Tom Schamberger created FLINK-11186:
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             Summary: Support for event-time balancing for multiple Kafka 
comsumer partitions
                 Key: FLINK-11186
                 URL: https://issues.apache.org/jira/browse/FLINK-11186
             Project: Flink
          Issue Type: New Feature
          Components: DataStream API, Kafka Connector
            Reporter: Tom Schamberger


Currently, it is not possible with Flink to back-pressure individual Kafka 
partitions, which are faster in terms of event-time. This leads to unnecessary 
memory consumption and can lead to deadlocks in the case of back-pressure.

When multiple Kafka topics are consumed, succeeding event-time window operators 
have to wait until the last Kafka partition has produced a sufficient watermark 
to be triggered. If individual Kafka partitions differ in read performance or 
the event-time of messages within partitions is not monotonically distributed, 
this can lead to a situation, where 'fast' partitions (event-time makes fast 
progress) outperform slower partitions until back-pressuring prevents all 
partitions from being further consumed. This leads to a deadlock of the 
application.

I suggest, that windows should be able to back-pressure individual partitions, 
which progress faster in terms of event-time, so that slow partitions can keep 
up.



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