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https://issues.apache.org/jira/browse/KAFKA-13647?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17488332#comment-17488332
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Guozhang Wang commented on KAFKA-13647:
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TLDR: I think the `NO_FILE_OPENS` statistics is right, what's wrong is that
`NO_FILE_CLOSES` is never recorded..
I did a quick check on rocksDB code and here's all the places `NO_FILE_OPENS`
is recorded:
1)
https://github.com/facebook/rocksdb/blob/2e09a54c4fb82e88bcaa3e7cfa8ccbbbbf3635d5/db/blob/blob_file_cache.cc#L69
2)
https://github.com/facebook/rocksdb/blob/fc9d4071f0c504e107d7e1e11ed173175003a99b/db/table_cache.cc#L117-L125
But there's zero places where `NO_FILE_CLOSES` is recorded.
I searched in the rocksDB commit history and found that the recording seems
lost during a commit, and filed a ticket in rocksDB:
https://github.com/facebook/rocksdb/issues/9514 that contains more context.
> RocksDb metrics 'number-open-files' is not correct
> --------------------------------------------------
>
> Key: KAFKA-13647
> URL: https://issues.apache.org/jira/browse/KAFKA-13647
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Affects Versions: 3.0.0
> Reporter: Sylvain Le Gouellec
> Priority: Major
> Attachments: image-2022-02-07-16-06-25-304.png,
> image-2022-02-07-16-06-39-821.png, image-2022-02-07-16-06-53-164.png
>
>
> We were looking at RocksDB metrics and noticed that the {{number-open-files}}
> metric behaves like a counter, rather than a gauge.
> Looking at the code, we think there is a small error in the type of metric
> for that specific mbean (should be a value metric rather than a sum metric).
> See [
> https://github.com/apache/kafka/blob/ca5d6f9229c170beb23809159113037f05a1120f/streams/src/main/java/org/apache/kafka/streams/state/internals/metrics/RocksDBMetrics.java#L482|https://github.com/apache/kafka/blob/99b9b3e84f4e98c3f07714e1de6a139a004cbc5b/streams/src/main/java/org/apache/kafka/streams/state/internals/metrics/RocksDBMetrics.java#L482]
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