Vcl.list and the maximum number of loaded VCL

[alexis at madrzejewski.com]

Hello,

I use Varnish 6.1 and I'm using the vcl.load technique to load custom 
VCL based on the domain name.
Basically, I follow what is explained on this article :
https://info.varnish-software.com/blog/one-vcl-per-domain

I have a huge number of domains and each domain have a specific and 
different configuration. Like a vhost.

I used to have multiple VCL file and include them all but it wasn't 
effective. Each time I changed the configuration of one domain, I had to 
reload varnish and all the VCL were recompiled which took a huge amount 
of time (5+ minutes).
So I switched to the "load.vcl" technique to just recompile the VCL I 
needed and it's much more effective.

But I have an issue related to the huge number of domains and loaded VCL 
I manage.
This problem was first reported here :
https://github.com/varnishcache/varnish-cache/issues/2713

I understood that it's fixed and that I needed to add the "max_vcl" to 
define the maximum number of loaded VCL.
I did that, the max_vcl is on 2000 on my case but the vcl.list is not 
showing the loaded VCL.
The vcl are loaded, my configuration works but I can't list the loaded 
VCL and it's a problem for me because I need discard old config.

[root at cache-01 ~]# varnishadm
200
-----------------------------
Varnish Cache CLI 1.0
-----------------------------
Linux,3.10.0-514.el7.x86_64,x86_64,-junix,-smalloc,-sfile,-sdefault,-hcritbit
varnish-6.1.1 revision efc2f6c1536cf2272e471f5cff5f145239b19460

Type 'help' for command list.
Type 'quit' to close CLI session.

param.show max_vcl
200
max_vcl
         Value is: 2000
         Default is: 100
         Minimum is: 0

         Threshold of loaded VCL programs.  (VCL labels are not
         counted.)  Parameter max_vcl_handling determines behaviour.


vcl.list
200

quit
500
Closing CLI connection

Right now, I have ~960 active vcl :

[root at cache-01 ~]# ls /etc/varnish/vhosts/ | wc -l
957

On another somewhat related note, is it a good idea to have that much 
loaded VCL ?
Can it become a problem in the long term ?

I ask because I noticed, two time, that my instance of varnish is a 100% 
CPU utilization after 2 weeks.
I dynamically add, remove, update vhosts but I can't clean old loaded 
VCL because of this vcl.list problem.
After two weeks, varnish seems to use all the CPU and I suspected that 
it's related. If a restart varnish, then it's OK for another two weeks.
I suspect that all the old loaded VCL, not discarded, clogged up my 
instance of varnish. Is that plausible, possible ?
I'm not familiar with varnish internals so it's a guess.

Thanks in advance,
Kind regards,
Alexis