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https://issues.apache.org/jira/browse/CASSANDRA-864?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12843243#action_12843243
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Jonathan Ellis commented on CASSANDRA-864:
------------------------------------------
What's happening is, we're relying on the synchronization done by the caller of
response() to make us thread-safe. And this works fine _if_ responses arrive
before the timeout; then the assumption that responses are never added after
the wait in get completes holds true (since no responses may be added after the
signal is fired).
But if the request times out, then the signal has not actually been fired, and
a response may arrive during iteration of the messages and cause a CME, as seen
here.
> ConcurrentModificationException during QuorumResponseHandler
> ------------------------------------------------------------
>
> Key: CASSANDRA-864
> URL: https://issues.apache.org/jira/browse/CASSANDRA-864
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Affects Versions: 0.6
> Reporter: B. Todd Burruss
> Assignee: Jonathan Ellis
>
> using cassandra-0.6.0-beta2/
> 2010-03-09 09:17:26,827 ERROR [pool-1-thread-675] [Cassandra.java:1166]
> Internal error processing get
> java.util.ConcurrentModificationException
> at
> java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372)
> at java.util.AbstractList$Itr.next(AbstractList.java:343)
> at
> org.apache.cassandra.service.QuorumResponseHandler.get(QuorumResponseHandler.java:68)
> at
> org.apache.cassandra.service.StorageProxy.strongRead(StorageProxy.java:470)
> at
> org.apache.cassandra.service.StorageProxy.readProtocol(StorageProxy.java:401)
> at
> org.apache.cassandra.thrift.CassandraServer.readColumnFamily(CassandraServer.java:101)
> at
> org.apache.cassandra.thrift.CassandraServer.multigetInternal(CassandraServer.java:309)
> at
> org.apache.cassandra.thrift.CassandraServer.get(CassandraServer.java:274)
> at
> org.apache.cassandra.thrift.Cassandra$Processor$get.process(Cassandra.java:1156)
> at
> org.apache.cassandra.thrift.Cassandra$Processor.process(Cassandra.java:1114)
> at
> org.apache.thrift.server.TThreadPoolServer$WorkerProcess.run(TThreadPoolServer.java:253)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> at java.lang.Thread.run(Thread.java:619)
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