Creating a PostgreSQL Cluster using Helm

Editor’s note: Today’s guest post is by Jeff McCormick, a developer at Crunchy Data, showing how to deploy a PostgreSQL cluster using Helm, a Kubernetes package manager.

In this post we’ll show you how to deploy a PostgreSQL cluster using .

This example will create the following in your Kubernetes cluster:

  • postgres master service
  • postgres replica service
  • postgres 9.5 master database (pod)
  • postgres 9.5 replica database (replication controller)

HelmBlogDiagram.jpg

This example creates a simple Postgres streaming replication deployment with a master (read-write), and a single asynchronous replica (read-only). You can scale up the number of replicas dynamically.

Contents

The example is made up of various Chart files as follows:
values.yaml This file contains values which you can reference within the database templates allowing you to specify in one place values like database passwords
templates/master-pod.yaml The postgres master database pod definition. This file causes a single postgres master pod to be created.
templates/master-service.yaml The postgres master database has a service created to act as a proxy. This file causes a single service to be created to proxy calls to the master database.
templates/replica-rc.yaml The postgres replica database is defined by this file. This file causes a replication controller to be created which allows the postgres replica containers to be scaled up on-demand.
templates/replica-service.yaml This file causes the service proxy for the replica database container(s) to be created.

Installation

helm init

cd crunchy-containers/examples/kubehelm

helm install ./crunchy-postgres

Testing

After installing the Helm chart, you will see the following services:

kubectl get services  
NAME              CLUSTER-IP   EXTERNAL-IP   PORT(S)    AGE  
crunchy-master    10.0.0.171   \<none\>        5432/TCP   1h  
crunchy-replica   10.0.0.31    \<none\>        5432/TCP   1h  
kubernetes        10.0.0.1     \<none\>        443/TCP    1h

It takes about a minute for the replica to begin replicating with the master. To test out replication, see if replication is underway with this command, enter password for the password when prompted:

psql -h crunchy-master -U postgres postgres -c 'table pg\_stat\_replication'

If you see a line returned from that query it means the master is replicating to the slave. Try creating some data on the master:

psql -h crunchy-master -U postgres postgres -c 'create table foo (id int)'

psql -h crunchy-master -U postgres postgres -c 'insert into foo values (1)'

Then verify that the data is replicated to the slave:

psql -h crunchy-replica -U postgres postgres -c 'table foo'

You can scale up the number of read-only replicas by running the following kubernetes command:

kubectl scale rc crunchy-replica --replicas=2

It takes 60 seconds for the replica to start and begin replicating from the master.

The Kubernetes Helm and Charts projects provide a streamlined way to package up complex applications and deploy them on a Kubernetes cluster. Deploying PostgreSQL clusters can sometimes prove challenging, but the task is greatly simplified using Helm and Charts.

--Jeff McCormick, Developer, Crunchy Data