[jira] [Created] (FLINK-2527) If a VertexUpdateFunction calls setNewVertexValue more than once, the MessagingFunction will only see the first value set

["Gabor Gevay (JIRA)" <ji...@apache.org>]

Gabor Gevay created FLINK-2527:
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             Summary: If a VertexUpdateFunction calls setNewVertexValue more than once, the MessagingFunction will only see the first value set
                 Key: FLINK-2527
                 URL: https://issues.apache.org/jira/browse/FLINK-2527
             Project: Flink
          Issue Type: Bug
          Components: Gelly
            Reporter: Gabor Gevay
            Assignee: Gabor Gevay
             Fix For: 0.10, 0.9.1


The problem is that if setNewVertexValue is called more than once, it sends each new value to the out Collector, and these all end up in the workset, but then the coGroups in the two descendants of MessagingUdfWithEdgeValues use only the first value in the state Iterable. I see three ways to resolve this:

1. Add it to the documentation that setNewVertexValue should only be called once, and optionally add a check for this.
2. In setNewVertexValue, do not send the newValue to the out Collector at once, but only record it in outVal, and send the last recorded value after updateVertex returns.
3. Iterate over the entire Iterable in MessagingUdfWithEVsSimpleVV.coGroup and MessagingUdfWithEVsVVWithDegrees.coGroup. (This would probably still need some documentation addition.)

I like 2. the best. What are your opinions?



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