I am searching for a compose configuration, but I didn’t found, what I was looking for:
I want 2 containers, lets say an app and its database. The app container must have network access to the host network (i.e. host as network_mode) and access to the database container (e.g. via bridge as network_mode). Currently, my database container exposes its port to the host, where the app container is able to connect, but I consider this as a workaround/dirty hack.
If you start them from the same compose file they can connect to each other using their service names, without additional configuration.
Why does the app need access to the host network? Containers should be isolated as much as possible.
I’m using a container for fhem, a house automation server, which needs to connect to other devices in my network. I don’t want to add rules for every connection/port/device. In this case I use docker to simplify the update procedure rather than to isolate as much as possible.
Here is my docker-compose.yml. Within the fhem container I cannot reach the database container by its hostname/servicename, e.g. ping database.
If you just want to read information for example from a device tracker you should be able to access it at its IP address. Of course if you need multicast and such things then you have to integrate it into the host network.
Did you try to access it with the MariaDB client (on the default port)?
Yes, it should work. For the start, don’t configure anything and let docker-compose manage the networks.
You can always send requests from a container to devices in the host network. For example I have a Homematic CCU at 192.168.1.42 and I can access it with:
docker container run --rm debian ping 192.168.1.42
Most of the time the attempt to modify the settings manually is the reason why the networking is broken.
Create an internal network and connect fhem and database to it, in addition to that connect fhem to the host network. Take a look at Networking in Compose and Network configuration reference. (At the moment I’ve no time to write more and I know these documentations are often a bit complicated.)