[jira] [Created] (KAFKA-9978) Improve poll(Duration) and KafkaConsumer Javadoc

["Benoit Delbosc (Jira)" <ji...@apache.org>]

Benoit Delbosc created KAFKA-9978:
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             Summary: Improve poll(Duration) and KafkaConsumer Javadoc
                 Key: KAFKA-9978
                 URL: https://issues.apache.org/jira/browse/KAFKA-9978
             Project: Kafka
          Issue Type: Improvement
          Components: consumer
    Affects Versions: 2.0.0
            Reporter: Benoit Delbosc


Kafka 2.0.0 introduces {{poll(Duration)}} and deprecates {{poll(long)}}.

The new method behaves differently it can timeout and returns while the consumer is in the middle of a rebalance.

In this case, invoking {{commitSync}} will fail, from Kafka 2.0 to 2.4 with a {{CommitFailedException }}containing a wrong message related poll interval. In Kafka 2.5.0 it raises a {{RebalanceInProgressException.}}

This behavior creates weird regressions when upgrading from Kafka 1.x and is hard to understand because it is not reflected in the Javadoc.

For instance, the code snippet given in the KafkaConsumer Javadoc "Manual Offset Control" explains that duplicates processing happens only in case of failure. Since Kafka 2.0 this code will produce duplicates randomly depending on rebalancing duration.

I think that Javadoc should be updated and provide code snippets based on  {{ConsumerRebalanceListener.}}

 



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