Set custom variables using Kubernetes operator

This artical explains how to set custom variables using the Kubernetes operator. custom variables are nothing but additional properties specified in HiveMQCluster specification.

With the help of operator.templateConfigMap and controllerTemplate we can set custom variables.

Let's take the example of setting custom annotations with help of a custom variable.

Instructions

Generate default operator templates for configMap using the following steps.

$ helm template -s templates/hivemq-operator/operator-templates.yaml hivemq hivemq/hivemq-operator >> custom-template.yaml

Edit the custom-template.yaml to incorporate your changes which was generated by step 1

apiVersion: v1
kind: ConfigMap
metadata:
  name: <your custom template name>
data:
  cluster-daemon-set.yaml: |-
  ...
  cluster-deployment.yaml: |-
      apiVersion: apps/v1
      kind: Deployment
      metadata:
        name: "{{ spec.name }}"
        namespace: "{{ spec.namespace }}"
        ...
      spec:
        minReadySeconds: 30
        ...
        template:
          metadata:
            labels:
              app: "hivemq"
              hivemq-cluster: "{{ spec.name }}"
              hivemq.com/node-offline: "false"
            annotations:
              mycustomValue: "{{ spec.customProperties.myCustomProperty }}"

Apply the config map by using the following command

$ kubectl apply -f <your custom template yaml filename>

Set templateConfigMap config in values.yaml of Kubernetes operator

operator:
  deployCr: false  
  templateConfigMap: <configmap name you created in step3 >
  ...

Execute helm upgrade / install the operator with the following command.

$ helm upgrade --install -f values.yaml <cluster name> hivemq/hivemq-operator

Add custom controller template in HiveMQ cluster yaml. This will refer to the custom template which was created and configured in step 1 and step 2 respectively.

apiVersion: hivemq.com/v1
kind: HiveMQCluster
metadata:
  name: hivemq-cluster
spec:
  controllerTemplate: "cluster-deployment.yaml"
  customProperties:
    myCustomProperty: "testvalue"
...

Deploy HiveMQ cluster with the following command
- ```
$ kubectl apply -f < hivemq cluster.yaml 
```

You can check your changes are applied correctly or not by executing the following command

$ kubectl get pods
$ kubectl describe pod <one of running pod name>

The output of the describe command will include changes.
Please refer following output as an example.

Name:         hivemq-cluster1123-6fd545799f-4xnc5
Namespace:    XXXXX
Priority:     0
Node:         node11/10.2.1.218
Start Time:   Mon, 31 May 2021 11:39:10 +0200
Labels:       app=hivemq
              hivemq-cluster=hivemq-cluster1123
              hivemq.com/node-offline=false
              pod-template-hash=6fd545799f
Annotations:  mycustomValue: test123
Status:       Running
...

Set custom variables using Kubernetes operator

Instructions

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