[jira] [Commented] (FLINK-5479) Per-partition watermarks in FlinkKafkaConsumer should consider idle partitions

["Tzu-Li (Gordon) Tai (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-5479?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16334671#comment-16334671 ] 

Tzu-Li (Gordon) Tai commented on FLINK-5479:
--------------------------------------------

[~eronwright]regarding your suggestion for using {{max.message.time.difference.ms}} as basis - we'll need to think about how this interplays with the configuration we're planning to expose with FLINK-5018.

> 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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