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https://issues.apache.org/jira/browse/FLINK-5479?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16389051#comment-16389051
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ASF GitHub Bot commented on FLINK-5479:
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Github user tzulitai commented on the issue:

    https://github.com/apache/flink/pull/5634
  
    A few points to mention:
    
    1. @StephanEwen there is already common idleness detection implemented 
within `SourceContext`s, see `StreamSourceContexts`. The idleness detection, 
however, is currently always disabled and we do not allow users to configure it.
    
    2. I agree that we shouldn't add anything more to the connector, have also 
discussed this offline with @aljoscha. We should maybe do this only as part of 
the new connector rework that @tweise and I were talking about, in 1.6.


> 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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