Sync Mutex

Lease-based lock. Server version uses Redis SET NX PX, browser version uses an in-memory store. One mutex instance per lock namespace, one lock per resource string.

Decision Guide

• Must-have exclusivity: withLockOrThrow(resource, fn) — throws LockError if acquire fails.
• Best-effort exclusivity: withLock(resource, fn) — returns null if acquire fails.
• Manual control: acquire() → work → release() in finally block.
• Long work: call extend(lock, ttlMs) before expiry. If extend() returns false, the lock was lost — stop exclusive work immediately.

Gotchas

• defaultTtl is 10s. If critical section takes longer and you don't extend(), the lock expires and another process can acquire it.
• retryCount default is 10, retryDelay default 200ms (+0-100ms jitter). Total acquire budget is ~2-3s.
• Resources > 128 chars are auto-hashed: key becomes {prefix}:{id}:hash:{sha256}.
• Release and extend use Lua owner-check scripts — only the lock holder can release/extend.
• No automatic lease renewal — you must call extend() explicitly.
• No fairness: contenders are not queued in order.