OpenClaw Perf Cache

A 200-line OpenClaw plugin that wraps fs.statSync / fs.lstatSync / fs.realpathSync (and their fs.promises async siblings) with a 1-second TTL memo, scoped to plugin-tree paths only, as a workaround for an upstream openclaw performance bug.

Why this exists

loadPluginMetadataSnapshot() in openclaw's dist/plugin-metadata-snapshot-*.js keeps a memo of the resolved plugin registry, but its cache-validity check runs hashWatchedFiles(memo.watchedFiles) on every lookup. That call re-fingerprints every plugin's package.json + openclaw.plugin.json + source + setupSource paths via realpathSync → ancestor lstat chain.

On a prod gateway with ~100 installed plugins (the bundled dist/extensions/* set), one cache-check pass is roughly:

100 plugins × 4 watched-files × 2 realpath/file × ~8 lstat/realpath
  ≈ 6 400 lstat + ~400 stat per call
  ≈ 6–7 s CPU

The check fires from many call sites — every agent turn (tool middleware loader), every loadConfig() call, every channel routing decision — turning what should be a cheap snapshot hit into a sustained CPU drain.

Same hot path is observed in these upstream tickets:

• #86791 — repeated lstat/realpathSync in InstalledPluginIndex fingerprinting (memoization missing) — open, P2, exact same call chain (lstat and realpathSync under resolvePackageJsonPath -> buildInstalledManifestRegistryIndexKey -> resolveInstalledManifestRegistryIndexFingerprint). Two linked PRs (#86797, #86850) both try the same WeakMap-keyed-by-index-object memo strategy; both are blocked on review (type-check + real-behavior-proof). They only cover resolveInstalledManifestRegistryIndexFingerprint — they don't help with discoverInDirectory walks or with realpathSync's ancestor-lstat chain. Even after they merge, this plugin's fs-layer TTL still catches stat traffic the WeakMap doesn't see; reevaluate then.
• #67040 — persist plugin discovery cache + defer plugin loading (closed as not planned)
• #75297 — gateway event-loop saturation, very slow sessions.list after 2026.4.23 (workaround: rollback to 2026.4.23)
• #28587 — plugin runtime eagerly loads channel SDKs causing sustained high CPU on startup (closed by PR #28620, but only fixed the startup path, not the per-turn cost)

What this plugin does

On register() it patches the global fs functions:

Wrapped	Pass-through when
fs.statSync	path does NOT match a plugin-tree needle
fs.lstatSync	path does NOT match a plugin-tree needle
fs.realpathSync	path does NOT match a plugin-tree needle
fs.promises.stat	path does NOT match a plugin-tree needle
fs.promises.lstat	path does NOT match a plugin-tree needle
fs.promises.realpath	path does NOT match a plugin-tree needle

Plugin-tree needles (substring match — any one matches):

• /openclaw/dist/extensions/
• /.openclaw/plugins/
• /node_modules/@openclaw/
• /openclaw/plugin-sdk/

Matched calls get a 1 000 ms TTL memo keyed by (fn-name, path, JSON(opts)). Cached errors throw the same error on subsequent reads within the window.

Counters are logged once a minute:

[perf-cache] last 60s: hits=812 misses=27 (hit-ratio 96.8%) passthrough=1493 errors=0 cache_size=804

passthrough = calls that bypassed memo because the path wasn't a plugin tree path — that count is essentially "rest of the system" and should be mostly unchanged by us.

Safety notes

• Pass-through for non-plugin paths. Business code (logs, session files, skills/, secrets/, anything outside the whitelist) sees the unmodified fs. Only plugin-discovery paths are intercepted.
• 1 s TTL. Plugin manifest mtime resolution is millisecond level, so a manifest change becomes visible at most ~1 s later. Dev-loop impact is negligible.
• Bounded memory. cache.clear() fires when entries > 4 000.
• Idempotent. Module re-import (jiti reload) is a no-op via a sentinel flag on globalThis.
• Argument-aware. Cache key includes a JSON of trailing args so statSync(p) and statSync(p, { bigint: true }) don't collide.

Install

git clone https://git.hangman-lab.top/hzhang/OpenclawPerfCache.git
cd OpenclawPerfCache
npm --prefix plugin install
node scripts/install.mjs --install
systemctl --user restart openclaw-gateway

Update (rebuild + recopy, no config touch)

node scripts/install.mjs --update
systemctl --user restart openclaw-gateway

Uninstall

node scripts/install.mjs --uninstall
systemctl --user restart openclaw-gateway

If openclaw ever fixes the upstream cache-validity-check, this plugin can be uninstalled with no consequence.