Creating a replicated deployment for the application and MongoDB

Follow these steps:

1. To create an external disk, we'll use the following command:

$ gcloud compute disks create --size 1GB mongo-disk \
--zone us-east1-c

2. We'll first create the MongoDB deployment because the application expects the database's presence. A deployment object creates the desired number of pods indicated by our replica count. Notice the label given to the pods that are created. The Kubernetes system manages the pods, the deployment, and their linking to their corresponding services via label selectors. Navigate to /Chapter01/mysite-gke/db-deployment.yml:

apiVersion: apps/v1beta1 
kind: Deployment 
metadata: 
  name: mongo-deployment 
spec: 
  replicas: 1 
  template: 
    metadata: 
      labels: 
        name: mongo 
    spec: 
      containers: 
      - image: mongo 
        name: mongo 
        ports: 
        - name: mongo 
          containerPort: 27017 
          hostPort: 27017 
        volumeMounts: 
          - name: mongo-persistent-storage 
            mountPath: /data/db 
      volumes: 
        - name: mongo-persistent-storage 
          gcePersistentDisk: 
            pdName: mongo-disk #The created disk name 
            fsType: ext4 

3. Use kubectl to deploy the deployment to the cluster:

$ kubectl create -f db-deployment.yml

4. You can view the deployments using the command:

$ kubectl get deployments 

5. The pods created by the deployment can be viewed using the command:

$ kubectl get pods

6. To present the MongoDB pods to the application layer, we'll need to create a service. A service exposes a single static IP address to the underlying set of pods. Navigate to /Chapter01/mysite-gke/db-service.yml:

apiVersion: v1 
kind: Service 
metadata: 
 labels: 
   name: mongo 
 name: mongo 
spec: 
 ports: 
   - port: 27017 
     targetPort: 27017 
 selector: 
name: mongo #The key-value pair is matched with the label on the deployment 

7. The kubectl command to create a service is:

$ kubectl create -f db-service.yml

8. You can view the status of the creation using the commands:

$ kubectl get services
$ kubectl describe service mongo

9. We'll repeat the same process for the Node.js application. For the deployment, we'll choose to have two replicas of the application pod to serve the web requests. Navigate to /Chapter01/mysite-gke/web-deployment.yml and update the <Project ID> in the image item:

apiVersion: apps/v1beta1 
kind: Deployment 
metadata: 
  name: mysite-app 
  labels: 
    name: mysite 
spec: 
  replicas: 2 
  template: 
    metadata: 
      labels: 
        name: mysite 
    spec: 
      containers: 
      - image: gcr.io/<Project ID>/mysite 
        name: mysite 
        ports: 
        - name: http-server 
  containerPort: 8080 #KeystoneJS app is exposed on port 8080 

10. Use kubectl to create the deployment:

$ kubectl create -f web-deployment.yml 

11. Finally, we'll create the service to manage the application pods. Navigate to /Chapter01/mysite-gke/web-service.yml: 

apiVersion: v1 
kind: Service 
metadata: 
 name: mysite 
 labels: 
   name: mysite 
spec: 
 type: LoadBalancer 
 ports: 
   - port: 80 #The application is exposed to the external world on port 80 
     targetPort: http-server 
     protocol: TCP 
 selector: 
name: mysite 

To create the service execute the below command:

$ kubectl create -f web-service.yml

12. Get the external IP of the mysite service and open it in a browser to view the application:

$ kubectl get services

NAME       CLUSTER-IP    EXTERNAL-IP        PORT(S)    AGE
kubernetes 10.27.240.1      <none>          443/TCP    49m
mongo      10.27.246.117    <none>        27017/TCP    30m
mysite     10.27.240.33 1x4.1x3.38.164 80:30414/TCP     2m