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https://issues.apache.org/jira/browse/KAFKA-12487?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17319412#comment-17319412
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Chris Egerton commented on KAFKA-12487:
---------------------------------------
Based on recent
[KIP-726|https://lists.apache.org/thread.html/%3CCAFLS_9gOHobj-had=7SVBibJTxfzKCuf7WM+shTL_aTvSeyq=g...@mail.gmail.com%3E]
discussion, we'll also want to implement the
[Consumer::onPartitionsLost|https://kafka.apache.org/27/javadoc/org/apache/kafka/clients/consumer/ConsumerRebalanceListener.html#onPartitionsLost-java.util.Collection-]
method in order to avoid task failures due to offset commit failures if/when
the consumer rebalance protocol is automatically downgraded from
{{COOPERATIVE}} to {{EAGER}}.
> Sink connectors do not work with the cooperative consumer rebalance protocol
> ----------------------------------------------------------------------------
>
> Key: KAFKA-12487
> URL: https://issues.apache.org/jira/browse/KAFKA-12487
> Project: Kafka
> Issue Type: Bug
> Components: KafkaConnect
> Affects Versions: 3.0.0, 2.4.2, 2.5.2, 2.8.0, 2.7.1, 2.6.2
> Reporter: Chris Egerton
> Assignee: Chris Egerton
> Priority: Major
>
> The {{ConsumerRebalanceListener}} used by the framework to respond to
> rebalance events in consumer groups for sink tasks is hard-coded with the
> assumption that the consumer performs rebalances eagerly. In other words, it
> assumes that whenever {{onPartitionsRevoked}} is called, all partitions have
> been revoked from that consumer, and whenever {{onPartitionsAssigned}} is
> called, the partitions passed in to that method comprise the complete set of
> topic partitions assigned to that consumer.
> See the [WorkerSinkTask.HandleRebalance
> class|https://github.com/apache/kafka/blob/b96fc7892f1e885239d3290cf509e1d1bb41e7db/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/WorkerSinkTask.java#L669-L730]
> for the specifics.
>
> One issue this can cause is silently ignoring to-be-committed offsets
> provided by sink tasks, since the framework ignores offsets provided by tasks
> in their {{preCommit}} method if it does not believe that the consumer for
> that task is currently assigned the topic partition for that offset. See
> these lines in the [WorkerSinkTask::commitOffsets
> method|https://github.com/apache/kafka/blob/b96fc7892f1e885239d3290cf509e1d1bb41e7db/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/WorkerSinkTask.java#L429-L430]
> for reference.
>
> This may not be the only issue caused by configuring a sink connector's
> consumer to use cooperative rebalancing. Rigorous unit and integration
> testing should be added before claiming that the Connect framework supports
> the use of cooperative consumers with sink connectors.
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