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https://issues.apache.org/jira/browse/CASSANDRA-2350?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13008419#comment-13008419
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Gary Dusbabek commented on CASSANDRA-2350:
------------------------------------------
+1
> Races between schema changes and StorageService operations
> ----------------------------------------------------------
>
> Key: CASSANDRA-2350
> URL: https://issues.apache.org/jira/browse/CASSANDRA-2350
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Affects Versions: 0.7.0
> Reporter: Jeffrey Wang
> Assignee: Jonathan Ellis
> Priority: Minor
> Fix For: 0.7.5
>
> Attachments: 2350.txt
>
>
> I only tested this on 0.7.0, but it judging by the 0.7.3 code (latest I've
> looked at) the same thing should happen.
> The case in particular that I ran into is this: I force a compaction for all
> CFs in a keyspace, and while the compaction is happening I add another CF to
> the keyspace. I get the following exception because the underlying set of CFs
> has changed while being iterated over.
> {noformat}
> java.util.ConcurrentModificationException
> at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
> at java.util.HashMap$ValueIterator.next(Unknown Source)
> at java.util.Collections$UnmodifiableCollection$1.next(Unknown Source)
> at
> org.apache.cassandra.service.StorageService.forceTableCompaction(StorageService.java:1140)
> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
> at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
> at java.lang.reflect.Method.invoke(Unknown Source)
> at com.sun.jmx.mbeanserver.StandardMBeanIntrospector.invokeM2(Unknown
> Source)
> at com.sun.jmx.mbeanserver.StandardMBeanIntrospector.invokeM2(Unknown
> Source)
> at com.sun.jmx.mbeanserver.MBeanIntrospector.invokeM(Unknown Source)
> at com.sun.jmx.mbeanserver.PerInterface.invoke(Unknown Source)
> at com.sun.jmx.mbeanserver.MBeanSupport.invoke(Unknown Source)
> at
> com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(Unknown Source)
> at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(Unknown Source)
> at javax.management.remote.rmi.RMIConnectionImpl.doOperation(Unknown
> Source)
> at javax.management.remote.rmi.RMIConnectionImpl.access$200(Unknown
> Source)
> at
> javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(Unknown
> Source)
> at
> javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(Unknown
> Source)
> at javax.management.remote.rmi.RMIConnectionImpl.invoke(Unknown
> Source)
> at sun.reflect.GeneratedMethodAccessor84.invoke(Unknown Source)
> at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
> at java.lang.reflect.Method.invoke(Unknown Source)
> at sun.rmi.server.UnicastServerRef.dispatch(Unknown Source)
> at sun.rmi.transport.Transport$1.run(Unknown Source)
> at java.security.AccessController.doPrivileged(Native Method)
> at sun.rmi.transport.Transport.serviceCall(Unknown Source)
> at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source)
> at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown
> Source)
> at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown
> Source)
> at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown
> Source)
> at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
> at java.lang.Thread.run(Unknown Source)
> {noformat}
> The problem is a little more fundamental than that, though, as I believe any
> schema change of CFs in the keyspace during one of these operations (e.g.
> flush, compaction, etc) has the potential to cause a race. I'm not sure what
> would happen if the set of CFs to compact was acquired and one of them was
> dropped before it had been compacted.
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