php-fpm backend, sigsegv and limit_conn

[Maxim Dounin]

Hello!

On Thu, Apr 19, 2012 at 02:23:40PM +0200, Grégory Pakosz wrote:

> I'm facing the situation where worker process crashes in the php-fpm
> backend with SIGSEGV: [alert] 5712#0: worker process 5713 exited on signal
> 11

You mean nginx worker process crash, right?

> In such a case, what happens to the connection? is it dangling?
> Crashes in the backend are random, and I have the impression that when too
> many crashes happen in a row, connection stay open and eventually I'm
> hitting limit_conn.

The limit_conn numbers are kept in a shared memory and will not be 
decremented on nginx worker process crash, leading to a limit 
hits eventually.  To clear the numbers you may do an online 
upgrade, see http://nginx.org/en/docs/control.html#upgrade.

Or, better, you may want to debug crashes, see here for basic 
instructions:

http://wiki.nginx.org/Debugging

Note well that crashes might lead to much more severe 
consequences, e.g. if the crash happens during shared memory 
update it may be left in an inconsistent state, leading to 
unpredictable behaviour (usually more crashes).

Maxim Dounin