wehub-resource-sync
85 lines
3.2 KiB
TypeScript
85 lines
3.2 KiB
TypeScript
/**
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* Sliding-window rate limiter (free-claude-code port, Fase 8.2).
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*
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* A small, dependency-free fallback limiter for providers that do NOT expose
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* rate-limit headers (so the adaptive Bottleneck path in rateLimitManager never
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* learns a reservoir) but have a documented fixed cap. Bottleneck's reservoir is a
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* fixed-window counter that refills in one burst every interval; a true sliding
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* window enforces "no more than N requests in ANY trailing windowMs", which avoids
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* the 2× burst at window boundaries that can trip an upstream 429.
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*
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* It is intentionally a pure allowed/blocked oracle (no internal queueing) — the
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* caller decides whether to wait `retryAfterMs` or fall back. See
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* `withRateLimit` in rateLimitManager.ts for the opt-in wiring, gated on
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* PROVIDER_DEFAULT_RATE_LIMITS so existing providers are unaffected.
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*/
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export interface RateLimitWindow {
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/** Max requests permitted in any trailing `windowMs`. */
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requests: number;
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/** Window length in milliseconds. */
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windowMs: number;
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}
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export interface AcquireResult {
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allowed: boolean;
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/** When blocked, ms until the oldest in-window hit ages out and a slot frees. 0 when allowed. */
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retryAfterMs: number;
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}
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// Hard ceiling on distinct keys tracked, so a pathological key space (e.g. a
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// per-request id leaking into the key) can never grow the map without bound.
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const MAX_KEYS = 5000;
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export class SlidingWindowLimiter {
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private readonly hits = new Map<string, number[]>();
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private readonly now: () => number;
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constructor(opts: { now?: () => number } = {}) {
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this.now = opts.now ?? Date.now;
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}
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/**
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* Try to consume one slot for `key`. Records a timestamp and returns
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* `{allowed:true}` when under the cap; returns `{allowed:false, retryAfterMs}`
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* (without recording) when the trailing window is saturated.
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*/
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tryAcquire(key: string, window: RateLimitWindow): AcquireResult {
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const { requests, windowMs } = window;
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// A non-positive cap or window means "no limit configured" → always allow.
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if (!(requests > 0) || !(windowMs > 0)) return { allowed: true, retryAfterMs: 0 };
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const now = this.now();
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const cutoff = now - windowMs;
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const previous = this.hits.get(key);
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// Drop timestamps that have aged out of the trailing window.
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const live = previous ? previous.filter((ts) => ts > cutoff) : [];
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if (live.length >= requests) {
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// The oldest in-window hit is the first to expire and free a slot.
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const retryAfterMs = Math.max(0, live[0] + windowMs - now);
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this.hits.set(key, live); // persist the pruned list; do NOT record a blocked attempt
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return { allowed: false, retryAfterMs };
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}
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live.push(now);
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this.set(key, live);
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return { allowed: true, retryAfterMs: 0 };
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}
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/** Clear history for one key, or all keys when called with no argument. */
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reset(key?: string): void {
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if (key === undefined) this.hits.clear();
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else this.hits.delete(key);
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}
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private set(key: string, live: number[]): void {
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if (!this.hits.has(key) && this.hits.size >= MAX_KEYS) {
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// Evict the least-recently-inserted key (Map preserves insertion order).
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const oldest = this.hits.keys().next().value;
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if (oldest !== undefined) this.hits.delete(oldest);
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}
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this.hits.set(key, live);
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}
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}
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