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From "Shixiong Zhu (JIRA)" <>
Subject [jira] [Updated] (SPARK-24699) Watermark / Append mode should work with Trigger.Once
Date Fri, 10 Aug 2018 20:50:00 GMT


Shixiong Zhu updated SPARK-24699:
    Fix Version/s: 2.4.0

> Watermark / Append mode should work with Trigger.Once
> -----------------------------------------------------
>                 Key: SPARK-24699
>                 URL:
>             Project: Spark
>          Issue Type: Bug
>          Components: Structured Streaming
>    Affects Versions: 2.3.1
>            Reporter: Chris Horn
>            Assignee: Tathagata Das
>            Priority: Major
>             Fix For: 2.4.0, 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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