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https://issues.apache.org/jira/browse/FLINK-22882?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17361733#comment-17361733
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Piotr Nowojski commented on FLINK-22882:
----------------------------------------
This turned out to be another symptom of FLINK-22881. After broadcasting stream
status, but before emitting the actual record, task could end up with zero
available buffers which was causing exactly this observed behaviour.
> Tasks are blocked while emitting records
> ----------------------------------------
>
> Key: FLINK-22882
> URL: https://issues.apache.org/jira/browse/FLINK-22882
> Project: Flink
> Issue Type: Bug
> Components: Runtime / Network, Runtime / Task
> Affects Versions: 1.14.0
> Reporter: Piotr Nowojski
> Assignee: Piotr Nowojski
> Priority: Critical
>
> On a cluster I observed symptoms of tasks being blocked for long time,
> causing long delays with unaligned checkpointing. 1% of those cases were
> caused by emitting records:
> {noformat}
> 2021-06-04 14:40:24,115 ERROR
> org.apache.flink.runtime.io.network.buffer.LocalBufferPool [] - Blocking
> wait [16497 ms] for an available buffer.
> java.lang.Exception: Stracktracegenerator
> at
> org.apache.flink.runtime.io.network.buffer.LocalBufferPool.requestMemorySegmentBlocking(LocalBufferPool.java:323)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.runtime.io.network.buffer.LocalBufferPool.requestBufferBuilderBlocking(LocalBufferPool.java:290)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.runtime.io.network.partition.BufferWritingResultPartition.requestNewBufferBuilderFromPool(BufferWritingResultPartition.java:338)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.runtime.io.network.partition.BufferWritingResultPartition.requestNewUnicastBufferBuilder(BufferWritingResultPartition.java:314)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.runtime.io.network.partition.BufferWritingResultPartition.appendUnicastDataForRecordContinuation(BufferWritingResultPartition.java:258)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.runtime.io.network.partition.BufferWritingResultPartition.emitRecord(BufferWritingResultPartition.java:147)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.runtime.io.network.api.writer.RecordWriter.emit(RecordWriter.java:104)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.runtime.io.network.api.writer.ChannelSelectorRecordWriter.emit(ChannelSelectorRecordWriter.java:54)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.io.RecordWriterOutput.pushToRecordWriter(RecordWriterOutput.java:105)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.io.RecordWriterOutput.collect(RecordWriterOutput.java:90)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.io.RecordWriterOutput.collect(RecordWriterOutput.java:44)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.api.operators.CountingOutput.collect(CountingOutput.java:56)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.api.operators.CountingOutput.collect(CountingOutput.java:29)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.api.operators.StreamMap.processElement(StreamMap.java:38)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.tasks.ChainingOutput.pushToOperator(ChainingOutput.java:101)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.tasks.ChainingOutput.collect(ChainingOutput.java:82)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.tasks.ChainingOutput.collect(ChainingOutput.java:39)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.tasks.SourceOperatorStreamTask$AsyncDataOutputToOutput.emitRecord(SourceOperatorStreamTask.java:182)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.api.operators.source.SourceOutputWithWatermarks.collect(SourceOutputWithWatermarks.java:110)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.api.operators.source.SourceOutputWithWatermarks.collect(SourceOutputWithWatermarks.java:101)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.api.connector.source.lib.util.IteratorSourceReader.pollNext(IteratorSourceReader.java:98)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.api.operators.SourceOperator.emitNext(SourceOperator.java:294)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.io.StreamTaskSourceInput.emitNext(StreamTaskSourceInput.java:69)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.io.StreamOneInputProcessor.processInput(StreamOneInputProcessor.java:66)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.processInput(StreamTask.java:422)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.tasks.mailbox.MailboxProcessor.runMailboxLoop(MailboxProcessor.java:204)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.runMailboxLoop(StreamTask.java:680)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.executeInvoke(StreamTask.java:635)
> ~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.runWithCleanUpOnFail(StreamTask.java:646)
> [flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:619)
> [flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:779)
> [flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at org.apache.flink.runtime.taskmanager.Task.run(Task.java:566)
> [flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
> at java.lang.Thread.run(Thread.java:748) [?:1.8.0_282]
> {noformat}
> *All of those cases that I have seen were always coming from SourceOperator*
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