maaz519
0f923303d3
Task O.1: AsyncLocalStorage trace context (currentTraceId/runWithTrace/toTraceparent) read by singleton services with no DI churn; Express traceMiddleware derives a trace id per request (x-trace-id → traceparent → generated), echoes x-trace-id on the response, runs the request in-context, and logs a structured http.request line on finish. Minimal JSON structured logger stamps traceId on every line. Wired via app.use in main.ts. 4 tests: scope, concurrency isolation, traceparent shape/parse. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
44 lines
1.6 KiB
TypeScript
44 lines
1.6 KiB
TypeScript
import { AsyncLocalStorage } from 'node:async_hooks';
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import { randomBytes, randomUUID } from 'node:crypto';
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/**
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* Request-scoped trace context (P9 observability). A module-level AsyncLocalStorage
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* so singleton services can read the current request's trace id via `currentTraceId()`
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* WITHOUT threading it through every method or constructor. The middleware runs each
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* request inside `runWithTrace(...)`; async projectors run outside a request and
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* simply see `undefined` (their events already carry the trace from the emitting call).
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*/
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export interface TraceStore {
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traceId: string;
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correlationId?: string;
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}
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const als = new AsyncLocalStorage<TraceStore>();
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export function runWithTrace<T>(traceId: string, fn: () => T): T {
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return als.run({ traceId }, fn);
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}
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export function currentTraceId(): string | undefined {
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return als.getStore()?.traceId;
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}
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/** A fresh trace id (used when no inbound trace context is present). */
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export function newTraceId(): string {
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return randomUUID();
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}
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/** W3C traceparent for a trace id: 00-<32 hex>-<16 hex span>-01. */
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export function toTraceparent(traceId: string): string {
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const trace = traceId.replace(/-/g, '').padEnd(32, '0').slice(0, 32);
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const span = randomBytes(8).toString('hex');
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return `00-${trace}-${span}-01`;
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}
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/** Extract a trace id from an inbound traceparent header (the 2nd field), else undefined. */
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export function traceIdFromTraceparent(traceparent?: string): string | undefined {
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if (!traceparent) return undefined;
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const parts = traceparent.split('-');
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return parts.length >= 3 && /^[0-9a-f]{32}$/i.test(parts[1]) ? parts[1] : undefined;
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}
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