RabbitMQ Cluster Lifecycle Management

This guide demonstrates how to manage a RabbitMQ 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 RabbitMQ Cluster

KubeBlocks uses a declarative approach for managing RabbitMQ Clusters. Below is an example configuration for deploying a RabbitMQ Cluster with 3 replicas.

Apply the following YAML configuration to deploy the cluster:

apiVersion: apps.kubeblocks.io/v1
kind: Cluster
metadata:
  name: rabbitmq-cluster
  namespace: demo
spec:
  terminationPolicy: Delete
  clusterDef: rabbitmq
  topology: clustermode
  componentSpecs:
    - name: rabbitmq
      serviceVersion: 3.13.7
      replicas: 3
      resources:
        limits:
          cpu: "0.5"
          memory: "0.5Gi"
        requests:
          cpu: "0.5"
          memory: "0.5Gi"
      volumeClaimTemplates:
        - name: data
          spec:
            storageClassName: ""
            accessModes:
              - ReadWriteOnce
            resources:
              requests:
                storage: 20Gi

Verifying the Deployment

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

kubectl get cluster rabbitmq-cluster -n demo -w

Expected Output:

kubectl get cluster rabbitmq-cluster -n demo
NAME               CLUSTER-DEFINITION   TERMINATION-POLICY   STATUS     AGE
rabbitmq-cluster   rabbitmq             Delete               Creating   15s
rabbitmq-cluster   rabbitmq             Delete               Running    83s

Check the pod status and roles:

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

Expected Output:

NAME                          READY   STATUS    RESTARTS   AGE
rabbitmq-cluster-rabbitmq-0   2/2     Running   0          106s
rabbitmq-cluster-rabbitmq-1   2/2     Running   0          82s
rabbitmq-cluster-rabbitmq-2   2/2     Running   0          47s

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

Cluster Lifecycle Operations

Stopping the Cluster

Stopping a RabbitMQ 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: rabbitmq-cluster-stop-ops
  namespace: demo
spec:
  clusterName: rabbitmq-cluster
  type: Stop

kubectl patch cluster rabbitmq-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 rabbitmq-cluster -n demo -w
   

   Example Output:

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

2. Verify no running pods:

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

   Example Output:

   No resources found in demo namespace.
   

3. Confirm persistent volumes remain:
  ```bash
  kubectl get pvc -l app.kubernetes.io/instance=rabbitmq-cluster -n demo

Example Output:

NAME                               STATUS   VOLUME     CAPACITY   ACCESS MODES   STORAGECLASS         VOLUMEATTRIBUTESCLASS   AGE
data-rabbitmq-cluster-rabbitmq-0   Bound    pvc-uuid   20Gi       RWO            <STORAGECLASS>       <unset>                 22m
data-rabbitmq-cluster-rabbitmq-1   Bound    pvc-uuid   20Gi       RWO            <STORAGECLASS>       <unset>                 21m
data-rabbitmq-cluster-rabbitmq-2   Bound    pvc-uuid   20Gi       RWO            <STORAGECLASS>       <unset>                 21m

Starting the Cluster

Starting a stopped RabbitMQ 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: rabbitmq-cluster-start-ops
  namespace: demo
spec:
  # Specifies the name of the Cluster resource that this operation is targeting.
  clusterName: rabbitmq-cluster
  type: Start

Verifying Cluster Start

To confirm a successful start operation:

1. Check cluster status transition:

   kubectl get cluster rabbitmq-cluster -n demo -w
   

   Example Output:

   NAME               CLUSTER-DEFINITION     TERMINATION-POLICY   STATUS     AGE
   rabbitmq-cluster   rabbitmq               Delete               Updating   24m
   rabbitmq-cluster   rabbitmq               Delete               Running    24m
   rabbitmq-cluster   rabbitmq               Delete               Running    24m
   

2. Verify pod recreation:

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

   Example Output:

   NAME                          READY   STATUS    RESTARTS   AGE
   rabbitmq-cluster-rabbitmq-0   2/2     Running   0          55s
   rabbitmq-cluster-rabbitmq-1   2/2     Running   0          44s
   rabbitmq-cluster-rabbitmq-2   2/2     Running   0          33s
   

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 specific components rabbitmq for restart:

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

Verifying Restart Completion

To verify a successful component restart:

1. Track OpsRequest progress:

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

   Example Output:

   NAME                           TYPE      CLUSTER            STATUS    PROGRESS   AGE
   rabbitmq-cluster-restart-ops   Restart   rabbitmq-cluster   Running   0/3        4s
   rabbitmq-cluster-restart-ops   Restart   rabbitmq-cluster   Running   1/3        28s
   rabbitmq-cluster-restart-ops   Restart   rabbitmq-cluster   Running   2/3        56s
   rabbitmq-cluster-restart-ops   Restart   rabbitmq-cluster   Running   2/3        109s
   

2. Check pod status:

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

   Note: Pods will show new creation timestamps after restart

3. Verify component health:

   kbcli cluster describe rabbitmq-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 RabbitMQ 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 RabbitMQ 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.