Send 502 when all php-fpm workers are in use

[Maxim Dounin]

Hello!

On Sat, Jul 05, 2014 at 10:47:43PM -0400, justink101 wrote:

> I have a php-fpm pool of workers which is 6. There are long running requests
> being sent, so I have the following fastcgi directives set:
> 
> fastcgi_connect_timeout 15;
> fastcgi_send_timeout 1200;
> fastcgi_read_timeout 1200;
> 
> However right now, if the php-fpm pool of workers is full, a request waits
> the full 20 minutes. I'd like requests to fail with a 502 status code if the
> php-fpm pool of workers is full instead. This change should still allow long
> running requests (max 20 minutes) though. I would have thought if the
> php-fpm pool workers are all being used, a request would timeout in 15
> seconds according to fastcgi_connect_timeout, but this does not seem to be
> the case.

>From nginx side a connection in a backend listen queue isn't 
distinguishable from an accepted connection, hence 
fastcgi_connect_timeout doesn't apply as long as a backend is 
reacheable and it's listen queue isn't full.  (And 
fastcgi_send_timeout doesn't apply either if a request is small 
enough to fit into socket send buffer.)

To reduce a number of affected requests you may consider using 
smaller backlog in php-fpm, see here:

http://www.php.net/manual/en/install.fpm.configuration.php#listen-backlog

-- 
Maxim Dounin
http://nginx.org/