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https://issues.apache.org/jira/browse/BEAM-9439?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17070826#comment-17070826
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Paweł Kaczmarczyk commented on BEAM-9439:
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I don't remember why it was implemented this way. As I understand, to fix
{{getTotalBacklogBytes}}() we would need the watermark of the whole stream, not
just current split, right?
On the other hand, {{getSplitBacklogBytes}}() can be implemented using the
[Enhanced Shard-level
Metrics|[https://docs.aws.amazon.com/streams/latest/dev/monitoring-with-cloudwatch.html#kinesis-metrics-shard]]
but these are not enabled by default and charged additionally. So even with
this implementation, we would still need a proper {{getTotalBacklogBytes}}().
What do you think?
> KinesisReader does not report correct backlog statistics
> ---------------------------------------------------------
>
> Key: BEAM-9439
> URL: https://issues.apache.org/jira/browse/BEAM-9439
> Project: Beam
> Issue Type: Bug
> Components: io-java-kinesis
> Reporter: Sam Whittle
> Priority: Major
>
> The KinesisReader implementing KinesisIO reports backlog by implementing the
> UnboundedSource.getTotalBacklogBytes()
> method as opposed to the
> UnboundedSource.getSplitBacklogBytes()
> This value is supposed to represent the total backlog across all shards.
> This function is implemented by calling
> SimplifiedKinesisClient.getBacklogBytes with the watermark of the kinesis
> shards managed within the UnboundedReader instance. As this watermark may be
> further ahead than the watermark across all shards, this may miss backlog
> bytes.
> An additional concern is that the watermark is calculated using a
> WatermarkPolicy, which means that the watermark may be inconsistent to the
> kinesis timestamp for querying backlog.
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