express-opentracing

import * as express from "express"; import middleware from "express-opentracing"; import * as opentracing from 'opentracing'; // NOTE: In a real application, you'd replace the NoopTracer // with a vendor-specific implementation like Jaeger, LightStep, or Zipkin. // For demonstration, we use a basic console logger (MockTracer). class MockTracer extends opentracing.Tracer { _startSpan(name, options) { console.log(`[MockTracer] Starting span: ${name}`); return new MockSpan(this, name, options.references); } } class MockSpan extends opentracing.Span { _finish() { console.log(`[MockTracer] Finishing span: ${this.operationName()}`); } _context() { return { traceId: 'mock-trace', spanId: 'mock-span' }; } _setOperationName(name) { return this; } _log(fields, timestamp) { console.log(`[MockTracer] Log for ${this.operationName()}:`, fields); return this; } _setTag(key, value) { console.log(`[MockTracer] Tag for ${this.operationName()}: ${key}=${value}`); return this; } } const myTracer = new MockTracer(); opentracing.initGlobalTracer(myTracer); const app = express(); // Apply the express-opentracing middleware app.use(middleware({ tracer: myTracer })); app.get('/', (req, res) => { // The span is available on req.span if the middleware created one if (req.span) { req.span.log({ event: 'homepage_access', userId: 'test-user-123' }); // Simulate some async work setTimeout(() => { res.send('Hello from Express with OpenTracing!'); req.span.setTag(opentracing.Tags.HTTP_STATUS_CODE, 200); }, 100); } else { res.send('Hello from Express (no tracing)'); } }); app.get('/error', (req, res) => { if (req.span) { req.span.setTag(opentracing.Tags.ERROR, true); req.span.setTag(opentracing.Tags.HTTP_STATUS_CODE, 500); req.span.log({ event: 'error_occurred', message: 'Something went wrong' }); } res.status(500).send('An error occurred!'); }); const PORT = process.env.PORT || 3000; app.listen(PORT, () => { console.log(`Server running on http://localhost:${PORT}`); console.log('Try visiting / and /error'); });