title	description
GKE Persistent Disks Custom StorageClass	Use Custom storageclass to provision Google Disks for Kubernetes Workloads

Step-00: Pre-requisites

1. Verify if GKE Cluster is created
2. Verify if kubeconfig for kubectl is configured in your local terminal

# Configure kubeconfig for kubectl
gcloud container clusters get-credentials <CLUSTER-NAME> --region <REGION> --project <PROJECT>

# Replace Values CLUSTER-NAME, ZONE, PROJECT
gcloud container clusters get-credentials standard-cluster-private-1 --region us-central1 --project kdaida123

3. Feature: Compute Engine persistent disk CSI Driver

• Verify the Feature Compute Engine persistent disk CSI Driver enabled in GKE Cluster.
• This is required for mounting the Google Compute Engine Persistent Disks to Kubernetes Workloads in GKE Cluster.

Step-01: Introduction

• Feaute-1: Create custom Kubernetes StorageClass instead of using predefined one in GKE Cluster. custom storage class gke-pd-standard-rwo-sc
• Feature-2: Test allowVolumeExpansion: true in Storage Class
• Feature-3: Use reclaimPolicy: Retain in Storage Class and Test it

Step-02: List Kubernetes Storage Classes in GKE Cluster

# List Storage Classes
kubectl get sc

Step-03: 00-storage-class.yaml

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata: 
  name: gke-pd-standard-rwo-sc
provisioner: pd.csi.storage.gke.io
volumeBindingMode: WaitForFirstConsumer 
allowVolumeExpansion: true
reclaimPolicy: Retain 
parameters:
  type: pd-balanced

# STORAGE CLASS 
# 1. A StorageClass provides a way for administrators 
# to describe the "classes" of storage they offer.
# 2. Here we are offering GCP PD Storage for GKE Cluster

Step-04: 01-persistent-volume-claim.yaml

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pv-claim
spec: 
  accessModes:
    - ReadWriteOnce
  storageClassName: gke-pd-standard-rwo-sc
  resources: 
    requests:
      storage: 4Gi

Step-05: Other Kubernetes YAML Manifests

• No changes to other Kubernetes YAML Manifests
• They are same as previous section
• 02-UserManagement-ConfigMap.yaml
• 03-mysql-deployment.yaml
• 04-mysql-clusterip-service.yaml
• 05-UserMgmtWebApp-Deployment.yaml
• 06-UserMgmtWebApp-LoadBalancer-Service.yaml

Step-06: Deploy kube-manifests

# Deploy Kubernetes Manifests
kubectl apply -f kube-manifests/

# List Storage Classes
kubectl get sc
Observation: 
1. You should find the new custom storage class object created with name as "gke-pd-standard-rwo-sc"

# List PVC
kubectl get pvc

# List PV
kubectl get pv

# List ConfigMaps
kubectl get configmap

# List Deployments
kubectl get deploy

# List Pods
kubectl get pods

# List Services
kubectl get svc

# Verify Pod Logs
kubectl get pods
kubectl logs -f <USERMGMT-POD-NAME>
kubectl logs -f usermgmt-webapp-6ff7d7d849-7lrg5

Step-07: Verify Persistent Disks

• Go to Compute Engine -> Storage -> Disks
• Search for 4GB Persistent Disk
• Observation: You should see the disk type as Balanced persistent disk

Step-08: Access Application

# List Services
kubectl get svc

# Access Application
http://<ExternalIP-from-get-service-output>
Username: admin101
Password: password101

# Create New User (Used for testing  `allowVolumeExpansion: true` Option)
Username: admin102
Password: password102
First Name: fname102
Last Name: lname102
Email Address: admin102@stacksimplify.com
Social Security Address: ssn102

Step-09: Update 01-persistent-volume-claim.yaml from 4Gi to 8Gi

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pv-claim
spec: 
  accessModes:
    - ReadWriteOnce
  storageClassName: gke-pd-standard-rwo-sc
  resources: 
    requests:
      #storage: 4Gi # Commment at Step-09
      storage: 8Gi # UnCommment at Step-09

Step-10: Deploy updated kube-manifests

# Deploy Kubernetes Manifests
kubectl apply -f kube-manifests/

# List PVC
kubectl get pvc
Observation:
1. Wait for 2 to 3 mins and automatically CAPACITY value changes from 4Gi to 8Gi

# List PV
kubectl get pv
Observation:
1. Wait for 2 to 3 mins and automatically CAPACITY value changes from 4Gi to 8Gi

# Access Application
http://<ExternalIP-from-get-service-output>
Username: admin101
Password: password101
Observation:
1. No impact to underlying MySQL Database data.
2. VolumeExpansion is seamless without impacting the real data. 
3. We should find the two users which are present before VolumeExpansion as-is.

Step-11: Verify Persistent Disks

• Go to Compute Engine -> Storage -> Disks
• Search for 8GB Persistent Disk, as 4GB disk expaned to 8GB now.
• Observation: You should see the disk type as Balanced persistent disk

Step-12: Verify reclaimPolicy: Retain

# Delete kube-manifests
kubectl delete -f kube-manifests/

# List Storage Class
kubectl get sc
Observation:
1. Custom storage class deleted

# List PVC
kubectl get pvc
Observation:
1. PVC deleted

# List PV
kubectl get pv
Observation:
1. PV still present
2. PV STATUS will be in "Released", not used by anyoe.

Step-13: Verify Persistent Disks

• Go to Compute Engine -> Storage -> Disks
• Search for 8GB Persistent Disk.
• Observation: You should see the disk is still present even after all kube-manifests (storageclass, pvc) all deleted.
• This is due to we have used reclaimPolicy: Retain in Custom Storage Class

Step-14: Clone Persistent Disk

• Question: Why we are cloning the disk ?
• Answer: In the next demo, we are going use the pre-existing persistent disk in our demo. For that purpose we are cloning it.
• Go to Compute Engine -> Storage -> Disks
• Search for 8GB Persistent Disk.
• Click on Clone Disk
• Name: preexisting-pd
• Description: preexisting-pd Demo with GKE
• Location: Single
• Snapshot Schedule: UNCHECK
• Click on CREATE

Step-15: Delete Retained Persistent Disk from this Demo

• Go to Compute Engine -> Storage -> Disks
• Search for 8GB Persistent Disk.
• Disk Name: pvc-3f2c1daa-122d-4bdb-a7b6-b9943631cc14
• Click on DELETE DISK

# List PV
kubectl get pv

# Delete  PV 
kubectl delete pv pvc-3f2c1daa-122d-4bdb-a7b6-b9943631cc14 

# List PV
kubectl get pv

Step-16: Change PVC 8Gi to 4Gi: 01-persistent-volume-claim.yaml

• Change PVC 8Gi to 4Gi so that kube-manifests will be demo ready for students.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pv-claim
spec: 
  accessModes:
    - ReadWriteOnce
  storageClassName: gke-pd-standard-rwo-sc
  resources: 
    requests:
      storage: 4Gi # Commment at Step-09
      #storage: 8Gi # UnCommment at Step-09

Reference

• Using the Compute Engine persistent disk CSI Driver