Redis主从切换

案例 易车网：
http://www.greatops.net/?id=232

redis主从切换：
http://www.cnblogs.com/itdragon/p/7932178.html
https://segmentfault.com/a/1190000011207953#articleHeader31

redis-sentinel-keepalived:
http://blog.51cto.com/dgd2010/1742766