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Posted to issues@flink.apache.org by "Johannes (JIRA)" <ji...@apache.org> on 2016/09/06 21:48:20 UTC
[jira] [Commented] (FLINK-4586) NumberSequenceIterator and
Accumulator threading issue
[ https://issues.apache.org/jira/browse/FLINK-4586?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15468729#comment-15468729 ]
Johannes commented on FLINK-4586:
---------------------------------
The testcase also fails, when just using a plain collection and a rebalance to create some form of a parallel collection
{code}
fromCollection(1 to 100).rebalance()
{code}
So it seems to be not specific to the NumberSequenceIterator.
So either the initialization of the accumulator is wrong in the sample code, or there is a deeper issue.
> NumberSequenceIterator and Accumulator threading issue
> ------------------------------------------------------
>
> Key: FLINK-4586
> URL: https://issues.apache.org/jira/browse/FLINK-4586
> Project: Flink
> Issue Type: Bug
> Components: DataSet API
> Affects Versions: 1.1.2
> Reporter: Johannes
> Priority: Minor
> Attachments: FLINK4586Test.scala
>
>
> There is a strange problem when using the NumberSequenceIterator in combination with an AverageAccumulator.
> It seems like the individual accumulators are reinitialized and overwrite parts of intermediate solutions.
> The following scala snippit exemplifies the problem.
> Instead of printing the correct average, the result should be {{50.5}} but is something completely different, like {{8.08}}, dependent on the number of cores used.
> If the parallelism is set to {{1}} the result is correct, which indicates a likely threading problem.
> The problem occurs using the java and scala API.
> {code}
> env
> .fromParallelCollection(new NumberSequenceIterator(1, 100))
> .map(new RichMapFunction[Long, Long] {
> var a : AverageAccumulator = _
> override def map(value: Long): Long = {
> a.add(value)
> value
> }
> override def open(parameters: Configuration): Unit = {
> a = new AverageAccumulator
> getRuntimeContext.addAccumulator("test", a)
> }
> })
> .reduce((a, b) => a + b)
> .print()
> val lastJobExecutionResult: JobExecutionResult = env.getLastJobExecutionResult
> println(lastJobExecutionResult.getAccumulatorResult("test"))
> {code}
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