DNS problem

[ywsample]

I know nginx 1.7.4 fixes a bug about DNS resolver, but i do not quite
understand why this would lead to a request hang, Because there is a
timeout handling, at a specified time if there is no response the timeout
callback will be called，so why here can lead to request hang，

Could someone show me a example about how lead to request hang?

I ask this,because i recently encountered a problem online product(it use
nginx-1.7.2), may be caused by this problem

-- 
ywsample :)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.nginx.org/pipermail/nginx/attachments/20140817/6cade3b0/attachment.html>