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From "Enis Soztutar (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5623) Race condition when rolling the HLog and hlogFlush
Date Fri, 23 Mar 2012 22:41:27 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5623?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13237234#comment-13237234
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Enis Soztutar commented on HBASE-5623:
--------------------------------------

bq. Ran the about 300 times now, no failure.
Lars, did you run the Stack's patch as it is? It does not fail also in trunk, but the problem
is that the threads exit with NPE, and it gets written to the log, but the test passes. 

                
> 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.txt, 5623v2.txt, HBASE-5623_v0.patch, HBASE-5623_v4.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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