Fabric8 - ZooKeeper Docker Image

A ZooKeeper Docker Image for use with Kubernetes.

The image supports the following ZooKeeper modes:

• Standalone
• Clustered

Standalone Mode

To start the image in standalone mode you can simply use:

docker run fabric8/zookeeper

Clustered Mode

To start the image in clustered mode you need to specify a couple of environment variables for the container.

Environment Variable	Description
SERVER_ID	The id of the server
MAX_SERVERS	The number of servers in the ensemble

Each container started with both of the above variables will use the following env variable setup:

server.1=zookeeper-1:2888:3888
server.2=zookeeper-2:2888:3888
server.3=zookeeper-3:2888:3888
...
server.N=zookeeper-N:2888:3888

Ensuring that zookeeper-1, zookeeper-2 ... zookeeper-N can be resolved is beyond the scope of this image. You can use DNS, or Kubernetes services, etc depending on your environment (see below).

Inside Kubernetes

Inside Kubernetes you can use a pod setup that looks like:

{
  "kind": "Pod",
  "apiVersion": "v1beta3",
  "metadata": {
    "name": "zookeeper-1",
    "labels": {
      "name": "zookeeper",
      "server-id": "1"
    }
  },
  "spec": {
    "containers": [
      {
        "name": "server",
        "image": "fabric8/zookeeper",
        "env":[
          { "name": "SERVER_ID", "value": "1" },
          { "name": "MAX_SERVERS", "value": "3" }
        ],
        "ports":[
          {
            "containerPort": 2181
          },
          {
            "containerPort": 2888
          },
          {
            "containerPort": 3888
          }
        ]
      }
    ]
  }

In the example above we are creating a pod that creates a container using this image. The container is configured to use the environment variable required for a clustered setup. Last but not least pod is carefully named (as zookeeper-${SERVER_ID}) so that the other zookeeper servers can easily find it by hostname.