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https://issues.apache.org/jira/browse/FLINK-10473?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16701939#comment-16701939
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ASF GitHub Bot commented on FLINK-10473:
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azagrebin opened a new pull request #7188: [FLINK-10473][State TTL] TTL state
incremental cleanup for heap backend
URL: https://github.com/apache/flink/pull/7188
## What is the purpose of the change
Introduce TTL state incremental cleanup for heap backend.
See docs in PR for high-level idea description.
## Brief change log
- Add namespace/key iterator method to internal KV state interface.
- Implement it for CopyOnWriteStateTable and NestedMapsStateTable in heap
backend
- Add TtlIncrementalCleanup class which is called back for each state
access and optionally for each keyed context change (record processing) and
performs the cleanup using state namespace/key iterator
- Add config for incremental cleanup in StateTtlConfig
- Construct TtlIncrementalCleanup in TtlStateFactory
- Add unit test TtlStateTestBase.testIncrementalCleanup
- smaller improvements in unit/e2e TTL tests
## Verifying this change
Unit test TtlStateTestBase.testIncrementalCleanup.
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): (yes / no)
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: (yes / no)
- The serializers: (yes / no / don't know)
- The runtime per-record code paths (performance sensitive): (yes / no /
don't know)
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Yarn/Mesos, ZooKeeper: (yes / no / don't know)
- The S3 file system connector: (yes / no / don't know)
## Documentation
- Does this pull request introduce a new feature? (yes / no)
- If yes, how is the feature documented? (not applicable / docs / JavaDocs
/ not documented)
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> State TTL incremental cleanup using Heap backend key iterator
> -------------------------------------------------------------
>
> Key: FLINK-10473
> URL: https://issues.apache.org/jira/browse/FLINK-10473
> Project: Flink
> Issue Type: New Feature
> Components: State Backends, Checkpointing
> Affects Versions: 1.7.0
> Reporter: Andrey Zagrebin
> Assignee: Andrey Zagrebin
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.8.0
>
>
> This feature enables lazy background cleanup of state with time-to-live in
> state keyed backend which stores state in JVM heap. The idea is to keep a
> global state lazy iterator with loose consistency. Every time a state value
> for some key is accessed or a record is processed, the iterator is advanced,
> TTL of iterated state entries is checked and the expired entries are cleaned
> up. When the iterator reaches the end of state storage it just starts over.
> This way the state with TTL is regularly cleaned up to prevent ever growing
> memory consumption. The caveat of this cleanup strategy is that if state is
> not accessed or no records are processed then accumulated expired state still
> occupies the storage.
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