passenger upstream prematurely closed connection while reading response header from upstream

这两天弄passenger

一开始编译好之后，一配置，马上就运行出来了，觉得十分容易。

第二天再配置的时候，就出502 Bad Gateway

nginx erro log里显示

upstream prematurely closed connection while reading response header from upstream

google了很多结果，竟然还有时不时发生这种情况，大部分都能正常运行的例子。

https://groups.google.com/forum/?fromgroups=#!topic/phusion-passenger/kcWP9T8uksg

后来也没看到彻底的解决。先还是用unicorn好了，这个调试还熟悉。