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Fix divide by 0 bug in exemplar sharding calculations #3936

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Merged
mdisibio merged 2 commits into from
Aug 5, 2024
Merged

Fix divide by 0 bug in exemplar sharding calculations #3936

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0253051
Fix divide by 0 bug in exemplar sharding calculations
mdisibio Aug 5, 2024
b753b1c
changelog
mdisibio Aug 5, 2024
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,7 @@
* [BUGFIX] Fix frontend parsing error on cached responses [#3759](https://github.com/grafana/tempo/pull/3759) (@mdisibio)
* [BUGFIX] Fix autocomplete of a query using scoped instrinsics [#3865](https://github.com/grafana/tempo/pull/3865) (@mdisibio)
* [BUGFIX] Fix metrics query histograms and quantiles on traceDuration [#3879](https://github.com/grafana/tempo/pull/3879) (@mdisibio)
* [BUGFIX] Fix divide by 0 bug in query frontend exemplar calculations [#3936](https://github.com/grafana/tempo/pull/3936) (@mdisibio)
* [BUGFIX] max_global_traces_per_user: take into account ingestion.tenant_shard_size when converting to local limit [#3618](https://github.com/grafana/tempo/pull/3618) (@kvrhdn)
* [BUGFIX] Fix http connection reuse on GCP and AWS by reading io.EOF through the http body. [#3760](https://github.com/grafana/tempo/pull/3760) (@bmteller)
* [BUGFIX] Improved handling of complete blocks in localblocks processor after enabling flusing [#3805](https://github.com/grafana/tempo/pull/3805) (@mapno)
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11 changes: 9 additions & 2 deletions modules/frontend/metrics_query_range_sharder.go
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Expand Up @@ -368,7 +368,7 @@ func (s *queryRangeSharder) buildBackendRequests(ctx context.Context, tenantID s

queryHash := hashForQueryRangeRequest(&searchReq)

exemplars := s.exemplarsPerShard(uint32(len(metas)))
exemplarsPerBlock := s.exemplarsPerShard(uint32(len(metas)))
for _, m := range metas {
if m.EndTime.Before(m.StartTime) {
// Ignore blocks with bad timings from debugging
Expand All @@ -380,6 +380,13 @@ func (s *queryRangeSharder) buildBackendRequests(ctx context.Context, tenantID s
continue
}

exemplars := exemplarsPerBlock
if exemplars > 0 {
// Scale the number of exemplars per block to match the size
// of each sub request on this block. For very small blocks or other edge cases, return at least 1.
exemplars = max(uint32(float64(exemplars)*float64(m.TotalRecords)/float64(pages)), 1)
}

for startPage := 0; startPage < int(m.TotalRecords); startPage += pages {
subR := parent.Clone(ctx)

Expand Down Expand Up @@ -415,7 +422,7 @@ func (s *queryRangeSharder) buildBackendRequests(ctx context.Context, tenantID s
Size_: m.Size,
FooterSize: m.FooterSize,
DedicatedColumns: dc,
Exemplars: max(exemplars/(m.TotalRecords/uint32(pages)), 1),
Exemplars: exemplars,
}

subR = api.BuildQueryRangeRequest(subR, queryRangeReq)
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