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From "Zhihong Yu (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5171) Potential NullPointerException while obtaining row lock
Date Tue, 10 Jan 2012 18:04:39 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5171?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13183429#comment-13183429
] 

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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