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* Middleware Chain - 中间件链实现
*
* 设计模式：Middleware 链模式
* 来源：2026-04-09 13:00 小时学习（DeerFlow 架构）
*/
/**
* 日志中间件
*/
class LoggingMiddleware {
constructor(options = {}) {
this.logLevel = options.logLevel || 'info';
this.logger = options.logger || console;
}
async handle(event) {
const logEntry = {
timestamp: new Date(event.timestamp).toISOString(),
eventId: event.id,
eventName: event.name,
correlationId: event.metadata.correlationId
};
switch (this.logLevel) {
case 'debug':
this.logger.debug('[EVENT]', JSON.stringify(logEntry), 'Payload:', event.payload);
break;
case 'info':
this.logger.info('[EVENT]', event.name, '→', event.id);
break;
case 'warn':
case 'error':
// 只记录警告和错误
break;
}
return true; // 继续处理
}
}
/**
* 验证中间件
*/
class ValidationMiddleware {
constructor(validatorFn) {
this.validatorFn = validatorFn;
}
async handle(event) {
try {
const isValid = await this.validatorFn(event);
if (!isValid) {
return false; // 阻止事件处理
}
return true;
} catch (error) {
console.error('Validation error:', error.message);
return false;
}
}
}
/**
* 重试中间件
*/
class RetryMiddleware {
constructor(options = {}) {
this.maxRetries = options.maxRetries || 3;
this.retryDelay = options.retryDelay || 1000;
}
async handle(event) {
const { retryCount } = event.metadata;
if (retryCount >= this.maxRetries) {
console.warn(`Event ${event.name} exceeded max retries (${this.maxRetries})`);
return false;
}
return true;
}
async retry(event, handler) {
let lastError;
for (let i = 0; i < this.maxRetries; i++) {
try {
return await handler(event);
} catch (error) {
lastError = error;
console.warn(`Retry ${i + 1}/${this.maxRetries} for event ${event.name}`);
await this._delay(this.retryDelay * (i + 1)); // 指数退避
}
}
throw lastError;
}
_delay(ms) {
return new Promise(resolve => setTimeout(resolve, ms));
}
}
/**
* 速率限制中间件
*/
class RateLimitMiddleware {
constructor(options = {}) {
this.maxEvents = options.maxEvents || 100;
this.windowMs = options.windowMs || 60000; // 1 分钟
this.eventCounts = new Map();
}
async handle(event) {
const now = Date.now();
const windowStart = now - this.windowMs;
// 清理过期计数
for (const [key, timestamps] of this.eventCounts.entries()) {
const validTimestamps = timestamps.filter(t => t > windowStart);
Iif (validTimestamps.length === 0) {
this.eventCounts.delete(key);
} else {
this.eventCounts.set(key, validTimestamps);
}
}
// 检查速率限制
const currentCount = (this.eventCounts.get(event.name) || []).length;
if (currentCount >= this.maxEvents) {
console.warn(`Rate limit exceeded for event ${event.name}`);
return false;
}
// 记录事件
if (!this.eventCounts.has(event.name)) {
this.eventCounts.set(event.name, []);
}
this.eventCounts.get(event.name).push(now);
return true;
}
}
/**
* 中间件链执行器
*/
class MiddlewareChainExecutor {
constructor() {
this.middlewares = [];
}
use(middleware) {
this.middlewares.push(middleware);
}
async execute(event) {
for (const middleware of this.middlewares) {
try {
const result = typeof middleware.handle === 'function'
? await middleware.handle(event)
: await middleware(event);
if (result === false) {
return { stopped: true, at: middleware.constructor.name };
}
} catch (error) {
console.error(`Middleware ${middleware.constructor.name} error:`, error.message);
// 继续执行下一个中间件
}
}
return { stopped: false };
}
}
module.exports = {
LoggingMiddleware,
ValidationMiddleware,
RetryMiddleware,
RateLimitMiddleware,
MiddlewareChainExecutor
};
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