Issue 4632: fix exemplars calculation#5115
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ruslan-mikhailov merged 5 commits intografana:mainfrom May 19, 2025
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Pull Request Overview
This PR fixes issue 4632 by correcting the exemplars calculation and ensuring at least one exemplar is requested per shard.
- Adjusted pagesPerRequest logic to search the entire block when its size is below the request threshold.
- Corrected the exemplarsPerShard computation and division order in backend request building to use pages as the numerator and totalRecords as the denominator.
Reviewed Changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| modules/frontend/search_sharder.go | Added early return for small blocks in page calculation. |
| modules/frontend/metrics_query_range_sharder.go | Updated exemplarsPerShard and backendRequests exemplar calculation. |
| modules/frontend/metrics_query_range_sharder_test.go | Added tests for various block and exemplar configurations. |
Comments suppressed due to low confidence (2)
modules/frontend/metrics_query_range_sharder.go:172
- The exemplarsPerShard calculation now correctly returns at least one exemplar per shard by applying the max function, but please verify that integer division does not inadvertently truncate values beyond the intended behavior.
return max(uint32(math.Ceil(float64(exemplars)*1.2))/total, 1) // require at least 1 exemplar per shard
modules/frontend/metrics_query_range_sharder.go:247
- The adjustment in the backendRequests function now correctly uses pages as the numerator and totalRecords as the denominator; please ensure that this division reflects the intended exemplar scaling for each block.
exemplars = max(uint32(float64(exemplars)*float64(pages)/float64(m.TotalRecords)), 1)
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| "github.com/grafana/tempo/tempodb/backend" | ||
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| func FuzzExemplarsPerShard(f *testing.F) { |
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This looks correct to me. Nice work on the tests.
| }, | ||
| } | ||
| tenantID := "test-tenant" | ||
| targetBytesPerRequest := 1000 |
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Leaving this static I suppose is desired because the test cases have blocksizes and records above and below this number to test each side of the calculation.
In case exemplars * 1.2 is less than total it could lead to dropping all exemplars
Search the entire block if it's small
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+ rebase from latest master to resolve merge conflicts |
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What this PR does:
small block)Which issue(s) this PR fixes:
Fixes #4632
Checklist
CHANGELOG.mdupdated - the order of entries should be[CHANGE],[FEATURE],[ENHANCEMENT],[BUGFIX]