nginx verify backend

[André Cruz]

Hello.

Perlbal has a nice feature called verify_backend that what it does is  
send an OPTIONS request each time a new connection to a backend is  
made to ensure that it has the backend's atention.

With persistent backend connections this makes more sense since the  
overhead is minimized but, even so, I think it's an interesting  
feature since apache tends to keep clients waiting when MaxClients is  
reached. We can lower ListenBacklog but still some clients get stuck  
after the connection is accepted.

proxy_read_timeout is not very useful here since specifying a  
different timeout for each type of request being made can quickly get  
out of hand... We just want to be sure that apache is processing the  
request.

I think this would be a useful feature for nginx.

André Cruz