Ensure instrumentation register only call once (#67805)

### What

Ensure instrumentation.js register only called once

### Why

In #67539 we accidentally make it call twice in both next-dev-ser and
next-server. Adding a condition to ensure the one in next-server is only
called in production runtime.

packages/next/src/server/dev/next-dev-server.ts

@@ -290,9 +290,6 @@ export default class DevServer extends Server {
     const telemetry = new Telemetry({ distDir: this.distDir })
 
     await super.prepareImpl()
-    await this.startServerSpan
-      .traceChild('run-instrumentation-hook')
-      .traceAsyncFn(() => this.runInstrumentationHookIfAvailable())
     await this.matchers.reload()
 
     // Store globals again to preserve changes made by the instrumentation hook.
@@ -623,10 +620,10 @@ export default class DevServer extends Server {
     return instrumentationModule
   }
 
-  private async runInstrumentationHookIfAvailable() {
-    if (this.instrumentation) {
-      await this.instrumentation.register?.()
-    }
+  protected async runInstrumentationHookIfAvailable() {
+    await this.startServerSpan
+      .traceChild('run-instrumentation-hook')
+      .traceAsyncFn(() => this.instrumentation?.register?.())
   }
 
   protected async ensureEdgeFunction({

packages/next/src/server/next-server.ts

@@ -309,7 +309,7 @@ export default class NextNodeServer extends BaseServer<
   protected async loadInstrumentationModule() {
     if (
       !this.serverOptions.dev &&
-      this.nextConfig.experimental.instrumentationHook
+      !!this.nextConfig.experimental.instrumentationHook
     ) {
       try {
         this.instrumentation = await dynamicRequire(
@@ -332,10 +332,11 @@ export default class NextNodeServer extends BaseServer<
 
   protected async prepareImpl() {
     await super.prepareImpl()
+    await this.runInstrumentationHookIfAvailable()
+  }
 
-    if (this.instrumentation) {
-      await this.instrumentation.register?.()
-    }
+  protected async runInstrumentationHookIfAvailable() {
+    await this.instrumentation?.register?.()
   }
 
   protected loadEnvConfig({

test/e2e/instrumentation-hook/register-once/instrumentation.js

@@ -0,0 +1,5 @@
+export function register() {
+  if (process.env.NEXT_RUNTIME === 'nodejs') {
+    console.log('register-log')
+  }
+}

test/e2e/instrumentation-hook/register-once/next.config.js

@@ -0,0 +1,5 @@
+module.exports = {
+  experimental: {
+    instrumentationHook: true,
+  },
+}

test/e2e/instrumentation-hook/register-once/pages/foo.js

@@ -0,0 +1,3 @@
+export default function Page() {
+  return 'foo'
+}

test/e2e/instrumentation-hook/register-once/register-once.test.ts

@@ -0,0 +1,17 @@
+import { nextTestSetup } from 'e2e-utils'
+
+describe('instrumentation-hook - register-once', () => {
+  const { next, skipped } = nextTestSetup({
+    files: __dirname,
+    skipDeployment: true,
+  })
+
+  if (skipped) {
+    return
+  }
+
+  it('should only register once', async () => {
+    await next.fetch('/foo')
+    expect(next.cliOutput).toIncludeRepeated('register-log', 1)
+  })
+})