Erlang
Erlang is a computer language originally built by Ericsson for fault-tolerant telephone switches. Programs are structured as modules that can be replaced (hot swapped) without having to restart the entire program. If a module crashes or needs to be updated it can be restarted or replaced without affecting any other part of the program. Within the Open Telecom Platform, which often is used together with Erlang, there exist frameworks to simplify and automate this task.
Read more about this topic: Crash-only Software