fix: improve otel span map cleanup performance#1200
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Previously the span map was holding all span information in a tree structure. When a span finished, MarkFinished acquired a global write lock and recursively traversed the tree to clean up. The fix usees the already existin spanRecorder to keep track of the spans in the transaction. Instead of linking each child, we keep track of the root transaction and override the ParentSpanID so that the spanRecorder reconstructs the span hierarchy.
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giortzisg
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Feb 20, 2026
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| if entry.activeCount.Add(-1) <= 0 { | ||
| // CompareAndSwap(CAS) is used to prevent a race between Set and MarkFinished. | ||
| // The race has two windows: | ||
| // 1. MarkFinished decremented activeCount to 0 but hasn't CAS'd yet -> Set Adds(1), and CAS fails keeping the | ||
| // transaction, since we just added a new span. | ||
| // 2. MarkFinished already CAS'd -> Set will store on the transaction marked for deletion (better than | ||
| // creating a new orphaned span). | ||
| if entry.activeCount.CompareAndSwap(0, -1) { | ||
| ssm.transactions.CompareAndDelete(traceID, entry) | ||
| } |
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@sl0thentr0py @Litarnus would appreciate if you can verify my logic here. Added the fix due to this comment and I think it makes sense.
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It looks good to me, your comments describe it accurately imo
Litarnus
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Feb 20, 2026
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| if entry.activeCount.Add(-1) <= 0 { | ||
| // CompareAndSwap(CAS) is used to prevent a race between Set and MarkFinished. | ||
| // The race has two windows: | ||
| // 1. MarkFinished decremented activeCount to 0 but hasn't CAS'd yet -> Set Adds(1), and CAS fails keeping the | ||
| // transaction, since we just added a new span. | ||
| // 2. MarkFinished already CAS'd -> Set will store on the transaction marked for deletion (better than | ||
| // creating a new orphaned span). | ||
| if entry.activeCount.CompareAndSwap(0, -1) { | ||
| ssm.transactions.CompareAndDelete(traceID, entry) | ||
| } |
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It looks good to me, your comments describe it accurately imo
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Cursor Bugbot has reviewed your changes and found 1 potential issue.
Bugbot Autofix is OFF. To automatically fix reported issues with Cloud Agents, enable Autofix in the Cursor dashboard.
HasSpan should be enough to distinguish if the span should be a child of an active span
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Description
Previously the span map was holding all span information in a tree structure. When a span finished, MarkFinished acquired a global write lock and recursively traversed the tree to clean up. The fix usees the already existin spanRecorder to keep track of the spans in the transaction. Instead of linking each child, we keep track of the root transaction and override the ParentSpanID so that the spanRecorder reconstructs the span hierarchy.
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