Custom listen ports document (#3715)

Author: jasonwilliams14

docs/content/tutorials/custom-listen-ports.md

@@ -0,0 +1,158 @@
+---
+title: Customizing NGINX Ingress Controller Ports
+description: |
+  How to customize F5 NGINX Ingress Controller ports.
+weight: 1800
+doctypes: ["concept"]
+toc: true
+---
+## Customizing NGINX Ingress Controller Ports
+
+This document explains how to change the default ports that NGINX Ingress Controller is configured to use, as well as how to add additional `listen` settings. For more information, please read the [NGINX Listen documentation](http://nginx.org/en/docs/http/ngx_http_core_module.html#listen).
+
+## Changing Default Ports
+
+By default, NGINX Ingress Controller listens on ports 80 and 443. These ports can be changed easily, but modifying the `listen` ports for your NGINX Ingress resources will require the editing of `.tmpl` files.
+
+If you are using NGINX Ingress Controller CRDs (VirtualServer):
+- `nginx-plus-virtualserver.tmpl` for NGINX Plus
+- `nginx-virtualserver.tmpl` if using NGINX OSS
+
+If you are using `Ingress` resource you will need to modify:
+- `nginx-plus-ingress.tmpl` if using NGINX Plus
+- `nginx-ingress.tmpl` if using NGINX OSS
+
+In this example, we will use the `nginx-virtualserver.tmpl` template to change the port from 80 to 85.
+You can find the [nginx-virtualserver template files in our repository](https://github.com/nginxinc/kubernetes-ingress/tree/main/internal/configs/version2).
+
+We start by modifying `nginx-virtualserver.tmpl` to change the port setting:
+
+```nginx
+server {
+    listen 80{{ if $s.ProxyProtocol }} proxy_protocol{{ end }};
+
+    server_name {{ $s.ServerName }};
+
+    set $resource_type "virtualserver";
+    set $resource_name "{{$s.VSName}}";
+    set $resource_namespace "{{$s.VSNamespace}}";
+```
+To change the listen port from `80` to `85`, edit the `listen` line at the start of the server configuration block.
+
+After changing the number, the file looks like this:
+
+```nginx
+server {
+    listen 85{{ if $s.ProxyProtocol }} proxy_protocol{{ end }};
+
+    server_name {{ $s.ServerName }};
+
+    set $resource_type "virtualserver";
+    set $resource_name "{{$s.VSName}}";
+    set $resource_namespace "{{$s.VSNamespace}}";
+```
+
+Modify the file you need (per the example above). In the example, we modified `nginx-plus-virtualserver.tmpl`:
+
+
+## Rebuild the NGINX Ingress Controller image
+
+You must rebuild the NGINX Ingress Controller image for the new port settings to take effect.
+Once the image is built and pushed, make sure you update your deployment to point to the new image and deploy.
+Once deployed, create a new `VirtualServer` resource and run `nginx -T` to confirm if the port change has taken effect.
+
+Ensure that your `Deployment` and your `Service` match up to the new port you configured in the templates.
+Below is an example of  `Deployment` and `Service` matching to the new port that NGINX Ingress Controller now listens on.
+
+```yaml
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: nginx-ingress
+  namespace: nginx-ingress
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: nginx-ingress
+  template:
+    metadata:
+      labels:
+        app: nginx-ingress
+      annotations:
+       prometheus.io/scrape: "true"
+       prometheus.io/port: "9113"
+       prometheus.io/scheme: http
+    spec:
+      serviceAccountName: nginx-ingress
+      containers:
+      - image: nginx/nginx-ingress:3.0.2
+        imagePullPolicy: IfNotPresent
+        name: nginx-ingress
+        ports:
+        - name: http
+          containerPort: 85
+        - name: https
+          containerPort: 443
+        - name: readiness-port
+          containerPort: 8081
+        - name: prometheus
+          containerPort: 9113
+        readinessProbe:
+          httpGet:
+            path: /nginx-ready
+            port: readiness-port
+          periodSeconds: 1
+        securityContext:
+```
+
+Notice that now, the `http` port is set to `85`, which reflects the change we made in the template file.
+
+Here is the `service` file:
+
+```yaml
+apiVersion: v1
+kind: Service
+metadata:
+  name: nginx-ingress
+  namespace: nginx-ingress
+spec:
+  externalTrafficPolicy: Local
+  type: LoadBalancer
+  ports:
+  - port: 80
+    targetPort: 85
+    protocol: TCP
+    name: http
+  - port: 8443
+    targetPort: 8443
+    protocol: TCP
+    name: https
+  selector:
+    app: nginx-ingress
+```
+
+Since NGINX Ingress Controller is now listening on ports 85 and 8443, you must modify the `targetPort` in the NGINX Ingress Controller service to match the change in the deployment to ensure traffic will be sent to the proper port.
+
+The parameter to change above is `targetPort`. Since we have changed NGINX Ingress Controller to listen on port 85, we need to match that in the service: requests will be sent to NGINX Ingress Controller on port 85 instead of the default value, port 80.
+
+If you view the `NGINX` configuration .conf file using `nginx -T`, you should see the port you defined in the .template file is now set on the `listen` line.
+
+Here is an example output of the `NGINX` configuration that has been generated:
+
+```console
+kubectl exec -it -n nginx-ingress nginx-ingress-54bffd78d9-v7bns -- nginx -T
+```
+
+```nginx
+server {
+    listen 85;
+    listen [::]:85;
+    listen 8011;
+
+    server_name cafe.example.com;
+
+    set $resource_type "virtualserver";
+    set $resource_name "cafe";
+    set $resource_namespace "default";
+```