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 by kbcli or by Helm.

• 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.

  kbcli

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

  kubectl

  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.

  kbcli

  kbcli clusterdefinition list
  kbcli clusterversion list

  kubectl

  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.

kbcli

1. Create a PostgreSQL cluster.

   Here is an example of creating a Standalone.

   kbcli cluster create postgresql mycluster -n demo

   kbcli provides various options for you to customize your cluster specifications, such as setting cluster version, termination policy, CPU, and memory. You can view these options by adding --help or -h flag.

   kbcli cluster create postgresql --help
   kbcli cluster create postgresql -h

   For example, you can create a Replication Cluster with the --replicas flag.

   kbcli cluster create postgresql mycluster --replicas=2 -n demo

   If you only have one node for deploying a Replication Cluster, set the --topology-keys as null when creating a Replication Cluster. But you should note that for a production environment, it is not recommended to deploy all replicas on one node, which may decrease the cluster availability.

   kbcli cluster create postgresql mycluster --replicas=2 --availability-policy='none' -n demo

2. Verify whether this cluster is created successfully.

   kbcli cluster list -n demo
   >
   NAME        NAMESPACE   CLUSTER-DEFINITION   VERSION             TERMINATION-POLICY   STATUS    CREATED-TIME
   mycluster   demo        postgresql           postgresql-14.8.0   Delete               Running   Sep 28,2024 16:47 UTC+0800

kubectl

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:
     clusterDefinitionRef: postgresql
     clusterVersionRef: postgresql-14.8.0
     terminationPolicy: Delete
     affinity:
       podAntiAffinity: Preferred
       topologyKeys:
       - kubernetes.io/hostname
     tolerations:
       - key: kb-data
         operator: Equal
         value: 'true'
         effect: NoSchedule
     componentSpecs:
     - name: postgresql
       componentDefRef: postgresql
       enabledLogs:
       - running
       disableExporter: true
       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

   Field	Definition
   spec.clusterDefinitionRef	It specifies the name of the ClusterDefinition for creating a specific type of cluster.
   spec.clusterVersionRef	It is the name of the cluster version CRD that defines the cluster version.
   spec.terminationPolicy	It 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.affinity	It 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.podAntiAffinity	It 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.topologyKeys	It represents the key of node labels used to define the topology domain for Pod anti-affinity and Pod spread constraints.
   spec.tolerations	It is an array that specifies tolerations attached to the cluster's Pods, allowing them to be scheduled onto nodes with matching taints.
   spec.componentSpecs	It is the list of components that define the cluster components. This field allows customized configuration of each component within a cluster.
   spec.componentSpecs.componentDefRef	It 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.name	It specifies the name of the component.
   spec.componentSpecs.disableExporter	It defines whether the monitoring function is enabled.
   spec.componentSpecs.replicas	It specifies the number of replicas of the component.
   spec.componentSpecs.resources	It 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

kbcli

kbcli cluster connect mycluster  --namespace demo

kubectl

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

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/mycluster-postgresql 5432:5432 

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

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

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