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https://issues.apache.org/jira/browse/KAFKA-2400?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14660903#comment-14660903
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Jason Gustafson commented on KAFKA-2400:
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[~onurkaraman] The goal of the ticket was specifically to decouple the
heartbeat frequency from the session timeout to allow longish session timeouts
but still have quick expected rebalance times. I think this is a helpful
feature for users who want to limit the impact from rebalances. Since
heartbeats are pretty cheap, I don't feel too much concern hammering the
server, but perhaps it would help to have a minimum value? I also wouldn't be
opposed to having a hard-coded value that was fairly low.
> Expose heartbeat frequency in new consumer configuration
> --------------------------------------------------------
>
> Key: KAFKA-2400
> URL: https://issues.apache.org/jira/browse/KAFKA-2400
> Project: Kafka
> Issue Type: Sub-task
> Reporter: Jason Gustafson
> Assignee: Jason Gustafson
> Priority: Minor
> Fix For: 0.8.3
>
>
> 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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