[Docker] Autobuild Docker Images from Github Repos you don't own

With Docker Hub it is dead simple to just link your Github Account to Docker, choose an Github Repo which contains your Dockerfiles and Apps - and build them as soon as you push new code. But as soon as you're not the owner of the repo (i.e. you're a fan and want to provide Dockerbuilds for Docker Hub) - things get messy. But actually, it works quite easy: Just apply some IFTTT - and you're set ;).

Ok, a little bit more detail: If this then that is a nice Website which lets you create some small but powerful Applets. I.e.: If the weather is cloudy, sent me an email. Things like that. Just sign up on https://ifttt.com, its free! 🙂

After that, just go over to https://hub.docker.com. Link your Github Account with Docker Hub and create and Auto Build Repo on Github with the Dockerfile of the project you want to build. In my case, the program I'd like is developed on Github itself, so my Dockerfile contains some instructions to just check out that repo, build the program and.. done :)! After this is working, go to the "Build Settings" Dialog of your Docker Hub Repo and go to the "Build Triggers" area. Activate the Build Triggers and Copy Down the Trigger URL. Every time the URL is used, your Repo is going to be build a new :).

The only thing we now need, is to know when a new commit is made. And Github makes that very easy: Go to your wanted Github Repo (I will use pklaus awesome brother_ql as example: https://github.com/pklaus/brother_ql), click on commits in the branch you like to use (i.e. master in my case) - and you will be redirected to the page showing you all commits: https://github.com/pklaus/brother_ql/commits/master. Just add an .atom after that URL, and voilá: You got yourself an RSS Feed of that commit stream ;)!. ( https://github.com/pklaus/brother_ql/commits/master.atom )

Copy that link as well, we're going to combine both links via the "magic" of IFTTT ;): Click on "my Applets", "New Applet" and on the "+ this" part. Select the Feed Service, and "New Feed item". Paste the collected Atom/RSS Feed URL in the Feed URL field and click "Create Trigger" (https://github.com/pklaus/brother_ql/commits/master.atom).

After that, click on the "+ that" part and search for "Maker" - and choose it as action service - the action should be "Make a web request". Now enter the Build trigger URL from Docker Hub you noted down, choose the "POST" Method, "application/json" as Content Type and enter "build": true as Body. After that, click save.

Activate your newly made Applet - and you're done: As soon as someone pushes a new commit, IFTTT will see that and start an rebuild of your Docker Hub Repo :).

(Yeah, that is a really hacked-together part, but it works ;))