feat(api): add Prometheus metrics and OpenTelemetry instrumentation for HTTP, auth, classifications, and diagnoses

apps/api/src/index.ts

@@ -9,6 +9,9 @@ import { diagnosisRoutes } from './routes/diagnoses';
 import { dashboardRoutes } from './routes/dashboard';
 import { authRoutes } from './routes/auth';
 import { expertRoutes } from './routes/expert';
+import { metricsRoutes } from './routes/metrics';
+import { httpRequestCounter, httpRequestDuration, httpRequestsActive } from './lib/telemetry';
+import './types';
 
 assertRequiredEnv();
 
@@ -17,6 +20,24 @@ const app = new Elysia()
     origin: env.webAppUrl,
     credentials: true,
   }))
+  .use(metricsRoutes)
+  .onBeforeHandle(({ request, path }) => {
+    httpRequestsActive.inc();
+    request.metricsStart = performance.now();
+    request.metricsPath = path;
+  })
+  .onAfterHandle(({ request, set }) => {
+    const start = (request as any).metricsStart as number | undefined;
+    const path = (request as any).metricsPath as string | undefined;
+    if (start && path) {
+      const duration = (performance.now() - start) / 1000;
+      const method = request.method;
+      const status = set.status ?? 200;
+      httpRequestCounter.labels(method, path, String(status)).inc();
+      httpRequestDuration.labels(method, path).observe(duration);
+    }
+    httpRequestsActive.dec();
+  })
   .use(healthRoutes)
   .use(statusRoutes)
   .use(authRoutes)