"Libprocess is a library written in C/C++ that provides an actor style message-passing programming model that leverages efficient operating system event mechanisms. Libprocess is very similar to Erlang's process model, including basic constructs for sending and receiving messages. I'm excited about giving people an opportunity to use this software, so look for lots more details to be added here shortly!"
It's the actor library at the core of Mesos (and a many other things). It's what makes it scale to 10,000s of nodes, and probably more. It's just nobody was able to test it on more nodes without breaking the bank.
[0] - https://github.com/apache/mesos/tree/master/3rdparty/libproc...