How to expose Kafka from Docker to the outside world?

Question

Having to communicate with Kafka from a Dockerized Spring-Boot application, the only option I was able to get working was Dockerizing Kafka too.

Here is my docker-compose-yml:

version: '3.5'
services:
  zookeeper:
    image: wurstmeister/zookeeper
    ports:
      - "2181:2181"
    networks:
      - kafka-network
  kafka:
    image: wurstmeister/kafka
    ports:
      - "9092:9092"
    networks:
      - kafka-network
    environment:
      KAFKA_ADVERTISED_HOST_NAME: kafka
      KAFKA_AUTO_CREATE_TOPICS_ENABLE: 'true'
      KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
    depends_on:
      - zookeeper
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
networks:
  kafka-network:
    name: kafka-network

This way I'm able to connect to the Kafka broker from anothe container on the kafka-network using the url kafka:9092

How do I make it also available from the localhost and from other machines?

UPDATE I updated my docker-compose as follows:

version: '3.5'
services:
  zookeeper:
    image: wurstmeister/zookeeper
    ports:
      - "2181:2181"
    networks:
      - kafka-network
  kafka:
    image: wurstmeister/kafka
    ports:
      - "9092:9092"
    networks:
      - kafka-network
    environment:
      KAFKA_ADVERTISED_HOST_NAME: kafka
      KAFKA_AUTO_CREATE_TOPICS_ENABLE: 'true'
      KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
      KAFKA_LISTENERS: ${KAFKA_LISTENERS:-PLAINTEXT://:9092}
      KAFKA_ADVERTISED_LISTENERS: ${KAFKA_ADVERTISED_LISTENERS:-PLAINTEXT://127.0.0.1:9092}
    depends_on:
      - zookeeper
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
networks:
  kafka-network:
    name: kafka-network

and created a .env file with the following content :

KAFKA_ADVERTISED_LISTENERS=PLAINTEXT://the.ip.of.machine:9092

I tested it on my PC (without the .env file) and I'm able to communicate with the broker using kafkakat from localhost:

$ docker ps
CONTAINER ID        IMAGE                    COMMAND                  CREATED             STATUS              PORTS                                                NAMES
6844a16fa14f        wurstmeister/kafka       "start-kafka.sh"         5 seconds ago       Up 3 seconds        0.0.0.0:9092->9092/tcp                               kafka-compose_kafka_1_9573f71109c7
15d62557f3bd        wurstmeister/zookeeper   "/bin/sh -c '/usr/sb…"   6 seconds ago       Up 4 seconds        22/tcp, 2888/tcp, 3888/tcp, 0.0.0.0:2181->2181/tcp   kafka-compose_zookeeper_1_61a19213cde7

$ kafkacat -P -b localhost:9092 -t topic1
New test 
^C

$ kafkacat -C -b localhost:9092 -t topic1
New test
% Reached end of topic topic1 [0] at offset 1

$ kafkacat  -b localhost:9092 -L
Metadata for all topics (from broker -1: localhost:9092/bootstrap):
 1 brokers:
  broker 1001 at 127.0.0.1:9092
 4 topics:
 ...

However I'm not able to do the same on the server, the only difference is the IP of the host machine for KAFKA_ADVERTISED_LISTENERS.

What I can see is that it keeps saying leader not available

# kafkacat  -b localhost:9092 -L
Metadata for all topics (from broker -1: localhost:9092/bootstrap):
 1 brokers:
  broker 1002 at the.ip.of.machine:9092


 topic "__consumer_offsets" with 50 partitions:
    partition 0, leader -1, replicas: 1001, isrs: , Broker: Leader not available
    partition 1, leader -1, replicas: 1001, isrs: , Broker: Leader not available
    partition 2, leader -1, replicas: 1001, isrs: , Broker: Leader not available
    partition 3, leader -1, replicas: 1001, isrs: , Broker: Leader not available
    partition 4, leader -1, replicas: 1001, isrs: , Broker: Leader not available
    partition 5, leader -1, replicas: 1001, isrs: , Broker: Leader not available

Shouldn't I set the IP of the server for the KAFKA_ADVERTISED_LISTENERS ?

Latten

Answer 1

You have to set the LISTENERS in environments in order to expose the Kafka brokers to external network like below :

KAFKA_LISTENERS: PLAINTEXT://:9092
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://one.prod.com:9092

Here is the example :
https://github.com/wurstmeister/kafka-docker/blob/85821409d4d49a4edc7c5be83b68b71eceeab1bc/docker-compose-swarm.yml

You can refer here for more details: https://github.com/wurstmeister/kafka-docker/wiki/Connectivity

Chessy

Thanks @Nishu, I kept KAFKA_LISTENERS as you said, and edited KAFKA_ADVERTISED_LISTENERS with the IP of the server on which runs docker, but I keep getting leader not available when testing the localhost:9092 broker using kafkakat. I updated my question with your suggestions and my errors. Am I missing something? – Latten

You should use the IP or DNS host name instead of localhost. – Chessy

You might find this useful too: rmoff.net/2018/08/02/kafka-listeners-explained – Tala

What is one.prod.com ? – Maleficent

@Maleficent : That is an example of broker URL – Chessy

Answer 2

For new kafka versions try to look here:

https://www.kaaproject.org/kafka-docker

https://github.com/bitnami/bitnami-docker-kafka/issues/29#issuecomment-435216430

For old kafka if you have only one computer might help this kafka variables:

environment:
  ADVERTISED_HOST: ${COMPUTERNAME}
  ADVERTISED_PORT: "9092"

Downpour