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https://issues.apache.org/jira/browse/FLINK-5479?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16390245#comment-16390245
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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
@tweise @tzulitai
I would suggest to solve this the following way, which should be both
simple and cover our cases:
- We extend the current periodic watermark generators for idleness. We
can do that for example by maintaining a record counter and remembering the
last counter and a System.nanoTime() timestamp each time the call whether to
generate a watermark is called. If no record came for too long, return a
special watermark object that indicated "idle". Or change the return type to
return either 'none', 'idle', or 'watermark'
- The Kinesis Concumer needs per-shard watermarks, same way as the Kafka
Consumer does. That part needs to be added to the Kinesis consumer anyways.
That way, we automatically get per-shard idleness in Kinesis and
per-partition idleness in Kafka without doing anything specific for the source
connectors.
We can then also remove the idleness logic from the source context - it
would be duplicate there.
> 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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