Create a Postgres Cluster

If you came here through the quickstart, you may have already created a cluster. If you created a cluster by using the example in the kustomize/postgres directory, feel free to skip to connecting to a cluster, or read onward for a more in depth look into cluster creation!

Create a Postgres Cluster

Creating a Postgres cluster is pretty simple. Using the example in the kustomize/postgres directory, all we have to do is run:

kubectl apply -k kustomize/postgres

and PGO will create a simple Postgres cluster named hippo in the postgres-operator namespace. You can track the status of your Postgres cluster using kubectl describe on the postgresclusters.postgres-operator.crunchydata.com custom resource:

kubectl -n postgres-operator describe postgresclusters.postgres-operator.crunchydata.com hippo

and you can track the state of the Postgres Pod using the following command:

kubectl -n postgres-operator get pods \
  --selector=postgres-operator.crunchydata.com/cluster=hippo,postgres-operator.crunchydata.com/instance

What Just Happened?

PGO created a Postgres cluster based on the information provided to it in the Kustomize manifests located in the kustomize/postgres directory. Let’s better understand what happened by inspecting the kustomize/postgres/postgres.yaml file:

apiVersion: postgres-operator.crunchydata.com/v1beta1
kind: PostgresCluster
metadata:
  name: hippo
spec:
  image: registry.developers.crunchydata.com/crunchydata/crunchy-postgres:ubi8-14.6-2
  postgresVersion: 14
  instances:
    - name: instance1
      dataVolumeClaimSpec:
        accessModes:
        - "ReadWriteOnce"
        resources:
          requests:
            storage: 1Gi
  backups:
    pgbackrest:
      image: registry.developers.crunchydata.com/crunchydata/crunchy-pgbackrest:ubi8-2.41-2
      repos:
      - name: repo1
        volume:
          volumeClaimSpec:
            accessModes:
            - "ReadWriteOnce"
            resources:
              requests:
                storage: 1Gi

When we ran the kubectl apply command earlier, what we did was create a PostgresCluster custom resource in Kubernetes. PGO detected that we added a new PostgresCluster resource and started to create all the objects needed to run Postgres in Kubernetes!

What else happened? PGO read the value from metadata.name to provide the Postgres cluster with the name hippo. Additionally, PGO knew which containers to use for Postgres and pgBackRest by looking at the values in spec.image and spec.backups.pgbackrest.image respectively. The value in spec.postgresVersion is important as it will help PGO track which major version of Postgres you are using.

PGO knows how many Postgres instances to create through the spec.instances section of the manifest. While name is optional, we opted to give it the name instance1. We could have also created multiple replicas and instances during cluster initialization, but we will cover that more when we discuss how to scale and create a HA Postgres cluster.

A very important piece of your PostgresCluster custom resource is the dataVolumeClaimSpec section. This describes the storage that your Postgres instance will use. It is modeled after the Persistent Volume Claim. If you do not provide a spec.instances.dataVolumeClaimSpec.storageClassName, then the default storage class in your Kubernetes environment is used.

As part of creating a Postgres cluster, we also specify information about our backup archive. PGO uses pgBackRest, an open source backup and restore tool designed to handle terabyte-scale backups. As part of initializing our cluster, we can specify where we want our backups and archives (write-ahead logs or WAL) stored. We will talk about this portion of the PostgresCluster spec in greater depth in the disaster recovery section of this tutorial, and also see how we can store backups in Amazon S3, Google GCS, and Azure Blob Storage.

Troubleshooting

PostgreSQL / pgBackRest Pods Stuck in Pending Phase

The most common occurrence of this is due to PVCs not being bound. Ensure that you have set up your storage options correctly in any volumeClaimSpec. You can always update your settings and reapply your changes with kubectl apply.

Also ensure that you have enough persistent volumes available: your Kubernetes administrator may need to provision more.

If you are on OpenShift, you may need to set spec.openshift to true.

Next Steps

We’re up and running – now let’s connect to our Postgres cluster!