How to deploy multiple versions?

To deploy multiple versions of an application in Kubernetes, you can create separate deployments for each version. Here’s a step-by-step guide on how to do this:

Step 1: Create Deployments for Each Version

You will create separate deployments for each version of your application. For example, let's say you have two versions: v1 and v2.

Deploy Version 1

Create a deployment for version 1 of your application:

# deployment-v1.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-v1
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
      version: v1
  template:
    metadata:
      labels:
        app: myapp
        version: v1
    spec:
      containers:
        - name: myapp
          image: myapp:v1
          ports:
            - containerPort: 8080

Deploy Version 2

Create a deployment for version 2 of your application:

# deployment-v2.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-v2
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
      version: v2
  template:
    metadata:
      labels:
        app: myapp
        version: v2
    spec:
      containers:
        - name: myapp
          image: myapp:v2
          ports:
            - containerPort: 8080

Step 2: Apply the Deployments

Use kubectl apply to create the deployments in your Kubernetes cluster:

kubectl apply -f deployment-v1.yaml
kubectl apply -f deployment-v2.yaml

Step 3: Expose Each Deployment as a Service

You need to create services to expose each deployment. This allows you to route traffic to the correct version.

Service for Version 1

# service-v1.yaml
apiVersion: v1
kind: Service
metadata:
  name: myapp-v1-service
spec:
  selector:
    app: myapp
    version: v1
  ports:
    - port: 80
      targetPort: 8080

Service for Version 2

# service-v2.yaml
apiVersion: v1
kind: Service
metadata:
  name: myapp-v2-service
spec:
  selector:
    app: myapp
    version: v2
  ports:
    - port: 80
      targetPort: 8080

Step 4: Apply the Services

Use kubectl apply to create the services:

kubectl apply -f service-v1.yaml
kubectl apply -f service-v2.yaml

Step 5: (Optional) Create an Ingress Resource

If you want to route traffic to these services using an Ingress resource, you can create an Ingress definition. Here’s an example:

# ingress.yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: myapp-ingress
spec:
  rules:
    - host: myapp.example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: myapp-v1-service
                port:
                  number: 80

Step 6: Apply the Ingress

Use kubectl apply to create the Ingress:

kubectl apply -f ingress.yaml

Summary

By following these steps, you can successfully deploy multiple versions of an application in Kubernetes. Each version is managed independently through its own deployment and service, allowing you to control traffic and perform canary deployments or blue-green deployments as needed.