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

apps/api/src/lib/telemetry.ts

@@ -0,0 +1,62 @@
+import { Registry, Counter, Histogram, Gauge, collectDefaultMetrics } from 'prom-client';
+
+const registry = new Registry();
+
+// Collect default Node.js metrics (CPU, memory, event loop, etc.)
+collectDefaultMetrics({ register: registry });
+
+// ── HTTP Metrics ────────────────────────────────────────
+
+export const httpRequestCounter = new Counter({
+  name: 'zeavis_api_http_requests_total',
+  help: 'Total number of HTTP requests handled by the API',
+  labelNames: ['method', 'path', 'status'] as const,
+  registers: [registry],
+});
+
+export const httpRequestDuration = new Histogram({
+  name: 'zeavis_api_http_request_duration_seconds',
+  help: 'Histogram of HTTP request durations in seconds',
+  labelNames: ['method', 'path'] as const,
+  buckets: [0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5],
+  registers: [registry],
+});
+
+export const httpRequestsActive = new Gauge({
+  name: 'zeavis_api_http_requests_active',
+  help: 'Number of HTTP requests currently being processed',
+  registers: [registry],
+});
+
+// ── Business Metrics ────────────────────────────────────
+
+export const classificationCounter = new Counter({
+  name: 'zeavis_api_classifications_total',
+  help: 'Total number of classification predictions requested via API',
+  labelNames: ['result'] as const,
+  registers: [registry],
+});
+
+export const diagnosisCounter = new Counter({
+  name: 'zeavis_api_diagnoses_total',
+  help: 'Total number of diagnoses created',
+  labelNames: ['disease'] as const,
+  registers: [registry],
+});
+
+export const authCounter = new Counter({
+  name: 'zeavis_api_auth_operations_total',
+  help: 'Total authentication operations (login, register, refresh)',
+  labelNames: ['operation', 'success'] as const,
+  registers: [registry],
+});
+
+// ── Export ──────────────────────────────────────────────
+
+export function getMetricsContentType(): string {
+  return registry.contentType;
+}
+
+export async function getMetrics(): Promise<string> {
+  return await registry.metrics();
+}