MCP Time Server Node

/** * Sliding window rate limiter for MCP server * Tracks requests in a time window and enforces limits */ import { debug } from './debug'; export class SlidingWindowRateLimiter { private requests: number[] = []; private readonly limit: number; private readonly windowMs: number; constructor(limit?: number, windowMs?: number) { // Default values const DEFAULT_LIMIT = 100; const DEFAULT_WINDOW_MS = 60000; // If constructor params provided, use them if (limit !== undefined) { this.limit = limit; } else { // Try to parse from environment const envLimit = process.env.RATE_LIMIT; if (envLimit) { const parsed = parseInt(envLimit, 10); // Validate parsed value if (!isNaN(parsed) && parsed > 0) { this.limit = parsed; } else { this.limit = DEFAULT_LIMIT; } } else { this.limit = DEFAULT_LIMIT; } } // Same logic for windowMs if (windowMs !== undefined) { this.windowMs = windowMs; } else { // Try to parse from environment const envWindow = process.env.RATE_LIMIT_WINDOW; if (envWindow) { const parsed = parseInt(envWindow, 10); // Validate parsed value if (!isNaN(parsed) && parsed > 0) { this.windowMs = parsed; } else { this.windowMs = DEFAULT_WINDOW_MS; } } else { this.windowMs = DEFAULT_WINDOW_MS; } } debug.rateLimit('Creating rate limiter - limit: %d, window: %dms', this.limit, this.windowMs); } /** * Check if a request is allowed under the rate limit * @returns true if allowed, false if rate limited */ checkLimit(): boolean { const now = Date.now(); this.cleanupOldRequests(now); if (this.requests.length >= this.limit) { debug.rateLimit( 'Rate limit exceeded - usage: %d/%d, retry after: %ds', this.requests.length, this.limit, this.getRetryAfter(), ); return false; } this.requests.push(now); debug.rateLimit('Request allowed - usage: %d/%d', this.requests.length, this.limit); return true; } /** * Get current usage count within the window */ getCurrentUsage(): number { const now = Date.now(); this.cleanupOldRequests(now); return this.requests.length; } /** * Get seconds until the rate limit resets * @returns seconds to wait, or 0 if under limit */ getRetryAfter(): number { const now = Date.now(); this.cleanupOldRequests(now); if (this.requests.length < this.limit) { return 0; } if (this.requests.length === 0) { return 0; } // Time until the oldest request expires const oldestRequest = this.requests[0]; const expiresAt = oldestRequest + this.windowMs; const msToWait = expiresAt - now; return Math.ceil(msToWait / 1000); } /** * Reset the rate limiter, clearing all request history */ reset(): void { this.requests = []; } /** * Get information about the current rate limit state */ getInfo(): { limit: number; window: number; current: number; remaining: number; retryAfter: number; } { const current = this.getCurrentUsage(); return { limit: this.limit, window: this.windowMs, current, remaining: Math.max(0, this.limit - current), retryAfter: this.getRetryAfter(), }; } /** * Remove requests outside the current window */ private cleanupOldRequests(now: number): void { const cutoff = now - this.windowMs; const oldCount = this.requests.length; this.requests = this.requests.filter((timestamp) => timestamp > cutoff); if (oldCount > this.requests.length) { debug.rateLimit('Cleaned up %d old requests', oldCount - this.requests.length); } } }