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 create and connect a cluster by kbcli.

• Install KubeBlocks: You can install KubeBlocks by kbcli or by Helm.

• Make sure the PostgreSQL add-on is enabled.

  kbcli

  kbcli addon list
  >
  NAME                       TYPE   STATUS     EXTRAS         AUTO-INSTALL   INSTALLABLE-SELECTOR
  ...
  postgresql                 Helm   Enabled                   true
  ...

  kubectl

  kubectl get addons.extensions.kubeblocks.io postgresql
  >
  NAME         TYPE   STATUS    AGE
  postgresql   Helm   Enabled   23m

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

  kbcli

  kbcli clusterdefinition list
  
  kbcli clusterversion list

  kubectl

  Make sure the postgresql cluster definition is installed with kubectl get clusterdefinitions postgresql.

  kubectl get clusterdefinition postgresql
  >
  NAME         MAIN-COMPONENT-NAME   STATUS      AGE
  postgresql   postgresql            Available   25m

  View all available versions for creating a cluster

  kubectl get clusterversions -l clusterdefinition.kubeblocks.io/name=postgresql

• 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. And to ensure high availability, Primary and Secondary are distributed on different nodes by default.

kbcli

Create a Standalone.

kbcli cluster create postgresql <clustername>

Create a Replication Cluster.

kbcli cluster create postgresql --mode replication <clustername>

If you only have one node for deploying a Replication, set the availability-policy as none when creating a Replication Cluster.

kbcli cluster create postgresql --mode replication --availability-policy none <clustername>

note

• In the production environment, it is not recommended to deploy all replicas on one node, which may decrease cluster availability.

• Run the command below to view the flags for creating a PostgreSQL cluster and the default values.

  kbcli cluster create postgresql -h

kubectl

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

cat <<EOF | kubectl apply -f -
apiVersion: apps.kubeblocks.io/v1alpha1
kind: Cluster
metadata:
  name: pg-cluster
  namespace: demo
  labels: 
    helm.sh/chart: postgresql-cluster-0.6.0-alpha.36
    app.kubernetes.io/version: "14.8.0"
    app.kubernetes.io/instance: pg
spec:
  clusterVersionRef: postgresql-14.8.0
  terminationPolicy: Delete  
  affinity:
    podAntiAffinity: Preferred
    topologyKeys:
      - kubernetes.io/hostname
    tenancy: SharedNode
  clusterDefinitionRef: postgresql
  componentSpecs:
    - name: postgresql
      componentDefRef: postgresql      
      monitor: false      
      replicas: 1
      enabledLogs:
        - running
      serviceAccountName: kb-pg
      switchPolicy:
        type: Noop      
      resources:
        limits:
          cpu: "0.5"
          memory: "0.5Gi"
        requests:
          cpu: "0.5"
          memory: "0.5Gi"      
      volumeClaimTemplates:
        - name: data # ref clusterDefinition components.containers.volumeMounts.name
          spec:
            accessModes:
              - ReadWriteOnce
            resources:
              requests:
                storage: 20Gi      
      services:
EOF

• spec.clusterDefinitionRef is the name of the cluster definition CRD that defines the cluster components.
• spec.clusterVersionRef is the name of the cluster version CRD that defines the cluster version.
• spec.componentSpecs is the list of components that define the cluster components.
• spec.componentSpecs.componentDefRef is the name of the component definition that is defined in the cluster definition, you can get the component definition names with kubectl get clusterdefinition postgresql -o json | jq '.spec.componentDefs[].name'.
• spec.componentSpecs.name is the name of the component.
• spec.componentSpecs.replicas is the number of replicas of the component.
• spec.componentSpecs.resources is the resource requirements of the component.
• spec.componentSpecs.volumeClaimTemplates is the list of volume claim templates that define the volume claim templates for the component.
• spec.terminationPolicy is the policy of cluster termination. The default value is Delete. Valid values are DoNotTerminate, Halt, Delete, WipeOut. DoNotTerminate blocks delete operation. Halt deletes workload resources such as statefulset and deployment workloads but keep PVCs. Delete is based on Halt and deletes PVCs. WipeOut is based on Delete and wipe out all volume snapshots and snapshot data from the backup storage location.

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=pg-cluster -n demo.

