How to Clone a PostgreSQL Helm Release on OpenShift

By June 7, 2019 June 26th, 2019 Blog, OpenShift

In this tutorial, we will create a clone of the PostgreSQL database that is deployed on OpenShift. We will then make changes to the clone and verify that the original database has remained unaffected by changes that were done to the clone.

Before you begin this tutorial, make sure you have installed ROBIN Storage on your existing OpenShift cluster, your PostgreSQL database is deployed on OpenShift, has data loaded in it, and the Helm release is registered with ROBIN and you have taken a snapshot of your deployed PostgreSQL database.

How to Clone a PostgreSQL Database on OpenShift

ROBIN lets you clone not just the storage volumes (PVCs) but the entire database application including all its resources such as Pods, StatefulSets, PVCs, Services, ConfigMaps, etc. with a single command.

Application cloning improves the collaboration across Dev/Test/Ops teams. Teams can share app+data quickly, reducing the procedural delays involved in re-creating environments. Each team can work on their clone without affecting other teams. Clones are useful when you want to run a report on a database without affecting the source database application, or for performing UAT tests or for validating patches before applying them to the production database, etc.

ROBIN clones are ready-to-use “thin copy” of the entire app/database, not just storage volumes. Thin-copy means that data from the snapshot is NOT physically copied, therefore clones can be made very quickly. ROBIN clones are fully-writable and any modifications made to the clone are not visible to the source app/database.

To create a clone from the existing snapshot created above, run the following command. Use the snapshot id from the snapshot tutorial.

robin clone create my-movies-clone Your_Snapshot_ID --wait

Let’s verify ROBIN has cloned all relevant Kubernetes resources.

kubectl get all | grep "my-movies-clone"

You should see an output similar to below.

Clone PostgreSQL on OpenShift - Snapshot ID

Notice that ROBIN automatically clones all the required Kubernetes resources, not just storage volumes (PVCs), that are required to stand up a fully-functional clone of our database. After the clone is complete, the cloned database is ready for use.

Get Service IP address of our PostgreSQL database clone, and note the IP address.

export IP_ADDRESS=$(kubectl get service movies-clone-movies-postgresql
-o jsonpath={.spec.clusterIP})

Get Password of our PostgreSQL database clone from Kubernetes Secret

export POSTGRES_PASSWORD=$(kubectl get secret movies-clone-movies-postgresql
-o jsonpath="{.data.postgresql-password}" | base64 --decode;)

To verify we have successfully created a clone of our PostgreSQL database, run the following command.

PGPASSWORD="$POSTGRES_PASSWORD" psql -h $IP_ADDRESS 
-U postgres -d testdb -c "SELECT * from movies;"

You should see an output similar to the following with 9 movies.

Clone PostgreSQL on OpenShift 9 movies

We have successfully created a clone of our original PostgreSQL database, and the cloned database also has a table called “movies” with 9 rows, just like the original.

Now, let’s make changes to the clone and verify the original database remains unaffected by changes to the clone. Let’s delete the movie called “Super Troopers 2”.

PGPASSWORD="$POSTGRES_PASSWORD" psql -h $IP_ADDRESS -U postgres -d testdb
-c "DELETE from movies where title = 'Super Troopers 2';"

Let’s verify the movie has been deleted.

PGPASSWORD="$POSTGRES_PASSWORD" psql -h $IP_ADDRESS
-U postgres -d testdb -c "SELECT * from movies;"

You should see an output similar to the following with 8 movies.

Clone PostgreSQL on OpenShift 8 movies

Now, let’s connect to our original PostgreSQL database and verify it is unaffected.

Get Service IP address of our original PostgreSQL database.

export IP_ADDRESS=$(kubectl get service movies-postgresql
-o jsonpath={.spec.clusterIP})

Get Password of our original PostgreSQL database from Kubernetes Secret.

export POSTGRES_PASSWORD=$(kubectl get secret
--namespace default movies-postgresql
-o jsonpath="{.data.postgresql-password}" | base64 --decode;)

To verify that our PostgreSQL database is unaffected by changes to the clone, run the following command. Let’s connect to “testdb” and check the record.

PGPASSWORD="$POSTGRES_PASSWORD" psql -h $IP_ADDRESS
-U postgres -d testdb -c "SELECT * from movies;"

You should see an output similar to the following, with all 9 movies present.

Clone PostgreSQL on OpenShift 9 movies

This concludes the Clone Postgres on OpenShift tutorial.

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Author Ripul Patel, Sr Software Engineer

More posts by Ripul Patel, Sr Software Engineer