Prepare Kubernetes Cluster for Confluent Operator¶

This guide describes the tasks to prepare your Kubernetes cluster for Confluent Platform deployment with Confluent Operator. The user performing these tasks will need certain Kubernetes cluster-level permissions.

The examples in this guide use the following assumptions:

$VALUES_FILE refers to the configuration file you set up in Create the global configuration file.
To present simple and clear examples in the Operator documentation, all the configuration parameters are specified in the config file ($VALUES_FILE). However, in your production deployments, use the --set or --set-file option when applying sensitive data with Helm. For example:
```
helm upgrade --install kafka \
 --set kafka.services.mds.ldap.authentication.simple.principal="cn=mds\,dc=test\,dc=com" \
 --set kafka.services.mds.ldap.authentication.simple.credentials=”Developer!” \
 --set kafka.enabled=true
```
operator is the namespace that Confluent Platform is deployed in.
All commands are executed in the helm directory under the directory Confluent Operator was downloaded to.

Create a namespace for Confluent Platform¶

Create a Kubernetes namespace to deploy Confluent Platform into:

kubectl create namespace <namespace-name>

Grant permissions for namespaced deployment¶

To allow a user who does not have cluster-level access to deploy Operator and Confluent Platform in a namespace, perform the following tasks as a Kubernetes cluster admin before deploying Operator and Confluent Platform. The snippets in this section uses the operator namespace.

Pre-install the Confluent Operator CRDs with the following command:

kubectl apply -f <Operator home directory>/resources/crds -n operator

Create the rolebinding.yaml file with the permissions required for a namespaced deployment.

The content contains the minimum permissions required. Add any other resource permissions you might additionally require.

The role and role binding should be in the same namespace as Operator.

The subject in the role binding must be the user/account existing in the given namespace.

---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  labels:
    component: operator
  name: cc-operator
  namespace: operator
rules:
- apiGroups:
  - cluster.confluent.com
  resources:
  - '*'
  verbs:
  - '*'
- apiGroups:
  - operator.confluent.cloud
  resources:
  - '*'
  verbs:
  - '*'
- apiGroups:
  - policy
  resources:
  - poddisruptionbudgets
  verbs:
  - '*'
- apiGroups:
  - apps
  resources:
  - deployments
  - deployments/scale
  - deployments/status
  - replicasets
  - replicasets/scale
  - replicasets/status
  - statefulsets
  - statefulsets/scale
  - statefulsets/status
  verbs:
  - '*'
- apiGroups:
  - ""
  resources:
  - configmaps
  - endpoints
  - events
  - persistentvolumeclaims
  - pods
  - pods/exec
  - secrets
  - services
  - serviceaccounts
  verbs:
  - '*'
---
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  labels:
    component: operator
  name: operator-cc-operator
  namespace: operator
subjects:
- kind: ServiceAccount
  name: cc-operator
  namespace: operator
roleRef:
  kind: Role
  name: cc-operator
  apiGroup: rbac.authorization.k8s.io

Creates the role and the role binding with the following command to grant the required permissions to the service account named cc-operator. The cc-operator service account will install Operator and Confluent Platform.
```
kubectl apply -f rolebinding.yaml -n operator
```
Delete the following files from the <Operator home directory>/helm/confluent-operator/charts/operator/templates directory:
- clusterrole.yaml
- clusterrolebinding.yaml

Set up statically-provisioned disks¶

Starting in Confluent Operator 5.5, you can instruct Operator to use a specific StorageClass for all PersistentVolumes it creates.

This is optional in Confluent Operator if you have Kubernetes clusters that are not capable of dynamically provisioning storage and need to statically provision disks up front.

Configure a StorageClass in Kubernetes for local provisioning. For example:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: my-storage-class
provisioner: kubernetes.io/no-provisioner
volumeBindingMode: WaitForFirstConsumer

For every Kafka broker instance you expect to create, decide:
- Which worker node you expect to place it on.
- Which directory path on that worker node’s host filesystem that you intend to use as the PersistentVolume to be exposed to the broker instance.
Create a PersistentVolume with the desired host path and the hostname label of the desired worker node as described here.
```
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-1                             ----- [1]
spec:
  capacity:
    storage: 1Gi                        ------ [2]
  volumeMode: Filesystem
  accessModes:
  - ReadWriteOnce
  persistentVolumeReclaimPolicy: Retain  ----- [3]
  storageClassName: my-storage-class     ------[4]
  local:
     path: /mnt/data/broker-1-data       ----- [5]
  nodeAffinity:
    required:
      nodeSelectorTerms:
      - matchExpressions:
        - key: kubernetes.io/hostname
          operator: In
          values:
          - ip-172-20-114-199.ec2.internal --- [6]
```
- [1] Choose a name for the PersistentVolume.
- [2] Choose a storage size that is greater than or equal to the storage you’re requesting for each Kafka broker instance.
- [3] Choose Retain if you want the data to be retained after you delete the PersitentVolumeClaim that the Operator will eventually create and which Kubernetes will eventually bind to this PersistentVolume.
  
  Choose Delete if you want this data to be garbage-collected when the PersistentVolumeClaim is deleted.
  
  Important
  
  With persistentVolumeReclaimPolicy: Delete, your data on the volume will be deleted when you delete the pod and consequently its persistent volume.
- [4] The storageClassName must match the global.storage.storageClassName you put in your configuration file ($VALUES_FILE).
- [5] This is the directory path you want to use on the worker node for the broker as its persistent data volume.
- [6] This is the value of the kubernetes.io/hostname label of the worker node you want to host this broker instance. To find this hostname:
```
kubectl get nodes -o 'custom-columns=NAME:metadata.name,HOSTNAME:metadata.labels.kubernetes.io/hostname'

NAME       HOSTNAME
node-1     ip-172-20-114-199.ec2.internal
```
Repeat steps 2 and 3 for every broker you intend to create. This is determined by the kafka.replicas field in your configuration file ($VALUES_FILE).