How to write varnish script to do something very particular

Question

Varnish scripting seems rather robust for the vcl but I can't yet figure out how to make it do what I need. I run various sites from the same code base and I want a unified varnish cache for most of the directories so

x.mysite.org/theme/something.gif and y.mysite.org/theme/something.gif should not store two copies of the same gif in varnish cache

However

x.mysite.org/file.php/1 and y.mysite.org/file.php/1 should have separate caches based on the url.

Also mysite.org is a whole other site that has its own cache.

My current direction is as follows

sub vcl_fetch {
  if (req.url ~ ".*\.org/file\.php") {
    # do normal site specific caching
  } elseif (req.url ~ "^+?\.mysite.org") {
    # cache all found material in a base directory so everyone knows where to look
    set req.url = regsub(req.url, "(.*\.org)(.*)", "base.mysite.org\2");
  } else {
    # do normal site specific caching for base site
  }
}

sub vcl_recv {
  # do I need to do something here to look in base.mysite.org
}

I can make base.mysite.org a real apache served site if necessary so the requests can fall through if no cache.

Am I on the write path, any help.

Answer 1

You should normalize req.http.host instead of req.url, so

sub vcl_fetch {
  # if it starts with /theme or /static, or contains .gif,.png etc, 
  #   then consider the host to the normalized/common host
  if (req.url ~ "^/(theme|static)" || req.url ~ "\.(gif|png)" ) {
    set req.http.host = "base.mysite.org";
    return (lookup);
  }
  # else, do non shared stuff here
}