Commit Graph
6 Commits
Author SHA1 Message Date
claudeandClaude Fable 5.1 07ba53ca79 fix(prune): reclaim merged branches, and size the volume for the clone
Two assumptions in the eviction pass did not hold on this forge, and
between them a volume filled up three times in three days with nothing
reclaimed automatically. Both are replaced here; the pass also moves
ahead of the seed, which is the only order in which its work can help
the run performing it.

LIVENESS. Pass 1 evicted a cache only when its branch was gone from
origin. Gitea keeps a PR's branch after the merge unless the repo opts
into delete-on-merge, and zemyna does not — so ls-remote reports fifty
merged branches and the signal fires for none of them. A second signal
is added beside it: a branch still on origin whose tip is an ancestor of
a protected branch's tip holds no commit that branch does not, so its
cache will never be read again and goes in the same unconditional pass.

Ancestry is answered from the commits in the job's own checkout, so the
answer "cannot tell" exists and stays distinct from "not merged" at both
granularities. A shallow checkout withholds the signal entirely, since a
missing object is its normal case rather than evidence. A single branch
whose tip is not in the checkout is kept, with a warning naming it. A
squash or rebase merge leaves no ancestry and reads as live until the
branch is deleted. All three are missed reclamations, which cost disk;
the other direction costs a branch its cache mid-build.

HEADROOM. Passes 2 and 3 gated on a percentage of the volume, which
cannot express the failure they have to prevent: a clone runs out of
disk while unsharing its mutable paths, and how much that needs is a
property of the snapshot rather than of the disk. Staging failed at 34 G
free and passed at 74 G, so a 10% floor — 19 G here — never fired first.
The requirement is now measured per run off the very source the seed
will read, the pass evicts oldest-first until it is met and stops there,
and falling short of it fails with the shortfall and every directory it
kept, rather than letting the seed fail seconds later against a staging
path that names none of that. min-free-percent survives as an additional
floor, defaulting to 0, and falling short of that one is still a warning
and a self-clear.

ORDERING. The prune step ran after the seed, so each run freed space for
the next one. It now runs between resolve and seed. Two things that
makes newly reachable are closed: the source about to be cloned is
excluded from every pass by name, and a concurrent job's target dir
already carries its lock from the instant it appears under its final
name, so nothing is seen unlocked that is in use.

Red-proven: sixteen assertions across the four new scenarios fail
against the pre-fix scripts, including the zemyna layout evicting
nothing where it should evict exactly one directory, and the headroom
scenario exiting 0 where it should exit 1.

Refs #20.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JXMQCJ5Eg5f9G9cfYzyh4Z
2026-09-07 00:21:12 -05:00
claude fb7a788c90 feat(cache): give same-ref jobs separate build directories via cache-lineage
CI / shellcheck + selftests (pull_request) Failing after 1m19s
A cache key names a REF. What a target directory holds is the product of a ref
and a build configuration, and emowheel builds the same ref twice on every
push — once for the host, once for wasm32, in two jobs that start together.
Keyed on the ref alone, `cargo-cache@v1` handed both the same
CARGO_TARGET_DIR, and Cargo's target-directory lock is exclusive: the second
job sat on "Blocking waiting for file lock on build directory" for the length
of the first while holding a runner capacity slot, so a third repo's queued
job waited behind a job doing nothing.

`cache-lineage` is that second dimension. It names ONE directory level under
the cache root:

    <cache-root>/target-<key>              no lineage (unchanged)
    <cache-root>/<lineage>/target-<key>    a lineage

Nesting, not a suffix on the key, and that is the whole design decision.
`prune-cache.sh`'s liveness pass classifies a directory by recomputing
`target-<cache_key(branch)>` for every branch on origin and evicting whatever
does not match — a `target-<key>-wasm32` matches nothing, so it would be
classified dead and evicted unconditionally on every run. daniel/gitdan's
host-level arbiter reads the same shape (BRANCH_DIR_RE); a suffixed name falls
out of that too, so those caches would never be reclaim candidates and a whole
lineage would go missing from the shared disk budget. Nesting leaves both
matchers reading exactly the names they already read, one level down — which
is a layout that arbiter already walks (CI_CACHE_MAX_DEPTH is 2, and its own
suite pins the depth-2 case).

