Konstantin Knauf created FLINK-3688:
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Summary: ClassCastException in StreamRecordSerializer when
WindowOperator.trigger() is called and TimeCharacteristic = ProcessingTime
Key: FLINK-3688
URL: https://issues.apache.org/jira/browse/FLINK-3688
Project: Flink
Issue Type: Bug
Affects Versions: 1.0.0
Reporter: Konstantin Knauf
Priority: Critical
Hi,
when using {{TimeCharacteristics.ProcessingTime}} a ClassCastException is
thrown in {{StreamRecordSerializer}} when {{WindowOperator.processWatermark()}}
is called from {{WindowOperator.trigger()}}, i.e. whenever a
ProcessingTimeTimer is triggered.
The problem seems to be that {{processWatermark()}} is also called in
{{trigger()}}, when time characteristic is ProcessingTime, but in
{{RecordWriterOutput}} {{enableWatermarkMultiplexing}} is {{false}} and the
{{TypeSerializer}} is a {{StreamRecordSerializer}}, which ultimately leads to
the ClassCastException. Do you agree?
If this is indeed a bug, there several possible solutions.
# Only calling {{processWatermark()}} in {{trigger()}}, when TimeCharacteristic
is EventTime
# Not calling {{processWatermark()}} in {{trigger()}} at all, instead wait for
the next watermark to trigger the EventTimeTimers with a timestamp behind the
current watermark. This is, of course, a trade off.
# Using {{MultiplexingStreamRecordSerializer}} all the time, but I have no idea
what the side effect of this change would be. I assume there is a reason for
existence of the StreamRecordSerializer ;)
StackTrace:
{quote}
TimerException\{java.lang.RuntimeException:
org.apache.flink.streaming.api.watermark.Watermark cannot be cast to
org.apache.flink.streaming.runtime.streamrecord.StreamRecord\}
at
org.apache.flink.streaming.runtime.tasks.StreamTask$TriggerTask.run(StreamTask.java:716)
at
java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:178)
at
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:292)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)
Caused by: java.lang.RuntimeException:
org.apache.flink.streaming.api.watermark.Watermark cannot be cast to
org.apache.flink.streaming.runtime.streamrecord.StreamRecord
at
org.apache.flink.streaming.runtime.io.RecordWriterOutput.emitWatermark(RecordWriterOutput.java:93)
at
org.apache.flink.streaming.runtime.tasks.OperatorChain$BroadcastingOutputCollector.emitWatermark(OperatorChain.java:370)
at
org.apache.flink.streaming.runtime.operators.windowing.WindowOperator.processWatermark(WindowOperator.java:293)
at
org.apache.flink.streaming.runtime.operators.windowing.WindowOperator.trigger(WindowOperator.java:323)
at
org.apache.flink.streaming.runtime.tasks.StreamTask$TriggerTask.run(StreamTask.java:710)
... 7 more
Caused by: java.lang.ClassCastException:
org.apache.flink.streaming.api.watermark.Watermark cannot be cast to
org.apache.flink.streaming.runtime.streamrecord.StreamRecord
at
org.apache.flink.streaming.runtime.streamrecord.StreamRecordSerializer.serialize(StreamRecordSerializer.java:42)
at
org.apache.flink.runtime.plugable.SerializationDelegate.write(SerializationDelegate.java:56)
at
org.apache.flink.runtime.io.network.api.serialization.SpanningRecordSerializer.addRecord(SpanningRecordSerializer.java:79)
at
org.apache.flink.runtime.io.network.api.writer.RecordWriter.broadcastEmit(RecordWriter.java:109)
at
org.apache.flink.streaming.runtime.io.StreamRecordWriter.broadcastEmit(StreamRecordWriter.java:95)
at
org.apache.flink.streaming.runtime.io.RecordWriterOutput.emitWatermark(RecordWriterOutput.java:90)
... 11 more
{quote}
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