solution: using multiple separate varnish configurations (labels)

[iham]

according to this article, since varnish 5 you can separate configurations by using labels.

situation:

• single machine
• 1 varnish
• 2 (or even more) plone projects (running in separate zope instances)
• (optionally using load balancing)

problem:

• not able to configure that in the recipe
• therefore manually adapting the generated vcl file(s)

here is a small introduction how to solve this:

create a section per domain/project to achieve its varnish config you desire:
buildout.cfg

[buildout]

parts+=
    varnish-conf-1
    varnish-conf-2

[varnish-configuration-base]
recipe = plone.recipe.varnish:configuration
# whatever settings you see fit for all the generated config files
# most commonly will be stuff like
# bind =
# cookie-whitelist =
# grace-* =
# health-probe-* =
# balancer =
# whatever else ...

[varnish-conf-1]
<= varnish-configuration-base
backends =
    {domain-a}:127.0.0.1:{port-a like 8080}
    {domain-a}:127.0.0.1:{port-b like 8081}

zope2_vhm_map =
     {domain-a}:{plone instance inside zope; most often /Plone}

[varnish-conf-2]
<= varnish-configuration-base
backends =
    {domain-b}:127.0.0.1:{port-a like 8090}
    {domain-b}:127.0.0.1:{port-b like 8091}
    {domain-b}:127.0.0.1:{port-b like 8092}

zope2_vhm_map =
     {domain-b}:{plone instance inside zope; most often /Plone}

this will generate two files:

• ./parts/varnish-conf-1/default.vcl
• ./parts/varnish-conf-2/default.vcl

we can copy both files to /etc/varnish (assuming you are on Debian/ubuntu)

sudo cp ./parts/varnish-conf-1/default.vcl /etc/varnish/varnish-conf-1.vcl
sudo cp ./parts/varnish-conf-2/default.vcl /etc/varnish/varnish-conf-2.vcl

now lets go for the labels as mentioned in https://info.varnish-software.com/blog/one-vcl-per-domain and update/replace the /etc/varnish/default.vcl:

vcl 4.0;

# fake, never-used backend
# to silence the compiler
backend fake {
	.host = "0:0";
}
sub vcl_recv {
	if (req.http.host == "domain-a") {
		return (vcl(conf-1));
	} else if (req.http.host == "domain-b") {
		return (vcl(conf-2));
	} else {
		return (synth(404));
	}	
}

see the "vcl(conf-*)" lines?
those are the varnish labels which are loading the vcl files.

in order to make varnish do its label "magic" on each startup we need a script:
/etc/varnish/start.cli

vcl.load vcl-conf-1 /etc/varnish/conf-1.vcl
vcl.load vcl-conf-2 /etc/varnish/conf-2.vcl
vcl.label conf-1 vcl-conf-1
vcl.label conf-2 vcl-conf-2
vcl.load vcl-default /etc/varnish/default.vcl
vcl.use vcl-default

in the systemd varnish.service change the parameters to use the start.cli instead of a file to load (empty -f is necessary):

ExecStart=/usr/sbin/varnishd \
    -I /etc/varnish/start.cli \
    -f '' \
    -what-ever-params-you-have

and reload systemctl and service varnish restart.

done - no more handwritten code inside the generated varnish configs.