Hi Rahul,
Thanks for providing the detailed report. This looks like a bug rather
than a limitation of the Flink Runner. We have integration tests for
session windows with the Flink Runner but they seemed to have missed
this issue.
Let me investigate and get back to you. Tracking issue:
https://jira.apache.org/jira/browse/BEAM-6929
Thanks,
Max
On 28.03.19 03:01, rahul patwari wrote:
+dev
On Wed 27 Mar, 2019, 9:47 PM rahul patwari, <rahulpatwari8...@gmail.com
<mailto:rahulpatwari8...@gmail.com>> wrote:
Hi,
I am using Beam 2.11.0, Runner - beam-runners-flink-1.7, Flink
Cluster - 1.7.2.
I have this flow in my pipeline:
KafkaSource(withCreateTime()) --> ApplyWindow(SessionWindow with
gapDuration=1 Minute, lateness=3 Minutes, AccumulatingFiredPanes,
default trigger) --> BeamSQL(GroupBy query) -->
Window.remerge() --> Enrichment --> KafkaSink
I am generating data in such a way that the first two records belong
to two different sessions. And, generating the third record before
the first session expires with the timestamp for the third record in
such a way that the two sessions will be merged to become a single
session.
For Example, These are the sample input and output obtained when I
ran the same pipeline in DirectRunner.
Sample Input:
{"Col1":{"string":"str1"}, "Timestamp":{"string":"2019-03-27 15-27-44"}}
{"Col1":{"string":"str1"}, "Timestamp":{"string":"2019-03-27 15-28-51"}}
{"Col1":{"string":"str1"}, "Timestamp":{"string":"2019-03-27 15-28-26"}}
Sample Output:
{"Col1":{"string":"str1"},"NumberOfRecords":{"long":1},"WST":{"string":"2019-03-27
15-27-44"},"WET":{"string":"2019-03-27 15-28-44"}}
{"Col1":{"string":"str1"},"NumberOfRecords":{"long":1},"WST":{"string":"2019-03-27
15-28-51"},"WET":{"string":"2019-03-27 15-29-51"}}
{"Col1":{"string":"str1"},"NumberOfRecords":{"long":3},"WST":{"string":"2019-03-27
15-27-44"},"WET":{"string":"2019-03-27 15-29-51"}}
Where "NumberOfRecords" is the count, "WST" is the Avro field Name
which indicates the window start time for the session window.
Similarly "WET" indicates the window End time of the session window.
I am getting "WST" and "WET" after remerging and applying
ParDo(Enrichment stage of the pipeline).
The program ran successfully in DirectRunner. But, in FlinkRunner, I
am getting this exception when the third record arrives:
2019-03-27 15:31:00,442 INFO
org.apache.flink.runtime.executiongraph.ExecutionGraph -
Source: DfleKafkaSource/KafkaIO.Read/Read(KafkaUnboundedSource) ->
Flat Map ->
DfleKafkaSource/ParDo(ConvertKafkaRecordtoRow)/ParMultiDo(ConvertKafkaRecordtoRow)
-> (Window.Into()/Window.Assign.out ->
DfleSql/SqlTransform/BeamIOSourceRel_4/Convert.ConvertTransform/ParDo(Anonymous)/ParMultiDo(Anonymous)
->
DfleSql/SqlTransform/BeamAggregationRel_45/Group.CombineFieldsByFields/Group.ByFields/Group
by fields/ParMultiDo(Anonymous) -> ToKeyedWorkItem,
DfleKafkaSink/ParDo(RowToGenericRecordConverter)/ParMultiDo(RowToGenericRecordConverter)
-> DfleKafkaSink/KafkaIO.KafkaValueWrite/Kafka values with default
key/Map/ParMultiDo(Anonymous) ->
DfleKafkaSink/KafkaIO.KafkaValueWrite/KafkaIO.Write/Kafka
ProducerRecord/Map/ParMultiDo(Anonymous) ->
DfleKafkaSink/KafkaIO.KafkaValueWrite/KafkaIO.Write/KafkaIO.WriteRecords/ParDo(KafkaWriter)/ParMultiDo(KafkaWriter))
(1/1) (d00be62e110cef00d9d772042f4b87a9) switched from DEPLOYING to
RUNNING.
