Merge pull request #29811 from eddiehale3/otel-doc-example-update

updated OTEL example referenced in #29282

docs/tutorials/setup-opentelemetry.md

@@ -28,25 +28,25 @@ In your `packages/backend/src` folder, create an `instrumentation.js` file.
 
 ```typescript title="in packages/backend/src/instrumentation.js"
 // Prevent from running more than once (due to worker threads)
-if (!require('node:worker_threads').isMainThread) {
-  return;
+const { isMainThread } = require('node:worker_threads');
+
+if (isMainThread) {
+  const { NodeSDK } = require('@opentelemetry/sdk-node');
+  const {
+    getNodeAutoInstrumentations,
+  } = require('@opentelemetry/auto-instrumentations-node');
+  const { PrometheusExporter } = require('@opentelemetry/exporter-prometheus');
+
+  // By default exports the metrics on localhost:9464/metrics
+  const prometheus = new PrometheusExporter();
+  const sdk = new NodeSDK({
+    // You can add a traceExporter field here too
+    metricReader: prometheus,
+    instrumentations: [getNodeAutoInstrumentations()],
+  });
+
+  sdk.start();
 }
-
-const { NodeSDK } = require('@opentelemetry/sdk-node');
-const {
-  getNodeAutoInstrumentations,
-} = require('@opentelemetry/auto-instrumentations-node');
-const { PrometheusExporter } = require('@opentelemetry/exporter-prometheus');
-
-// By default exports the metrics on localhost:9464/metrics
-const prometheus = new PrometheusExporter();
-const sdk = new NodeSDK({
-  // You can add a traceExporter field here too
-  metricReader: prometheus,
-  instrumentations: [getNodeAutoInstrumentations()],
-});
-
-sdk.start();
 ```
 
 You probably won't need all of the instrumentation inside `getNodeAutoInstrumentations()` so make sure to