Possible memory leak?

[lists at lazygranch.com]

On Thu, 07 Mar 2019 13:33:39 -0500
"wkbrad" <nginx-forum at forum.nginx.org> wrote:

> Hi all,
> 
> I just wanted to share the details of what I've found about this
> issue. Also thanks to Maxim Dounin and Reinis Rozitis who gave some
> really great answers!
> 
> The more I look into this the more I'm convinced this is an issue
> with Nginx itself.  I've tested this with 3 different builds now and
> all have the exact same issue.
> 
> The first 2 types of servers I tested were both running Nginx 1.15.8
> on Centos 7 ( with 1 of them being on 6 ).  I tested about 10 of our
> over 100 servers.  This time I tested in a default install of Debian
> 9 with Nginix version 1.10.3 and the issue exists there too.  I just
> wanted to test on something completely different.
> 
> For the test, I created 50k very simple vhosts which used about 1G of
> RAM. Here is the ps_mem output.
>  94.3 MiB +   1.0 GiB =   1.1 GiB	nginx (3)
> 
> After a normal reload it then uses 2x the ram:
> 186.3 MiB +   1.9 GiB =   2.1 GiB	nginx (3)
> 
> And if I reload it again it briefly jumps up to about 4G during the
> reload and then goes back down to 2G.
> 
> If I instead use the "upgrade" option.  In the case of Debian,
> service nginx upgrade, then it reloads gracefully and goes back to
> using 1G again. 100.8 MiB +   1.0 GiB =   1.1 GiB	nginx (3)
> 
> The difference between the "reload" and "upgrade" process is
> basically only that reload sends a HUP signal to Nginx and upgrade
> sends a USR2 and then QUIT signal.  What happens with all of those
> signals is entirely up to Nginx.  It could even ignore them if chose
> too.
> 
> Additionally, I ran the same test with Apache.  Not because I want to
> compare Nginx to Apache, they are different for a reason.  I just
> wanted to test if this was a system issue.  So I did the same thing
> on Debian 9, installed Apache and created 50k simple vhosts.  It used
> about 800M of ram and reloading did not cause that to increase at all.
> 
> All of that leads me to these questions.
> 
> Why would anyone want to use the normal reload process to reload the
> Nginx configuration?
> Shouldn't we always be using the upgrade process instead?
> Are there any downsides to doing that?
> Has anyone else noticed these issues and have you found another fix?
> 
> Look forward to hearing back and thanks in advance!
> 
> Posted at Nginx Forum:
> https://forum.nginx.org/read.php?2,283216,283309#msg-283309
> 
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Well for what it's worth, here is my result.
centos 7 3.10.0-957.5.1.el7.x86_64 #1 SMP Fri Feb 1 14:54:57 UTC 2019
x86_64 x86_64 x86_64 GNU/Linux

sh-4.2# nginx -v
nginx version: nginx/1.14.0


sh-4.2# ps_mem | grep nginx
  4.7 MiB +   2.1 MiB =   6.7 MiB       nginx (2)
sh-4.2# systemctl reload nginx
sh-4.2# ps_mem | grep nginx
  1.7 MiB +   4.0 MiB =   5.7 MiB       nginx (2)
sh-4.2# systemctl restart nginx
sh-4.2# ps_mem | grep nginx
804.0 KiB +   3.5 MiB =   4.2 MiB       nginx (2)
sh-4.2# ps_mem | grep nginx
  2.9 MiB +   2.9 MiB =   5.8 MiB       nginx (2)
sh-4.2# ps_mem | grep nginx
  2.9 MiB +   2.9 MiB =   5.8 MiB       nginx (2)