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Posted to notifications@couchdb.apache.org by "SENSEi-James (via GitHub)" <gi...@apache.org> on 2023/03/03 15:25:57 UTC
[GitHub] [couchdb] SENSEi-James opened a new issue, #4451: Request time in stats wrong or misunderstood
SENSEi-James opened a new issue, #4451:
URL: https://github.com/apache/couchdb/issues/4451
Our sys admin is reporting some very high max request times using the stats endpoint: `http://$1:$2@127.0.0.1:5984/_node/_local/_stats/couchdb/request_time`
I examined the stats using my local instance of couchDB. If I let couchDB sit idle, the times coming back from that endpoint are all 0.0, presumably because no requests are being made.
If I then use curl to make a **single** request for a single document, the transaction completes in around 2 milliseconds.
If I then immediately query the stats again, the max request time shows as > 10,000
If just one request was made, and it completed in 2 milliseconds, how can the max request time be > 10,000 milliseconds?
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[GitHub] [couchdb] nickva commented on issue #4451: Max request time in stats wrong or misunderstood
Posted by "nickva (via GitHub)" <gi...@apache.org>.
nickva commented on issue #4451:
URL: https://github.com/apache/couchdb/issues/4451#issuecomment-1726016505
The new histogram backend should not have this problem: https://github.com/apache/couchdb/pull/4672
It should record every single value.
It's not part of a the release and will likely be part of 3.4
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[GitHub] [couchdb] nickva commented on issue #4451: Max request time in stats wrong or misunderstood
Posted by "nickva (via GitHub)" <gi...@apache.org>.
nickva commented on issue #4451:
URL: https://github.com/apache/couchdb/issues/4451#issuecomment-1454236489
I have observed the oddness. I think it's because of how slide_uniform histograms are used for statistics
The update code seems to be in [couchdb-folsom](https://github.com/apache/couchdb-folsom/blob/67742acd21b561343ff9e3075f017201852a6424/src/folsom_sample_slide_uniform.erl#L42-L56)
The initialization code is: https://github.com/apache/couchdb/blob/c0b8839bf28bd2c914d71a4dfafd3ea508c3040a/src/couch_stats/src/couch_stats.erl#L61-L62 where `DEFAULT_INTERVAL` is `10` (seconds)
The histogram might work better with a constant stream of request and fails on rare, intermittent ones.
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[GitHub] [couchdb] nickva closed issue #4451: Max request time in stats wrong or misunderstood
Posted by "nickva (via GitHub)" <gi...@apache.org>.
nickva closed issue #4451: Max request time in stats wrong or misunderstood
URL: https://github.com/apache/couchdb/issues/4451
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