2019-03-27 15:33:25,427 INFO
org.apache.flink.runtime.executiongraph.ExecutionGraph -
DfleSql/SqlTransform/BeamAggregationRel_45/Group.CombineFieldsByFields/Group.ByFields/GroupByKey
->
DfleSql/SqlTransform/BeamAggregationRel_45/Group.CombineFieldsByFields/Combine.GroupedValues/ParDo(Anonymous)/ParMultiDo(Anonymous)
->
DfleSql/SqlTransform/BeamAggregationRel_45/mergeRecord/ParMultiDo(Anonymous)
-> DfleSql/SqlTransform/BeamCalcRel_46/ParDo(Calc)/ParMultiDo(Calc)
-> DfleSql/Window.Remerge/Identity/Map/ParMultiDo(Anonymous) ->
DfleSql/ParDo(EnrichRecordWithWindowTimeInfo)/ParMultiDo(EnrichRecordWithWindowTimeInfo)
->
DfleKafkaSink2/ParDo(RowToGenericRecordConverter)/ParMultiDo(RowToGenericRecordConverter)
-> DfleKafkaSink2/KafkaIO.KafkaValueWrite/Kafka values with default
key/Map/ParMultiDo(Anonymous) ->
DfleKafkaSink2/KafkaIO.KafkaValueWrite/KafkaIO.Write/Kafka
ProducerRecord/Map/ParMultiDo(Anonymous) ->
DfleKafkaSink2/KafkaIO.KafkaValueWrite/KafkaIO.Write/KafkaIO.WriteRecords/ParDo(KafkaWriter)/ParMultiDo(KafkaWriter)
(1/1) (d95af17b7457443c13bd327b46b282e6) switched from RUNNING to
FAILED.
org.apache.beam.sdk.util.UserCodeException:
java.lang.NullPointerException
at
org.apache.beam.sdk.util.UserCodeException.wrap(UserCodeException.java:34)
at
org.apache.beam.runners.core.GroupAlsoByWindowViaWindowSetNewDoFn$DoFnInvoker.invokeProcessElement(Unknown
Source)
at
org.apache.beam.runners.core.SimpleDoFnRunner.invokeProcessElement(SimpleDoFnRunner.java:275)
at
org.apache.beam.runners.core.SimpleDoFnRunner.processElement(SimpleDoFnRunner.java:240)
at
org.apache.beam.runners.core.LateDataDroppingDoFnRunner.processElement(LateDataDroppingDoFnRunner.java:80)
at
org.apache.beam.runners.flink.metrics.DoFnRunnerWithMetricsUpdate.processElement(DoFnRunnerWithMetricsUpdate.java:63)
at
org.apache.beam.runners.flink.translation.wrappers.streaming.DoFnOperator.processElement(DoFnOperator.java:457)
at
org.apache.flink.streaming.runtime.io.StreamInputProcessor.processInput(StreamInputProcessor.java:202)
at
org.apache.flink.streaming.runtime.tasks.OneInputStreamTask.run(OneInputStreamTask.java:104)
at
org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:306)
at org.apache.flink.runtime.taskmanager.Task.run(Task.java:712)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException
at
org.apache.beam.sdk.transforms.Combine$BinaryCombineLongFn.mergeAccumulators(Combine.java:703)
at
org.apache.beam.sdk.transforms.Combine$BinaryCombineLongFn.mergeAccumulators(Combine.java:674)
at
org.apache.beam.runners.flink.translation.wrappers.streaming.state.FlinkStateInternals$FlinkCombiningState.mergeAccumulators(FlinkStateInternals.java:517)
at
org.apache.beam.runners.core.StateMerging.mergeCombiningValues(StateMerging.java:192)
at
org.apache.beam.runners.core.StateMerging.mergeCombiningValues(StateMerging.java:162)
at
org.apache.beam.runners.core.NonEmptyPanes$GeneralNonEmptyPanes.onMerge(NonEmptyPanes.java:132)
at
org.apache.beam.runners.core.ReduceFnRunner$OnMergeCallback.onMerge(ReduceFnRunner.java:507)
at
org.apache.beam.runners.core.MergingActiveWindowSet$MergeContextImpl.recordMerges(MergingActiveWindowSet.java:211)
at
org.apache.beam.runners.core.MergingActiveWindowSet.merge(MergingActiveWindowSet.java:229)
at
org.apache.beam.runners.core.ReduceFnRunner.mergeWindows(ReduceFnRunner.java:436)
at
org.apache.beam.runners.core.ReduceFnRunner.processElements(ReduceFnRunner.java:329)
at
org.apache.beam.runners.core.GroupAlsoByWindowViaWindowSetNewDoFn.processElement(GroupAlsoByWindowViaWindowSetNewDoFn.java:136)
Is this a known issue with FlinkRunner? Is Session Windows with
lateness @experimental in FlinkRunner?
I have also tried with Runner - beam-runners-flink_2.11, Flink
Cluster - 1.5.3 and came across the same exception.
I have also tried generating data with lateness as 0, and everything
is working as expected. Seems like there is no problem in merging
the windows of the records which belong to the same session.
Thanks,
Rahul
