Separate VCL files¶
Having multiple different vhosts in the same Varnish is a very typical use-case, and from Varnish 5.0 it is possible to have a separate VCL files for separate vhosts or any other distinct subset of requests.
Assume that we want to handle varnish.org
with one VCL file
and varnish-cache.org
with another VCL file.
First load the two VCL files:
vcl.load vo_1 /somewhere/vo.vcl
vcl.load vc_1 /somewhere/vc.vcl
These are 100% normal VCL files, as they would look if you ran only that single domain on your varnish instance.
Next we need to point VCL labels to them:
vcl.label l_vo vo_1
vcl.label l_vc vc_1
Next we write the top-level VCL program, which branches out to the other two, depending on the Host: header in the request:
import std;
# We have to have a backend, even if we do not use it
backend default { .host = "127.0.0.1"; }
sub vcl_recv {
# Normalize host header
set req.http.host = std.tolower(req.http.host);
if (req.http.host ~ "\.?varnish\.org$") {
return (vcl(l_vo));
}
if (req.http.host ~ "\.?varnish-cache\.org$") {
return (vcl(l_vc));
}
return (synth(302, "http://varnish-cache.org"));
}
sub vcl_synth {
if (resp.status == 301 || resp.status == 302) {
set resp.http.location = resp.reason;
set resp.reason = "Moved";
return (deliver);
}
}
Finally, we load the top level VCL and make it the active VCL:
vcl.load top_1 /somewhere/top.vcl
vcl.use top_1
If you want to update one of the separated VCLs, you load the new one and change the label to point to it:
vcl.load vo_2 /somewhere/vo.vcl
vcl.label l_vo vo_2
If you want to change the top level VCL, do as you always did:
vcl.load top_2 /somewhere/top.vcl
vcl.use top_2
Details, details, details:¶
- All requests always start in the active VCL - the one from
vcl.use
- Only VCL labels can be used in
return(vcl(name))
. Without this restriction the top level VCL would have to be reloaded every time one of the separate VCLs were changed. - You can only switch VCLs from the active VCL. If you try it from one of the separate VCLs, you will get a 503
- You cannot remove VCL labels (with
vcl.discard
) if any VCL containsreturn(vcl(name_of_that_label))
- You cannot remove VCLs which have a label attached to them.
- This code is tested in testcase c00077
- This is a very new feature, it may change
- We would very much like feedback how this works for you