nginx.md

Using NGINX

We demonstrate running an nginx container within the same pod as the aladdin-demo-server app. Our template sets up nginx as a simple proxy server that will listen to all traffic on a port and forward it to the falcon app. We specify the nginx values in the values.yaml file.

app:
  uwsgi:
    port: 8000
  nginx:
    use: true
    port: 80
    httpPort: 80
    httpsPort: 443

Set the use field to true. This is all you need to do to see nginx work, you can verify this by restarting the app with aladdin start. Navigate to the aladdin-demo-server service pod in the Kubernetes dashboard and you should be able to see two containers running. Read on for how we did it.

Since we are just using the nginx:1.12-alpine image without modifications, there is no need to create a separate Dockerfile for it.

We add the nginx configuration files using the templating method described in the Configuration Files section. We then add another container for nginx in server/deploy.yaml.

        - name: {{ .Chart.Name }}-nginx
          image: nginx:1.12-alpine
          ports: 
            - containerPort: {{ .Values.app.nginx.port }}
              protocol: TCP
          volumeMounts:
            - mountPath: /etc/nginx/
              name: {{ .Chart.Name }}-nginx

In the server/service.yaml, we expose the nginx port for the pod so that all incoming requests get routed to nginx first.

Nginx InitContainer

We have added a simple initContainer for nginx.

In the same server/deploy.yaml file, we add a field for initContainers.

    initContainers:
  {{ if .Values.app.nginx.use }}
    # writes a short message into index.html into a mounted volume file shared by nginx
    # this will be the default page that shows up when sending get requests to nginx that
    # are not forwarded to uWSGI
    - name: install
      image: busybox
      command: ["sh", "-c", "printf '\n You have reached NGINX \n \n' > /work-dir/index.html"]
      volumeMounts:
      - name: workdir
        mountPath: "/work-dir"
  {{ end }}

This initContainer, which we named install, only needs to run a simple shell command that writes a short welcome message into a file. Therefore, it doesn't need a docker image that has any application code, it can just use a lightweight image, in this case busybox.

Since the index.html file needs to be shared with the nginx container, we put it into a shared volume called workdir. This volume also needs to be added in the volumes field for the deployment

      - name: workdir 
        emptyDir: {}

We also mounth this volume in the nginx container

     volumeMounts:
    # mount html that should contain an index.html file written by the init container
    - mountPath: /usr/share/nginx/html
      name: workdir

This is all that is needed for this simple initContainer to run. We can verify that it wrote the index.html file by simpling running $ curl $(minikube service --url aladdin-demo-server), which should return You have reached NGINX.