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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-4829) Accumulators are not thread safe
Date Tue, 18 Oct 2016 13:58:58 GMT

    [ https://issues.apache.org/jira/browse/FLINK-4829?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15585520#comment-15585520
] 

ASF GitHub Bot commented on FLINK-4829:
---------------------------------------

Github user asfgit closed the pull request at:

    https://github.com/apache/flink/pull/2649


> Accumulators are not thread safe
> --------------------------------
>
>                 Key: FLINK-4829
>                 URL: https://issues.apache.org/jira/browse/FLINK-4829
>             Project: Flink
>          Issue Type: Bug
>          Components: Local Runtime
>    Affects Versions: 1.2.0, 1.1.3
>            Reporter: Till Rohrmann
>             Fix For: 1.2.0, 1.1.4
>
>
> Flink's {{Accumulators}} are not thread safe. With the introduction of live accumulator
snapshots which are sent to the {{JobManager}}, we've introduced a concurrent access to accumulators
without properly guard them against concurrent modifications. So if an accumulator snapshot
is taken for an accumulator which is at the same time modified, it can cause an {{ConcurrentModificationException}}
as it was reported by an user: 
> {code}
> WARN  org.apache.flink.runtime.accumulators.AccumulatorRegistry     - Failed to serialize
accumulators for task.
> java.util.ConcurrentModificationException
>         at java.util.TreeMap$PrivateEntryIterator.nextEntry(TreeMap.java:1211)
>         at java.util.TreeMap$EntryIterator.next(TreeMap.java:1247)
>         at java.util.TreeMap$EntryIterator.next(TreeMap.java:1242)
>         at java.util.TreeMap.writeObject(TreeMap.java:2436)
>         at sun.reflect.GeneratedMethodAccessor491.invoke(Unknown Source) 
>         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>         at java.lang.reflect.Method.invoke(Method.java:498)
>         at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:1028)
>         at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496)
>         at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
>         at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
>         at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
>         at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
>         at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
>         at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
>         at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
>         at java.util.HashMap.internalWriteEntries(HashMap.java:1785)
>         at java.util.HashMap.writeObject(HashMap.java:1362)
>         at sun.reflect.GeneratedMethodAccessor189.invoke(Unknown Source) 
>         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>         at java.lang.reflect.Method.invoke(Method.java:498)
>         at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:1028)
>         at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496)
>         at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
>         at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
>         at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
>         at org.apache.flink.util.InstantiationUtil.serializeObject(InstantiationUtil.java:301)
>         at org.apache.flink.util.SerializedValue.<init>(SerializedValue.java:52)
>         at org.apache.flink.runtime.accumulators.AccumulatorSnapshot.<init>(AccumulatorSnapshot.java:58)
>         at org.apache.flink.runtime.accumulators.AccumulatorRegistry.getSnapshot(AccumulatorRegistry.java:75)
>         at org.apache.flink.runtime.taskmanager.TaskManager$$anonfun$sendHeartbeatToJobManager$2.apply(TaskManager.scala:1286)
> {code}



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