Details
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Improvement
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Status: Resolved
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Minor
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Resolution: Fixed
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None
Description
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
[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)
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