cloud-computing-msc-ai-examples/kubernetes-example/kubectl-intro.md

# Introduction to kubectl 

## Deployment of the needed description in kubernetes

These are two approaches to create the description in Kuberentes: 

```bash
# create a namespace 
kubectl create namespace web-test

# Then choose one of the following ways:
# (1) Create the description
kubectl create -f nginx.yml -f service.yml

# (2) Create or update descriptions if existing
kubectl apply -f nginx.yml -f service.yml
```

## To show it is working

Here are some useful commands:

```bash
# show nodes
kubectl get nodes

# show pods for our namespace
kubectl get -n web-test pods 

# show deployments for our namespace
kubectl get -n web-test deployment

# show services for our namespace
kubectl get -n web-test service

# show logs of deployed nginx instances
kubectl logs -n web-test deployment/nginx-deployment
```

## Scaling up and down

```bash
# scale up instances to 5
kubectl scale deployment/nginx-deployment --replicas=5

# scale down instances again to 3
kubectl scale deployment/nginx-deployment --replicas=3

```


## To see it is working in the browser ;)

The nginx instances are reachable at the floating ips of the **node**-instances at port **30007** in our case.


## Many other things can be done ;)

- Autoscaling 
- Detailled Service functions (LoadBalancer, ...)
- Dashboard
- FaaS Setup ;) 
- ...


## Appendix

### Nginx description

*nginx.yml:*
```yml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  namespace: web-test
spec:
  selector:
    matchLabels:
      app: nginx-deployment
  replicas: 3 # tells deployment to run 3 pods matching the template
  template:
    metadata:
      labels:
        app: nginx-deployment
    spec:
      containers:
      - name: nginx
        image: nginx:latest
        ports:
        - containerPort: 80

```

### Nginx service description

*service.yml:*
```yml
apiVersion: v1
kind: Service
metadata:
  name: nginx-service
  namespace: web-test
spec:
  type: NodePort
  selector:
    app: nginx-deployment
  ports:
      # By default and for convenience, the `targetPort` is set to the same value as the `port` field.
    - port: 80
      targetPort: 80
      # Optional field
      # By default and for convenience, the Kubernetes control plane will allocate a port from a range (default: 30000-32767)
      nodePort: 30007
```