Varnish URL Rewriting at Docunext Technology

Varnish the reverse proxy can do some pretty cool stuff. I just realized that it compiles its VCL rules into C so that they are process quite efficiently. Here’s a few examples:

Route to a different backend based upon location (i.e. url):

backend server1 {
    set backend.host = "192.168.222.222";
    set backend.port = "80";
}

sub vcl_recv {
    if (req.url ~ "^/location-url") {
        set req.backend = server1;
        set req.http.host = "www.example.com";
    }
}

Explanation: when a client requests the url “/location-url” from varnish, it “routes” the request server1, which is located at the ip address 192.168.222.222, and uses the http host name www.example.com.

Backend choice with a traditional rewrite:

backend server1 {
    set backend.host = "192.168.222.222";
    set backend.port = "80";
}

sub vcl_recv {
    if (req.url ~ "^/location-url") {
        set req.backend = server1;
        set req.url = regsub(req.url, "^/location-url", "/url-location");
        set req.http.host = "www.example.com";
    }
}

Explanation: this is the same example, but the request prefix is changed from location-url to url-location. Pretty nifty, huh?

2 Responses to “Varnish URL Rewriting”

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1 Shahid
Jul 30th, 2008 at 7:19 am

I have an issue when backen port is set to 80.

Varnish listen on port 6081 and the backend haproxy listen on port 80.

Varnish is passing 6081 to backend.

This is the varnish log

12 RxRequest c GET
12 RxURL c /frontend_dev.php/
12 RxProtocol c HTTP/1.1
12 RxHeader c Host: example.com:6081
12 RxHeader c User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9) Gecko/2008061015 Firefox/3.0
12 RxHeader c Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
12 RxHeader c Accept-Language: en-us,en;q=0.5
12 RxHeader c Accept-Encoding: gzip,deflate
12 RxHeader c Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
12 RxHeader c Keep-Alive: 300
12 RxHeader c Connection: keep-alive
12 RxHeader c Cookie: mobshare=954986349020f015115b99df238a8a75
12 VCL_call c recv
12 VCL_return c pass
12 VCL_call c pass
12 VCL_return c pass
13 BackendOpen b default 127.0.0.1 51345 0.0.0.0 80
13 BackendXID b 118910221
12 Backend c 13 default
13 TxRequest b GET
13 TxURL b /frontend_dev.php/
13 TxProtocol b HTTP/1.1
13 TxHeader b Host: haproxy.com:6081
13 TxHeader b User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9) Gecko/2008061015 Firefox/3.0
13 TxHeader b Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
2 Albert
Aug 1st, 2008 at 1:14 pm

What does your VCL look like?

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