[jira] [Resolved] (KAFKA-3806) Adjust default values of log.retention.hours and offsets.retention.minutes

["Jason Gustafson (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-3806?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jason Gustafson resolved KAFKA-3806.
------------------------------------
    Resolution: Fixed
      Assignee: Ewen Cheslack-Postava

> 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
>            Assignee: Ewen Cheslack-Postava
>            Priority: Minor
>             Fix For: 1.2.0
>
>
> 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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