Statefulset PostgreSQL Cluster


This example deploys a statefulset named statefulset. The statefulset is a new feature in Kubernetes as of version 1.5 and in OpenShift Origin as of version 3.5. Statefulsets have replaced PetSets going forward.

Please view this Kubernetes description to better understand what a Statefulset is and how it works.

This example creates 2 PostgreSQL containers to form the set. At startup, each container will examine its hostname to determine if it is the first container within the set of containers.

The first container is determined by the hostname suffix assigned by Kubernetes to the pod. This is an ordinal value starting with 0. If a container sees that it has an ordinal value of 0, it will update the container labels to add a new label of:


In this example, PG_PRIMARY_HOST is specified as statefulset-primary.

By default, the containers specify a value of name=statefulset-replica.

There are 2 services that end user applications will use to access the PostgreSQL cluster, one service (statefulset-primary) routes to the primary container and the other (statefulset-replica) to the replica containers.

$ ${CCP_CLI} get service
kubernetes       <none>        443/TCP    22h
statefulset-primary   <none>        5432/TCP   1h
statefulset-replica   <none>        5432/TCP   1h

To shutdown the instance and remove the container for each example, run the following:


Kubernetes and OpenShift

First, start the example with the following command:

cd $CCPROOT/examples/kube/statefulset

You can access the primary database as follows:

psql -h statefulset-primary -U postgres postgres

You can access the replica databases as follows:

psql -h statefulset-replica -U postgres postgres

You can scale the number of containers using this command; this will essentially create an additional replica database.

${CCP_CLI} scale --replicas=3 statefulset statefulset


This example resides under the $CCPROOT/examples/helm directory. View the README to run this example using Helm here.