New to kafka, trying to get a working system for handling high throughput. Testing on docker windows. It works, but if I use K6 to do a load test, it stops after publishing around 28000 msgs with the following error.

phpApp          | %3|1718821570.096|FAIL|rdkafka#producer-2836| [thrd:kafka:9092/bootstrap]: kafka:9092/bootstrap: Failed to connect to broker at kafka-3.7.kafka-producer-k6_default:9092: Cannot assign requested address (after 6ms in state CONNECT)
phpApp          | %3|1718821570.096|FAIL|rdkafka#producer-2816| [thrd:kafka:9092/bootstrap]: kafka:9092/bootstrap: Failed to connect to broker at kafka-3.7.kafka-producer-k6_default:9092: Cannot assign requested address (after 6ms in state CONNECT, 1 identical error(s) suppressed)

I have tried a few different things from what I could find, but they all lead to the same issue. At present, I have the following in Dockercompose.yml kafka section

kafka:
    image: 'bitnami/kafka:3.7.0'
    container_name: kafka-3.7
    ports:
      - 9092:9092
    environment:
      # KRaft settings. No longer using zookeeper method.
      - KAFKA_CFG_NODE_ID=0
      - KAFKA_KRAFT_CLUSTER_ID=NDllYzhlNzNjMmZmNDEyNT
      - KAFKA_CFG_PROCESS_ROLES=controller,broker
      - KAFKA_CFG_CONTROLLER_QUORUM_VOTERS=0@kafka:9093
      - KAFKA_CFG_ADVERTISED_HOST_NAME=kafka
      - KAFKA_AUTO_CREATE_TOPICS_ENABLE:true
      # Listeners
      - KAFKA_CFG_LISTENERS=PLAINTEXT://:9092,CONTROLLER://:9093
      - KAFKA_CFG_ADVERTISED_LISTENERS=PLAINTEXT://kafka:9092
      - KAFKA_CFG_LISTENER_SECURITY_PROTOCOL_MAP=CONTROLLER:PLAINTEXT,PLAINTEXT:PLAINTEXT
      - KAFKA_CFG_CONTROLLER_LISTENER_NAMES=CONTROLLER
      - KAFKA_CFG_INTER_BROKER_LISTENER_NAME=PLAINTEXT

Producer.php

<?php

    $payload=trim($_POST['payload']);   
    $conf = new RdKafkaConf();
    $conf->set('metadata.broker.list', 'kafka:9092');
    $producer = new RdKafkaProducer($conf);
    $topic="testData";
    $kafkaTopic = $producer->newTopic($topic);
    $kafkaTopic->produce(0, 0, $payload);
    $producer->poll(0);
    for ($flushRetries = 0; $flushRetries < 10; $flushRetries++) {
            $result = $producer->flush(5000);
            if (RD_KAFKA_RESP_ERR_NO_ERROR === $result) {
                break;
            }
    }
?>

For K6, I am generating a string that is some 200 bytes long, with the following setup.

export let options = {
  vus: 30, // 30 virtual users
  duration: '30s', // Run test for 30 seconds
};
export default function () {
  // Generate data
  let fakeData = generateFakeDataStringForKafka();
  
  let res = http.post('http://localhost/producer.php', `payload=${fakeData}`, {
    headers: {
      'Content-Type': 'application/x-www-form-urlencoded',
    },
  });
}

And this keeps running, until hitting around 28000 publishes, after which the kafka error happens.

     data_received..................: 6.0 MB 174 kB/s
     data_sent......................: 11 MB  311 kB/s
     http_req_blocked...............: avg=10.97µs  min=0s      med=0s      max=9.51ms  p(90)=0s      p(95)=0s
     http_req_connecting............: avg=630ns    min=0s      med=0s      max=991.8µs p(90)=0s      p(95)=0s
     http_req_duration..............: avg=33.99ms  min=13.23ms med=21.11ms max=6.02s   p(90)=22.47ms p(95)=23.2ms
       { expected_response:true }...: avg=33.99ms  min=13.23ms med=21.11ms max=6.02s   p(90)=22.47ms p(95)=23.2ms
     http_req_failed................: 0.00%  ✓ 0          ✗ 28301
     http_req_receiving.............: avg=603.81µs min=0s      med=526.2µs max=12.01ms p(90)=1.04ms  p(95)=1.1ms
     http_req_sending...............: avg=17.87µs  min=0s      med=0s      max=1.62ms  p(90)=0s      p(95)=0s
     http_req_tls_handshaking.......: avg=0s       min=0s      med=0s      max=0s      p(90)=0s      p(95)=0s
     http_req_waiting...............: avg=33.37ms  min=12.7ms  med=20.53ms max=6.02s   p(90)=21.74ms p(95)=22.37ms
     http_reqs......................: 28301  822.663185/s
     iteration_duration.............: avg=34.31ms  min=16.75ms med=21.38ms max=6.02s   p(90)=22.81ms p(95)=23.67ms
     iterations.....................: 28301  822.663185/s
     vus............................: 10     min=10       max=30
     vus_max........................: 30     min=30       max=30


running (0m34.4s), 00/30 VUs, 28301 complete and 0 interrupted iterations
default ✓ [======================================] 30 VUs  30s

What am I missing that is causing the failure on load test? Any hints much appreciated.