How is the networking setup in docker? (with a reverse proxy)

[wsw70]

I am trying to run Firefly III in docker, proxied via Traefik.

I started with the idea that, similarly to all my other containers, I do not need to map any ports (the traffic goes though Traefik, then the proxy network, ultimately reaching the exposed port directly on the container).

There is an error at start in that case, I have to bind 80:8080 to the host. With this setup the container starts, it mentions

firefly_iii-1       | [30-May-2025 16:18:36] NOTICE: fpm is running, pid 143
firefly_iii-1       | [30-May-2025 16:18:36] NOTICE: ready to handle connections
firefly_iii-1       | ✅ NGINX + PHP-FPM is running correctly.

but without any information on the port. I tried 80 and 8080 but the proxy connection fails. Since the container does not have ip or netstat and I cannot get a root prompt I am stuck.

Could someone share how what they pointed to upstream when setting up a proxy in docker?

Note: I read the docs at https://docs.firefly-iii.org/references/faq/docker/

[Styleflix]

I don't know if I understand your setup corretly but it doens't sound so different from mine.
I user docker (with compose) and an apache reverse proxy.

When you start the firefly docker container you can specify the ports - or edit them in the compose file.
For me I chose 8230:8080. So 8080 is the port "inside" the container that firefly servs. While (in my case) 8230 gets "redirected to the host".
That given, I configured the apache reverse proxy to forward incomming traffic to "subdomain.mydomain.tld" with port 443 for default https, to port 8230 of the docker container.

TL;DR: Firefly runs on port 8080 but with docker you can map it to a port of your choice on the host to which you can point your reverse proxy to

Edit: I think the root cause of your problem may be, that you use port 80 for the container which may be in use by another application. Just try a custom configuration with the reverse proxy setup. Like 1234:8080

[wsw70]

Thanks for the reply, I should have been more clear:

I have a docker network (proxy) that all my containers are attached to. My reverse proxy (Traefik) is also attached there, and to the host. This way I never need to expose the ports of the containers (-p or ports:), they run on their owns, on their container, and traefik points to them via the container name (automagically resolved by docker) and their port).

Firefly III somehow needed to have the ports exposed to the host for some kind of healthcheck (I will have a look at that later because this is not a typical way to check for "up-ness" but anyway).

My question was whether someone has setup docker the typical way (using the docker network), ideally without exposing ports.

I could not find anywhere what the port of the container was but you confirmed it is 8080 so I will look further for why it does not work with the typical setting I have for my other 30 services :)

[wsw70]

OK, I found the problem: somehow the host port I had to bind to was taken. Changed the port and everything is fine (well, except the health check which I will look into nad possibly send a PR)

[Styleflix]

Glad you figured it out :)
I think I can't help about the health check though.