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https://issues.apache.org/jira/browse/KAFKA-2400?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14660921#comment-14660921
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Guozhang Wang commented on KAFKA-2400:
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Hey [~onurkaraman], yeah that is indeed an issue. However after thinking it
twice I feel for different types of consumer clients these may end up with the
same effect:
1. Malicious client: a consumer could always claim "my heartbeat frequency is
X" upon join-group but actually sends a heartbeat every 1ms, for this case I
think the only shield would be throttling; i.e. protocols between the
coordinator / consumer does not really help here.
2. Mis-configured client: a consumer could mistakenly config its heartbeat
frequency too small; the min heartbeat could help in this cases while
throttling might just result in the same effect.
3. Not-care client: they will not override the defaults at all, so all we need
to do is to make sure the default values are reasonable.
A side note is that we'd better be careful throttling heatbeats since this
would possibly increase the false positives of consumer failure if we throttle
heartbeat the wrong way.
> 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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