Salt从0.11.0版本开始引入Reactor System。
Event System
The event system is a local ZeroMQ PUB interface which fires salt events. This event bus is an open system used for sending information notifying Salt and other systems about operations.
Reactor SLS files and event tags are associated in the master config file. By default this is /etc/salt/master,or /etc/salt/master.d/reactor.conf.
参考文章：
http://docs.saltstack.com/en/2014.7/topics/reactor/index.html
