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Version: release-0.9

Create and connect to a PostgreSQL cluster

This tutorial shows how to create and connect to a PostgreSQL cluster.

Create a PostgreSQL cluster​

Before you start​

  • Install kbcli if you want to manage the PostgreSQL cluster by kbcli.

  • Install KubeBlocks.

  • Make sure the PostgreSQL Addon is enabled. The PostgreSQL Addon is installed and enabled by KubeBlocks by default. But if you disable it when installing KubeBlocks, enable it first.

    kubectl get addons.extensions.kubeblocks.io postgresql
    >
    NAME         TOPOLOGIES   SERVICEREFS   STATUS      AGE
    postgresql                              Available   30m

  • View all the database types and versions available for creating a cluster.

    kubectl get clusterdefinition postgresql
    >
    NAME         TOPOLOGIES   SERVICEREFS   STATUS      AGE
    postgresql                              Available   30m

    View all available versions for creating a cluster.

    kubectl get clusterversions -l clusterdefinition.kubeblocks.io/name=postgresql
    >
    NAME                 CLUSTER-DEFINITION   STATUS      AGE
    postgresql-12.14.0   postgresql           Available   30m
    postgresql-12.14.1   postgresql           Available   30m
    postgresql-12.15.0   postgresql           Available   30m
    postgresql-14.7.2    postgresql           Available   30m
    postgresql-14.8.0    postgresql           Available   30m
    postgresql-15.7.0    postgresql           Available   30m
    postgresql-16.4.0    postgresql           Available   30m

  • To keep things isolated, create a separate namespace called demo throughout this tutorial.

    kubectl create namespace demo

Create a cluster​

KubeBlocks supports creating two types of PostgreSQL clusters: Standalone and Replication Cluster. Standalone only supports one replica and can be used in scenarios with lower requirements for availability. For scenarios with high availability requirements, it is recommended to create a Replication Cluster, which creates a cluster with a Replication Cluster to support automatic failover. To ensure high availability, Primary and Secondary are distributed on different nodes by default.

  1. Create a PostgreSQL cluster.

    KubeBlocks implements a Cluster CRD to define a cluster. Here is an example of creating a Replication.

    cat <<EOF | kubectl apply -f -
    apiVersion: apps.kubeblocks.io/v1alpha1
    kind: Cluster
    metadata:
      name: mycluster
      namespace: demo
    spec:
      terminationPolicy: Delete
      componentSpecs:
      - name: postgresql
        componentDef: postgresql-12
        enabledLogs:
        - running
        disableExporter: true
        affinity:
          podAntiAffinity: Preferred
          topologyKeys:
          - kubernetes.io/hostname
          tenancy: SharedNode
        tolerations:
        - key: kb-data
          operator: Equal
          value: 'true'
          effect: NoSchedule
        replicas: 2
        resources:
          limits:
            cpu: '0.5'
            memory: 0.5Gi
          requests:
            cpu: '0.5'
            memory: 0.5Gi
        volumeClaimTemplates:
        - name: data
          spec:
            accessModes:
            - ReadWriteOnce
            resources:
              requests:
                storage: 20Gi
    EOF
    FieldDefinition
    spec.terminationPolicyIt is the policy of cluster termination. The default value is Delete. Valid values are DoNotTerminate, Delete, WipeOut. For the detailed definition, you can refer to Termination Policy.
    spec.affinityIt defines a set of node affinity scheduling rules for the cluster's Pods. This field helps control the placement of Pods on nodes within the cluster.
    spec.affinity.podAntiAffinityIt specifies the anti-affinity level of Pods within a component. It determines how pods should spread across nodes to improve availability and performance.
    spec.affinity.topologyKeysIt represents the key of node labels used to define the topology domain for Pod anti-affinity and Pod spread constraints.
    spec.tolerationsIt is an array that specifies tolerations attached to the cluster's Pods, allowing them to be scheduled onto nodes with matching taints.
    spec.componentSpecsIt is the list of components that define the cluster components. This field allows customized configuration of each component within a cluster.
    spec.componentSpecs.componentDefRefIt is the name of the component definition that is defined in the cluster definition and you can get the component definition names with kubectl get clusterdefinition postgresql -o json | jq '.spec.componentDefs[].name'.
    spec.componentSpecs.nameIt specifies the name of the component.
    spec.componentSpecs.disableExporterIt defines whether the monitoring function is enabled.
    spec.componentSpecs.replicasIt specifies the number of replicas of the component.
    spec.componentSpecs.resourcesIt specifies the resource requirements of the component.

    KubeBlocks operator watches for the Cluster CRD and creates the cluster and all dependent resources. You can get all the resources created by the cluster with kubectl get all,secret,rolebinding,serviceaccount -l app.kubernetes.io/instance=mycluster -n demo.

    kubectl get all,secret,rolebinding,serviceaccount -l app.kubernetes.io/instance=mycluster -n demo

    Run the following command to see the created PostgreSQL cluster object:

    kubectl get cluster mycluster -n demo -o yaml

  2. Verify whether this cluster is created successfully.

    kubectl get cluster mycluster -n demo
    >
    NAME        CLUSTER-DEFINITION   VERSION             TERMINATION-POLICY   STATUS    AGE
    mycluster   postgresql           postgresql-14.8.0   Delete               Running   9m21s

Connect to a PostgreSQL Cluster​

You can use kubectl exec to exec into a Pod and connect to a database.

KubeBlocks operator has created a new Secret called mycluster-conn-credential to store the connection credential of the mycluster cluster. This secret contains following keys:

  • username: the root username of the PostgreSQL cluster.
  • password: the password of root user.
  • port: the port of the PostgreSQL cluster.
  • host: the host of the PostgreSQL cluster.
  • endpoint: the endpoint of the PostgreSQL cluster and it is the same as host:port.

  1. Run the command below to get the username and password for the kubectl exec command.

    kubectl get secrets -n demo mycluster-conn-credential -o jsonpath='{.data.username}' | base64 -d
    >
    postgres

    kubectl get secrets -n demo mycluster-conn-credential -o jsonpath='{.data.password}' | base64 -d
    >
    h62rg2kl

  2. Exec into the Pod mycluster-postgresql-0 and connect to the database using username and password.

    kubectl exec -ti -n demo mycluster-postgresql-0 -- bash

    root@mycluster-postgresql-0:/home/postgres# psql -U postgres -W
    Password: h62rg2kl

For the detailed database connection guide, refer to Connect database.