perf(sdk): store InstrumentationScope in Arc to avoid clone per processor#3378
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bryantbiggs wants to merge 4 commits intoopen-telemetry:mainfrom
Open
perf(sdk): store InstrumentationScope in Arc to avoid clone per processor#3378bryantbiggs wants to merge 4 commits intoopen-telemetry:mainfrom
bryantbiggs wants to merge 4 commits intoopen-telemetry:mainfrom
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…ssor SdkTracer now wraps InstrumentationScope in Arc internally, which makes tracer cloning significantly cheaper (pointer bump instead of deep clone with attribute Vec allocation). The multi-processor span export path is also optimized: instead of calling build_export_data() per processor (which clones the scope from the tracer each time), SpanData is now built once and cloned for each additional processor. The last processor receives the original without a clone. This is a non-breaking change — SpanData's public instrumentation_scope field remains InstrumentationScope (not Arc). Supersedes open-telemetry#3267, thanks to @taisho6339 for the original approach.
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #3378 +/- ##
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Coverage 82.2% 82.3%
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Files 128 128
Lines 24626 24648 +22
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+ Hits 20267 20296 +29
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Verifies that when multiple span processors are configured, all processors receive the span data with correct name and attributes.
Use split_last() instead of index tracking for the multi-processor on_end loop. Removes unnecessary break statement and makes the clone-for-rest, move-for-last intent explicit. Fix changelog entry to describe what actually changed without overstating the scope clone savings.
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Summary
Two changes to reduce allocation in the tracing pipeline:
SdkTracernow stores itsInstrumentationScopeinArc. Since tracers are cloned on every span creation (build_recording_spancallsself.clone()), this turns the scope copy from a deep clone (allocates a newVec<KeyValue>for attributes) into an Arc refcount increment.The multi-processor
on_endpath now callsbuild_export_data()once and clones the result for additional processors, instead of rebuilding export data from scratch per processor. The last processor receives the original via move. Note: the per-processor clone cost is similar either way — this avoids the redundant rebuild, not the clone itself.This is a non-breaking change.
SpanData.instrumentation_scoperemainsInstrumentationScope, notArc. Theinstrumentation_scope()accessor still returns&InstrumentationScopeviaDeref.Supersedes #3267 — thanks to @taisho6339 for the original approach and discussion.
Relates to #3368.
Changes
SdkTracer.scope:InstrumentationScope→Arc<InstrumentationScope>(internal field, not public API)on_end: build once, clone for rest, move for last