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>
28 lines
1.2 KiB
TypeScript
28 lines
1.2 KiB
TypeScript
import type { Request, Response, NextFunction } from 'express';
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import { runWithTrace, newTraceId, traceIdFromTraceparent } from './trace-context';
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import { logJson } from './logger';
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/**
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* Express middleware (P9 observability). Derives a trace id per request (inbound
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* x-trace-id → traceparent → generated), echoes it as `x-trace-id` on the response,
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* runs the whole request inside the trace context, and logs a structured line when
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* the response finishes (method, path, status, ms). Wired via app.use() in main.ts.
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*/
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export function traceMiddleware(req: Request, res: Response, next: NextFunction): void {
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const headerTrace = (req.headers['x-trace-id'] as string | undefined)?.trim();
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const traceId = headerTrace || traceIdFromTraceparent(req.headers['traceparent'] as string | undefined) || newTraceId();
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res.setHeader('x-trace-id', traceId);
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const startedAt = Date.now();
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runWithTrace(traceId, () => {
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res.on('finish', () => {
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logJson('info', 'http.request', {
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method: req.method,
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path: (req.originalUrl || req.url || '').split('?')[0],
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status: res.statusCode,
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ms: Date.now() - startedAt,
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});
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});
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next();
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});
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}
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