A Quick and Dirty Docker-Compose Managed Reverse Proxy

This one is going to be short and sweet. Many of you have probably read and/or used the very popular docker nginx-proxy by jwilder. This is not another guide for that. I recommend you read the readme on the linked GitHub for that, or find a different guide.

No, this guide is for proxying non-dockerized services through the same reverse proxy, and the same docker-compose.yml file. I made a small alpine container just for this purpose. You can find it on GitHub and Docker Hub.

For example, I have a VM running docker, with nginx-proxy performs proxy services for a Ghost blog and Grafana. The file would look something like this:

version: '3'

services:
  nginx-proxy:
    restart: always
    image: jwilder/nginx-proxy:alpine
    container_name: nginx-proxy
    ports:
      - "80:80"
      - "443:443"
    volumes:
      - "/etc/nginx/vhost.d"
      - "/usr/share/nginx/html"
      - "/var/run/docker.sock:/tmp/docker.sock:ro"
  
  ghost:
    image: ghost:latest
    restart: always
    environment:
      url: https://blog.example.com
      VIRTUAL_HOST: blog.example.com
  
  grafana:
    image: grafana/grafana:latest
    restart: always
    environment:
      VIRTUAL_HOST: monitor.example.com

Now lets say I have a PRTG server running on a separate VM I want to add to the proxy service. You could add the following to the bottom of the docker-compose.yml file:

...
  prtg:
    image: soarinferret/iptablesproxy:latest
    restart: always
    cap_add:
      - NET_ADMIN
      - NET_RAW
    environment:
      SERVERIP: 192.168.0.5
      SERVERPORT: 80
      HOSTPORT: 80
      VIRTUAL_HOST: prtg.kanto.cloud
    expose:
      - '80'

Now after doing running docker-compose up -d, the new container will spin up, and simply forward all traffic destined to port 80 on the container to port 80 of 192.168.0.5.