we go to
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// the NN to reget block locations. Only go here on first read.
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chosenNode = chooseDataNode(block, ignored);
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bb = ByteBuffer.wrap(buf, offset, len);
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bb = ByteBuffer.allocate(len);
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Callable<ByteBuffer> getFromDataNodeCallable = getFromOneDataNode(
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chosenNode, block, start, end, bb,
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corruptedBlocks, hedgedReadId++);
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@ -1290,7 +1290,9 @@ public class DFSInputStream extends FSInputStream
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Future<ByteBuffer> future = hedgedService.poll(
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conf.getHedgedReadThresholdMillis(), TimeUnit.MILLISECONDS);
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if (future != null) {
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future.get();
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ByteBuffer result = future.get();
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System.arraycopy(result.array(), result.position(), buf, offset,
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len);
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return;
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}
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DFSClient.LOG.debug("Waited {}ms to read from {}; spawning hedged "
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@ -1328,13 +1330,9 @@ public class DFSInputStream extends FSInputStream
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ByteBuffer result = getFirstToComplete(hedgedService, futures);
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// cancel the rest.
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cancelAll(futures);
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if (result.array() != buf) { // compare the array pointers
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dfsClient.getHedgedReadMetrics().incHedgedReadWins();
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System.arraycopy(result.array(), result.position(), buf, offset,
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len);
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} else {
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dfsClient.getHedgedReadMetrics().incHedgedReadOps();
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}
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dfsClient.getHedgedReadMetrics().incHedgedReadWins();
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System.arraycopy(result.array(), result.position(), buf, offset,
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len);
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return;
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} catch (InterruptedException ie) {
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// Ignore and retry
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