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Wgray/zstd store/conflict resolution - #2719

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MarcusSorealheis:wgray/zstd-store/conflict-resolution
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Wgray/zstd store/conflict resolution#2719
MarcusSorealheis wants to merge 29 commits into
TraceMachina:mainfrom
MarcusSorealheis:wgray/zstd-store/conflict-resolution

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@MarcusSorealheis

@MarcusSorealheis MarcusSorealheis commented Aug 27, 2026

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What and why

Resolved known merge conflicts. The project was ultimately verified by running bazel test //... and observing all tests passing.

Risk

If consumers enable zstd compression for gRPC store there could be high CPU costs for little benefit.


This change is Reviewable

walter-zeromatter and others added 28 commits July 30, 2026 14:35
Adds a downcast helper that checks only the immediate inner StoreDriver,
without following inner_store() like the existing recursive downcast_ref.
Needed so callers (e.g. the service layer) can detect a directly-configured
representation-changing store such as the upcoming ZstdStore at an instance
boundary, rather than resolving through pass-through wrappers.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
nativelink-store failed to compile (E0004) because the StoreSpec::ZstdStore
variant had no match arm in default_store_factory.rs. Add the arm, wiring
ZstdStore::new to its backend store like the other pass-through stores, and
add a factory test that builds a ZstdStore via store_factory and downcasts
to confirm the concrete type.
…dation tests

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
… concat-frame test

Register staged/recompression temp file paths in TempFileGuard before
create_empty_temp_file runs, so a set_permissions failure or cancellation
during file creation can't leak an untracked file. Add a post_init
write-probe so a read-only or mispermissioned temp_path fails at startup
instead of on first upload. Document that the 0o600 permission is unix-only.
Add a test proving get_for_batch's raw-decode path handles a concatenated
multi-frame zstd physical stream.
…rite

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
…sion

The ZstdStore fast path in inner_batch_update_blobs took a client's
zstd-compressed blob and stored it verbatim via update_zstd_oneshot
whenever the instance's CAS store happened to be a ZstdStore, without
checking remote_cache_compression_enabled. This let a ZstdStore-backed
instance silently accept zstd uploads even when remote cache
compression was disabled for it, unlike the non-ZstdStore path (which
already rejects zstd via decompress_batch_update) and capabilities
(which stops advertising zstd when disabled).

Require remote_cache_compression_enabled alongside the ZstdStore/Zstd
compressor check so a disabled instance falls through to
decompress_batch_update and gets the same rejection as any other
store. Also moved the size_bytes computation into the else branch
since it is only used there.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
…fast-path sites

Add a non-recursive owned-Arc sibling to downcast_ref_immediate for callers
that must move the concrete store into a spawned/'static future, and replace
the four repeated `store.clone().into_inner().as_any_arc().downcast::<ZstdStore>()`
idioms in the ByteStream and CAS servers with it. Behavior is unchanged:
into_inner() returns the immediate inner Arc.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
ZstdStore's identity encode/decode paths run inside `spawn_blocking!` and
need `std::io::Read`/`Write` views over a buf_channel pair. Add
`BufChannelReader`/`BufChannelWriter` to `nativelink_util::buf_channel`,
where the underlying `DropCloserReadHalf`/`DropCloserWriteHalf` already
live, and drop the private copies from zstd_store.rs.

`BufChannelWriter` deliberately does not send EOF on drop: the caller sends
it explicitly once an upload has been validated, so a failed write never
commits downstream.

The service wire codecs used to need the same adapter, but no longer do —
they drive the zstd raw decoder from an async loop instead of a blocking
one — so these adapters now exist solely for the store's blocking paths.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
…tore

Introduce a single private decode_all_zstd(data, size_hint, on_err) helper and
use it at the three whole-buffer decode sites (two zstd::stream::decode_all and
one zstd::bulk::decompress). The size_hint selects bulk vs streaming decode and
the on_err closure preserves each site's exact error code and message
(InvalidArgument for client input, DataLoss for stored data). The two streaming
decoders are left untouched. Behavior is unchanged.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Under Bazel (unlike cargo, which inherits crate deps) the store
integration test suite needs `@crates//:zstd` declared explicitly for the
ZstdStore tests. Caught by the clippy/build aspect.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
…pinned staging

Harden the ZstdStore fast path against resource-exhaustion, starvation, and
staging path-replacement races, and clean the patch-specific CI failures.

Issue 1 — bounded decompression at the output sink:
- DecodeSink enforces the decoded-output ceiling inside Write::write using
  checked_add; output past the digest's uncompressed size is rejected
  immediately (InvalidArgument) before hashing/collecting, stopping a zstd
  bomb at the first over-limit block.
- Zero-digest validation streams through the same bounded decoder with an
  output cap of zero (no whole-buffer decode/allocation) and now acquires the
  staged-upload semaphore, so it participates in concurrency admission.

Issue 2 — slow-client / stall starvation:
- The compressed ByteStream client pump applies an idle timeout to waiting for
  the next WriteRequest (reusing persist_stream_on_disconnect_timeout_s); a
  client making progress is never timed out. On timeout the channel sender is
  dropped so the blocking validation unwinds through the existing join, and
  DeadlineExceeded is surfaced as the primary error.
- Inner-store commit (and recompression) is bounded by a new commit_timeout_s
  (default 300s); on expiry the upload fails DeadlineExceeded and the staged
  file/permit are released, so a stalled backend cannot hold a slot forever.

