Ingester lock tweaks to minimize headblock locking during search #3328
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mdisibio
requested review from
joe-elliott,
annanay25,
mapno,
yvrhdn,
zalegrala,
electron0zero,
ie-pham and
stoewer
as code owners
|
Putting back to draft because allocating the channel size based on the limit doesn't work for cases where the limit is large (1,000,000+) |
zalegrala
reviewed
Jan 26, 2024
| @@ -699,6 +699,7 @@ func (b *walBlock) FetchTagValues(ctx context.Context, req traceql.AutocompleteR | |||
| if err != nil { | |||
| return fmt.Errorf("error opening file %s: %w", page.path, err) | |||
| } | |||
| defer file.Close() | |||
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Is the defer inside the loop enough, or do we want to close it out each iteration through blockFlushes?
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That's correct, it's inside the loop and all of them get closed at the end, which is not optimal. This func and several others are all following the same pattern, and I was aiming to have minimum changes necessary. But happy to make larger changes and defer as expected if we want.
joe-elliott
reviewed
Jan 29, 2024
mdisibio
changed the title
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What this PR does:
We have seen occasional high read latencies on ingesters where tag lookups and searches take 20+ seconds instead of the typical few. Investigation showed that it is contention on the block mutexes, and specifically due to the design of
instance.SearchandSearchResults. Instead of searching and releasing the headblock asap, the lock was held until after also acquiring a lock on the rest of the blocks and beginning to read fromSearchResults. High latency occurs when read/write access to the mutexes stack up, such that it might have to wait for a current search to finish (releasing read lock), then a block flush (write lock), then acquiring read lock again.This moves away from
SearchResultsand the channel-based flow to a simpler setup like the other endpoints. Since this was the only usage ofSearchResultsthis seems better than trying to patch it (again).Which issue(s) this PR fixes:
Fixes #
Checklist
CHANGELOG.mdupdated - the order of entries should be[CHANGE],[FEATURE],[ENHANCEMENT],[BUGFIX]