THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
Status
Current state: Accepted
Discussion thread: here
JIRA: here
Pull Request: here
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
Motivation
Kafka Streams treats repartition topics differently to regular topics. Instead of setting arbitrary retention criteria and having the broker cleanup old records, Kafka Streams sets infinite retention on repartition topics and explicitly deletes records once they've been committed to the next topic in their Topology. Currently, this is done every time the Task is committed, resulting in explicit "delete records" requests being sent every commit.interval.ms milliseconds.
When commit.interval.ms is set very low, for example when processing.guarantee is set to exactly_once_v2, this causes delete records requests to be sent extremely frequently, potentially reducing throughput and causing a high volume of log messages to be logged by the brokers.
Public Interfaces
New configuration options
| Name | Type | Importance | Default | Description |
|---|---|---|---|---|
repartition.purge.interval.ms | Long | LOW | 30000 | The minimum interval in milliseconds with which to delete fully consumed records from repartition topics. Purging will occur after at least this value since the last purge, but may be delayed until later. (Note, unlike commit.interval.ms, the default for this value remains unchanged when processing.guarantee is set to exactly_once_v2). |
Proposed Changes
Adding a new configuration option, repartition.purge.interval.ms, that configures the period of these explicit record deletions, will resolve the issue by enabling users to tune the commit.interval.ms and repartition.purge.interval.ms separately.
Compatibility, Deprecation, and Migration Plan
- The interval between explicit delete requests for repartition records will no longer be coupled to
commit.interval.ms. Default behaviour is unchanged, however:- When
commit.interval.msis explicitly modified by the user, old repartition records will no longer be deleted on every commit. - When
processing.guaranteeis set toexactly_once_v2, since the defaultcommit.interval.msis changed internally to100 ms, old repartition records will no longer be deleted on every commit. - Users can regain this coupling by explicitly configuring both
commit.interval.msandrepartition.purge.interval.msto the same value.
- When
Rejected Alternatives
- Purging after exactly the configured amount of time has elapsed was rejected, as it would necessitate a design that would likely have a negative performance or correctness impact.
- Purging after a specified multiple of commits was rejected, as it would be tightly coupled to the value of another config parameter (
commit.interval.ms), which would cause a likely unintended change to purge behavior whenever the commit interval was reconfigured, including implicitly when the processing.guarantee is changed.