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https://issues.apache.org/jira/browse/KAFKA-15541?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17772133#comment-17772133
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Nicholas Telford commented on KAFKA-15541:
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I didn't see that ticket, my bad. Feel free to close either ticket as you see
fit. Since yours was created first, it might make more sense to link the KIP to
it and close this one instead.
> RocksDB Iterator Metrics
> ------------------------
>
> Key: KAFKA-15541
> URL: https://issues.apache.org/jira/browse/KAFKA-15541
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: Nicholas Telford
> Assignee: Nicholas Telford
> Priority: Major
> Labels: kip, kip-required
>
> [KIP-989: RocksDB Iterator
> Metrics|https://cwiki.apache.org/confluence/display/KAFKA/KIP-989%3A+RocksDB+Iterator+Metrics]
> RocksDB {{Iterators}} must be closed after use, to prevent memory leaks due
> to [blocks being "pinned"
> in-memory|https://github.com/facebook/rocksdb/wiki/Memory-usage-in-RocksDB#blocks-pinned-by-iterators].
> Pinned blocks can currently be tracked via the per-store
> {{block-cache-pinned-usage}} metric. However, it's common [(and even
> recommended)|https://docs.confluent.io/platform/current/streams/developer-guide/memory-mgmt.html#rocksdb]
> to share the Block Cache among all stores in an application, to enable users
> to globally bound native memory used by RocksDB. This results in the
> {{block-cache-pinned-usage}} reporting the same memory usage for every store
> in the application, irrespective of which store is actually pinning blocks in
> the block cache.
> To aid users in finding leaked Iterators, as well as identifying the cause of
> a high number of pinned blocks, we introduce two new metrics.
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