Copilot review round 2, both comments upheld.
**ELOCKED must not degrade.** Exhausting the retries on a held lock means the
lock is *working* and something else demonstrably holds it — so running the
mutation anyway entered the exact interleaving the lock exists to prevent,
and entered it knowing a concurrent writer was there. `set` now fails
instead. Two supporting changes:
- The retry budget went from ~3.3s to ~15s so it outlasts the 10s stale
window. Refusing is only defensible because a *crashed* holder resolves by
takeover first; with the shorter budget, one Inspector killed mid-save
would have failed every later save on the box until someone deleted the
lock by hand. Pinned by a new test that stages a dead holder's lock
directly (mkdir + backdated mtime) and asserts the save succeeds.
- Acquire is now probe-then-wait. `proper-lockfile` drives its whole acquire
through `retry`, which re-attempts on *any* error — so with a 20-retry
budget a read-only `$HOME` would have spent the full 15s re-issuing an
identical failing `mkdir` on every save before degrading. One retry-less
probe separates "held" (worth waiting out) from "unavailable" (not).
**The comment overclaimed what proper-lockfile provides, and the reviewer was
right about the mechanism.** Verified against lib/lockfile.js@4.1.2: on
EEXIST it stats, and if stale it rmdirs and re-mkdirs *without* checking the
directory it removed is the one it found stale — so a slow waiter can still
delete a fast waiter's fresh lock and both proceed. That is the same race the
hand-rolled version could not close, and it is not closable without
renameat2(RENAME_EXCHANGE).
What the library actually adds is that the loser is *detected*: its refresh
tick compares the lock's mtime against the value recorded at acquire, so a
compromised holder is told rather than proceeding silently. And what is
genuinely exclusive is the case that matters — mkdir is atomic and a live
holder refreshes its mtime, so its lock never goes stale and two running
Inspectors are serialized. The residual window opens only after a holder dies
without releasing, and the optimistic verify still covers it.
file-lock.ts, README.md, specification/v2_servers_file.md and AGENTS.md all
carried the overclaim; all four now state the narrower, true version.
Also fixes a test that was quietly asserting the opposite of its name: its
holder used stale: 60_000 while the waiter used 10_000, and staleness is
judged by the *waiter's* threshold — so the holder was declared stale after
10s and the save succeeded by takeover.
Not done: a two-process stale-takeover race test. It would be testing the
library rather than this code, and is inherently nondeterministic; the honest
response to that finding was to stop claiming the race is closed.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JTHVxSu8AUgHRLvo1ntZ8H
Signed-off-by: cliffhall <cliff@futurescale.com>
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