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http://jira.amdatu.org/jira/browse/AMDATUCASSANDRA-130?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=11863#comment-11863
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Ivo Ladage - van Doorn edited comment on AMDATUCASSANDRA-130 at 11/4/11 1:57 PM:
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After analyzing the issue, I found out that it is caused by the HashBiMap used
in org.apache.cassandra.config.CFMetaData not being thread-safe. This
bidirectional map comes from the Guava project (guava-r08) and never claimed to
be thread-safe. Cassandra uses this map and does not take any precautions to
prevent concurrency problems. By running the attached Unit test you can
reproduce the concurrency issue quite easily. If you uncomment the synchronized
stuff around the map access methods, the unit test will fail.
Of course, this could easily be fixed in Cassandra (by adding synchronized
snippets), but there is a trade-off between thread-safety and lock contention.
Since this map maps CF name onto CF id, it is justifiable to not be
thread-safe. ColumnFamilies are not created very often, so the use case
performed by our performance test is not likely to occur in a real life
situation.
was (Author: ivol):
After analyzing the issue, I found out that it is caused by the HashBiMap
used in org.apache.cassandra.config.CFMetaData not being thread-safe. This
bidirectional map comes from the Guava project (guava-r08) and never claimed to
be thread-safe. Cassandra uses this map and does not take any precautions to
prevent concurrency problems. By running the attached Unit test you can
reproduce the concurrency issue quite easily.
> NullPointerExceptions occur during running the cassandra performance tests
> --------------------------------------------------------------------------
>
> Key: AMDATUCASSANDRA-130
> URL: http://jira.amdatu.org/jira/browse/AMDATUCASSANDRA-130
> Project: Amdatu Cassandra
> Issue Type: Bug
> Components: Cassandra daemon
> Affects Versions: 0.2.0
> Reporter: Ivo Ladage - van Doorn
> Attachments: ConcurrencyTest.java
>
>
> When I run the Cassandra performance test, sometimes I get this
> NullPointerException:
> [2011-10-18 11:05:38] ERROR: Fatal exception in thread
> Thread[COMMIT-LOG-WRITER,5,main] [org.amdatu.core.loghandler]
> java.lang.RuntimeException: java.lang.NullPointerException
> at
> org.apache.cassandra.utils.WrappedRunnable.run(WrappedRunnable.java:34)
> at java.lang.Thread.run(Thread.java:662)
> Caused by: java.lang.NullPointerException
> at
> org.apache.cassandra.db.RowMutation$RowMutationSerializer.serialize(RowMutation.java:352)
> at
> org.apache.cassandra.db.RowMutation.getSerializedBuffer(RowMutation.java:236)
> at
> org.apache.cassandra.db.commitlog.CommitLogSegment.write(CommitLogSegment.java:106)
> at
> org.apache.cassandra.db.commitlog.CommitLog$LogRecordAdder.run(CommitLog.java:498)
> at
> org.apache.cassandra.db.commitlog.PeriodicCommitLogExecutorService$1.runMayThrow(PeriodicCommitLogExecutorService.java:49)
> at
> org.apache.cassandra.utils.WrappedRunnable.run(WrappedRunnable.java:30)
> ... 1 more
> This happens randomly every now and then, but you have to run the test for a
> long time to reproduce it. However, the problem always appears.
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