Using Varnish to Proxy 1000s of different sites

Tony Primerano tony.primerano at
Thu Aug 5 16:33:17 CEST 2010

I suspect what I am trying to do here falls outside of Varnish's intended
purpose but here is what I am trying to do...

Instead of using Varnish to cache content for a single site with several
backends,  I want to use it to allow me to serve existing sites on different

For example I can run varnish on and serve content from
example.comusing this configuration.

backend test {
  .host = "";
  .port = "80";

sub vcl_recv {
  set = "";
  set req.backend = test;

But what if I have 1000s of backends and I choose them based on the domain
that user's hit varnish with.   Is this something Varnish handles or is it
only intended to work with a handful of backends?

Also, it would be really cool if I could do something like this..
sub vcl_recv {
  set = "";
  set  =;

I'm guessing backends are defined ahead of time for connection pooling but
maybe not.

Anyway, this is long enough,  tell me if I would be nuts to try to do this
with Varnish and if so what would be better.   I'm tempted to write my own
proxy but that seems like such a waste.  :-)

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