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…s uploads The optimize phase runs right after finalize, but finalize's PauseAndUpload pushes its uploads (snapshot data and the pre-prefetch metadata) onto the build's UploadErrGroup and returns immediately — the only wait for that group runs after every phase. The optimize phase then collected its mapping and re-uploaded metadata with no ordering against the finalize goroutine, so the two writers raced on the same metadata object for the build: an interleaving where the finalize upload finished last clobbered the just-uploaded prefetch mapping (silent loss, manifests as "prefetch mapping sometimes missing"). finalizeUploadsSettled now waits on the build's UploadErrGroup before the optimize phase re-uploads metadata. A failed finalize upload skips publishing — the remote build is incomplete, and the same error resurfaces at the builder-level wait, so the build still fails loudly. Test: TestFinalizeUploadsSettled covers the settled, failed, blocked (ordering invariant: the gate does not return while the finalize upload is in flight) and nil-group cases. Co-Authored-By: Claude <noreply@anthropic.com>
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Problem
The optimize phase (
packages/orchestrator/pkg/template/build/phases/optimize, from #1705)runs right after finalize, but finalize's
PauseAndUploadpushes its uploads — snapshotdata and the pre-prefetch metadata — onto the build's
UploadErrGroupand returnsimmediately. The only wait for that group runs at the builder level, after every
phase has completed.
So the optimize phase collects its intersection mapping and calls
updateMetadatawithno ordering against the finalize goroutine: two writers race on the same metadata
object for the build. An interleaving where the finalize upload finishes last clobbers
the just-uploaded prefetch mapping — a silent loss that would manifest as "prefetch
mapping sometimes missing" for freshly built templates, with nothing in the logs.
Solution
finalizeUploadsSettled()gates the optimize phase's metadata re-upload on the build'sUploadErrGroup:updateMetadatapublishes the prefetch-enriched metadata. The mapping can no longerinterleave with the finalize upload.
same error resurfaces at the builder-level
UploadErrGroup.Wait(), so the buildstill fails loudly rather than dangling a mapping over uploads that never landed.
The gate sits after
collectMemoryPrefetchMapping(the expensive part), so the waitoverlaps the tail of the finalize upload rather than adding to the critical path.