feat(observability): Replace Prometheus package with OpenTelemetry

src/open-telemetry/sdk.ts

@@ -0,0 +1,48 @@
+import { AsyncLocalStorageContextManager } from "@opentelemetry/context-async-hooks";
+import { PrometheusExporter } from "@opentelemetry/exporter-prometheus";
+import { OTLPTraceExporter } from "@opentelemetry/exporter-trace-otlp-http";
+import { DnsInstrumentation } from "@opentelemetry/instrumentation-dns";
+import { ExpressInstrumentation } from "@opentelemetry/instrumentation-express";
+import { HttpInstrumentation } from "@opentelemetry/instrumentation-http";
+import { NestInstrumentation } from "@opentelemetry/instrumentation-nestjs-core";
+import { PgInstrumentation } from "@opentelemetry/instrumentation-pg";
+import { PinoInstrumentation } from "@opentelemetry/instrumentation-pino";
+import { Resource } from "@opentelemetry/resources";
+import { NodeSDK, NodeSDKConfiguration } from "@opentelemetry/sdk-node";
+import { SemanticResourceAttributes } from "@opentelemetry/semantic-conventions";
+import { hostname } from "os";
+
+const metricsEnabled = process.env.OTEL_METRICS_ENABLED === "true";
+const tracesEnabled = process.env.OTEL_TRACES_ENABLED === "true";
+const anyEnabled = metricsEnabled || tracesEnabled;
+
+// We can not use ConfigService because the SDK needs to be initialized before
+// Nest is allowed to start.
+let sdkOptions: Partial<NodeSDKConfiguration> = {};
+
+if (metricsEnabled) {
+  sdkOptions.metricExporter = new PrometheusExporter();
+}
+
+if (tracesEnabled) {
+  sdkOptions.traceExporter = new OTLPTraceExporter({});
+  sdkOptions.contextManager = new AsyncLocalStorageContextManager();
+  sdkOptions.resource = new Resource({
+    [SemanticResourceAttributes.SERVICE_NAMESPACE]: "listory",
+    [SemanticResourceAttributes.SERVICE_NAME]: "api",
+    [SemanticResourceAttributes.SERVICE_INSTANCE_ID]: hostname(),
+  });
+}
+
+if (anyEnabled) {
+  sdkOptions.instrumentations = [
+    new DnsInstrumentation(),
+    new HttpInstrumentation(),
+    new ExpressInstrumentation(),
+    new NestInstrumentation(),
+    new PgInstrumentation(),
+    new PinoInstrumentation(),
+  ];
+}
+
+export const otelSDK = new NodeSDK(sdkOptions);