Every interacting part, checked rather than assumed:

- SEED: `seed-target-dir.sh` takes the root as an argument, so a PR branch in
  a lineage layers over THAT lineage's base snapshot. Asserted.
- PUBLISH: `publish-snapshot.sh` derives both ends of the swap from the root.
  The publish action now takes the root from the `CARGO_CACHE_ROOT` the
  consume step exported, and CHECKS its own inputs against it — a publish step
  left at the default while its consume step nested would otherwise republish
  a different lineage's live target dir over that lineage's snapshot, on every
  push, silently. `mode: release-lock` is exempt: it releases a lock on
  `$CARGO_TARGET_DIR` and never touches a root.
- WATERMARK: per target dir, so it follows the lineage. Unchanged.
- PRUNE and LIVENESS: scoped to the root they are given, so a pass in one
  lineage neither evicts nor sees a sibling's caches, or the flat layout's.
  Liveness keeps resolving real branch names, which is what a key suffix would
  have broken.
- ci_cache_reclaim: verified by dry-run against a fixture in this layout —
  all six nested and flat dirs collected as candidates, protection resolved
  correctly on the nested ones, and a `.stage-` stranded inside the lineage
  found by the leftover sweep.

Refused lineage names are refused at resolve time, each rejection naming the
reader that imposes it: a path separator (the arbiter's depth budget), a
Cargo profile name (its no-descend list), a `target-`/`snapshot-` prefix (this
repo's own prune globs), a hex suffix (its per-branch-dir shape), a dot prefix
(the leftover-naming contract). None of these fails visibly on its own — each
produces a working directory that some pass silently stops seeing.

Setting no lineage resolves to the cache root byte for byte, so lublub, zemyna
and emowheel's `ci` job keep the exact directories they have on the volume.

New suite `cache-root-selftest.sh` (19 assertions), red-proven against three
deliberate breakages: a `cache_root_for` that ignores the lineage, a disabled
validator, and a `verify` that never rejects a mismatch.
2026-08-26 12:32:21 -05:00
claude df6f1b91fb docs(cache): producer half of the depended-upon names contract (#11)
Co-authored-by: Claude <claude@gitdan.com>
Co-committed-by: Claude <claude@gitdan.com>
2026-08-24 23:03:29 +00:00
claudeandClaude Opus 5 f57e2a6013 fix(cargo-cache): close the seed-vs-republish race the design claimed to close
The shared action's justification over zemyna's and emowheel's schemes was
that hardlink-cloning from a published snapshot closes gitdan #911 "by
construction, not by the single job slot". Review disproved that. This makes
the claim true, and corrects the README where it could only be bounded.

Finding 1 (verdict-level) — silent partial clone
------------------------------------------------
`hardlink_clone_into` ran `cp -al` with no exit-status check, and both call
sites invoked it as a condition, which suppresses `set -e` for the whole call.
A publisher's `rm -rf` of the generation it rotated away therefore unlinked
entries beneath an in-flight consumer walk, and the truncated tree was renamed
into place and reported as success.

Both layers are fixed:

* The consumer verifies its own clone. Every attempt checks `cp -al`'s status
  explicitly, the source directory's inode before and after (a wholesale
  replacement mid-walk splices two generations), and the entry count — the
  only signal for a subtree unlinked before its parent was listed, since
  `cp -al` reports no error for one it never saw. Any failure discards the
  staging tree and retries; exhausting the attempts returns a distinct status
  2 and fails the job rather than seeding a partial cache. `unshare_subtree` /
  `_unshare_files` now propagate failure too — a swallowed unshare leaves the
  clone aliasing its source, the exact corruption that step exists to prevent.
* The publisher does not unlink under a reader. A consumer publishes a
  `.reading-<snapshot>-<tag>` marker before it resolves the snapshot path; the
  publisher scans for markers after its first rename. A consumer holding the
  old generation therefore published its marker before that scan and cannot be
  missed; one arriving after the scan necessarily resolves to the new
  generation. The publisher waits for readers to drain and, on timeout,
  DEFERS reclamation rather than forcing it — the old generation is left as
  `.publish-old-<key>-<tag>` and swept by a later publish.

So correctness is closed by construction; disk reclamation is bounded, not
immediate. The residual is capped at one deferred generation per publisher
ref, and the README now says exactly that instead of the disproved claim.

Finding 2 — restore-mtimes.sh ran with no errexit
-------------------------------------------------
`set -euo pipefail` was glued to the end of a comment (`# soundness.set -euo
pipefail`), so it was entirely commented out: a partial failure of the
`git log | awk` pipeline would have produced wrong mtimes across the whole
restore instead of failing loudly. Moved to its own line. Audited every other
script for the same defect — this was the only instance. Independent
confirmation: shellcheck's two SC2164 warnings on this file's `cd "$repo_root"`
disappear now that errexit is actually in effect.

Finding 3 — lock-acquire window
-------------------------------
A just-seeded directory was unlocked until a later action step, so a
concurrent job's prune pass could evict it. `seed-target-dir.sh` now takes an
optional lock-id and writes the lock marker on every path out of the script,
including into the staging tree before its rename, so the directory carries a
lock the instant it appears under its final name. The action's acquire step
stays (it is idempotent and stamps the LRU marker).

