[ 
https://issues.apache.org/jira/browse/FLINK-4829?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15585534#comment-15585534
 ] 

Maximilian Michels commented on FLINK-4829:
-------------------------------------------

To mitigate the problem, we have best-effort reporting for accumulators now.

master: 783dca56eedc95f0a8974a9b50f2b532ca8cf849, 
d95929e0110b53f03452e1ad453de2522f79a6b8
release-1.1: c1d6b24600e40700fa06caa28bc81788d8e92386, 
210230c4ab44b84c28b9a62ff461de0955e67f8f

> 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}



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

Reply via email to