backup-helper: parallelise prepare hashing + curio import-pieces --result compatibility - #7
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June 4, 2026 20:14
prepare computes a piece CID for every shard missing one via the pure-JS @filoz/synapse-core/piece hash. That hash is CPU-bound and single-threaded, so on a multi-core node prepare pins one core and leaves the rest idle. Move the hashing into a worker_threads pool sized to --concurrency. Each worker calls the same calculateFromIterable, so output piece CIDs are byte-identical to the single-thread path; only throughput changes. DB writes and shard->piece renames stay on the main thread (sqlite is not shared with workers). Measured on a 64-core machine (~10 MB avg CARs): ~20 MB/s at -c 8, ~69 MB/s at -c 24, ~84 MB/s at -c 32 (knee ~32 on that box). No change to default concurrency or any existing flag.
curio toolbox import-pieces moved its JSON result off stdout into a file passed via a now-required --result <path> flag, and writes that file even on non-zero exit. Against a curio build with that change, runParkingBinary fails with 'ERROR: result is required'. Pass --result <dir>/.parking-result.json, read the JSON from there on both success and failure (surfacing curio's structured error field), and remove the file afterward. Tracks filecoin-project/curio#1264 (commit 7c8297ca). Note that #1264 is currently a draft; if the flag contract shifts before it merges this will need a follow-up.
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Closing this, since the the worker_threads commit was added to the PR #8 |
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Summary
Two independent changes to
backup-helper, kept as separate commits so they can be reviewed (or split) independently:1.
prepare— parallel CommP hashing (perf)preparecomputes a piece CID for every shard missing one, via the pure-JS@filoz/synapse-core/piecehash. That hash is CPU-bound and single-threaded, so on a multi-core nodepreparepins one core and leaves the rest idle.This moves the hashing into a
worker_threadspool sized to--concurrency. Each worker calls the samecalculateFromIterable, so output piece CIDs are byte-identical to the single-thread path — only throughput changes. DB writes and shard→piece renames stay on the main thread (sqlite isn't shared with workers).Measured on a 64-core machine, single dataset (~10 MB average CARs):
--concurrencyKnee around 32 on that box (the per-core JS hash is the ceiling); scales with available cores. Piece-CID output verified identical to the pre-change path.
2.
commit— adapt to curioimport-pieces --result(fix)curio toolbox import-piecesmoved its JSON result off stdout into a file passed via a now-required--result <path>flag, and writes that file even on non-zero exit. Against a curio build with that change,runParkingBinaryfails withERROR: result is required.This passes
--result <dir>/.parking-result.json, reads the JSON from there on both success and failure (surfacing curio's structurederrorfield), and cleans the file up afterward.Tracks filecoin-project/curio#1264 (commit
7c8297ca, "always write in json file").Testing
prepare: run end-to-end on a real customer dataset —failed=0, piece CIDs match the single-thread output.commit: parking step succeeds against a curio build carrying #1264; structured errors propagate on failure.Notes