[processor/coldstart] pair cold start spans using faas.invocation_id - #2520
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wpessers merged 1 commit intoAug 10, 2026
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The processor identifies execution spans by the faas.execution attribute, which semantic conventions v1.19.0 renamed to faas.invocation_id. Current instrumentations set only the new name, so no execution span is ever recognized. When that happens the cold start span is held indefinitely: it is removed from the batch while waiting for an execution span to pair with, and once the batch is empty the processor returns ErrSkipProcessingData, dropping the data. The result is that adding the coldstart processor to a pipeline silently loses the platform.initRuntimeDone span rather than enriching it. Look up both attribute names so current and older instrumentations are handled. Keeping the old name working avoids breaking instrumentations that still emit it, which is why this does not simply rename the attribute. Relates to open-telemetry#2099 and open-telemetry#1652.
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tylerbenson
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Aug 5, 2026
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Thanks for resubmitting this. I think it's a good contribution. Sorry @borchero that the original PR didn't get reviewed in a timely fashion.
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No worries, thanks for reviving @naari3 :) |
wpessers
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Aug 10, 2026
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Description
The processor identifies execution spans by
faas.execution, which semantic conventions renamed tofaas.invocation_idin v1.19.0. Current instrumentations set only the new name, so no execution span is ever recognized and the cold start span is never released.The failure is silent rather than a no-op: a held cold start span is removed from the batch, so a batch containing only that span becomes empty and the processor returns
ErrSkipProcessingData. Adding the coldstart processor to a pipeline dropsplatform.initRuntimeDoneinstead of enriching it.This accepts both attribute names, so current and older instrumentations both work.
Relation to #1216
@borchero submitted #1216 for this in March 2024. It went without review and was closed by the author. That PR renamed the attribute outright; this one keeps
faas.executionworking. Credit for finding the issue goes there, and I'm happy to close this in favour of a revived #1216.Testing
TestPairingByInvocationIDcovers a cold start span released by an execution span carryingfaas.invocation_id. It fails without the fix. The existing tests were left onfaas.executionas the backward-compatibility regression test and pass unchanged.Note
This also moves off
go.opentelemetry.io/collector/semconv, deprecated since collector v0.126.0, togo.opentelemetry.io/otel/semconvas already used bytelemetryapireceiver.Relates to #2099 and #1652.