efeg opened a new pull request #8579:
URL: https://github.com/apache/kafka/pull/8579
When does UnknownTopicOrPartitionException typically occur?
* Upon a topic creation, a follower broker of a new partition starts
replica fetcher before the prospective leader broker of the new partition
receives the leadership information from the controller (see
[KAFKA-6221](https://issues.apache.org/jira/browse/KAFKA-6221)).
* Upon a topic deletion, a follower broker of a to-be-deleted partition
starts replica fetcher after the leader broker of the to-be-deleted partition
processes the deletion information from the controller.
* As expected, clusters with frequent topic creation and deletion report
UnknownTopicOrPartitionException with relatively higher frequency.
What is the impact?
* Exception tracking systems identify the error logs with
UnknownTopicOrPartitionException as an exception. This results in a lot of
noise for a transient issue that is expected to recover by itself and a natural
process in Kafka due to its asynchronous state propagation.
Why not move it to a lower than warn-level log?
* Despite typically being a transient issue,
UnknownTopicOrPartitionException may also indicate real issues if it doesn't
fix itself after a short period of time. To ensure detection of such scenarios,
we set the log level to warn.
*More detailed description of your change,
if necessary. The PR title and PR message become
the squashed commit message, so use a separate
comment to ping reviewers.*
*Summary of testing strategy (including rationale)
for the feature or bug fix. Unit and/or integration
tests are expected for any behaviour change and
system tests should be considered for larger changes.*
### Committer Checklist (excluded from commit message)
- [ ] Verify design and implementation
- [ ] Verify test coverage and CI build status
- [ ] Verify documentation (including upgrade notes)
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