This Dockerfile creates a Docker image that can be used as the base for running Kafka within a Docker container. The Kafka service is ran by the run.sh script which is in charge of setting up the Kafka configuration from environment variables passed to the container when it is run.

The version of Kafka is defined in the Dockerfile and currently points at the last available beta release.

The following environment variables are understood by the startup script to seed the service's configuration:

• SERVICE_NAME should contain the logical name of the service this container is an instance of;

• CONTAINER_NAME should contain the logical name of the container, which will be used for looking up links and ports informations from the other environment variables. For this, the name is uppercased and non-alphanumeric characters are replaced by underscores;

• CONTAINER_HOST_ADDRESS should contain the address of the Docker container's host. It' used by Kafka as the address advertised to ZooKeeper for broker discovery and is required for the container to start;

• ZOOKEEPER_BASE, the ZooKeeper tree chroot for Kafka to use in the zookeeper.connect string and properly namespace the Kafka zNodes for this deployment. Defaults to /local/kafka;

• BROKER_ID, which controls the broker.id configuration setting and useful for multi-node Kafka clusters. Defaults to 0.

• <SERVICE_NAME>_<CONTAINER_NAME>_BROKER_PORT, which controls which port the Kafka broker will listen on. Defaults to 9092;

Kafka depends on ZooKeeper for discovery. It thus expects the following environment variables to be defined for each ZooKeeper node to construct the node list: ZOOKEEPER_<ZK_NODE_NAME>_HOST and ZOOKEEPER_<ZK_NODE_NAME>_CLIENT_PORT. The ZOOKEEPER_BASE will be append to each host:port to set the zNode path chroot. The resulting list is used for the zookeeper.connect configuration setting.

The Kafka image uses the following volumes you may want to bind from the container's host:

• /var/lib/kafka, where the Kafka logs will be stored for each topic.

To build a new image, simply run from this directory:

$ docker build -t `whoami`/kafka .

The Docker image will be built and now available in Docker to start a new container from:

$ docker images | grep kafka
mpetazzoni/kafka       latest         6c58d1f6ff3c        5 seconds ago       12.29 kB (virtual 900.1 MB)