[jira] [Created] (FLINK-1587) coGroup throws NoSuchElementException on iterator.next()

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[jira] [Created] (FLINK-1587) coGroup throws NoSuchElementException on iterator.next()

Shang Yuanchun (Jira)
Carsten Brandt created FLINK-1587:
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             Summary: coGroup throws NoSuchElementException on iterator.next()
                 Key: FLINK-1587
                 URL: https://issues.apache.org/jira/browse/FLINK-1587
             Project: Flink
          Issue Type: Bug
          Components: Gelly
         Environment: flink-0.8.0-SNAPSHOT
            Reporter: Carsten Brandt


I am receiving the following exception when running a simple job that extracts outdegree from a graph using Gelly. It is currently only failing on the cluster and I am not able to reproduce it locally. Will try that the next days.

{{{
02/20/2015 02:27:02: Map (Map at count(GraphUtils.java:26)) (36/64) switched to RUNNING
02/20/2015 02:27:02: CoGroup (CoGroup at inDegrees(Graph.java:675)) (5/64) switched to FAILED
java.util.NoSuchElementException
        at java.util.Collections$EmptyIterator.next(Collections.java:3006)
        at flink.graphs.Graph$CountNeighborsCoGroup.coGroup(Graph.java:665)
        at org.apache.flink.runtime.operators.CoGroupDriver.run(CoGroupDriver.java:130)
        at org.apache.flink.runtime.operators.RegularPactTask.run(RegularPactTask.java:493)
        at org.apache.flink.runtime.operators.RegularPactTask.invoke(RegularPactTask.java:360)
        at org.apache.flink.runtime.execution.RuntimeEnvironment.run(RuntimeEnvironment.java:257)
        at java.lang.Thread.run(Thread.java:745)

02/20/2015 02:27:02: Job execution switched to status FAILING

...
}}}

The error occurs in Gellys Graph.java at this line: https://github.com/apache/flink/blob/a51c02f6e8be948d71a00c492808115d622379a7/flink-staging/flink-gelly/src/main/java/org/apache/flink/graph/Graph.java#L636

Is there any valid case where a coGroup Iterator may be empty? As far as I see there is a bug somewhere.

I'd like to write a test case for this to reproduce the issue. Where can I put such a test?



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