Richard Yu created KAFKA-8438:
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Summary: Add API to allow user to define end behavior of consumer
failure
Key: KAFKA-8438
URL: https://issues.apache.org/jira/browse/KAFKA-8438
Project: Kafka
Issue Type: New Feature
Components: consumer
Reporter: Richard Yu
Recently, in a concerted effort to make Kafka's rebalances less painful,
various approaches has been used to reduce the number of and impact of
rebalances. Often, the trigger of a rebalance is a failure of some sort, in
which case, the workload will be redistributed among surviving threads. Working
to reduce rebalances due to random consumer crashes, a recent change to Kafka
internals had been made (which introduces the concept of static membership)
that prevents a rebalance from occurring within {{session.timeout.ms}} in the
hope that the consumer thread which crashed would recover in that time interval.
However, in some cases, some consumer threads would permanently go down or
remain dead for long periods of time. In these scenarios, users of Kafka would
possibly not be aware of such a crash until hours later after it happened which
forces Kafka users to manually start a new KafkaConsumer process a considerable
period of time after the failure had occurred. That is where the addition of a
callback such as {{onConsumerFailure}} would help. There are multiple use cases
for this callback (which is defined by the user). {{onConsumerFailure}} is
called when a particular consumer thread goes under for some specified time
interval (i.e. a config called {{acceeptable.consumer.failure.timeout.ms}}).
When called, this method could be used to log a consumer failure or should the
user wish it, create a new thread which would then rejoin the consumer group
(which could also include the required {{group.instance.id}} so that a
rebalance wouldn't be re-triggered).
Should the old thread recover and attempt to rejoin the consumer group (with
the substitute thread being part of the group), the old thread will be denied
access and an exception would be thrown (to indicate that another process has
already taken its place).
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