Replacing Apache2 for Varnish as a reverse proxy

Question

I'm having some troubles replacing a Apache2 reverse proxy rule for a Varnish ACL.

The apache rule is:

<Location /MySite>
    ProxyPass       http://192.168.0.123/OtherSite
</Location>

My Varnish ACL:

if (req.url ~ "^/(?i)MySite") {
    set req.backend = myhost; # 192.168.0.123
    set req.url = regsub(req.url, "^/(?i)MySite", "/OtherSite");
    return (pipe);
}

This is causing the URL on the client side to change to "/OtherSite", which I do not want to happen. On this scenario, when user enters http://www.myhost.com/MySite, the response is redirecting the user's browser to http://www.myhost.com/OtherSite. I want this "redirection" to happen only on varnish back-end request, having the same behavior as Apache's ProxyPass.

How can I achieve this?

Thank you

Well.. Varnish isn't sending a redirect with that config. Can you figure out where the `30x` response is coming from? — Shane Madden, Sep 27 '13 at 06:41
It' a 302 but I don't know where it's coming from. I'll try harder to find it, thanks! — Renato Todorov, Sep 27 '13 at 12:26
Ok! What's the application it's proxying to - are there access logs there you can check? — Shane Madden, Sep 27 '13 at 15:34

score 0 · Answer 1 · answered Sep 28 '13 at 09:08

Please try this:

sub vcl_recv {
  ...
  if (req.url ~ "(?i)^/MySite") {
    set req.backend = myhost;
    set req.url = regsub(reg.url, "(?i)^/MySite", "/OtherSite");
  }
  ..
  return (lookup);
}

Options for regular expressions must be entered right behind the opening quotes. See here: https://www.varnish-cache.org/docs/3.0/reference/vcl.html#regular-expressions
Actually for Varnish req.url will start with "/" as this is the part of a URL following the port or (if no port given) the host part of an URL. Therefore you can replace the "/?" with "/".
As long as you want to use Varnish as a reverse proxy (speaking of web acceleration by caching) you should avoid this "return (pipe);". This means stream back-end data but do not touch or cache it. Therefore I have removed this line. You see instead the default method "return (lookup);" to process the request in the reverse proxy cache. See here the flow-chart of Varnish: https://www.varnish-software.com/static/book/VCL_Basics.html#vcl-request-flow

Good luck a have fun with Varnish.

Replacing Apache2 for Varnish as a reverse proxy

1 Answers1