Varnish - set backend if statuscode is 404

[Jan-Frode Myklebust]

If you manage to do this, I would much appreciate you post a recipie :-)
I've been struggeling trying to achieve the same thing, without
success..

Actually my setup is a bit different, we have a director, and just want
to check the other backend if the first backend gives 404, but the same
solution might apply.

backend backend1 {
        .host = "backend1.example.com";
        .probe = { 
                .url = "/alive.html";
                .timeout = 34 ms; 
                .interval = 2s; 
                .window = 10;
                .threshold = 8;
        }
}
backend backend2 {
        .host = "backend2.example.com";
        .probe = { 
                .url = "/alive.html";
                .timeout = 34 ms; 
                .interval = 2s; 
                .window = 10;
                .threshold = 8;
        }
}
director dir1 client {
    { .backend = backend1; .weight = 1; }
    { .backend = backend2; .weight = 1; }
}
sub vcl_recv {
        if ( req.http.host ~ "(?i)www.example.com$"  ) {
                set req.backend = dir1;
                return(lookup);
        }
}



  -jf