fr24feed in Docker

I'm tired of keeping track of all the hacks I needed to introduce to my Arch Linux installation on my Raspberry Pi to get fr24feed running, so here's a Docker configuration.

Usage

Type in your sharing key in fr24feed/fr24feed.ini.
```
fr24key="0123456789abcdef"
```

Optionally, edit dump1090/config.js to set the correct coordinates of the receiver.

DefaultCenterLat = 66.5;
DefaultCenterLon = 25.19;

SiteShow    = true;
SiteLat     = 66.5;
SiteLon     = 25.19;
SiteName    = "My receiver";

Optionally, edit dump1090/supervisord.conf to set the correct coordinates of the receiver in dump1090-fa's arguments (--lat and --lon).
```
command=/usr/bin/dump1090-fa ... --lat 66.5 --lon 25.19 ...
```

Start the containers using

make pull && make up

You can now access the interactive map at http://0.0.0.0:8080/dump1090-fa/ and the fr24feed web interface at http://0.0.0.0:8754/.

Stop the containers using

make down

Development

TL;DR: build the native images using

make compose/build

Or, if you have Compose version 1.24.x or below,

make docker/build

Dependencies

Docker with BuildKit support (18.09 or higher),
Compose with BuildKit support for compose-build (1.25.0 or higher).

CI

I used a guide to set up multiarch builds (1). I don't understand it completely at the moment, but whatever.

The goal is to have a single multiarch repo on Docker Hub for each of the services. The approach is to use Docker's new BuildKit builder + the buildx command line plugin.

Other possibilities are:

use QEMU + multiarch base images directly (2, 3), and create a manifest file manually,
build natively on multiple architectures (not sure how to combine them in a single manifest then though).

The disadvantages of the approach taken are:

newer Docker version is required,
docker-compose doesn't seem to support that method natively.

TODO

Docker Hub automated builds instead of Travis?
docker-compose instead of docker buildx?