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Bound a worker's input fetches with one pool across the actions it stages - #2952
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MarcusSorealheis merged 4 commits intoOct 16, 2026
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corcillo
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Oct 16, 2026
| /// slow store than the pool holds. | ||
| #[cfg(target_family = "unix")] | ||
| #[nativelink_test] | ||
| async fn download_to_directory_bounds_fetches_by_the_pool() |
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Request: please add a test where two or more downloads share one pool. That's the behavior this PR is for.
This test runs a single tree through a pool of 3, which a per-call limit would also pass. Something like two concurrent download_to_directory_bounded calls on one Semaphore::new(3), asserting max_in_flight() <= 3, would cover the cross-action limit. A case for 0 → 64 in RunningActionsManagerImpl::new would also be nice.
corcillo
previously approved these changes
Oct 16, 2026
…o feat/worker-download-fanout
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What and why
A worker staging several cold actions at once opened up to 64 input fetches per directory level per action, so four actions with wide trees could hold a few hundred reads open against the CAS or the object store together. That is what a throttled store sees from a fresh worker pool.
The worker now draws every blob fetch into its store from one pool shared across the actions it stages.
max_concurrent_input_downloadson the worker config sets its size (default 64, today's per-level constant). The permit covers the fetch alone, never the directory walk under it, so a deep tree cannot deadlock the pool, and a blob already in the store is linked without one.How was this verified?
A new test stages a 40 file tree through a pool of 3 against a slow store that counts in-flight reads and asserts the peak never passes 3 while every file lands. The existing worker tests, clippy and the pinned rustfmt pass.
Risk
Low. A single action behaves as before; only a worker staging several actions at once fetches less in parallel than it did.
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