Using the NGINX Ingress Controller

3 Using the NGINX Ingress Controller

This chapter includes two examples to test ingress rules with the NGINX Ingress Controller.

You can create ingress rules, using one, or more Kubernetes Ingress, VirtualServer, or VirtualServerRoute Custom Resource Definitions (CRDs). These definitions set up the ingress configuration.

Example 3-1 Single Application Routing Test

This example creates an ingress rule that directs incoming traffic to an NGINX application.

Create a Deployment and associated Service in a CRD YAML 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
  ports:
  - name: http
    port: 80
    targetPort: 80

Create the Deployment and Service using:
```
kubectl apply -f filename.yaml
```

Create an Ingress CRD in a YAML file for the NGINX service.

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
spec:
  ingressClassName: nginx
  rules:
  - http:
      paths:
        - path: /
          pathType: Prefix 
          backend:
            service: 
              name: nginx-service
              port:
                number: 80

You can then create the Ingress using:
```
kubectl apply -f filename.yaml
```

You can see the Ingress is created using:

kubectl get ingress

The output looks similar to:

NAME              CLASS   HOSTS   ADDRESS           PORTS   AGE
example-ingress   nginx   *       203.0.113.11      80      7m16s

The ADDRESS shown is also the address for the load balancer. You can confirm this using:

kubectl get service --namespace ingress-nginx

The output looks similar to:

NAME                                   TYPE           CLUSTER-IP       EXTERNAL-IP       PORT(S)                      AGE
myingress-nginx-controller             LoadBalancer   10.106.167.143   203.0.113.11      80:31036/TCP,443:32343/TCP   7d1h
myingress-nginx-controller-admission   ClusterIP      10.105.9.191     <none>            443/TCP                      7d1h

You can show the ingress rules using:

kubectl describe ingress example-ingress

The output looks similar to:

Name:             example-ingress
Labels:           <none>
Namespace:        default
Address:          203.0.113.11
Ingress Class:    nginx
Default backend:  <default>
Rules:
  Host        Path  Backends
  ----        ----  --------
  *           
              /   nginx-service:80 (10.244.1.4:80,10.244.3.4:80,10.244.4.3:80 + 1 more...)
Annotations:  <none>
Events:
  Type    Reason  Age                From                      Message
  ----    ------  ----               ----                      -------
  Normal  Sync    14m (x2 over 15m)  nginx-ingress-controller  Scheduled for sync

This shows that all traffic is to be routed to the nginx-service.

Use the curl command to create a request to the NGINX application. Use the IP address of the load balancer and the Ingress.

curl http://203.0.113.11

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 Ingress, Deployment, and Service using:

kubectl delete ingress example-ingress
kubectl delete service nginx-service
kubectl delete deployment nginx-deployment

Example 3-2 Two Applications and URL Redirection Test

This test application creates two NGINX Deployments with customized HTML pages and an Service for each Deployment. An ingress rule is then created to redirect traffic to these services depending on the path entered in the URL.

Create a YAML file that contains the HTML responses to be provided by NGINX instead of the default web server page. A ConfigMap is provided for each Service.

---
apiVersion: v1
kind: ConfigMap
metadata:
  name: configmap-nginx-a
data:
  index.html: |
    <html>
      <head>
        <title>NGINX Application A</title>
      </head>
      <body>
        <h1>This is from path /a to service nginx-a.</h1>
      </body>
    </html>
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: configmap-nginx-b
data:
  index.html: |
    <html>
      <head>
        <title>NGINX Application B</title>
      </head>
      <body>
        <h1>This is from path /b to service nginx-b.</h1>
      </body>
    </html>

You can then create the ConfigMaps using:
```
kubectl apply -f filename.yaml
```

Create two NGINX Deployments and associated Services in a CRD YAML file. Volumes are created on each Deployment to use the ConfigMaps. Each Deployment provides a different HTML page to show which application is returning data.

