[jira] [Created] (KAFKA-12487) Sink connectors do not work with the cooperative consumer rebalance protocol

["Chris Egerton (Jira)" <ji...@apache.org>]

Chris Egerton created KAFKA-12487:
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             Summary: 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


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 In other words, it assumes that whenever {{onPartitionsRevoked}} is called, all partitions have been revoked from that consumer, and whenever {{onPartitionsAssigned}} is called, the partitions passed in to that method comprise the complete set of topic partitions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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