Status of shared memory zones

[Maxim Dounin]

Hello!

On Wed, Aug 20, 2025 at 01:06:33PM +0200, Eirik Øverby via nginx wrote:

> Let me start with a (belated) thank you to all contributors for 
> the continued work on freenginx. We are in the process of 
> switching to it - late but hopefully good!
> 
> In the commercial F5 nginx, there has for some time been ways to 
> monitor the status/usage of shared memory zones and (presumably) 
> some other run-time stats that remain opaque to users of the 
> community version. I'm wondering if there are any such 
> facilities in freenginx - implemented or planned? It would be 
> nice if the VTS plugin could emit some statistics, for example.
> 
> We would be quite interested in such a feature, but realise it 
> will be a fair amount of work for a relatively narrow audience. 
> Is there any way we can "encourage" such functionality to be 
> added, e.g. through financial support or some other means? We 
> might even be able to produce code to do it, but would prefer if 
> it was done by someone who is already familiar with (free)nginx 
> and its architecture - we have no such people on-hand.

Providing better status information might indeed be an interesting 
area for improvements.

Right now, the only status information provided by freenginx is 
that shown by stub_status, which is quite limited and basically 
only shows connections in various states and total 
accepts/requests counters.  Everything else needs to be monitored 
either via logs or with 3rd party modules, like VTS you've 
mentioned.

It would be great if you could share which stats you use/monitor, 
and how.  In particular, it would be interesting to know preferred 
data formats.

It would also be interesting to know how you expect to use 
information about shared memory zones usage.

As for improving the VTS module, I don't think it's specific to 
freenginx.  Information about shared memory zone usage is in the 
ngx_slab_pool_t structure since nginx 1.11.7, and it's more or 
less a question of showing this information properly.  Just in 
case, relevant commits are:

changeset:   6828:99770a5ea14f
user:        Ruslan Ermilov <ru at nginx.com>
date:        Wed Dec 07 22:25:37 2016 +0300
summary:     Slab: slots statistics.

changeset:   6829:6e757036e588
user:        Ruslan Ermilov <ru at nginx.com>
date:        Wed Dec 07 22:25:37 2016 +0300
summary:     Slab: free pages statistics.

https://freenginx.org/hg/nginx/rev/99770a5ea14f
https://freenginx.org/hg/nginx/rev/6e757036e588

-- 
Maxim Dounin
http://mdounin.ru/