Blue-green deployment

In this exercise we're going to see how blue-green deployments work in Kubernetes using only its primitives.

Let's create our deploy and expose it with a NodePort service. Be sure to examine the manifests first!
```
kubectl apply -f deploy-v1.yaml
kubectl apply -f service-v1.yaml
```
You can now call the application using localhost on port 30080:
```
curl localhost:30080
```
We want to change the image from httpd:alpine to nginx:alpine, and we want this change to happen instantly.

Let's create a new deployment definition, with the following requirements:
- name: beautiful-v2
- image: nginx:alpine
- replicas: 4
- labels: app=beautiful,version=v2
And let's also apply it to our cluster, waiting for all the pods to be running.

You can use the v1 definition and change it accordingly, but be sure not to delete the v1 deployment!
You can try to call the application again and get the same response as before.
```
curl localhost:30080
```
Why is that? Well, because our Service is still routing traffic to the v1 application!
So, let's update the service definition.

Change the Service selector from version=v1 to version=v2.

You can use the kubectl edit command or edit the manifest and apply it again.
Let's call the application one last time.
```
curl localhost:30080
```
What is the response? Has it changed?
We don't need the v1 deployment anymore, let's scale it down.
```
kubectl scale deploy beautiful-v1 --replicas=0
```

Finally, you can cleanup everything.

kubectl delete deployment beautiful-v1 beautiful-v2
kubectl delete service beautiful

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