perf(cache): fan out large ranged reads through the remote tier#389
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worstell wants to merge 1 commit into
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perf(cache): fan out large ranged reads through the remote tier#389worstell wants to merge 1 commit into
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Generalize the S3 object-window adapter into objectWindow, a byte window over any pinned object revision, and use it to apply the large-range policy to Remote ranged reads: ranges of 8 MiB or more pay one Stat to learn the object's size and ETag, then split into parallel 4 MiB sub-range requests pinned with If-Match. Chunks stay below the remote's own S3 fan-out threshold so sub-ranges never fan out twice, and memory is bounded by the reader's reorder window (2*concurrency*chunkSize). Ranges the policy cannot pin or split delegate to a single stream.
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Generalizes the S3-only window adapter from the large-range work into
objectWindow, a byte window over any pinned object revision, and uses it to extend the large-range policy to the remote HTTP tier.s3ObjectWindowbecomes the genericobjectWindow(range resolution, header synthesis, and offset translation), parameterized by anopenRangefunction so S3 keeps issuing direct sub-range GETs with no behavior change.newCacheObjectWindowbuilds a window over any Range-capable cache via ETag-pinned conditional Opens.Remote.Opensplits ranged reads of ≥ 8 MiB into parallel 4 MiB sub-range requests (concurrency 8) pinned withIf-Match, mirroring how the S3 backend fans out internally. One preliminaryStatresolves the request's conditionals and range against the object's real size and revision; small explicit ranges skip the Stat entirely, and anything the policy cannot pin or split (no ETag, If-Range miss, sub-threshold after clamping) delegates to the existing single stream.Chunks stay below the remote's own S3 large-range threshold, so a sub-range arriving at a remote cachew backed by S3 maps to a single upstream request rather than fanning out twice. Memory per read is bounded by the reader's reorder window (2 × concurrency × chunk size = 64 MiB).
A tiered cache with a remote tier inherits the fan-out with no changes to
Tiereditself, so disk-tier ranged reads are untouched.