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https://issues.apache.org/jira/browse/KAFKA-3806?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16253555#comment-16253555
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John Crowley commented on KAFKA-3806:
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Am working on a PubSub project where the source is reference data - some of
which changes very slowly. (And, yes, this is not exactly the standard Kafka
use-case. Kafka is being used as a reliable persistent store supporting
multiple subscribers.) As a very simplistic example, assume one of the sources
is the holiday calendar for the following year for a company - this is probably
published in November, and unless an error is discovered will not be updated
until the following November. The PubSub logic must still monitor the topic so
that any change is published rapidly, but usually none occur - and even though
Kafka can handle the load, performing an artificial commit every N seconds
would seem to be a pure waste of resources. (And if the example is extended to
possibly 100s of topics, with multiple groupIds consuming each topic then the
overall load might be significant.)
On the topic side, the retention.ms can be set to a very large value per topic
so that the "log" is never deleted. Would it be possible to allow the
offsets.retention.minutes value to be set on a per groupId basis so that it
could be adjusted based on the use-case expectations of a particular consumer
group?
> Adjust default values of log.retention.hours and offsets.retention.minutes
> --------------------------------------------------------------------------
>
> Key: KAFKA-3806
> URL: https://issues.apache.org/jira/browse/KAFKA-3806
> Project: Kafka
> Issue Type: Improvement
> Components: config
> Affects Versions: 0.9.0.1, 0.10.0.0
> Reporter: Michal Turek
> Priority: Minor
> Fix For: 1.1.0
>
>
> Combination of default values of log.retention.hours (168 hours = 7 days) and
> offsets.retention.minutes (1440 minutes = 1 day) may be dangerous in special
> cases. Offset retention should be always greater than log retention.
> We have observed the following scenario and issue:
> - Producing of data to a topic was disabled two days ago by producer update,
> topic wasn't deleted.
> - Consumer consumed all data and properly committed offsets to Kafka.
> - Consumer made no more offset commits for that topic because there was no
> more incoming data and there was nothing to confirm. (We have auto-commit
> disabled, I'm not sure how behaves enabled auto-commit.)
> - After one day: Kafka cleared too old offsets according to
> offsets.retention.minutes.
> - After two days: Long-term running consumer was restarted after update, it
> didn't find any committed offsets for that topic since they were deleted by
> offsets.retention.minutes so it started consuming from the beginning.
> - The messages were still in Kafka due to larger log.retention.hours, about 5
> days of messages were read again.
> Known workaround to solve this issue:
> - Explicitly configure log.retention.hours and offsets.retention.minutes,
> don't use defaults.
> Proposals:
> - Prolong default value of offsets.retention.minutes to be at least twice
> larger than log.retention.hours.
> - Check these values during Kafka startup and log a warning if
> offsets.retention.minutes is smaller than log.retention.hours.
> - Add a note to migration guide about differences between storing of offsets
> in ZooKeeper and Kafka (http://kafka.apache.org/documentation.html#upgrade).
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