Scale: Redis-backed rate limiting + presence TTLs#76
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Harden the multi-process (REDIS_URL) path so the things that were per-process become correct cluster-wide. Rate limiting: - registerRateLimit now takes an optional Redis URL. With Redis, the per-IP fixed window is a shared INCR+PEXPIRE counter (PTTL for the reset header), so the limit holds across every process behind a load balancer. A Redis hiccup fails OPEN — a limiter outage must never take the API down. In-memory limiter unchanged when Redis is absent. Presence durability: - The Redis roster moves from a plain hash to a sorted set scored by expiry (member = cid) plus a cid→identity hash, with each process heartbeating its own members to push their expiry forward. If a process dies without a graceful leave, its members simply age out — no ghosts in the roster. members() evicts expired entries on read. (Redis 7.0 has no per-field hash TTL, hence the zset.) TTL/heartbeat are configurable for tests. Verification: 62/62 SQLite (in-memory limiter path unchanged), 44/44 Postgres 16, and the Redis suite (3/3): cross-process fan-out, a shared rate-limit window that blocks across two instances, and a crashed process's presence aging out. Docs updated (.env.example, README, /docs).
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What
Next-roadmap item 2/2 (operator side). Hardens the multi-process (
REDIS_URL) path so two things that were per-process become correct cluster-wide: per-IP rate limiting and the presence roster.How
Rate limiting (
src/rate-limit.ts)registerRateLimitnow takes an optional Redis URL. With Redis, the per-IP fixed window is a sharedINCR+PEXPIREcounter (PTTLfor the reset header), so the limit holds across every process behind a load balancer. Fails open on a Redis error — a limiter outage must never take the API down. The in-memory limiter is unchanged when Redis is absent.Presence durability (
src/modules/realtime/transport.ts)cid) + acid → identityhash, with each process heartbeating its own members to push their expiry forward. If a process dies without a graceful leave, its members simply age out — no ghosts in the roster;members()evicts expired entries on read. (Redis 7.0 has no per-field hash TTL, hence the zset.) TTL/heartbeat are configurable, defaulting to 30s/10s.Neither changes the API, and the single-process default is untouched.
Verification
npm run test:redis, against a realredis-server): cross-process fan-out; a shared rate-limit window where the 4th request is429even though it lands on the second instance (proving the counter is shared); and a "crashed" process's presence member aging out of the roster after its TTL.verifyjob already runstest:redisagainst theredis:7service. Docs updated (.env.example, README,/docs).This completes the two next-roadmap items we lined up (public realtime #75 + this). Happy to keep going down the roadmap — schemas, cursor pagination,
/metrics+/ready, orCREATE INDEX CONCURRENTLYare the next candidates.https://claude.ai/code/session_018efxvWw3MRjdtvE5xgBqya
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