ZooKeeper is a distributed, open-source coordination service for distributed applications. It exposes a simple set of primitives that distributed applications can build upon to implement higher level services for synchronization, configuration maintenance, and groups and naming. It is designed to be easy to program to, and uses a data model styled after the familiar directory tree structure of file systems. It runs in Java and has bindings for both Java and C.
For more informations about ZooKeeper visit:
http://zookeeper.apache.org/doc/r3.4.6/zookeeperOver.html
You can 'pre-pull' the Docker image used by this template by:
$ docker pull openshift/zookeeper-346-fedora20
It is not really required, but it will speed up the launch of the pods.
You can import this template to OpenShift using:
$ oc create -f examples/zookeeper/template.json
Then you can navigate to OpenShift UI and click the 'Create' button on top right and choose 'Browse templates...'. Choose the 'zookeeper' and hit create.
Another way, is to use the CLI only:
$ oc process -f examples/zookeeper/template.json | oc create -f -
This template create three ZooKeeper pods that will act as three independent servers. The ZooKeeper image is shipped with 'zoo.cfg' file that has these three servers pre-configured. Once the pods are running, they will elect 'leader'.
There are four services in this template. The 'zookeeper' service serves as entrypoint for clients to connect to ZooKeeper cluster. The other three services are used for the leader election and for the sharing replicas across ZooKeeper servers.
If you're done playing, you can remove all created resources by executing following command:
$ ./examples/zookeeper/teardown.sh
Note: This will also remove all data you have stored in the ZooKeeper.