fix(cache): serve S3 data object when companion metadata is stale#390
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fix(cache): serve S3 data object when companion metadata is stale#390worstell wants to merge 1 commit into
worstell wants to merge 1 commit into
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The S3 backend commits an object as two sequential writes: the data object, then a companion .meta object carrying mutable metadata. Between the two writes (or when concurrent writers to the same key interleave), the companion's tag doesn't match the data object, and reads reported a miss even though a valid, fully-committed data object exists. For large objects the commit window spans the entire upload of a competing writer, so hot keys could repeatedly appear missing. The data object is self-describing: its immutable headers (including ETag) travel in its own user metadata. On tag mismatch, serve it with those headers and its own expiry instead of returning a miss. The expiry-refresh path then rewrites the companion with the object's tag, reconciling the pair.
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The S3 backend commits an object as two sequential writes: the data object, then a companion
.metaobject carrying mutable metadata (ETag, refreshed expiry). Between the two writes — or when concurrent writers to the same key interleave — the companion's tag doesn't match the data object, and reads reported a miss even though a valid, fully-committed data object exists. For large objects the mismatch window spans a competing writer's entire upload, so hot keys can repeatedly appear missing.The data object is self-describing: its immutable headers (including ETag) travel in its own user metadata. On tag mismatch, serve it with those headers and its own expiry instead of returning a miss. The expiry-refresh path then rewrites the companion with the object's tag, reconciling the pair.