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https://issues.apache.org/jira/browse/BEAM-5063?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Krzysztof Trubalski updated BEAM-5063:
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Description:
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).
was:
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 2 events per minute + 4 events every 5 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 MovingFunction used to keep
>track of the watermark in KinesisReader is incorrectly used. In the current
>implementation, min is obtained first and then the significance is checked.
>Since obtaining the min value flushes stale values, 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).
> Watermark does not progress for low traffic streams
> ---------------------------------------------------
>
> Key: BEAM-5063
> URL: https://issues.apache.org/jira/browse/BEAM-5063
> Project: Beam
> Issue Type: Bug
> Components: io-java-kinesis
> Affects Versions: 2.5.0
> Reporter: Krzysztof Trubalski
> Assignee: Jean-Baptiste Onofré
> Priority: Major
>
> 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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