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https://issues.apache.org/jira/browse/HBASE-5171?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13183429#comment-13183429
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Zhihong Yu commented on HBASE-5171:
-----------------------------------
One workaround is to increase the value for "hbase.rowlock.wait.duration"
But a new exception should be introduced anyways.
> Potential NullPointerException while obtaining row lock
> --------------------------------------------------------
>
> Key: HBASE-5171
> URL: https://issues.apache.org/jira/browse/HBASE-5171
> Project: HBase
> Issue Type: Bug
> Components: regionserver
> Affects Versions: 0.90.5
> Reporter: Yves Langisch
>
> We have a table which is concurrently accessed (read/write) from many threads
> and we make use of row locks. Under heavy load we regularly get NPE while
> obtaining row locks. An example stack trace looks as follows:
> java.lang.NullPointerException
> at
> org.apache.hadoop.hbase.regionserver.HRegionServer.convertThrowableToIOE(HRegionServer.java:986)
> at
> org.apache.hadoop.hbase.regionserver.HRegionServer.lockRow(HRegionServer.java:2008)
> at sun.reflect.GeneratedMethodAccessor20.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.HBaseRPC$Server.call(HBaseRPC.java:570)
> at
> org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:1039)
> Caused by: java.lang.NullPointerException
> at
> java.util.concurrent.ConcurrentHashMap.put(ConcurrentHashMap.java:881)
> at
> org.apache.hadoop.hbase.regionserver.HRegionServer.addRowLock(HRegionServer.java:2018)
> at
> org.apache.hadoop.hbase.regionserver.HRegionServer.lockRow(HRegionServer.java:2004)
> ... 5 more
> After checking the source code I've noticed that the value which is going to
> be put into the HashMap can be null in the case where the waitForLock flag is
> true or the rowLockWaitDuration is expired (HRegion#internalObtainRowLock,
> line 2111ff). The latter I think happens in our case as we have heavy load
> hitting the server.
> IMHO this case should be handled somehow and must not lead to a NPE.
> -
> Yves
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