This document introduces JStorm, an open source distributed real-time computation system developed by Alibaba. It summarizes that JStorm was created by Alibaba engineers who found Storm to be insufficient for their enterprise needs. Key points are that JStorm is more powerful, stable, and faster than Storm; it has evolved quickly with 11 versions released in 2014; and it is used extensively within Alibaba to process over 3 trillion messages per day.