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Date: Fri, 23 Sep 2016 05:01:20 +0000 (UTC)
From: "Dima Spivak (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (ACCUMULO-4469) ConcurrentModificationException
 while running MultiTable.xml node in Random Walk
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archived-at: Fri, 23 Sep 2016 05:01:22 -0000


    [ https://issues.apache.org/jira/browse/ACCUMULO-4469?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15515418#comment-15515418 ] 

Dima Spivak commented on ACCUMULO-4469:
---------------------------------------

Hm... looked into the {{State}} class and realized it's just wrapping a {{HashMap}}, so not sure why it would be getting updated underneath me. :(

> ConcurrentModificationException while running MultiTable.xml node in Random Walk 
> ---------------------------------------------------------------------------------
>
>                 Key: ACCUMULO-4469
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-4469
>             Project: Accumulo
>          Issue Type: Bug
>          Components: test
>    Affects Versions: 1.7.2
>            Reporter: Dima Spivak
>            Assignee: Dima Spivak
>
> After the resolution of ACCUMULO-4467, I got back to playing with Random Walk and had a failure caused by a {{ConcurrentModificationException}}:
> {code}
> 23 01:03:04,316 [randomwalk.Framework] ERROR: Error during random walk
> java.lang.Exception: Error running node MultiTable.xml
>         at org.apache.accumulo.test.randomwalk.Module.visit(Module.java:346)
>         at org.apache.accumulo.test.randomwalk.Framework.run(Framework.java:59)
>         at org.apache.accumulo.test.randomwalk.Framework.main(Framework.java:119)
>         at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>         at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
>         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>         at java.lang.reflect.Method.invoke(Method.java:606)
>         at org.apache.accumulo.start.Main$2.run(Main.java:157)
>         at java.lang.Thread.run(Thread.java:745)
> Caused by: java.util.ConcurrentModificationException
>         at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:859)
>         at java.util.ArrayList$Itr.next(ArrayList.java:831)
>         at org.apache.accumulo.test.randomwalk.multitable.MultiTableFixture.tearDown(MultiTableFixture.java:64)
>         at org.apache.accumulo.test.randomwalk.Module.visit(Module.java:365)
>         at org.apache.accumulo.test.randomwalk.Module$1.call(Module.java:283)
>         at org.apache.accumulo.test.randomwalk.Module$1.call(Module.java:278)
>         at java.util.concurrent.FutureTask.run(FutureTask.java:262)
>         at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
>         at java.util.concurrent.FutureTask.run(FutureTask.java:262)
>         at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
>         at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
>         at org.apache.accumulo.fate.util.LoggingRunnable.run(LoggingRunnable.java:35)
>         ... 1 more
> {code}
> [This section of code|https://github.com/apache/accumulo/blob/master/test/src/main/java/org/apache/accumulo/test/randomwalk/multitable/MultiTableFixture.java#L61-L71] seems to be at fault. In particular, it looks like we're getting the table list, but then instead of doing a deep copy to a new {{ArrayList<String>}} from which we choose tables to delete, we're looping through and deleting tables while referring to the changing list, which has the effect of modifying it and making Java unhappy. Am I missing something more complex or can I fix this one myself by just doing the aforementioned deep copy of the table list? Or is a better way to use the {{TableOperations.list()}} method and iterate through the {{SortedSet<String>}} it provides?


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