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https://issues.apache.org/jira/browse/FLINK-5479?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16288928#comment-16288928
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Tzu-Li (Gordon) Tai commented on FLINK-5479:
--------------------------------------------
Raised this to blocker for 1.5.0, as we are seeing more users with this issue
on the mailing lists.
> 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: 1.5.0
>
>
> 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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