Nginx Active & Writing Connections exponential growth.

[Antonio Jerez Guillén]

Hi there!
First of all, I am a new user of the nginx mailing list so there is a short
introduction of myself. My name is Antonio, and I have been working for a
long time as Web Operations Engineer at Uptodown.com, VisualizeUs.com and
other minor projects.

We are running nginx in Uptodown.com for static content, without problems,
and in VisualizeUs.com, since 2 years ago, for static and dynamic content
without problems . But it is in visualizeUs where we are having some
problems, since we updated nginx to nginx/0.7.67, under debian Lenny 32 bits
(aws medium instance), with php-fcgi

There is the munin output for nginx connections.
http://i29.tinypic.com/21y781.png

We noticed, an exponential growth for connections, better apreciated through
the graphic.

There is our nginx configuration:

http://dpaste.com/hold/223096/

And our ulimit for www-data:

maxfds ..fs.file-max = 200000
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 20
file size               (blocks, -f) unlimited
pending signals                 (-i) unlimited
max locked memory       (kbytes, -l) unlimited
max memory size         (kbytes, -m) unlimited
open files                      (-n) 20480
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) unlimited
real-time priority              (-r) 1
stack size              (kbytes, -s) unlimited
cpu time               (seconds, -t) unlimited
max user processes              (-u) unlimited
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

As active connections grow, response time sligthly increases, so a nginx
reboot is needed to get back to optimal response time.Nginx reboots are
apreciated in munin graphic when it returns to normal values, in other case,
exponential grows continues.

We have been tweaking system limits without noticiable diferences. Also we
have been working around php-cgi configuration, finding out that the
exponential growth of connections still exists but in a slower rate.

Anything that make us point in the right direction will be appreciated.

Thanks in advanced.

Best Regards.
Antonio.
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