Taiwan Holiday MCP Server

/** * Circuit Breaker Pattern Implementation * * 防止對失敗服務的重複請求，提供降級機制 */ export enum CircuitState { CLOSED = 'CLOSED', // 正常狀態 OPEN = 'OPEN', // 斷路狀態 HALF_OPEN = 'HALF_OPEN' // 半開狀態（測試恢復） } export interface CircuitBreakerOptions { /** 失敗閾值 */ failureThreshold: number; /** 恢復超時時間 (ms) */ recoveryTimeout: number; /** 監控時間窗口 (ms) */ monitoringPeriod: number; /** 預期錯誤檢查函數 */ isExpectedError?: (error: Error) => boolean; } export interface CircuitBreakerStats { state: CircuitState; failureCount: number; successCount: number; nextAttempt: number; totalRequests: number; } /** * Circuit Breaker 實作 */ export class CircuitBreaker { private state: CircuitState = CircuitState.CLOSED; private failureCount: number = 0; private successCount: number = 0; private nextAttempt: number = 0; private totalRequests: number = 0; private lastFailureTime: number = 0; constructor(private readonly options: CircuitBreakerOptions) { if (options.failureThreshold <= 0) { throw new Error('failureThreshold must be greater than 0'); } if (options.recoveryTimeout <= 0) { throw new Error('recoveryTimeout must be greater than 0'); } } /** * 執行受保護的函數 */ async execute<T>(fn: () => Promise<T>): Promise<T> { return new Promise<T>((resolve, reject) => { this.totalRequests++; if (this.state === CircuitState.OPEN) { if (this.shouldAttemptReset()) { this.state = CircuitState.HALF_OPEN; } else { return reject(new CircuitBreakerError('Circuit breaker is OPEN', this.getStats())); } } fn() .then((result) => { this.onSuccess(); resolve(result); }) .catch((error) => { this.onFailure(error); reject(error); }); }); } /** * 成功回調 */ private onSuccess(): void { this.successCount++; if (this.state === CircuitState.HALF_OPEN) { this.reset(); } } /** * 失敗回調 */ private onFailure(error: Error): void { // 檢查是否為預期錯誤（不計入失敗） if (this.options.isExpectedError && this.options.isExpectedError(error)) { return; } this.failureCount++; this.lastFailureTime = Date.now(); if (this.state === CircuitState.HALF_OPEN) { this.state = CircuitState.OPEN; this.nextAttempt = Date.now() + this.options.recoveryTimeout; } else if (this.failureCount >= this.options.failureThreshold) { this.state = CircuitState.OPEN; this.nextAttempt = Date.now() + this.options.recoveryTimeout; } } /** * 重置 Circuit Breaker */ private reset(): void { this.state = CircuitState.CLOSED; this.failureCount = 0; this.nextAttempt = 0; } /** * 檢查是否應該嘗試重置 */ private shouldAttemptReset(): boolean { return Date.now() >= this.nextAttempt; } /** * 獲取統計資訊 */ getStats(): CircuitBreakerStats { return { state: this.state, failureCount: this.failureCount, successCount: this.successCount, nextAttempt: this.nextAttempt, totalRequests: this.totalRequests, }; } /** * 手動重置 */ forceReset(): void { this.reset(); } /** * 手動開啟 */ forceOpen(): void { this.state = CircuitState.OPEN; this.nextAttempt = Date.now() + this.options.recoveryTimeout; } } /** * Circuit Breaker 錯誤 */ export class CircuitBreakerError extends Error { constructor( message: string, public readonly stats: CircuitBreakerStats ) { super(message); this.name = 'CircuitBreakerError'; } }