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From "ASF GitHub Bot (JIRA)" <>
Subject [jira] [Work logged] (BEAM-5063) Watermark does not progress for low traffic streams
Date Mon, 13 Aug 2018 08:55:01 GMT


ASF GitHub Bot logged work on BEAM-5063:

                Author: ASF GitHub Bot
            Created on: 13/Aug/18 08:54
            Start Date: 13/Aug/18 08:54
    Worklog Time Spent: 10m 
      Work Description: krzysztof-tr opened a new pull request #6178: [BEAM-5063] Fix Watermark
does not progress for low traffic streams
   Kinesis watermark was extracted to separate class (`KinesisWatermark`) to encapsulate its
logic. Watermark calculation was changed to mitigate the problem with too low traffic on the
corresponding stream. In new implementation, when watermark was not updated within some period
of time, it's updated to the recent min from the `MovingFunction`, regardless of the number
of samples.
   @pawel-kaczmarczyk, @rtshadow, @kennknowles could you please take a look at the changes?
   Follow this checklist to help us incorporate your contribution quickly and easily:
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Issue Time Tracking

    Worklog Id:     (was: 134102)
    Time Spent: 2h 10m  (was: 2h)

> Watermark does not progress for low traffic streams
> ---------------------------------------------------
>                 Key: BEAM-5063
>                 URL:
>             Project: Beam
>          Issue Type: Bug
>          Components: io-java-kinesis
>    Affects Versions: 2.5.0
>            Reporter: Krzysztof Trubalski
>            Assignee: Jean-Baptiste Onofré
>            Priority: Major
>          Time Spent: 2h 10m
>  Remaining Estimate: 0h
> We have a Dataflow Job copying data from multiple Kinesis streams into Big Query. Recently
we have noticed that the watermark on one of the streams frequently gets stuck although data
from that stream is still being processed (it progress only when the traffic increases or
Dataflow autoscaling feature kicks in).
>  Looking at the CloudWatch statistics for the affected stream, it has a really low traffic
rate - only ~1 event every few minutes . After investigation and consulting the issue with
Google's Dataflow Team, it looks like with such small amount of data on the stream, the function
calculating the watermark in KinesisReader reports progress incorrectly.
>  From my initial investigation, I suspect that the issue might be related to usage of
MovingFunction in KinesisReader. In the current implementation, it covers 1 minute period
of samples, since obtaining the min value flushes stale values, if the traffic is very low
the following call to significance check always returns false (as it relies on the number
of samples, and most of them were flushed by get() invocation).

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