docker-zookeeper

The reason why we created this docker image is that we wanted to have a simple way to spin up multi-node ZooKeeper deployments. In particular, we wanted the docker container to create the ZooKeeper myID file autonomously, so that we could spawn ZooKeeper containers in single-line statements.
We are currently not aware of another easy approach to do that. More related resources:

• Our tutorial on how to use Storm with Docker Swarm
• the baqend/zookeeper on Docker Hub
• the the baqend/zookeeper on GitHub

Simple multi-node ensembles

Suppose you wanted a 3-node ZooKeeper ensemble on machines with the hostnames zk1, zk2 and zk3, run the following on every ensemble node:

docker run -d --restart=always \
      -p 2181:2181 \
      -p 2888:2888 \
      -p 3888:3888 \
      -v /var/lib/zookeeper:/var/lib/zookeeper \
      -v /var/log/zookeeper:/var/log/zookeeper  \
      baqend/zookeeper zk1,zk2,zk3 $ID

Obviously, the -p commands expose the ports required by ZooKeeper per default. The two -v commands provide persistence in case of container failure by mapping the directories the ZooKeeper container uses to the corresponding host directories. The comma-separated list of hostnames tells ZooKeeper what servers are in the ensemble. This is the same for every node in the ensemble. The only variable is the ZooKeeper ID ($ID), because it is unique for every container. This means you have to provide every container with its ID (1, 2 and 3, respectively). And that's it.
All ZooKeeper-related data are stored on the host. On start, the ZooKeeper myID file is created anew.

For an example of how we use this image, also see our tutorial on how to use Storm with Docker Swarm.

Note: ZooKeeper only accepts IDs between 1 and 255!