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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