That looks like a bug. Were you writing counters ? 


Can you please add it here https://issues.apache.org/jira/browse/CASSANDRA , include some information on the request that caused it and email the bug report back to the list. 

(note to self) I *think* the problem is the counter WritePerformer implementations are put into the REPLICATE_ON_WRITE TP and then update the hints on the AbstractWriteResponeHandler asynchronously. This could happen after the write thread has move on to wait on the handlers which involves waiting on the hints futures. 

thanks

-----------------
Aaron Morton
Freelance Developer
@aaronmorton

On 4/02/2012, at 4:49 AM, Viktor Jevdokimov wrote:

What may be cause of the following exception in 1.0.7 Cassandra:
 
ERROR [Thrift:134] 2012-02-03 15:51:02,800 Cassandra.java (line 3462) Internal error processing batch_mutate
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.utils.FBUtilities.waitOnFutures(FBUtilities.java:532)
        at org.apache.cassandra.service.AbstractWriteResponseHandler.waitForHints(AbstractWriteResponseHandler.java:89)
        at org.apache.cassandra.service.AbstractWriteResponseHandler.get(AbstractWriteResponseHandler.java:58)
        at org.apache.cassandra.service.StorageProxy.mutate(StorageProxy.java:201)
        at org.apache.cassandra.thrift.CassandraServer.doInsert(CassandraServer.java:639)
        at org.apache.cassandra.thrift.CassandraServer.internal_batch_mutate(CassandraServer.java:590)
        at org.apache.cassandra.thrift.CassandraServer.batch_mutate(CassandraServer.java:598)
        at org.apache.cassandra.thrift.Cassandra$Processor$batch_mutate.process(Cassandra.java:3454)
        at org.apache.cassandra.thrift.Cassandra$Processor.process(Cassandra.java:2889)
        at org.apache.cassandra.thrift.CustomTThreadPoolServer$WorkerProcess.run(CustomTThreadPoolServer.java:187)
        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:662)
 
 
 
Best regards/ Pagarbiai
 
Viktor Jevdokimov
Senior Developer
 
Phone: +370 5 212 3063. Fax: +370 5 261 0453
J. Jasinskio 16C, LT-01112 Vilnius, Lithuania
 
 

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