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Posted to issues@spark.apache.org by "Tathagata Das (JIRA)" <ji...@apache.org> on 2018/07/23 20:05:00 UTC
[jira] [Resolved] (SPARK-24699) Watermark / Append mode should work
with Trigger.Once
[ https://issues.apache.org/jira/browse/SPARK-24699?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Tathagata Das resolved SPARK-24699.
-----------------------------------
Resolution: Fixed
Fix Version/s: 3.0.0
Issue resolved by pull request 21746
[https://github.com/apache/spark/pull/21746]
> Watermark / Append mode should work with Trigger.Once
> -----------------------------------------------------
>
> Key: SPARK-24699
> URL: https://issues.apache.org/jira/browse/SPARK-24699
> Project: Spark
> Issue Type: Bug
> Components: Structured Streaming
> Affects Versions: 2.3.1
> Reporter: Chris Horn
> Assignee: Tathagata Das
> Priority: Major
> Fix For: 3.0.0
>
> Attachments: watermark-once.scala, watermark-stream.scala
>
>
> I have a use case where I would like to trigger a structured streaming job from an external scheduler (once every 15 minutes or so) and have it write window aggregates to Kafka.
> I am able to get my code to work when running with `Trigger.ProcessingTime` but when I switch to `Trigger.Once` the watermarking feature of structured streams does not persist to (or is not recollected from) the checkpoint state.
> This causes the stream to never generate output because the watermark is perpetually stuck at `1970-01-01T00:00:00Z`.
> I have created a failing test case in the `EventTimeWatermarkSuite`, I will create a [WIP] pull request on github and link it here.
>
> It seems that even if it generated the watermark, and given the current streaming behavior, I would have to trigger the job twice to generate any output.
>
> The microbatcher only calculates the watermark off of the previous batch's input and emits new aggs based off of that timestamp.
> This state is not available to a newly started `MicroBatchExecution` stream.
> Would it be an appropriate strategy to create a new checkpoint file with the most up to watermark or watermark and query stats?
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