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https://issues.apache.org/jira/browse/HBASE-5623?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13237437#comment-13237437
]
Lars Hofhansl commented on HBASE-5623:
--------------------------------------
bq. Should we verify that x.getCause() is NPE ?
I don't think so. Any IOException here warrants a retry.
bq. My first comment about tempWriter is that this.writer can be used directly
since the code is within synchronized block.
Sure, but it doesn't matter right. Since at this point the existing tempWriter
most likely bad, it needs to be updated to the current one (for the getLength()
check below). This way try and retry are the same.
> Race condition when rolling the HLog and hlogFlush
> --------------------------------------------------
>
> Key: HBASE-5623
> URL: https://issues.apache.org/jira/browse/HBASE-5623
> Project: HBase
> Issue Type: Bug
> Components: wal
> Affects Versions: 0.94.0
> Reporter: Enis Soztutar
> Assignee: Enis Soztutar
> Priority: Critical
> Fix For: 0.94.0
>
> Attachments: 5623-suggestion.txt, 5623-v7.txt, 5623-v8.txt, 5623.txt,
> 5623v2.txt, HBASE-5623_v0.patch, HBASE-5623_v4.patch, HBASE-5623_v5.patch,
> HBASE-5623_v6-alt.patch, HBASE-5623_v6-alt.patch
>
>
> When doing a ycsb test with a large number of handlers
> (regionserver.handler.count=60), I get the following exceptions:
> {code}
> Caused by: org.apache.hadoop.ipc.RemoteException: java.io.IOException:
> java.lang.NullPointerException
> at
> org.apache.hadoop.io.SequenceFile$Writer.getLength(SequenceFile.java:1099)
> at
> org.apache.hadoop.hbase.regionserver.wal.SequenceFileLogWriter.getLength(SequenceFileLogWriter.java:314)
> at org.apache.hadoop.hbase.regionserver.wal.HLog.syncer(HLog.java:1291)
> at org.apache.hadoop.hbase.regionserver.wal.HLog.sync(HLog.java:1388)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.doMiniBatchPut(HRegion.java:2192)
> at org.apache.hadoop.hbase.regionserver.HRegion.put(HRegion.java:1985)
> at
> org.apache.hadoop.hbase.regionserver.HRegionServer.multi(HRegionServer.java:3400)
> at sun.reflect.GeneratedMethodAccessor17.invoke(Unknown Source)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:597)
> at
> org.apache.hadoop.hbase.ipc.WritableRpcEngine$Server.call(WritableRpcEngine.java:366)
> at
> org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:1351)
> at org.apache.hadoop.hbase.ipc.HBaseClient.call(HBaseClient.java:920)
> at
> org.apache.hadoop.hbase.ipc.WritableRpcEngine$Invoker.invoke(WritableRpcEngine.java:152)
> at $Proxy1.multi(Unknown Source)
> at
> org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation$3$1.call(HConnectionManager.java:1691)
> at
> org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation$3$1.call(HConnectionManager.java:1689)
> at
> org.apache.hadoop.hbase.client.ServerCallable.withoutRetries(ServerCallable.java:214)
> {code}
> and
> {code}
> java.lang.NullPointerException
> at
> org.apache.hadoop.io.SequenceFile$Writer.checkAndWriteSync(SequenceFile.java:1026)
> at
> org.apache.hadoop.io.SequenceFile$Writer.append(SequenceFile.java:1068)
> at
> org.apache.hadoop.io.SequenceFile$Writer.append(SequenceFile.java:1035)
> at
> org.apache.hadoop.hbase.regionserver.wal.SequenceFileLogWriter.append(SequenceFileLogWriter.java:279)
> at
> org.apache.hadoop.hbase.regionserver.wal.HLog$LogSyncer.hlogFlush(HLog.java:1237)
> at
> org.apache.hadoop.hbase.regionserver.wal.HLog.syncer(HLog.java:1271)
> at
> org.apache.hadoop.hbase.regionserver.wal.HLog.sync(HLog.java:1391)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.doMiniBatchPut(HRegion.java:2192)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.put(HRegion.java:1985)
> at
> org.apache.hadoop.hbase.regionserver.HRegionServer.multi(HRegionServer.java:3400)
> at sun.reflect.GeneratedMethodAccessor33.invoke(Unknown Source)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:597)
> at
> org.apache.hadoop.hbase.ipc.WritableRpcEngine$Server.call(WritableRpcEngine.java:366)
> at
> org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:1351)
> {code}
> It seems the root cause of the issue is that we open a new log writer and
> close the old one at HLog#rollWriter() holding the updateLock, but the other
> threads doing syncer() calls
> {code}
> logSyncerThread.hlogFlush(this.writer);
> {code}
> without holding the updateLock. LogSyncer only synchronizes against
> concurrent appends and flush(), but not on the passed writer, which can be
> closed already by rollWriter(). In this case, since
> SequenceFile#Writer.close() sets it's out field as null, we get the NPE.
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