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* 熔断器 - 供应商级别的故障隔离
*
* 状态机: CLOSED → (N次连续失败) → OPEN → (冷却期过后) → HALF_OPEN → (成功) → CLOSED
*
* 使用方式:
* const breaker = new CircuitBreaker({ name: 'minimax', failureThreshold: 3, cooldownMs: 30000 });
* try {
* await breaker.call(async () => { ... });
* } catch (e) {
* // 熔断开启或调用失败
* }
*/
export type CircuitState = 'CLOSED' | 'OPEN' | 'HALF_OPEN';
export interface CircuitBreakerConfig {
name: string;
failureThreshold?: number; // 连续失败多少次后熔断，默认 3
cooldownMs?: number; // 熔断冷却时间，默认 30000ms
successThreshold?: number; // HALF_OPEN 状态下需要连续成功多少次才恢复，默认 2
}
export class CircuitBreaker {
readonly name: string;
private failureThreshold: number;
private cooldownMs: number;
private successThreshold: number;
private state: CircuitState = 'CLOSED';
private failureCount = 0;
private successCount = 0;
private openedAt = 0;
constructor(config: CircuitBreakerConfig) {
this.name = config.name;
this.failureThreshold = config.failureThreshold ?? 3;
this.cooldownMs = config.cooldownMs ?? 30000;
this.successThreshold = config.successThreshold ?? 2;
}
getState(): CircuitState {
// 如果 OPEN 且冷却期已过，自动进入 HALF_OPEN
if (this.state === 'OPEN' && Date.now() - this.openedAt >= this.cooldownMs) {
this.state = 'HALF_OPEN';
this.failureCount = 0;
this.successCount = 0;
console.log(`[熔断器] ${this.name}: OPEN → HALF_OPEN（冷却期已过）`);
}
return this.state;
}
isOpen(): boolean {
return this.getState() === 'OPEN';
}
/**
* 执行受保护的操作
* 返回操作成功的结果，抛出 CircuitBreakerOpenError 或原始错误
*/
async call<T>(fn: () => Promise<T>): Promise<T> {
const currentState = this.getState();
if (currentState === 'OPEN') {
const remainingMs = this.cooldownMs - (Date.now() - this.openedAt);
throw new CircuitBreakerOpenError(this.name, remainingMs);
}
try {
const result = await fn();
this.onSuccess();
return result;
} catch (error) {
this.onFailure();
throw error;
}
}
private onSuccess(): void {
if (this.state === 'HALF_OPEN') {
this.successCount++;
if (this.successCount >= this.successThreshold) {
this.state = 'CLOSED';
this.failureCount = 0;
this.successCount = 0;
console.log(`[熔断器] ${this.name}: HALF_OPEN → CLOSED（恢复）`);
}
} else {
// CLOSED 状态，重置失败计数
this.failureCount = 0;
}
}
private onFailure(): void {
this.failureCount++;
this.successCount = 0;
if (this.state === 'HALF_OPEN' || (this.state === 'CLOSED' && this.failureCount >= this.failureThreshold)) {
this.state = 'OPEN';
this.openedAt = Date.now();
console.log(`[熔断器] ${this.name}: → OPEN（连续失败 ${this.failureCount} 次，冷却 ${this.cooldownMs}ms）`);
}
}
/** 手动重置 */
reset(): void {
this.state = 'CLOSED';
this.failureCount = 0;
this.successCount = 0;
this.openedAt = 0;
}
}
export class CircuitBreakerOpenError extends Error {
public readonly breakerName: string;
public readonly remainingMs: number;
constructor(name: string, remainingMs: number) {
super(`[${name}] 熔断器已开启，剩余冷却时间 ${Math.ceil(remainingMs / 1000)}s`);
this.name = 'CircuitBreakerOpenError';
this.breakerName = name;
this.remainingMs = remainingMs;
}
}
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