This Docker images provides the apache/kafka image as base with the mDNS/ZeroConf stack on top. (2.x tags used wurstmeister/kafka, which required Zookeeper) So you can enjoy Apache Kafka while it is accessible by default as kafka.local (Port 9092) as a single-node cluster using KRaft without Zookeeper.

• Requirements
• Getting starting
• Host configs
• Configure a different mDNS hostname
• Other top level domains
• Further reading

Requirements

• Host enabled Avahi daemon
• Host enabled mDNS NSS lookup

Getting starting

To get a single broker Apache Kafka service up and running create a docker-compose.yml and insert the following snippet (based on the original example):

services:
  kafka:
    image: hausgold/kafka
    environment:
      MDNS_HOSTNAME: kafka.local
      # See: http://bit.ly/2UDzgqI for Kafka downscaling
      KAFKA_HEAP_OPTS: -Xmx256M -Xms32M
    ulimits:
      # Due to systemd/pam RLIMIT_NOFILE settings (max int inside the
      # container), the Java process seams to allocate huge limits which result
      # in a +unable to allocate file descriptor table - out of memory+ error.
      # Lowering this value fixes the issue for now.
      #
      # See: http://bit.ly/2U62A80
      # See: http://bit.ly/2T2Izit
      nofile:
        soft: 100000
        hard: 100000

Afterwards start the service with the following command:

$ docker-compose up

Host configs

Install the nss-mdns package, enable and start the avahi-daemon.service. Then, edit the file /etc/nsswitch.conf and change the hosts line like this:

hosts: ... mdns4_minimal [NOTFOUND=return] resolve [!UNAVAIL=return] dns ...

Configure a different mDNS hostname

The magic environment variable is MDNS_HOSTNAME. Just pass it like that to your docker run command:

$ docker run --rm -e MDNS_HOSTNAME=something.else.local hausgold/kafka

This will result in something.else.local.

You can also configure multiple aliases (CNAME's) for your container by passing the MDNS_CNAMES environment variable. It will register all the comma separated domains as aliases for the container, next to the regular mDNS hostname.

$ docker run --rm \
  -e MDNS_HOSTNAME=something.else.local \
  -e MDNS_CNAMES=nothing.else.local,special.local \
  hausgold/kafka

This will result in something.else.local, nothing.else.local and special.local.

Other top level domains

By default .local is the default mDNS top level domain. This images does not force you to use it. But if you do not use the default .local top level domain, you need to configure your host avahi to accept it.

Further reading

• Docker/mDNS demo: https://github.com/Jack12816/docker-mdns
• Archlinux howto: https://wiki.archlinux.org/index.php/avahi
• Ubuntu/Debian howto: https://wiki.ubuntuusers.de/Avahi/