Also hardened `prune-cache.sh` to treat a directory with live reader markers
as locked. Today no reachable configuration prunes a snapshot — only protected
refs publish them and protected refs are excluded from every pass — so this is
redundant by policy; it is here so that stops being the reason it is safe.

Verification
------------
New selftest scenario 8 races a real seed against a real publish rotation,
gating the rotation on the seed's *observed* clone progress so the window is
hit deterministically rather than on a fast machine's coin flip. Red-proven
against the unguarded scripts, three consecutive runs:

  ASSERTION FAILED: the seeded tree is truncated: 15443 entries against the
  snapshot's 493 (was 48805 before the rotation)      (15443 / 16986 / 16498)

Green after the fix, six consecutive runs, catching the clone mid-walk at
~10.5k of 48805 entries each time. Scenario 9 covers deferred reclamation and
its later sweep; scenario 10 covers an unreadable source failing loudly.

`bash scripts/selftest.sh`: 5 suites, exit 0, 75 assertions (was 63).
shellcheck over `scripts/`: no new findings, two SC2164 warnings resolved.

Docs: README's republish-safety paragraph replaced with what the code now
guarantees, including the bounded disk residual stated explicitly; new
`read-grace-seconds` / `reader-stale-seconds` inputs documented in the
`cargo-cache-publish` table; the selftest table names the new race.

Refs: daniel/gitdan#11, zemyna#911

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Sqh2vscfzisk83VuPVQX9L
2026-08-23 16:40:21 -05:00
claudeandClaude Opus 5 248af3061e feat(cargo-cache): hardlink-clone a per-ref Cargo cache from a published snapshot
Replaces the phase-0 resolution probe with the real actions, merging the two
independent per-branch Cargo cache implementations on this forge into the
design neither of them had.

## The merge

- zemyna seeds a PR branch by `cp -al` hardlink clone (near-free: cost scales
  with inode count, not bytes) from the base branch's LIVE target dir — a
  torn read waiting for a second job slot (its own #911).
- emowheel seeds from a PUBLISHED IMMUTABLE SNAPSHOT (no race by
  construction) but with `cp -a`, duplicating ~35 GB per branch.

This ships hardlink-clone FROM a published snapshot: zemyna's cost profile,
emowheel's soundness, and #911 closed structurally rather than by the runner
happening to have one execution slot.

## The bug both implementations have

A build inside a `cp -al` clone DOES mutate the directory it was cloned from.
Cargo replaces real artifacts, but writes its metadata — and build scripts
write their OUT_DIR — with a plain truncating write, straight through the
shared inode. Measured set: `.fingerprint/<unit>/dep-<target>` (under
CARGO_UNSTABLE_CHECKSUM_FRESHNESS), `build/<pkg>/{output,root-output,out/**}`,
`deps/*.d` and `<profile>/*.d`.

The checksum-freshness case is a wrong answer, not a slow build: a PR clone
rewrites the base's dep-info to describe the PR's sources while the base's
cache still holds the artifact built from the base's; once the PR merges, the
base's next run finds the checksums match, reports `Fresh`, and links a binary
built from the pre-merge code. Reproduced end to end.

Fix: hardlink the artifacts (the GB), real-copy the metadata (the MB) — about
3.7% of a 6.9 GB Bevy target dir, against 100% for a full copy.

## Contents

- `cargo-cache/action.yml` — consume: resolve keys, seed from the base's
  snapshot via staging + one atomic rename, strip Cargo lock files, unshare
  the mutable paths, restore mtimes from git history, lock, prune.
- `cargo-cache-publish/action.yml` — publish: record the build watermark,
  atomically republish the snapshot on a protected branch, release the lock
  (`mode: release-lock` for the `if: always()` step).
- `scripts/` — all logic, so it is testable standalone; the YAML is wiring.
- `scripts/*selftest.sh` + `selftest.sh` — five suites, 63 assertions, every
  fix paired with a control that reproduces the bug. All green locally.

Eviction merges emowheel's liveness pass (dead branches pruned
unconditionally, not gated on disk pressure) with LRU-under-pressure, but
inverts the order within the pressure pass: `target-*` before `snapshot-*`,
because a snapshot is hardlinked to everything cloned from it, so evicting one
frees almost no real bytes while costing every future PR its warm start.

restore-mtimes.sh is ported from emowheel (the watermark variant, which closes
the merge hazard zemyna's copy still has) with its provenance de-projectised.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Sqh2vscfzisk83VuPVQX9L
2026-08-23 14:18:01 -05:00
claude 8503883138 feat: cargo-cache composite action skeleton (phase-0 resolution probe) 2026-08-23 11:52:31 -05:00