（总结）Nginx 502 Bad Gateway错误触发条件与解决方法

（总结）Nginx 502 Bad Gateway错误触发条件与解决方法

http://blog.bypat.com/html/2011/11/18/%EF%BC%88%E6%80%BB%E7%BB%93%EF%BC%89nginx-502-bad-gateway%E9%94%99%E8%AF%AF%E8%A7%A6%E5%8F%91%E6%9D%A1%E4%BB%B6%E4%B8%8E%E8%A7%A3%E5%86%B3%E6%96%B9%E6%B3%95.html