ch1v4n(樵夫)的博客

March 18, 2005

Redirect Failing URLs To Other Webserver

Description:
A typical FAQ about URL rewriting is how to redirect failing requests on webserver A to webserver B. Usually this is done via ErrorDocument CGI-scripts in Perl, but there is also a mod_rewrite solution. But notice that this is less performant than using a ErrorDocument CGI-script!
Solution:
The first solution has the best performance but less flexibility and is less error safe:

RewriteEngine on
RewriteCond /your/docroot/%{REQUEST_FILENAME} !-f
RewriteRule ^(.+) http://webserverB.dom/$1

The problem here is that this will only work for pages inside the DocumentRoot. While you can add more Conditions (for instance to also handle homedirs, etc.) there is better variant:

RewriteEngine on
RewriteCond %{REQUEST_URI} !-U
RewriteRule ^(.+) http://webserverB.dom/$1

This uses the URL look-ahead feature of mod_rewrite. The result is that this will work for all types of URLs and is a safe way. But it does a performance impact on the webserver, because for every request there is one more internal subrequest. So, if your webserver runs on a powerful CPU, use this one. If it is a slow machine, use the first approach or better a ErrorDocument CGI-script.

Posted by ch1v4n at 01:54 PM | Comments (0) | TrackBack (0)