Ruby framework by Masahiro Nakagawa for implementing robust multi-process/multi-thread servers. Features: workers as processes, workers or threads; a server layer for external communication (soft restarts, reconfiguration); and a supervisor mechanic that restarts workers that die from memory or network issues. Presented by Nakagawa at RubyKaigi 2014 (Japanese) with a separate English presentation also available. Raise_permanent_job is a Ruby wrapper on top of it.