Way to queue connections until a uwsgi socket available?

[Maxim Dounin]

Hello!

On Wed, Dec 08, 2010 at 05:13:09PM -0500, kickme444 wrote:

> We are currently configuring nginx and uwsgi on ubuntu 9.10.  We are
> having a problem while load testing in that when uwsgi becomes
> saturated, nginx kills incoming connections rather than queueing.  I
> cannot figure out if there is a way to do this queueing in nginx.  The
> errors we get in the nginx error log look like:
> 
> 2010/12/08 12:57:03 [error] 15276#0: *10079 connect() to
> unix:///var/run/nginx-uwsgi/wsgi-app.sock failed (11: Resource
> temporarily unavailable) while connecting to upstream, client:
> xx.xxx.xx.xx, server: www.app.com, request: "GET /url/here/ HTTP/1.1",
> upstream: "uwsgi://unix:///var/run/nginx-uwsgi/wsgi-app.sock:", host:
> "ec2-xxx-xxx-xxx-xx.compute-1.amazonaws.com"

Enlarge listen queue on backend (i.e. uwsgi app).  According to 
[1] it should be possible via something like

<listen>4096</listen>

in uwsgi.xml.  Note that your OS may require tuning to make 4096 
possible, something like "echo 4096 > /proc/sys/net/core/somaxconn". 
Refer to your OS manuals for details.

[1] http://projects.unbit.it/uwsgi/wiki/Doc

> I have tried kqueue and poll to no avail. 

There is no kqueue on ubuntu, the best event method it has is 
epoll.  This is unrelated though.

Maxim Dounin