Rewriting URLs on the Citrix Netscaler

So today I had the task of setting up a failover configuration for our email deployment server, affectionately known as "Strongbad".

We created a VM to function as the failover server, but in order to get things to work we needed to modify the URL to capture the entire path and pass it as a value to a PHP script. For instance, the URL the user would click on would look like:

http://strongbad.company.com/track?type=click&mailingid=42&messageid=42&databaseid=test&serial=20090203&emailid=sb@strongbad.com&userid=1&extra=&&&2004&&&http://tracking.company.com/account/listings/?emailUserId=42

If the Strongbad box were to become unavailable, we want the VM to step in. There is a script called strongbad_redirect.php and to simplify things we're just passing the original path directly to this script. The script takes care of parsing out the data and redirecting the user to the appropriate page.

The pertinent lines in the Netscaler are:

add rewrite action act_sbad_req_rewrite insert_before HTTP.REQ.URL.PATH.GET(1) "\"strongbad_redirect.php?\""



add rewrite policy pol_sbad_rewrite "HTTP.REQ.HOSTNAME.SERVER.EQ(\"strongbad.company.com\")" act_sbad_req_rewrite



bind lb vserver mail1 -policyName pol_sbad_rewrite -priority 100 -gotoPriorityExpression END -type REQUEST