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querier: set minimum concurrency to 4 for query-scheduler's new querier-worker queue prioritization #9054

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francoposa
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@francoposa francoposa commented Aug 19, 2024

Docstring for constant should be a sufficient description, but will expand a bit here:

When we move to a new RequestQueue dequeuing algorithm, we will modulo querier-worker IDs to distribute them across 4 request queue dimensions, one each for the "expected query component" which is assigned to the query request: ingester, store-gateway, both, or unknown.
Having querier-worker connections < num queue dimensions will result in queue starvation unless not all 4 queue dimensions are active. In any minimally utilized cluster, we expect all 4 dimensions will exist at almost all times.

Because the queriers have no centralized knowledge or coordination of how many queriers exist in the cluster, we must set a minimum of 4 for each querier<->request queue instance connection, where a "request queue instance" is a query-frontend or a query-scheduler.

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Checklist

  • Tests updated.
  • Documentation added.
  • CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX].
  • about-versioning.md updated with experimental features.

@francoposa francoposa requested a review from a team as a code owner August 19, 2024 21:02
@francoposa francoposa marked this pull request as draft August 19, 2024 21:24
@francoposa francoposa marked this pull request as ready for review August 20, 2024 04:25
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Looks good! Thanks!

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oh no that damn suggestion thing created a merge commit

@francoposa francoposa force-pushed the francoposa/querier-set-minimum-concurrency-for-query-scheduler-queue-prioritization branch from 7667a58 to b1773af Compare August 20, 2024 18:39
@francoposa francoposa force-pushed the francoposa/querier-set-minimum-concurrency-for-query-scheduler-queue-prioritization branch from b1773af to 4aac9c1 Compare August 20, 2024 19:51
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chencs commented Aug 20, 2024

oh no that damn suggestion thing created a merge commit

Yeah, I never actually use the suggestion thing (or do any code changes like resolve merge conflicts in-browser) for this reason, I just copy the suggested changes into my branch. I'm not sure if there's a better way, but I haven't found it.

@francoposa francoposa requested a review from chencs August 20, 2024 21:19
@francoposa francoposa merged commit 3a46a70 into main Aug 21, 2024
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@francoposa francoposa deleted the francoposa/querier-set-minimum-concurrency-for-query-scheduler-queue-prioritization branch August 21, 2024 20:21
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3 participants