My microservice application throws a continuous error while trying to use Kafka. I am testing several configuration possibilities and I cannot understand why it doesn’t work.

Configuration of microservice:

# Kafka general configuration
spring.kafka.bootstrap-servers=localhost:9092

docker-compose.yml

  kafka:
    image: wurstmeister/kafka:2.13-2.7.0
    ports:
      - "9092:9093"
    environment:
      KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://localhost:9093
      KAFKA_LISTENERS: PLAINTEXT://0.0.0.0:9093
      KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181

Per my understanding:

• My application connects to localhost:9092
• docker-compose.yml has included mapping host:container ports which is 9092 (host where we connect):9093 (port which we access within container)

Expected result:

Kafka port is correctly mapped – application uses localhost:9092 which is mapped on port 9093 on Kafka therefore allowing us to use it properly

Actual result:

An error is thrown

2024-06-01T14:13:11.354+02:00  WARN 9560 --- [event] [ntainer#0-0-C-1] org.apache.kafka.clients.NetworkClient   : [Consumer clientId=consumer-example_group-1, groupId=example_group] Connection to node 1001 (localhost/127.0.0.1:9093) could not be established. Broker may not be available.
2024-06-01T14:13:12.282+02:00  INFO 9560 --- [event] [ntainer#0-0-C-1] org.apache.kafka.clients.NetworkClient   : [Consumer clientId=consumer-example_group-1, groupId=example_group] Node 1001 disconnected.

If I use one port everywhere, it works correctly. But I want to test out other possibilites.