Varnish with 2 backends, always reverts to first backend

Question

I am trying to set up a varnish (4) server with 2 backends. However when I try to access it with 2 different URLs it always reverts to server1's backend. Here are the relevant parts of my .vcl file.

Backend server configuration:

backend server1 {
    .host = "127.0.0.1";
    .port = "83";
    .connect_timeout = 600s;
    .first_byte_timeout = 600s;
    .between_bytes_timeout = 600s;
}

backend server2 {
    .host = "127.0.0.1";
    .port = "84";
    .connect_timeout = 600s;
    .first_byte_timeout = 600s;
    .between_bytes_timeout = 600s;
}

And the vcl_recv section

import std;
# Respond to incoming requests.
sub vcl_recv {

        if (req.method == "BAN") {
                # Same ACL check as above:
                if (!client.ip ~ purge) {
                        return(synth(403, "Not allowed."));
                }
                ban("req.http.host == " + req.http.host +
                      " && req.url == " + req.url);

                # Throw a synthetic page so the
                # request won't go to the backend.
                return(synth(200, "Ban added"));
        } else if (req.method == "PURGE") {
                if (!client.ip ~ purge) {
                        return(synth(405,"Not allowed."));
                }
                return (purge);
        } else if (req.method != "GET" && req.method != "POST" && req.method != "DELETE" && req.method != "PUT") {
                return( synth(405, "Method not allowed"));
        }

  if (req.url ~ "^/piwik/piwik.php") {
    set req.backend_hint = server1;
    return(pass);
  } else  if  (req.url ~ "^/piwik/piwik.js") {
    set req.backend_hint = server1;
    return(pass);
  } else if (req.url ~ "^/piwik"  ) {
#    error 404 "Not found";
#     return( synth(404, "File not found"));
     set req.url = "/404-page-not-found";
  } else if (req.url ~"/node/(\d+)/(.+)$") {
#     return( synth(404, "File not found"));
     set req.url = "/404-page-not-found";
  } else if (req.url ~"/monitoring") {
#     return( synth(404, "File not found"));
#     set req.url = "/404-page-not-found";
      return(pass);
  } else if (req.url ~"^/user") {
#     return( synth(404, "File not found"));
     set req.url = "/404-page-not-found";
  } else  if (req.url ~ "^/admin") {
#     return( synth(404, "File not found"));
     set req.url = "/404-page-not-found";
  } else  if (req.url ~ "^/team") {
#     return( synth(404, "File not found"));
     set req.url = "/404-page-not-found";
  } else  if (req.url ~ "^/administer") {
#     return( synth(404, "File not found"));
     set req.url = "/404-page-not-found";
  } else  if (req.url ~ "/edit?$") {
#     return( synth(404, "File not found"));
     set req.url = "/404-page-not-found";
  } else  if (req.url ~ "/add?$") {
#     return( synth(404, "File not found"));
     set req.url = "/404-page-not-found";
  } else  if (req.url ~ "^(www\.)?server2.com$") {
     set req.backend_hint = server2;
  } else  if (req.url ~ "^(www\.)?server1.com$") {
     set req.backend_hint = server1.com;
  }

If I add the following statement to the bottom of the vcl_recv section then I can access server2's backend:

else {
   set req.backend_hint = server2;
}

Answer 1

In your VLC you use

req.url ~ "^(www\.)?server2.com$"

but req.url does not contain the host name. What you want to do is probably

req.http.host ~ "^(www\.)?server2\.com$"

or maybe

req.http.host ~ "^(www\.)?server2\.com$" && req.url ~ "^/$"