Feature preview: Auto Instance-Switching

Behind the scenes I've been working on a system that switches instances automatically when one isn't available.

This has happened to me so often while developing, that an instance has gone offline, that I decided to do something about it.

Soon Nemmy will try out another instance if the requested (default or user specified) isn't available - and if that one isn't available as well, Nemmy will switch again - and so on.

The list of valid instances to switch to is hand-picked by me and consists of the instances with the most up-time and with the most federated instances to increase the chances of user requested content being available.

All-in-all, soon the possibility of using Nemmy and experiencing any downtime will be close to 0.