auto-instrument OpenTelemetry in the GB Proxy app (#68)

README.md

@@ -35,6 +35,9 @@ The GrowthBook Proxy repository is a mono-repo containing the following packages
 
 ### What's new
 
+**Version 1.1.8**
+- Auto-instrument OpenTelemetry when using `yarn start:with-tracing`
+
 **Version 1.1.4**
 - Support Redis-based sticky bucketing for remote evaluation
 - Update remote evaluation to allow for buffered sticky bucket writes
@@ -110,7 +113,7 @@ The GrowthBook Proxy supports a number of configuration options available via en
 
 ### Caching
 
-By default, features are cached in memory in GrowthBook Proxy; you may provide your own cache service via Redis or Mongo. To fully utilize the GrowthBook Proxy, we highly recommend using Redis, which is a prerequisite for real-time updates when your proxy is horizontally scaled (as proxy instances are kept in-sync using Redis pub/sub).
+By default, features are cached in memory in the GrowthBook Proxy; you may provide your own cache service via Redis or Mongo. To fully utilize the GrowthBook Proxy, we highly recommend using Redis, which is a prerequisite for real-time updates when your proxy is horizontally scaled (as proxy instances are kept in-sync using Redis pub/sub).
 
 - `CACHE_ENGINE` - One of: `memory`, `redis`, or `mongo` (default: `memory`)
 - `CACHE_CONNECTION_URL` - The URL of your Redis or Mongo Database
@@ -149,6 +152,14 @@ Although we recommend terminating SSL using your load balancer, you can also con
 
 If the GrowthBook app your proxy is connecting to is using a self-signed certificate, you can disable certificate verification by setting `NODE_TLS_REJECT_UNAUTHORIZED` to "0".
 
+### Observability (OpenTelemetry)
+
+The GrowthBook Proxy is instrumented with OpenTelemetry to publish observability metrics, traces, and logs.
+
+To enable, you must change the Docker CMD from the default `yarn start` to `yarn start:with-tracing`.
+
+The standard [OTEL\_\* Environment Variables](https://opentelemetry.io/docs/concepts/sdk-configuration/) are supported, such as `OTEL_SERVICE_NAME` and `OTEL_EXPORTER_OTLP_ENDPOINT`.
+
 ### Other common configuration options
 
 **Streaming**

package.json

@@ -18,6 +18,7 @@
     "build:proxy": "yarn build:deps:proxy && wsrun -p @growthbook/proxy -c build",
     "type-check": "wsrun -r type-check",
     "start": "wsrun -p @growthbook/proxy -c start",
+    "start:with-tracing": "wsrun -p @growthbook/proxy -c start:with-tracing",
     "dev": "wsrun -r dev",
     "dev:proxy": "wsrun -p @growthbook/proxy @growthbook/proxy-eval -c dev",
     "dev:edge": "wsrun -p @growthbook/edge-utils @growthbook/edge-express -c dev"

packages/apps/proxy/package.json

@@ -4,7 +4,7 @@
     "node": ">=18"
   },
   "description": "GrowthBook proxy server for caching, realtime updates, telemetry, etc",
-  "version": "1.1.6",
+  "version": "1.1.8",
   "main": "dist/app.js",
   "license": "MIT",
   "repository": {
@@ -19,6 +19,7 @@
     "build": "yarn build:clean && yarn build:typescript",
     "type-check": "tsc --pretty --noEmit",
     "start": "node dist/index.js",
+    "start:with-tracing": "node --require ./dist/tracing.js dist/index.js",
     "dev": "concurrently 'tsc --watch' 'nodemon -q dist/index.js | yarn pino-pretty'"
   },
   "dependencies": {
@@ -32,7 +33,11 @@
     "spdy": "^4.0.2",
     "uuid": "^9.0.0",
     "@growthbook/growthbook": "^1.1.0",
-    "@growthbook/proxy-eval": "^1.0.3"
+    "@growthbook/proxy-eval": "^1.0.3",
+    "@opentelemetry/api": "^1.9.0",
+    "@opentelemetry/auto-instrumentations-node": "^0.48.0",
+    "@opentelemetry/exporter-metrics-otlp-proto": "^0.52.1",
+    "@opentelemetry/sdk-metrics": "^1.25.1"
   },
   "devDependencies": {
     "@types/cors": "^2.8.14",

packages/apps/proxy/src/tracing.ts

@@ -0,0 +1,56 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import * as opentelemetry from "@opentelemetry/sdk-node";
+import { diag, DiagConsoleLogger } from "@opentelemetry/api";
+import {
+  getNodeAutoInstrumentations,
+  getResourceDetectors,
+} from "@opentelemetry/auto-instrumentations-node";
+import { OTLPMetricExporter } from "@opentelemetry/exporter-metrics-otlp-proto";
+import { PeriodicExportingMetricReader } from "@opentelemetry/sdk-metrics";
+
+diag.setLogger(
+  new DiagConsoleLogger(),
+  opentelemetry.core.getEnv().OTEL_LOG_LEVEL,
+);
+
+const metricReader = new PeriodicExportingMetricReader({
+  exporter: new OTLPMetricExporter(),
+  exportIntervalMillis: 10000,
+});
+
+const sdk = new opentelemetry.NodeSDK({
+  instrumentations: getNodeAutoInstrumentations(),
+  resourceDetectors: getResourceDetectors(),
+  metricReader,
+});
+
+try {
+  sdk.start();
+  diag.info("OpenTelemetry automatic instrumentation started successfully");
+} catch (error) {
+  diag.error(
+    "Error initializing OpenTelemetry SDK. Your application is not instrumented and will not produce telemetry",
+    error,
+  );
+}
+
+process.on("SIGTERM", () => {
+  sdk
+    .shutdown()
+    .then(() => diag.debug("OpenTelemetry SDK terminated"))
+    .catch((error) => diag.error("Error terminating OpenTelemetry SDK", error));
+});