Docker image for Apache ZooKeeper that supports a multi-node cluster setup.
dataDir is set to /tmp/zookeeper and is exposed as a volume, to be linked to a host directory.
To run in a cluster, you need to set the environment variable ZOO_NODE_ID, and it will becomes the content of myid file in the container: an integer (1-255) id of this particular zookeeper node. You also need to set the same number of ZOO_IP_x environment variables as the number of nodes in the cluster, in order to specify the IP addresses of all nodes, where x is the corresponding node id. These IP addresses will be properly inserted into the zookeeper config file.