构建拉取式指标聚合器

项目概述

本项目实现一个面向 metrics collection 的完整系统，核心要解决的问题是 scraping metrics from many endpoints on a schedule and exposing them for querying without losing samples。整体由 Scrape scheduler、Target manager、Sample parser、Downsampler、Query 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 a target that stalls and blocks the scrape loop, delaying samples for every other target in the same batch 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 time-indexed store of samples keyed by metric name and label set, filled by periodic scrapes of target exposition endpoints。Scrape scheduler 定义其余阶段共同依赖的数据形状并在边界处校验输入；Target manager 承载 metrics collection 的正确性逻辑；Sample parser 专门处理 a target that stalls and blocks the scrape loop, delaying samples for every other target in the same batch，在失败路径上给出明确的拒绝、重试或降级策略；Downsampler 提供可观测性，每次操作输出带关联 id 的结构化事件；Query 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 Scrape scheduler、Target manager、Sample parser、Downsampler、Query store，每阶段配套聚焦单测。集成测试组合各模块并驱动真实 metrics collection 场景：先验证正常路径，再刻意触发 a target that stalls and blocks the scrape loop, delaying samples for every other target in the same batch 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。
• Scrape scheduler 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 metrics-aggregator-pull
pnpm init
pnpm add fastify undici prom-client
pnpm add -D typescript tsx vitest

metrics_aggregator_pull/
├── src/index.ts
├── src/scrape-scheduler.ts
├── src/target-manager.ts
├── tests/metrics_aggregator_pull.test.ts
└── package.json

// Scrape scheduler: metrics collection core
export function scrapescheduler(input: ScrapeschedulerInput): ScrapeschedulerResult {
  // Build the scrape scheduler that anchors metrics collection and defines the core data shape.
  return processScrapescheduler(input);
}

// Target manager — handles metrics collection Add the target manager so
export class Targetmanager {
  constructor(private opts: TargetmanagerOptions) {}
  async run(ctx: Context): Promise<TargetmanagerOutput> {
    return this.execute(ctx);
  }
}

// Sample parser: metrics collection stage
export const sampleparser = (next: Next) => async (req: Request) => {
  const out = await transform(req);
  return next(out);
};

// Downsampler for metrics collection
export async function downsampler(stream: AsyncIterable<Chunk>): Promise<Aggregate> {
  let acc = init();
  for await (const c of stream) acc = merge(acc, c);
  return acc;
}

// Query store: metrics collection finalization
export function querystore(state: State): Result {
  validate(state);
  return finalize(state);
}

# run the metrics collection test suite
pnpm vitest run