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https://issues.apache.org/jira/browse/HDFS-17332?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17806216#comment-17806216
]
ASF GitHub Bot commented on HDFS-17332:
---------------------------------------
li-leyang commented on code in PR #6446:
URL: https://github.com/apache/hadoop/pull/6446#discussion_r1450967849
##########
hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSInputStream.java:
##########
@@ -1494,19 +1533,39 @@ private int pread(long position, ByteBuffer buffer)
try {
if (dfsClient.isHedgedReadsEnabled() && !blk.isStriped()) {
hedgedFetchBlockByteRange(blk, targetStart,
- targetEnd, buffer, corruptedBlocks);
+ targetEnd, buffer, corruptedBlocks, ioExceptionMap);
} else {
fetchBlockByteRange(blk, targetStart, targetEnd,
- buffer, corruptedBlocks);
+ buffer, corruptedBlocks, ioExceptionMap);
}
- } finally {
+ } catch (IOException e) {
+ // When we reach here, it means we fail to fetch the current block
from all available
+ // datanodes. Send IOExceptions in ioExceptionMap to the log and
rethrow the exception to
+ // fail this request.
+ String msg = String.format("Failed to read from all available
datanodes for block %s "
Review Comment:
This error handling is duplicated in multiple places. Can we abstract it in
a common function?
> DFSInputStream: avoid logging stacktrace until when we really need to fail a
> read request with a MissingBlockException
> ----------------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-17332
> URL: https://issues.apache.org/jira/browse/HDFS-17332
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs
> Reporter: Xing Lin
> Assignee: Xing Lin
> Priority: Minor
> Labels: pull-request-available
>
> In DFSInputStream#actualGetFromOneDataNode(), it would send the exception
> stacktrace to the dfsClient.LOG whenever we fail on a DN. However, in most
> cases, the read request will be served successfully by reading from the next
> available DN. The existence of exception stacktrace in the log has caused
> multiple hadoop users at Linkedin to consider this WARN message as the
> RC/fatal error for their jobs. We would like to improve the log message and
> avoid sending the stacktrace to dfsClient.LOG when a read succeeds. The
> stackTrace when reading reach DN is sent to the log only when we really need
> to fail a read request (when chooseDataNode()/refetchLocations() throws a
> BlockMissingException).
>
> Example stack trace
> {code:java}
> [12]<stderr>:23/11/30 23:01:33 WARN hdfs.DFSClient: Connection failure:
> Failed to connect to 10.150.91.13/10.150.91.13:71 for file
> /XXXX/part-yyyy-95b9909c-zzz-c000.avro for block
> BP-364971551-DatanodeIP-1448516588954:blk_zzzz_129864739321:java.net.SocketTimeoutException:
> 60000 millis timeout while waiting for channel to be ready for read. ch :
> java.nio.channels.SocketChannel[connected local=/ip:40492
> remote=datanodeIP:71] [12]<stderr>:java.net.SocketTimeoutException: 60000
> millis timeout while waiting for channel to be ready for read. ch :
> java.nio.channels.SocketChannel[connected local=/localIp:40492
> remote=datanodeIP:71] [12]<stderr>: at
> org.apache.hadoop.net.SocketIOWithTimeout.doIO(SocketIOWithTimeout.java:164)
> [12]<stderr>: at
> org.apache.hadoop.net.SocketInputStream.read(SocketInputStream.java:161)
> [12]<stderr>: at
> org.apache.hadoop.net.SocketInputStream.read(SocketInputStream.java:131)
> [12]<stderr>: at
> org.apache.hadoop.net.SocketInputStream.read(SocketInputStream.java:118)
> [12]<stderr>: at java.io.FilterInputStream.read(FilterInputStream.java:83)
> [12]<stderr>: at
> org.apache.hadoop.hdfs.protocolPB.PBHelperClient.vintPrefixed(PBHelperClient.java:458)
> [12]<stderr>: at
> org.apache.hadoop.hdfs.client.impl.BlockReaderRemote2.newBlockReader(BlockReaderRemote2.java:412)
> [12]<stderr>: at
> org.apache.hadoop.hdfs.client.impl.BlockReaderFactory.getRemoteBlockReader(BlockReaderFactory.java:864)
> [12]<stderr>: at
> org.apache.hadoop.hdfs.client.impl.BlockReaderFactory.getRemoteBlockReaderFromTcp(BlockReaderFactory.java:753)
> [12]<stderr>: at
> org.apache.hadoop.hdfs.client.impl.BlockReaderFactory.build(BlockReaderFactory.java:387)
> [12]<stderr>: at
> org.apache.hadoop.hdfs.DFSInputStream.getBlockReader(DFSInputStream.java:736)
> [12]<stderr>: at
> org.apache.hadoop.hdfs.DFSInputStream.actualGetFromOneDataNode(DFSInputStream.java:1268)
> [12]<stderr>: at
> org.apache.hadoop.hdfs.DFSInputStream.fetchBlockByteRange(DFSInputStream.java:1216)
> [12]<stderr>: at
> org.apache.hadoop.hdfs.DFSInputStream.pread(DFSInputStream.java:1608)
> [12]<stderr>: at
> org.apache.hadoop.hdfs.DFSInputStream.read(DFSInputStream.java:1568)
> [12]<stderr>: at
> org.apache.hadoop.fs.FSDataInputStream.read(FSDataInputStream.java:93)
> [12]<stderr>: at
> hdfs_metrics_shade.org.apache.hadoop.fs.InstrumentedFSDataInputStream$InstrumentedFilterInputStream.lambda$read$0(InstrumentedFSDataInputStream.java:108)
> [12]<stderr>: at
> com.linkedin.hadoop.metrics.fs.PerformanceTrackingFSDataInputStream.process(PerformanceTrackingFSDataInputStream.java:39)
> [12]<stderr>: at
> hdfs_metrics_shade.org.apache.hadoop.fs.InstrumentedFSDataInputStream$InstrumentedFilterInputStream.read(InstrumentedFSDataInputStream.java:108)
> [12]<stderr>: at
> org.apache.hadoop.fs.FSDataInputStream.read(FSDataInputStream.java:93)
> [12]<stderr>: at
> org.apache.hadoop.fs.RetryingInputStream.lambda$read$2(RetryingInputStream.java:153)
> [12]<stderr>: at
> org.apache.hadoop.fs.NoOpRetryPolicy.run(NoOpRetryPolicy.java:36)
> [12]<stderr>: at
> org.apache.hadoop.fs.RetryingInputStream.read(RetryingInputStream.java:149)
> [12]<stderr>: at
> org.apache.hadoop.fs.FSDataInputStream.read(FSDataInputStream.java:93){code}
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