Jason Gustafson created KAFKA-2400:
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Summary: Expose heartbeat frequency in new consumer configuration
Key: KAFKA-2400
URL: https://issues.apache.org/jira/browse/KAFKA-2400
Project: Kafka
Issue Type: Improvement
Reporter: Jason Gustafson
Assignee: Jason Gustafson
Priority: Minor
The consumer coordinator communicates the need to rebalance through responses
to heartbeat requests sent from each member of the consumer group. The
heartbeat frequency therefore controls how long normal rebalances will take.
Currently, the frequency is hard-coded to 3 heartbeats per the configured
session timeout, but it would be nice to expose this setting so that the user
can control the impact from rebalancing.
Since the consumer is currently single-threaded and heartbeats are sent in
poll(), we cannot guarantee that the heartbeats will actually be sent at the
configured frequency. In practice, the user may have to adjust their fetch size
to ensure that poll() is called often enough to get the desired heartbeat
frequency. For most users, the consumption rate is probably fast enough for
this not to matter, but we should make the documentation clear on this point.
In any case, we expect that most users will accept the default value.
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