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https://issues.apache.org/jira/browse/BEAM-9573?focusedWorklogId=408333&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-408333
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ASF GitHub Bot logged work on BEAM-9573:
----------------------------------------
Author: ASF GitHub Bot
Created on: 23/Mar/20 21:26
Start Date: 23/Mar/20 21:26
Worklog Time Spent: 10m
Work Description: mxm commented on pull request #11200: [BEAM-9573]
Correct computing of watermark hold for timer output timestamp
URL: https://github.com/apache/beam/pull/11200
This PR contains two related changes which would be hard to review in
separate PRs:
### BEAM-9573 Correct computing of watermark hold for timer output timestamp
With the introduction of timer output timestamps, a new watermark hold had
been
added to the Flink Runner. The watermark computation works on the keyed state
backend which computes a key-scoped watermark hold and not the desired
operator-wide watermark hold.
Computation:
https://github.com/apache/beam/blob/b564239081e9351c56fb0e7d263495b95dd3f8f3/runners/flink/src/main/java/org/apache/beam/runners/flink/translation/wrappers/streaming/DoFnOperator.java#L1140
Key-scoped state:
https://github.com/apache/beam/blob/b564239081e9351c56fb0e7d263495b95dd3f8f3/runners/flink/src/main/java/org/apache/beam/runners/flink/translation/wrappers/streaming/DoFnOperator.java#L1130
The solution is to iterate over all available state backend keys.
### BEAM-9566 Mitigate performance issue with watermark hold computation
Benchmarks have shown that the watermark computation over all keys is very
expensive. This introduces a cache which stores and updates the lowest
timestamps for watermark holds due to timer output timestamps.
In most cases only the cache should be hit, only when a large number of
timers
are added and then removed one-after-another, the cache might have to be
reloaded with data from the state backend.
Post-Commit Tests Status (on master branch)
------------------------------------------------------------------------------------------------
Lang | SDK | Apex | Dataflow | Flink | Gearpump | Samza | Spark
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Go | [](https://builds.apache.org/job/beam_PostCommit_Go/lastCompletedBuild/)
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| [](https://builds.apache.org/job/beam_PostCommit_Java_ValidatesRunner_Samza/lastCompletedBuild/)
| [](https://builds.apache.org/job/beam_PostCommit_Java_ValidatesRunner_Spark/lastCompletedBuild/)<br>[](https://builds.apache.org/job/beam_PostCommit_Java_PVR_Spark_Batch/lastCompletedBuild/)<br>[](https://builds.apache.org/job/beam_PostCommit_Java_ValidatesRunner_SparkStructuredStreaming/lastCompletedBuild/)
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| --- | --- | [](https://builds.apache.org/job/beam_PostCommit_XVR_Spark/lastCompletedBuild/)
Pre-Commit Tests Status (on master branch)
------------------------------------------------------------------------------------------------
--- |Java | Python | Go | Website
--- | --- | --- | --- | ---
Non-portable | [](https://builds.apache.org/job/beam_PreCommit_Java_Cron/lastCompletedBuild/)
| [](https://builds.apache.org/job/beam_PreCommit_Python_Cron/lastCompletedBuild/)<br>[](https://builds.apache.org/job/beam_PreCommit_PythonLint_Cron/lastCompletedBuild/)
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| --- | ---
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Issue Time Tracking
-------------------
Worklog Id: (was: 408333)
Remaining Estimate: 0h
Time Spent: 10m
> Watermark hold for timer output timestamp is not computed correctly
> -------------------------------------------------------------------
>
> Key: BEAM-9573
> URL: https://issues.apache.org/jira/browse/BEAM-9573
> Project: Beam
> Issue Type: Bug
> Components: runner-flink
> Affects Versions: 2.20.0
> Reporter: Maximilian Michels
> Assignee: Maximilian Michels
> Priority: Blocker
> Fix For: 2.20.0
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> With the introduction of timer output timestamp, a new watermark hold had
> been added to the Flink Runner. The watermark computation works on the keyed
> state backend which computes a key-scoped watermark hold and not the desired
> operator-wide watermark hold.
> Computation:
> https://github.com/apache/beam/blob/b564239081e9351c56fb0e7d263495b95dd3f8f3/runners/flink/src/main/java/org/apache/beam/runners/flink/translation/wrappers/streaming/DoFnOperator.java#L1140
> Key-scoped state:
> https://github.com/apache/beam/blob/b564239081e9351c56fb0e7d263495b95dd3f8f3/runners/flink/src/main/java/org/apache/beam/runners/flink/translation/wrappers/streaming/DoFnOperator.java#L1130
> We need to change this to operate on all keys. This has to be done before
> fixing BEAM-9566.
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