构建告警规则评估器

项目概述

本项目实现一个面向 alert evaluation 的完整系统，核心要解决的问题是 evaluating threshold and ratio rules over metric streams and firing alerts without flapping。整体由 Rule loader、Metric reader、Condition evaluator、Cooldown state、Notification dispatcher 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 rule that flaps around its threshold and fires repeatedly because the cooldown is shorter than the metric jitter 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 set of rules each with a condition over metric queries and a cooldown window that suppresses re-firing。Rule loader 定义其余阶段共同依赖的数据形状并在边界处校验输入；Metric reader 承载 alert evaluation 的正确性逻辑；Condition evaluator 专门处理 a rule that flaps around its threshold and fires repeatedly because the cooldown is shorter than the metric jitter，在失败路径上给出明确的拒绝、重试或降级策略；Cooldown state 提供可观测性，每次操作输出带关联 id 的结构化事件；Notification dispatcher 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 Rule loader、Metric reader、Condition evaluator、Cooldown state、Notification dispatcher，每阶段配套聚焦单测。集成测试组合各模块并驱动真实 alert evaluation 场景：先验证正常路径，再刻意触发 a rule that flaps around its threshold and fires repeatedly because the cooldown is shorter than the metric jitter 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。
• Rule loader 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 alerting-rule-evaluator
pnpm init
pnpm add fastify undici redis
pnpm add -D typescript tsx vitest

alerting_rule_evaluator/
├── src/index.ts
├── src/rule-loader.ts
├── src/metric-reader.ts
├── tests/alerting_rule_evaluator.test.ts
└── package.json

// Rule loader: alert evaluation core
export function ruleloader(input: RuleloaderInput): RuleloaderResult {
  // Build the rule loader that anchors alert evaluation and defines the core data shape.
  return processRuleloader(input);
}

// Metric reader — handles alert evaluation Add the metric reader so
export class Metricreader {
  constructor(private opts: MetricreaderOptions) {}
  async run(ctx: Context): Promise<MetricreaderOutput> {
    return this.execute(ctx);
  }
}

// Condition evaluator: alert evaluation stage
export const conditionevaluator = (next: Next) => async (req: Request) => {
  const out = await transform(req);
  return next(out);
};

// Cooldown state for alert evaluation
export async function cooldownstate(stream: AsyncIterable<Chunk>): Promise<Aggregate> {
  let acc = init();
  for await (const c of stream) acc = merge(acc, c);
  return acc;
}

// Notification dispatcher: alert evaluation finalization
export function notificationdispatcher(state: State): Result {
  validate(state);
  return finalize(state);
}

# run the alert evaluation test suite
pnpm vitest run