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment-a
  labels:
    app: nginx-a
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx-a
  template:
    metadata:
      labels:
        app: nginx-a
    spec:
      containers:
      - name: nginx-a
        image: container-registry.oracle.com/olcne/nginx:1.17.7
        ports:
        - containerPort: 80
        volumeMounts:
        - name: volume-a
          mountPath: /usr/share/nginx/html
      volumes:
      - name: volume-a
        configMap:
          name: configmap-nginx-a

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment-b
  labels:
    app: nginx-b
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx-b
  template:
    metadata:
      labels:
        app: nginx-b
    spec:
      containers:
      - name: nginx-b
        image: container-registry.oracle.com/olcne/nginx:1.17.7 
        ports:
        - containerPort: 80
        volumeMounts:
        - name: volume-b
          mountPath: /usr/share/nginx/html
      volumes:
      - name: volume-b
        configMap:
          name: configmap-nginx-b
---
kind: Service
apiVersion: v1
metadata:
  name: nginx-service-a
spec:
  selector:
    app: nginx-a
  ports:
  - name: http
    port: 80
    targetPort: 80

---
kind: Service
apiVersion: v1
metadata:
  name: nginx-service-b
spec:
  selector:
    app: nginx-b
  ports:
  - name: http
    port: 80
    targetPort: 80

Create the Deployments and Services using:
```
kubectl apply -f filename.yaml
```

Create an Ingress CRD in a YAML file for the NGINX Services. This Ingress directs any traffic that contains the path /a to nginx-service-a, and traffic that contains the path /b to nginx-service-b. No other traffic is allowed.

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: / 
spec:
  ingressClassName: nginx
  rules:
  - http:
      paths:
        - path: /a
          pathType: Prefix 
          backend:
            service: 
              name: nginx-service-a
              port:
                number: 80 
        - path: /b
          pathType: Prefix 
          backend:
            service: 
              name: nginx-service-b
              port:
                number: 80

You can then create the Ingress using:
```
kubectl apply -f filename.yaml
```

You can show the ingress rules using:

kubectl describe ingress example-ingress

The output looks similar to:

Name:             example-ingress
Labels:           <none>
Namespace:        default
Address:          203.0.113.11
Ingress Class:    nginx
Default backend:  <default>
Rules:
  Host        Path  Backends
  ----        ----  --------
  *           
              /a   nginx-service-a:80 (10.244.2.8:80,10.244.4.5:80)
              /b   nginx-service-b:80 (10.244.2.9:80,10.244.4.4:80)
Annotations:  nginx.ingress.kubernetes.io/rewrite-target: /
Events:       <none>

Use the curl command to create a request to the nginx-a application by including the /a path in the URL. Use the IP address of the load balancer and the Ingress.
```
curl http://203.0.113.11/a
```
The output looks similar to:
```
<html>
  <head>
    <title>NGINX Application A</title>
  </head>
  <body>
    <h1>This is from path /a to service nginx-a.</h1>
  </body>
</html>
```
The nginx-a Deployment responds with the default HTML page to show it's coming through the nginx-service-a Service.
Use the curl command to create a request to the nginx-b application by including the /b path in the URL.
```
curl http://203.0.113.11/b
```
The output looks similar to:
```
<html>
  <head>
    <title>NGINX Application B</title>
  </head>
  <body>
    <h1>This is from path /b to service nginx-b.</h1>
  </body>
</html>
```
The nginx-b Deployment responds with the default HTML page to show it's coming through the nginx-service-b Service.
Use the curl command to create a request without adding any path to the URL.
```
curl http://203.0.113.11
```
The output looks similar to:
```
<html>
<head><title>404 Not Found</title></head>
<body>
<center><h1>404 Not Found</h1></center>
<hr><center>nginx</center>
</body>
</html>
```
As no ingress rule is provided for this URL, no traffic is allowed.

You can delete the Ingress, Deployments, Services, and ConfigMaps using:

kubectl delete ingress example-ingress
kubectl delete service nginx-service-a
kubectl delete service nginx-service-b
kubectl delete deployment nginx-deployment-a
kubectl delete deployment nginx-deployment-b
kubectl delete configmaps configmap-nginx-a
kubectl delete configmaps configmap-nginx-b