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https://issues.apache.org/jira/browse/FLINK-7567?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16153629#comment-16153629
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Mikhail Lipkovich commented on FLINK-7567:
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Since DataStream.Iterate() already contains flag 'keepPartitioning' it seems
for me that we could align parallelism of input and feedback streams in this
method when it's possible and to throw an exception with more clear message
when it's not.
I'm a newbie here, so maybe I'm missing something important. What do you think
[~aljoscha] ?
> DataStream#iterate() on env.fromElements() / env.fromCollection() does not
> work
> -------------------------------------------------------------------------------
>
> Key: FLINK-7567
> URL: https://issues.apache.org/jira/browse/FLINK-7567
> Project: Flink
> Issue Type: Bug
> Components: DataStream API
> Affects Versions: 1.3.2
> Environment: OS X 10.12.6, Oracle JDK 1.8.0_144, Flink 1.3.2
> Reporter: Peter Ertl
>
> When I try to execute this simple snippet of code
> {code}
> @Test
> def iterateOnElements(): Unit = {
> val env = StreamExecutionEnvironment.getExecutionEnvironment
> // do something silly just do get iteration going ...
> val result = env.fromElements(1, 2, 3).iterate(it => {
> (it.filter(_ > 0).map(_ - 1), it.filter(_ > 0).map(_ => 'x'))
> })
> result.print()
> env.execute()
> }
> {code}
> I get the following exception:
> {code}
> java.lang.UnsupportedOperationException: Parallelism of the feedback stream
> must match the parallelism of the original stream. Parallelism of original
> stream: 1; parallelism of feedback stream: 8
> at
> org.apache.flink.streaming.api.transformations.FeedbackTransformation.addFeedbackEdge(FeedbackTransformation.java:87)
> at
> org.apache.flink.streaming.api.datastream.IterativeStream.closeWith(IterativeStream.java:77)
> at
> org.apache.flink.streaming.api.scala.DataStream.iterate(DataStream.scala:519)
> at atp.analytics.CassandraReadTest.iterate2(CassandraReadTest.scala:134)
> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> at
> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> at java.lang.reflect.Method.invoke(Method.java:498)
> at
> org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
> at
> org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
> at
> org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
> at
> org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
> at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
> at
> org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
> at
> org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
> at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
> at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
> at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
> at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
> at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
> at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
> at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
> at
> com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
> at
> com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
> at
> com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
> at
> com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
> {code}
> Since is just the simplest iterating stream setup I could imagine this error
> makes no sense to me :-P
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