uri rewrite based on the servername

For redirects based on contents in the URI, you can do it all from within the HTTP_REQUEST event.

Here's one way to do it.

when HTTP_REQUEST {
  set 
  if { [HTTP::host] ends_with "server_1.de" } {
    HTTP::redirect "http://server_4.de/server1[HTTP::uri]"
  } elseif { [HTTP::host] ends_with "server_2.de" } {
    HTTP::redirect "http://server_4.de/server2[HTTP::uri]"
  } elseif { [HTTP::host] ends_with "server_3.de" } {
    HTTP::redirect "http://server_4.de/server3[HTTP::uri]"
  }
  pool zone_xml_gw
}

This will look for the host portion of the URI and then issue the redirects. I've used the ends_with operator as opposed to the eq operator so that all requests to that domain are supported (www.server_1.de, etc). If you don't care about this then switch back to the eq operator.

A slightly more optimized version (using a switch instead of if/elseif) would be something like this:

when HTTP_REQUEST {
  switch -glob [HTTP::host] {
    "*server_1.de" {
      HTTP::redirect "http://server_4.de/server1[HTTP::uri]"
    }
    "*server_2.de" {
      HTTP::redirect "http://server_4.de/server2[HTTP::uri]"
    }
    "*server_3.de" {
      HTTP::redirect "http://server_4.de/server3[HTTP::uri]"
    }
  }
  pool zone_xml_gw
}

If you are needing to support many more hosts then it might make sense to use a data group in conjunction with the findclass command. A search of the forum on findclass should show you multiple examples.

Hope this helps...

-Joe