Issue 3 — descriptor-pinned staging:
- Staging files are created exclusively (create_new/O_EXCL, 0o600 atomic on
  unix); the validated descriptor is retained, rewound, and handed to the
  inner store at commit (never reopened by pathname), defeating
  observe-and-replace races. Recompression candidate handled the same way.
- post_init verifies temp_path is a directory and rejects a world-writable
  directory lacking the sticky bit. Adds fs::FileSlot::from_std.

Issue 4/5 — CI + docs:
- Regenerate stores-config.json5, add Vale vocabulary terms, fix MDX-unsafe
  comparison operators (windowLog <= 23 -> ≤), and reconcile store-overview
  docs with the new bounds/admission/deadline/temp_path/descriptor behavior.

Adds focused tests: sink bound + zero-digest bomb + over-decode rejection,
descriptor-pinned commit, commit-timeout slot release (store); ByteStream
idle-timeout slot release + progress-not-timed-out (service); batch per-blob
timeout sibling isolation (service).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Correctness and availability:

- Qualify the descriptor-pinning claim. Only backends using the default
  `update_with_whole_file` read the validated descriptor; `filesystem`
  drops it and commits by `rename(2)` on the path, where the defence is
  `O_EXCL` creation of an unguessable name in an operator-private dir.
  Adds a filesystem-backed commit test, which the previous
  `MemoryStore`-only test could not cover.
- Report the staging error, not the feeder's consequential channel error,
  when a large oneshot upload is rejected.
- Route the negotiated compressor through a single
  `wire_compressor_capability` helper instead of hardcoding zstd in the
  ByteStream read/write and BatchUpdate fast paths. The helper lives in
  `nativelink_util::wire_compression` next to the codecs and
  `WireCompressor`, and is re-exported from the service module.
- Add `stage_timeout_s`: a total validate-and-stage deadline, since a
  per-message idle timeout is reset by a client that trickles bytes to
  hold a staging slot open.
- Make recompression best-effort (`try_acquire`). It previously queued on
  the recompression semaphore while holding a staging permit, letting a
  pool of 1 throttle the whole upload path.
- Reject `max_recompression_size > 0` without `compression_level`, which
  silently disabled recompression.
- Add `max_concurrent_identity_ops` to bound identity reads/writes, each
  of which holds a blocking thread for a whole transfer.
- Add `max_inline_commit_size`: validate and commit small compressed
  uploads from memory, so BatchUpdateBlobs stops paying a per-blob fsync.
- Give compressed uploads their own `compressed_upload_idle_timeout_s`
  instead of borrowing `persist_stream_on_disconnect_timeout_s`.
- Publish metrics for fast-path hits, inline vs staged commits, in-flight
  gauges, recompression outcomes, and deadline expirations.

Fix an unbalanced brace that made
`deployment-examples/docker-compose/local-storage-cas-zstd.json5`
unparseable, and extend the json5 test to parse every deployment example
so nothing ships broken again.

Drop stale references to the abandoned two-candidate staging design,
consolidate the duplicated join/error/decode helpers, and cut the comment
density from 18% to 15% while adding the above.

Also adapts the branch to upstream API changes picked up by the rebase:
the `RemoveCallback` alias, `FilesystemSpec::evict_page_cache`, and the
newly denied `clippy::cast_possible_wrap` in tests.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Three CI failures, all in files this branch touches:

- rustfmt (the pinned nightly used by the Bazel aspect) reflows the
  `store_trait` import and the `register_remove_callback` signature in
  zstd_store.rs, both of which changed width when the rebase adopted the
  shorter `RemoveCallback` alias. It also wants the new
  `use crate::store_trait::WireCompressor` sorted after `digest_hasher`
  rather than after `buf_channel`.

- `nativelink-config/examples/stores-config.json5` is generated from the
  ```json blocks in stores.rs doc comments by `generate-stores-config`; it
  is not hand-editable. Add `max_concurrent_identity_ops` and
  `max_inline_commit_size` to the doc comment, which is the source of
  truth, so the generator reproduces the committed file exactly.

- Vale lints Rust doc comments as well as MDX. Rephrase to avoid the
  possessives `backend's`/`upload's` and the two words absent from its
  dictionary (`untrusted`, `expirations`) instead of widening the accepted
  vocabulary for ordinary prose.

Verified with `bazel test //...` (103/103, so the `unit_test` targets that
surfaced the rustfmt failures are covered this time) plus the cargo test,
clippy, and nightly rustfmt runs.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
The rules_rust rustfmt aspect (nightly/2026-03-24) wanted three
reformattings in zstd_store.rs that the local nightly/2026-04-09
rustfmt did not flag, breaking the Bazel Dev, asan, ubuntu-24.04,
and Bazel 8.7.0 jobs. Apply them so both rustfmts agree.

Vale flagged 'validator' as a spelling error in stores.rs and the
store-overview.mdx; it is a legitimate word for the blocking decode
task, so add it to the TraceMachina accept vocabulary.
The #[nativelink_macro::nativelink_test] attribute on the inline
batch_identity_decode_waits_for_identity_admission test expands to
tracing_test::logs_assert. The unit_test target's deps lacked
@crates//:tracing-test, so the rules_rust clippy aspect (run by
bazel test //...) failed with E0433/E0425. The integration test
suite already had it; this mirrors nativelink-util's unit_test.
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