Piotr Nowojski created FLINK-22882:
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Summary: 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
On a cluster I observed symptoms of tasks being blocked for long time, causing
long delays with unaligned checkpointing. 99% of those cases were caused by
`broadcastEmit` of the stream status
{noformat}
2021-06-04 14:41:44,049 ERROR
org.apache.flink.runtime.io.network.buffer.LocalBufferPool [] - Blocking wait
[11059 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.appendUnicastDataForNewRecord(BufferWritingResultPartition.java:246)
~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
at
org.apache.flink.runtime.io.network.partition.BufferWritingResultPartition.emitRecord(BufferWritingResultPartition.java:142)
~[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.broadcastEmit(ChannelSelectorRecordWriter.java:67)
~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
at
org.apache.flink.streaming.runtime.io.RecordWriterOutput.writeStreamStatus(RecordWriterOutput.java:136)
~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
at
org.apache.flink.streaming.runtime.streamstatus.AnnouncedStatus.ensureActive(AnnouncedStatus.java:65)
~[flink-dist_2.11-1.14-SNAPSHOT.jar:1.14-SNAPSHOT]
at
org.apache.flink.streaming.runtime.io.RecordWriterOutput.pushToRecordWriter(RecordWriterOutput.java:103)
~[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}
{{broadcastEmit}} can easily bypass our non blocking checks. There are two
questions:
# why is the stream idling so much? It’s like almost every ms it’s broadcasting
active status
# should we optimise this? Broadcasting CBs and other events is not an issue,
as those are events that do not request/require buffers
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