feat(api): add prometheus exporter

Signed-off-by: iverly <github@iverly.net>

apps/api/Dockerfile

@@ -65,8 +65,8 @@ COPY --from=deps /usr/src/app/node_modules ./node_modules
 COPY --from=build /usr/src/app/node_modules/.pnpm/@prisma+client@5.6.0_prisma@5.6.0 ./node_modules/.pnpm/@prisma+client@5.6.0_prisma@5.6.0
 COPY --from=build /usr/src/app/dist ./dist
 
-# Expose the port that the application listens on.
-EXPOSE 3100
+# Expose the ports that the application listens on.
+EXPOSE 3100 9100
 
 # Run the application.
 CMD ["node", "dist/apps/api/main.js"]

package.json

@@ -32,6 +32,7 @@
     "@opentelemetry/context-async-hooks": "^1.18.1",
     "@opentelemetry/core": "^1.18.1",
     "@opentelemetry/exporter-jaeger": "^1.18.1",
+    "@opentelemetry/exporter-prometheus": "^0.45.1",
     "@opentelemetry/instrumentation-fastify": "^0.32.4",
     "@opentelemetry/instrumentation-http": "^0.45.1",
     "@opentelemetry/instrumentation-nestjs-core": "^0.33.3",

packages/opentelemetry/src/lib/opentelemetry.module.ts

@@ -39,7 +39,16 @@ export class OpenTelemetryModule {
             },
           },
         }),
-        NestOpenTelemetryModule.forRoot(),
+        NestOpenTelemetryModule.forRoot({
+          metrics: {
+            hostMetrics: true,
+            apiMetrics: {
+              enable: true,
+              ignoreRoutes: ['/favicon.ico'],
+              ignoreUndefinedRoutes: true,
+            },
+          },
+        }),
       ],
       exports: [NestOpenTelemetryModule, LoggerModule],
     };

packages/opentelemetry/src/lib/tracing.ts

@@ -14,10 +14,14 @@ import { JaegerExporter } from '@opentelemetry/exporter-jaeger';
 import { FastifyInstrumentation } from '@opentelemetry/instrumentation-fastify';
 import { PrismaInstrumentation } from '@prisma/instrumentation';
 import { PinoInstrumentation } from '@opentelemetry/instrumentation-pino';
+import { PrometheusExporter } from '@opentelemetry/exporter-prometheus';
 
 export const otelEnabled = process.env['OTEL_ENABLED'] === 'true';
 
 export const otelSDK = new NodeSDK({
+  metricReader: new PrometheusExporter({
+    port: 9100,
+  }),
   spanProcessor: new BatchSpanProcessor(new JaegerExporter()),
   contextManager: new AsyncLocalStorageContextManager(),
   textMapPropagator: new CompositePropagator({