etcd is a distributed, consistent key value store for shared configuration and service discovery. For more details about etcd, visit:
https://github.com/coreos/etcd
You can 'pre-pull' the Docker image used by this template by:
$ docker pull openshift/etcd-20-centos7
You can also build this Docker image yourself, by using provided Makefile:
$ make
You can import this template to OpenShift using:
$ oc create -f examples/etcd/template.json
Then you can navigate to OpenShift UI and click the 'Create' button on top right and choose 'Browse templates...'. Choose the 'etcd' and hit create.
Another way, is to use the CLI only:
$ oc process -f examples/etcd/template.json | oc create -f -
This template creates two Services. The first service is used for initial discovery and stores information about running members. This service is used only internally by the cluster members and you should not need to access it. You can however obtain information about the current state/size of the cluster.
The second service 'etcd' is the main entrypoint for accessing the 'etcd' cluster. This service is exposing two ports. The port 2380 is used for internal server-to-server communication and the port 2379 is used for the client connections.
The 'etcd-discovery' pod created by this template will create an instance of etcd server, that is used as cluster discovery service. This pod can be stopped or deleted when desired size of the cluster is reached. If you want to add more members you will have to start this pod again manually.
The 'etcd' replication controller manage creation of the etcd cluster members. By default this template will start 3 members. The members then register themselves using the discovery service and elect the leader. You can adjust the number of replicas as long as the 'etcd-discovery' service is running.
If you're done playing, you can remove all the created resources by executing following command:
$ ./examples/etcd/teardown.sh
Note: This will also remove all data you have stored in the etcd.