test(node-integration-tests): Wait for kafkajs GROUP_JOIN before producing

Fixes #21044

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: 2 people

dev-packages/node-integration-tests/suites/tracing/kafkajs/scenario.mjs

@@ -23,15 +23,23 @@ async function run() {
   await consumer.connect();
   await consumer.subscribe({ topic: 'test-topic', fromBeginning: true });
 
-  consumer.run({
+  // Resolve once the consumer has actually joined its group. A fixed sleep
+  // here was racy on slow CI runners: if the producer sent before the
+  // consumer joined, the consumer transaction sometimes wasn't created
+  // within the test timeout. Register the listener before `run()` so the
+  // event can't fire before we're listening.
+  const groupJoined = new Promise(resolve => {
+    consumer.on(consumer.events.GROUP_JOIN, () => resolve());
+  });
+
+  await consumer.run({
     eachMessage: async ({ message }) => {
       // eslint-disable-next-line no-console
       console.debug('Received message', message.value.toString());
     },
   });
 
-  // Wait for the consumer to be ready
-  await new Promise(resolve => setTimeout(resolve, 4000));
+  await groupJoined;
 
   await producer.send({
     topic: 'test-topic',