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https://issues.apache.org/jira/browse/FLINK-9552?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16513890#comment-16513890
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Till Rohrmann commented on FLINK-9552:
--------------------------------------
Hi [~kien_truong], Flink currently does not fully support checkpointing of
cyclic topologies. See FLINK-3257 for more information. Part of it is that the
streaming iteration tasks don't honour the checkpoint lock. That's why we see
the NPE because a concurrent checkpointing operation can reset the
{{targetBuffer}} in {{SpanningRecordSerializer}}.
Since this is a known limitation, I will unblock {{1.6.0}} from this issue.
> NPE in SpanningRecordSerializer during checkpoint with iterations
> -----------------------------------------------------------------
>
> Key: FLINK-9552
> URL: https://issues.apache.org/jira/browse/FLINK-9552
> Project: Flink
> Issue Type: Bug
> Components: Type Serialization System
> Affects Versions: 1.5.0
> Reporter: Truong Duc Kien
> Assignee: vinoyang
> Priority: Blocker
>
> We're encountering NPE intermittently inside SpanningRecordSerializer during
> checkpoint.
>
> {code:java}
> 2018-06-08 08:31:35,741 [ka.actor.default-dispatcher-83] INFO
> o.a.f.r.e.ExecutionGraph IterationSource-22 (44/120)
> (c1b94ef849db0e5fb9fb7b85c17073ce) switched from RUNNING to FAILED.
> java.lang.RuntimeException
> at
> org.apache.flink.streaming.runtime.io.RecordWriterOutput.pushToRecordWriter(RecordWriterOutput.java:110)
> at
> org.apache.flink.streaming.runtime.io.RecordWriterOutput.collect(RecordWriterOutput.java:89)
> at
> org.apache.flink.streaming.runtime.tasks.StreamIterationHead.run(StreamIterationHead.java:91)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:306)
> at org.apache.flink.runtime.taskmanager.Task.run(Task.java:703)
> at java.lang.Thread.run(Thread.java:748)
> Caused by: java.lang.NullPointerException
> at
> org.apache.flink.runtime.io.network.api.serialization.SpanningRecordSerializer.addRecord(SpanningRecordSerializer.java:98)
> at
> org.apache.flink.runtime.io.network.api.writer.RecordWriter.sendToTarget(RecordWriter.java:129)
> at
> org.apache.flink.runtime.io.network.api.writer.RecordWriter.emit(RecordWriter.java:105)
> at
> org.apache.flink.streaming.runtime.io.StreamRecordWriter.emit(StreamRecordWriter.java:81)
> at
> org.apache.flink.streaming.runtime.io.RecordWriterOutput.pushToRecordWriter(RecordWriterOutput.java:107)
> ... 5 more
> 2018-06-08 08:31:35,746 [ka.actor.default-dispatcher-83] INFO
> o.a.f.r.e.ExecutionGraph Job xxx (8a4eaf02c46dc21c7d6f3f70657dbb17) switched
> from state RUNNING to FAILING.
> java.lang.RuntimeException
> at
> org.apache.flink.streaming.runtime.io.RecordWriterOutput.pushToRecordWriter(RecordWriterOutput.java:110)
> at
> org.apache.flink.streaming.runtime.io.RecordWriterOutput.collect(RecordWriterOutput.java:89)
> at
> org.apache.flink.streaming.runtime.tasks.StreamIterationHead.run(StreamIterationHead.java:91)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:306)
> at org.apache.flink.runtime.taskmanager.Task.run(Task.java:703)
> at java.lang.Thread.run(Thread.java:748)
> Caused by: java.lang.NullPointerException
> at
> org.apache.flink.runtime.io.network.api.serialization.SpanningRecordSerializer.addRecord(SpanningRecordSerializer.java:98)
> at
> org.apache.flink.runtime.io.network.api.writer.RecordWriter.sendToTarget(RecordWriter.java:129)
> at
> org.apache.flink.runtime.io.network.api.writer.RecordWriter.emit(RecordWriter.java:105)
> at
> org.apache.flink.streaming.runtime.io.StreamRecordWriter.emit(StreamRecordWriter.java:81)
> at
> org.apache.flink.streaming.runtime.io.RecordWriterOutput.pushToRecordWriter(RecordWriterOutput.java:107)
> ... 5 more
> {code}
> This issue is probably concurrency related, because the revelant Flink code
> seems to have proper null checking
> https://github.com/apache/flink/blob/fa024726bb801fc71cec5cc303cac1d4a03f555e/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/api/serialization/SpanningRecordSerializer.java#L98
> {code:java}
> // Copy from intermediate buffers to current target memory segment
> if (targetBuffer != null) {
> targetBuffer.append(lengthBuffer);
> targetBuffer.append(dataBuffer);
> targetBuffer.commit();
> }
> {code}
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