Yichen Jiang
54c60f4079
Two lifecycle holes the registry and the consumer helper left open. `AdapterRegistrationHandle.replace` had no liveness guard: after the handle's disposer ran, a replace put routes back into the registry with nothing left to release them, so the adapter leaked permanently. `owned` being empty cannot carry that fact, because `replace([])` is the legal empty-section state, so the disposer records it explicitly. `installSettingsSection`'s watcher lacked the guard its own disposer carries: a stored change landing while the consumer unloads reached `onChange`, which re-registers routes against a fiber whose resources are being released. Also documents `withFileLock` in the atomic-write README (it claimed one export), records the age-based lock takeover as a known limitation, and lists ctx.settings and ctx.credentials in the architecture capability table.
dsh-atomic-write
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Zero-dependency atomic file replacement shared by file-backed stores that must never leave partial, symlink-hijacked, or wider-than-intended content on disk — the user-settings document (dsh-settings-local) and the credentials store (dsh-credentials-local).
Surface
import { withFileLock, writeFileAtomic } from '@deepseek-ai/dsh-atomic-write'
declare const text: string
declare const render: (previous: string) => string
await writeFileAtomic('/home/u/.dsh/settings.yaml', text, { mode: 0o600 })
// Read-modify-write against the same file from several processes.
await withFileLock('/home/u/.dsh/settings.yaml', async () => {
await writeFileAtomic('/home/u/.dsh/settings.yaml', render(text), { mode: 0o600 })
})
writeFileAtomic commits one already-rendered string. The contract, in the order failures would exploit it:
- Exclusive-create temp (
wx, random suffix): the open refuses to follow a symlink planted at a guessable temp path. - The fresh inode carries
modethrough the rename: replacing a wider-permission file narrows it without a chmod race.modeis required so the permission decision stays visible at every call site (subject to the process umask, like every fresh inode). renamereplaces a symlinked target itself, never writing through to its referent.- Same-directory sibling keeps the rename on one filesystem, so the swap stays atomic.
- Parent directories are created; on any failure the temp is removed and the failure rethrown; readers observe either the old or the new complete content.
withFileLock serializes the writers of one file across processes, for the read-render-commit cycles a bare atomic commit cannot make safe on its own. The lock is a wx-created <filename>.lock sibling, so readers never contend; waiters back off exponentially and fail with a timeout rather than block forever. A lock older than the stale age is treated as a crashed holder and broken — see Known Limitations and Deferred Work for what that costs.
Model Experience
None, as this is a pure filesystem primitive; nothing here reaches a model request.
KV Cache effect
None; nothing here enters a request prefix.
Known Limitations and Deferred Work
- Atomic, not durable — no
fsyncof the file or its directory, so after a crash the rename may be observed unwound. The file-backed stores here re-read and republish on boot, keeping durability the caller's policy. - String content only — no
Bufferor stream form until a consumer needs one. - The lock takes over by age, not by ownership (
TODO(settings-lock-ownership)) — a holder slower than the stale age has its lock broken by a waiter, and release unlinks the path unconditionally, so a slow writer can remove a successor's lock. Two writers can then overlap and one cycle's result be lost. The stale age is set well above any write this repo performs, so the exposure is a paused or swapped-out process; ownership-safe acquisition and release is the fix.