Docker Container/Service with Same Port: Best Practices?

EliteCow@lemmy.dbzer0.com to Selfhosted@lemmy.world – 60 points –

I am very new to using docker. I have been used to using dedicated VM's and hosting the applications within the servers OS.

When hosting multiple applications/services that require the same port, is it best practice to spin up a whole new docker server or how should I go about the conflicts?

Ie. Hosting multiple web applications that utilize 443.

Thank you!

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Thank you! I am using Caddy and was able to define a unique random port for the other containers and access this via reverse proxy!

If the containers are all in the same network. You dont need to expose a port.

Lets assume you create a docker network called reverse_proxy and add all your contaiers that you want to be accessed by the reverse proxy to that network (including caddy).

Then you can address all containers through the hostname in you caddy file and the port would be the default configurated port from the container.

So in the end you just expose the caddy container and nothing more.

That wouldn't work if multiple containers use the same port (eg. 8000), right?

Without a docker network, I can just map 8001:8000 and don't have that issue.

Yes, it'd work just fine because each container listens on port 8000 of their own IP address, not the docker server's IP address. Caddy/Traefik just redirects traffic to that port.

Okay, thanks! Maybe I'll try it in the future.

I've just posted a little example. I'd recommend doing it this way. No more thinking about what port is allready exposed etc

In addition to Caddy being apart of the reverse_proxy network. Would I also have to add it to the Bridge network so that I can utilize the machine IP that docker is hosted on for port forwarding 443?

Caddy would have the bridge proxy network and the port 443 exposed.

version: "3.7"

networks:
  proxy-network:
    external: true
# needs to be created manually bevor running (docker create network proxy-network)
services:
  caddy:
    image: caddy
    container_name: caddy
    restart: unless-stopped
    ports:
      - 80:80
      - 443:443
    volumes:
      - ./data:/data
      - ./config:/config
      - ./Caddyfile:/etc/caddy/Caddyfile:ro
    networks:
      - proxy-network

Other services:

version: "3.7"

networks:
  proxy-network:
    external: true

services:
  app:
    image: app
    container_name: app
    restart: unless-stopped
    volumes:
      - ./app-data:/data
    networks:
      - proxy-network

Caddy can now talk to the app with the apps container_name.

Caddyfile:

homepage.domain.de {
    reverse_proxy app:80
}

So the reverse proxy network is an extra network only for containers that need to be exposed.