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https://issues.apache.org/jira/browse/FLINK-25728?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17479328#comment-17479328
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pc wang edited comment on FLINK-25728 at 1/21/22, 3:39 AM:
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The issue has the same symptoms as FLINK-24300, beside the momery issue, the
mass *CompletableFuture$UniRun* will also cause long period of CPU busy after
long idle.
was (Author: wpc009):
The issue has the same symptoms as FLINK-24300, beside the momery issue, the
mass *CompletableFuture$UniRun* will also cause CPU busy after long idle.
> Protential memory leeks in StreamMultipleInputProcessor
> -------------------------------------------------------
>
> Key: FLINK-25728
> URL: https://issues.apache.org/jira/browse/FLINK-25728
> Project: Flink
> Issue Type: Bug
> Components: API / DataStream
> Affects Versions: 1.12.5, 1.15.0, 1.13.5, 1.14.2
> Reporter: pc wang
> Priority: Blocker
> Attachments: flink-completablefuture-issue.tar.xz,
> image-2022-01-20-18-43-32-816.png
>
>
> We have an application that contains a broadcast process stage. The
> none-broadcast input has roughly 10 million messages per second, and the
> broadcast side is some kind of control stream, rarely has message follow
> through.
> After several hours of running, the TaskManager will run out of heap memory
> and restart. We reviewed the application code without finding any relevant
> issues.
> We found that the running to crash time was roughly the same. Then we make a
> heap dump before the crash and found mass `CompletableFuture$UniRun`
> instances.
> These `CompletableFuture$UniRun` instances consume several GibaByte memory.
>
> The following pic is from the heap dump we get from a mock testing stream
> with the same scenario.
> !image-2022-01-20-18-43-32-816.png|width=1161,height=471!
>
> After some source code research. We found that it might be caused by the
> *StreamMultipleInputProcessor.getAvailableFuture()*.
> *StreamMultipleInputProcessor* has multiple *inputProcessors* , it's
> *availableFuture* got completed when any of it's input's *availableFuture* is
> complete.
> The current implementation create a new *CompletableFuture* and a new
> *CompletableFuture$UniRun* append to delegate inputProcessor's
> *avaiableFuture*.
> The issue is caused by the stacking of *CompletableFuture$UniRun* on the slow
> inputProcessor's *avaiableFuture*.
> See the source code below.
> [StreamMultipleInputProcessor.java#L65|https://github.com/wpc009/flink/blob/d33c39d974f08a5ac520f220219ecb0796c9448c/flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/io/StreamMultipleInputProcessor.java#L65]
> Because the *UniRun* holds the reference of outside
> *StreamMultipleInputProcessor*'s avaiableFuture, that cause mass
> *CompletableFuture* instance which can not be recycled.
> We made some modifications to the
> *StreamMultipleInputProcessor*.*getAvaiableFuture* function, and verify that
> the issue is gone on our modified version.
> We are willing to make a PR for this fix.
> Heap Dump File [^flink-completablefuture-issue.tar.xz]
> PS: This is a YourKit heap dump. may be not compatible HPROF files.
>
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