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

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

kubectl get cluster pg-cluster -n demo -o yaml

Output

apiVersion: apps.kubeblocks.io/v1alpha1
kind: Cluster
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"apps.kubeblocks.io/v1alpha1","kind":"Cluster","metadata":{"annotations":{},"labels":{"app.kubernetes.io/instance":"pg","app.kubernetes.io/version":"14.8.0","helm.sh/chart":"postgresql-cluster-0.6.0-alpha.36"},"name":"pg-cluster","namespace":"demo"},"spec":{"affinity":{"podAntiAffinity":"Preferred","tenancy":"SharedNode","topologyKeys":["kubernetes.io/hostname"]},"clusterDefinitionRef":"postgresql","clusterVersionRef":"postgresql-14.8.0","componentSpecs":[{"componentDefRef":"postgresql","enabledLogs":["running"],"monitor":false,"name":"postgresql","replicas":1,"resources":{"limits":{"cpu":"0.5","memory":"0.5Gi"},"requests":{"cpu":"0.5","memory":"0.5Gi"}},"serviceAccountName":"kb-pg","services":null,"switchPolicy":{"type":"Noop"},"volumeClaimTemplates":[{"name":"data","spec":{"accessModes":["ReadWriteOnce"],"resources":{"requests":{"storage":"20Gi"}}}}]}],"terminationPolicy":"Delete"}}
  creationTimestamp: "2023-07-19T07:53:07Z"
  finalizers:
  - cluster.kubeblocks.io/finalizer
  generation: 1
  labels:
    app.kubernetes.io/instance: pg
    app.kubernetes.io/version: 14.8.0
    clusterdefinition.kubeblocks.io/name: postgresql
    clusterversion.kubeblocks.io/name: postgresql-14.8.0
    helm.sh/chart: postgresql-cluster-0.6.0-alpha.36
  name: pg-cluster
  namespace: demo
  resourceVersion: "8618"
  uid: c9f73d21-b79b-4956-aad0-a4e677cb8ba1
spec:
  affinity:
    podAntiAffinity: Preferred
    tenancy: SharedNode
    topologyKeys:
    - kubernetes.io/hostname
  clusterDefinitionRef: postgresql
  clusterVersionRef: postgresql-14.8.0
  componentSpecs:
  - componentDefRef: postgresql
    enabledLogs:
    - running
    monitor: false
    name: postgresql
    noCreatePDB: false
    replicas: 1
    resources:
      limits:
        cpu: "0.5"
        memory: 0.5Gi
      requests:
        cpu: "0.5"
        memory: 0.5Gi
    serviceAccountName: kb-pg
    switchPolicy:
      type: Noop
    volumeClaimTemplates:
    - name: data
      spec:
        accessModes:
        - ReadWriteOnce
        resources:
          requests:
            storage: 20Gi
  terminationPolicy: Delete
status:
  clusterDefGeneration: 2
  components:
    postgresql:
      phase: Running
      podsReady: true
      podsReadyTime: "2023-07-19T07:53:43Z"
      replicationSetStatus:
        primary:
          pod: pg-cluster-postgresql-0
  conditions:
  - lastTransitionTime: "2023-07-19T07:53:07Z"
    message: 'The operator has started the provisioning of Cluster: pg-cluster'
    observedGeneration: 1
    reason: PreCheckSucceed
    status: "True"
    type: ProvisioningStarted
  - lastTransitionTime: "2023-07-19T07:53:07Z"
    message: Successfully applied for resources
    observedGeneration: 1
    reason: ApplyResourcesSucceed
    status: "True"
    type: ApplyResources
  - lastTransitionTime: "2023-07-19T07:53:43Z"
    message: all pods of components are ready, waiting for the probe detection successful
    reason: AllReplicasReady
    status: "True"
    type: ReplicasReady
  - lastTransitionTime: "2023-07-19T07:53:43Z"
    message: 'Cluster: pg-cluster is ready, current phase is Running'
    reason: ClusterReady
    status: "True"
    type: Ready
  observedGeneration: 1
  phase: Running

Connect to a PostgreSQL Cluster

kbcli

kbcli cluster connect <clustername>  --namespace <name>

kubectl

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

KubeBlocks operator has created a new Secret called pg-cluster-conn-credential to store the connection credential of the pg-cluster 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 pg-cluster-conn-credential -o jsonpath='{.data.\username}' | base64 -d
   >
   postgres
   
   kubectl get secrets -n demo pg-cluster-conn-credential -o jsonpath='{.data.\password}' | base64 -d
   >
   h62rg2kl

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

   kubectl exec -ti -n demo pg-cluster-postgresql-0 -- bash
   
   root@pg-cluster-postgresql-0:/home/postgres# psql -U postgres -W
   Password: h62rg2kl

port-forward

You can also port forward the service to connect to the database from your local machine.

1. Run the following command to port forward the service.

   kubectl port-forward -n demo svc/pg-cluster-postgresql 5432:5432 

2. Open a new terminal and run the following command to connect to the database.

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

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