构建服务发现注册中心

项目概述

本项目实现一个面向 service discovery 的完整系统，核心要解决的问题是 maintaining a live directory of service instances that register, heartbeat, and deregister。整体由 Instance registry、Heartbeat tracker、TTL evictor、Watch notifier、Query endpoint 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 a network partition that splits registrations across a majority and minority that both serve stale instance lists 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 map of service names to instance lists, each instance evicted when its heartbeat TTL expires without renewal。Instance registry 定义其余阶段共同依赖的数据形状并在边界处校验输入；Heartbeat tracker 承载 service discovery 的正确性逻辑；TTL evictor 专门处理 a network partition that splits registrations across a majority and minority that both serve stale instance lists，在失败路径上给出明确的拒绝、重试或降级策略；Watch notifier 提供可观测性，每次操作输出带关联 id 的结构化事件；Query endpoint 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 Instance registry、Heartbeat tracker、TTL evictor、Watch notifier、Query endpoint，每阶段配套聚焦单测。集成测试组合各模块并驱动真实 service discovery 场景：先验证正常路径，再刻意触发 a network partition that splits registrations across a majority and minority that both serve stale instance lists 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。
• Instance registry 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 service-discovery-registry
pnpm init
pnpm add fastify redis
pnpm add -D typescript tsx vitest

service_discovery_registry/
├── src/index.ts
├── src/instance-registry.ts
├── src/heartbeat-tracker.ts
├── tests/service_discovery_registry.test.ts
└── package.json

// Instance registry: service discovery core
export function instanceregistry(input: InstanceregistryInput): InstanceregistryResult {
  // Build the instance registry that anchors service discovery and defines the core data shape.
  return processInstanceregistry(input);
}

// Heartbeat tracker — handles service discovery Add the heartbeat tracker so
export class Heartbeattracker {
  constructor(private opts: HeartbeattrackerOptions) {}
  async run(ctx: Context): Promise<HeartbeattrackerOutput> {
    return this.execute(ctx);
  }
}

// TTL evictor: service discovery stage
export const ttlevictor = (next: Next) => async (req: Request) => {
  const out = await transform(req);
  return next(out);
};

// Watch notifier for service discovery
export async function watchnotifier(stream: AsyncIterable<Chunk>): Promise<Aggregate> {
  let acc = init();
  for await (const c of stream) acc = merge(acc, c);
  return acc;
}

// Query endpoint: service discovery finalization
export function queryendpoint(state: State): Result {
  validate(state);
  return finalize(state);
}

# run the service discovery test suite
pnpm vitest run