PostgreSQL Cluster Lifecycle Management

This guide demonstrates how to manage a PostgreSQL cluster's operational state in KubeBlocks, including:

• Stopping the cluster to conserve resources
• Starting a stopped cluster
• Restarting cluster components

These operations help optimize resource usage and reduce operational costs in Kubernetes environments.

Lifecycle management operations in KubeBlocks:

Prerequisites

Before proceeding, ensure the following:

• Environment Setup:
  • A Kubernetes cluster is up and running.
  • The kubectl CLI tool is configured to communicate with your cluster.
  • KubeBlocks CLI and KubeBlocks Operator are installed. Follow the installation instructions here.
• Namespace Preparation: To keep resources isolated, create a dedicated namespace for this tutorial:

kubectl create ns demo
namespace/demo created

Deploy a PostgreSQL Cluster

KubeBlocks uses a declarative approach for managing PostgreSQL clusters. Below is an example configuration for deploying a PostgreSQL cluster with 2 replicas (1 primary, 1 replicas).

Apply the following YAML configuration to deploy the cluster:

apiVersion: apps.kubeblocks.io/v1
kind: Cluster
metadata:
  name: pg-cluster
  namespace: demo
spec:
  terminationPolicy: Delete
  clusterDef: postgresql
  topology: replication
  componentSpecs:
    - name: postgresql
      serviceVersion: 16.4.0
      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

Verifying the Deployment

Monitor the cluster status until it transitions to the Running state:

kubectl get cluster pg-cluster -n demo -w

Expected Output:

NAME         CLUSTER-DEFINITION   TERMINATION-POLICY   STATUS     AGE
pg-cluster   postgresql           Delete               Creating   50s
pg-cluster   postgresql           Delete               Running    4m2s

Once the cluster status becomes Running, your PostgreSQL cluster is ready for use.

Cluster Lifecycle Operations

Stopping the Cluster

Stopping a PostgreSQL cluster in KubeBlocks will:

1. Terminates all running pods
2. Retains persistent storage (PVCs)
3. Maintains cluster configuration

This operation is ideal for:

• Temporary cost savings
• Maintenance windows
• Development environment pauses

apiVersion: operations.kubeblocks.io/v1alpha1
kind: OpsRequest
metadata:
  name: pg-cluster-stop-ops
  namespace: demo
spec:
  clusterName: pg-cluster
  type: Stop

kubectl patch cluster pg-cluster -n demo --type='json' -p='[
  {
    "op": "add",
    "path": "/spec/componentSpecs/0/stop",
    "value": true
  }
]'

Verifying Cluster Stop

To confirm a successful stop operation:

1. Check cluster status transition:

   kubectl get cluster pg-cluster -n demo -w
   

   Example Output:

   NAME         CLUSTER-DEFINITION   TERMINATION-POLICY   STATUS     AGE
   pg-cluster   postgresql           Delete               Stopping   6m3s
   pg-cluster   postgresql           Delete               Stopped    6m55s
   

2. Verify no running pods:

   kubectl get pods -n demo
   

   Example Output:

   No resources found in demo namespace.
   

3. Confirm persistent volumes remain:

   kubectl get pvc -n demo
   

   Example Output:

   NAME                           STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
   data-pg-cluster-postgresql-0   Bound    pvc-dcfb1ebc-2773-4edd-9898-e11da76062c4   20Gi       RWO            standard       19m
   data-pg-cluster-postgresql-1   Bound    pvc-36366e01-0178-43fa-b1a0-4168b057dd10   20Gi       RWO            standard       19m
   

Starting the Cluster

Starting a stopped PostgreSQL cluster:

1. Recreates all pods
2. Reattaches persistent storage
3. Restores service endpoints

Expected behavior:

• Cluster returns to previous state
• No data loss occurs
• Services resume automatically

apiVersion: operations.kubeblocks.io/v1alpha1
kind: OpsRequest
metadata:
  name: pg-cluster-start-ops
  namespace: demo
spec:
  # Specifies the name of the Cluster resource that this operation is targeting.
  clusterName: pg-cluster
  type: Start

Verifying Cluster Start

To confirm a successful start operation:

1. Check cluster status transition:

   kubectl get cluster pg-cluster -n demo -w
   

   Example Output:

   NAME         CLUSTER-DEFINITION   TERMINATION-POLICY   STATUS     AGE
   pg-cluster   postgresql           Delete               Updating   22m
   pg-cluster   postgresql           Delete               Running    22m
   

2. Verify pod recreation:

   kubectl get pods -n demo -l app.kubernetes.io/instance=pg-cluster
   

   Example Output:

   NAME                     READY   STATUS    RESTARTS   AGE
   pg-cluster-postgresql-0   1/1     Running   0          2m
   pg-cluster-postgresql-1   1/1     Running   0          1m
   

3. Check service endpoints:

   kubectl get endpoints pg-cluster-postgresql-postgresql -n demo
   

Restarting Cluster

Restart operations provide:

• Pod recreation without full cluster stop
• Component-level granularity
• Minimal service disruption

Use cases:

• Configuration changes requiring restart
• Resource refresh
• Troubleshooting

Using OpsRequest API

Target a specific component for restart:

apiVersion: operations.kubeblocks.io/v1alpha1
kind: OpsRequest
metadata:
  name: pg-cluster-restart-ops
  namespace: demo
spec:
  clusterName: pg-cluster
  type: Restart
  restart:
  - componentName: postgresql

Verifying Restart Completion

To verify a successful component restart:

1. Track OpsRequest progress:

   kubectl get opsrequest pg-cluster-restart-ops -n demo -w
   

   Example Output:

   NAME                     TYPE      CLUSTER      STATUS    PROGRESS   AGE
   pg-cluster-restart-ops   Restart   pg-cluster   Running   0/2        10s
   pg-cluster-restart-ops   Restart   pg-cluster   Running   1/2        65s
   pg-cluster-restart-ops   Restart   pg-cluster   Running   2/2        2m5s
   pg-cluster-restart-ops   Restart   pg-cluster   Succeed   2/2        2m5s
   

2. Check pod status:

   kubectl get pods -n demo -l app.kubernetes.io/instance=pg-cluster
   

Note: Pods will show new creation timestamps after restart

3. Verify component health:

   kbcli cluster describe pg-cluster -n demo
   

Once the operation is complete, the cluster will return to the Running state.

Summary

In this guide, you learned how to:

1. Stop a PostgreSQL cluster to suspend operations while retaining persistent storage.
2. Start a stopped cluster to bring it back online.
3. Restart specific cluster components to recreate their Pods without stopping the entire cluster.

By managing the lifecycle of your PostgreSQL cluster, you can optimize resource utilization, reduce costs, and maintain flexibility in your Kubernetes environment. KubeBlocks provides a seamless way to perform these operations, ensuring high availability and minimal disruption.