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

["Andra Lungu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-1587?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14328583#comment-14328583 ] 

Andra Lungu commented on FLINK-1587:
------------------------------------

Hi Carsten, 

Nice catch. 
You can add the test here: https://github.com/apache/flink/blob/master/flink-staging/flink-gelly/src/test/java/org/apache/flink/graph/test/DegreesITCase.java

The coGroup Iterator may be empty because  you may have an ID in the edges that does not exist in the vertex data set.
 
The problem is that you cannot reproduce this locally. Maybe the dataset got tampered with on the cluster. Keep us posted on how things evolve. 

Best of luck, 
Andra 



> 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.
> {noformat}
> 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
> ...
> {noformat}
> 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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