Using MetalLB Load Balancers

3 Using MetalLB Load Balancers

This chapter discusses how to install and configure the MetalLB module, as a custom resource, to set up a network load balancer for Kubernetes applications in a bare metal environment.

Creating an Application Using MetalLB

This section contains a basic test to verify you can create a Kubernetes application that uses MetalLB to provide external IP addresses.

To create a test application to use MetalLB:

Create a Kubernetes application that uses a LoadBalancer service. The deployment in this example creates an NGINX application with a replica count of 2, and an associated LoadBalancer service.

On a control plane node, create a file named nginx-metallb.yaml and copy the following into the file.

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: container-registry.oracle.com/olcne/nginx:1.17.7 
        ports:
        - containerPort: 80
---
kind: Service
apiVersion: v1
metadata:
  name: nginx-service
spec:
  selector:
    app: nginx
  type: LoadBalancer
  ports:
  - name: http
    port: 80
    targetPort: 80

Start the NGINX deployment and LoadBalancer service:
```
kubectl apply -f nginx-metallb.yaml
```

You can see the nginx-deployment application is running using the kubectl get deployment command:

kubectl get deployments.apps

The output looks similar to:

NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   2/2     2            2           31s

You can see the nginx-deployment service is running using the kubectl get svc command:
```
kubectl get svc
```
The output looks similar to:
```
NAME            TYPE           CLUSTER-IP     EXTERNAL-IP     PORT(S)        AGE
kubernetes      ClusterIP      10.96.0.1      <none>          443/TCP        25h
nginx-service   LoadBalancer   10.99.253.99   192.168.1.240   80:31875/TCP   70s
```
You can see the EXTERNAL-IP for the nginx-service LoadBalancer has an IP address of 192.168.1.240. This IP address is provided by MetalLB and is the external IP address that you can use to connect to the application.

Use curl to connect to the NGINX application's IP address and add the port for the application (192.168.1.240:80 in this example) to show the NGINX default page.

curl 192.168.1.240:80

The output looks similar to:

<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

You can delete the nginx-service LoadBalancer service using:
```
kubectl delete svc nginx-service
```
You can delete the nginx-deployment application using:
```
kubectl delete deployments.apps nginx-deployment
```