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https://issues.apache.org/jira/browse/FLINK-5479?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16391304#comment-16391304
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ASF GitHub Bot commented on FLINK-5479:
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Github user StephanEwen commented on the issue:
https://github.com/apache/flink/pull/5634
Just saw a good comment from @EronWright
> I think the ideal would be that idleness would occur only for tail reads,
i.e. due to a timeout from `kafkaConsumer.poll(pollTimeout)`. In other words,
an intermittent connection issue would ideally not trigger idleness.
Let's see if we can get that into the design somehow, without having too
specific logic inside the Kafka Consumer (making the Kafka Consumer more
complex is my personal Pet Peeve)
> Per-partition watermarks in FlinkKafkaConsumer should consider idle partitions
> ------------------------------------------------------------------------------
>
> Key: FLINK-5479
> URL: https://issues.apache.org/jira/browse/FLINK-5479
> Project: Flink
> Issue Type: Improvement
> Components: Kafka Connector
> Reporter: Tzu-Li (Gordon) Tai
> Priority: Blocker
> Fix For: 1.6.0
>
>
> Reported in ML:
> http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Kafka-topic-partition-skewness-causes-watermark-not-being-emitted-td11008.html
> Similar to what's happening to idle sources blocking watermark progression in
> downstream operators (see FLINK-5017), the per-partition watermark mechanism
> in {{FlinkKafkaConsumer}} is also being blocked of progressing watermarks
> when a partition is idle. The watermark of idle partitions is always
> {{Long.MIN_VALUE}}, therefore the overall min watermark across all partitions
> of a consumer subtask will never proceed.
> It's normally not a common case to have Kafka partitions not producing any
> data, but it'll probably be good to handle this as well. I think we should
> have a localized solution similar to FLINK-5017 for the per-partition
> watermarks in {{AbstractFetcher}}.
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