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https://issues.apache.org/jira/browse/FLINK-7567?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16155310#comment-16155310
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Mikhail Lipkovich commented on FLINK-7567:
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I guess removing of parameter can be dangerous since it breaks the current API?
But if you think it's fine I can assign this task to myself and remove it.
Regarding to message I thought about adding the way to resolve the issue.
Something like
"Parallelism of original stream: 1; parallelism of feedback stream: 8.
Parallelism can be modified using DataStream#setParallelism() method"
> 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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