Using etcd to manage Django settings
I haven't used CoreOS or Docker but read a lot and think it's very sexy stuff.  I guess the solution depends on how you set up your app.  If you have the same sort of "touch-reload" support you see in many appservers (uWSGI f.ex.), you can set key_file in /etc/etcd/etcd.conf and make your appserver watch that.  This feels a ton heavier than it should be thou.  I'm quite sure someone with experience with the platform can come up with something much better.
Let's say that I have a Django app, and I've offloaded environment variable storage to etcd. When I deploy a new server, the app can read from etcd, write the vars into (for example) a Python file that can be conditionally loaded on the app boot. This much is acceptable.
When the configuration changes, however, I have no way of knowing. Afaik, etcd doesn't broadcast changes. Do I need to set up a daemon that polls and then reloads my app on value changes? Should I query etcd whenever I need to use one of these parameters? How do people handle this?