构建带重试的 Webhook 投递

项目概述

本项目实现一个面向 webhook delivery 的完整系统，核心要解决的问题是 delivering webhooks with exponential backoff and a dead letter sink so a failing endpoint does not block the queue。整体由 Delivery queue、Backoff scheduler、Attempt runner、Result classifier、Dead letter store 五个模块组成，每个模块单一职责、可独立测试，最后通过集成测试验证端到端正确性。设计上把 an endpoint that returns 200 to a malformed payload and silently swallows webhooks that never take effect 作为第一类需求先行处理，而非事后再补。

架构与关键决策

数据模型为 a queue of deliveries each with an attempt count and a next-try time, moved to a dead letter store after exhausting retries。Delivery queue 定义其余阶段共同依赖的数据形状并在边界处校验输入；Backoff scheduler 承载 webhook delivery 的正确性逻辑；Attempt runner 专门处理 an endpoint that returns 200 to a malformed payload and silently swallows webhooks that never take effect，在失败路径上给出明确的拒绝、重试或降级策略；Result classifier 提供可观测性，每次操作输出带关联 id 的结构化事件；Dead letter store 在过载时按既定方式降级，避免过载演变为数据损坏。配置与代码分离，使风险变更可经 diff 审阅。

实施与测试

按五个阶段依次实现 Delivery queue、Backoff scheduler、Attempt runner、Result classifier、Dead letter store，每阶段配套聚焦单测。集成测试组合各模块并驱动真实 webhook delivery 场景：先验证正常路径，再刻意触发 an endpoint that returns 200 to a malformed payload and silently swallows webhooks that never take effect 并断言系统降级而非损坏。所有依赖均在进程内或被桩替换，用例在 CI 中确定可复现。

限制与后续

• 单区域设计，多区域复制超出范围。
• Delivery queue 默认进程内，未水平共享。
• 无鉴权层，假定部署在强制身份的边缘之后。

代码示例

# setup for webhook-delivery-retry
pnpm init
pnpm add fastify undici redis
pnpm add -D typescript tsx vitest

webhook_delivery_retry/
├── src/index.ts
├── src/delivery-queue.ts
├── src/backoff-scheduler.ts
├── tests/webhook_delivery_retry.test.ts
└── package.json

// Delivery queue: webhook delivery core
export function deliveryqueue(input: DeliveryqueueInput): DeliveryqueueResult {
  // Build the delivery queue that anchors webhook delivery and defines the core data shape.
  return processDeliveryqueue(input);
}

// Backoff scheduler — handles webhook delivery Add the backoff scheduler so
export class Backoffscheduler {
  constructor(private opts: BackoffschedulerOptions) {}
  async run(ctx: Context): Promise<BackoffschedulerOutput> {
    return this.execute(ctx);
  }
}

// Attempt runner: webhook delivery stage
export const attemptrunner = (next: Next) => async (req: Request) => {
  const out = await transform(req);
  return next(out);
};

// Result classifier for webhook delivery
export async function resultclassifier(stream: AsyncIterable<Chunk>): Promise<Aggregate> {
  let acc = init();
  for await (const c of stream) acc = merge(acc, c);
  return acc;
}

// Dead letter store: webhook delivery finalization
export function deadletterstore(state: State): Result {
  validate(state);
  return finalize(state);
}

# run the webhook delivery test suite
pnpm vitest run