Archive for the 'Linuxadas' Category

With nginx and its embedded Perl module it is possible to automatically rewrite/redirect every incoming request to a lowercase URL with something like this:

http {
	...
	perl_modules  perl/lib;

 	perl_set $uri_lowercase 'sub {
   		my $r = shift;
   		my $uri = $r->uri;
   		$uri = lc($uri);
   		return $uri;
 	}';
	...
}

server {
	...

	location / {
               if ( $uri != $uri_lowercase ) {
                       rewrite . http://$host$uri_lowercase;
               }
# or just:
#		rewrite . $uri_lowercase;
	}
	...
}

The first option (with the if and http://$host) sends an HTTP redirect to the lowercase URL if the requested URL is not completely in lowercase. I like this approach better as it kind of normalizes all URL to a canonical form. The second option (without if nor http://) just accepts any URL and internally rewrites them to lowercase: if you rename all your directories and files to lowercase, this will imitate Windows’ case-insensitive behaviour.

Kudos to the following post on the nginx users list were I draw the “inspiration” :D from to get this done. The embedded perl doc and examples are indeed scarce. :-(

http://forum.nginx.org/read.php?2,39425,39944

Anyway I see two problems in this approach:

• you need the embedded perl module which according to the docs is experimental and can lead to memory leaks.
• the actual redirection is done with the rewrite, which you can put on the location you need. But the URL lowercase calculation, being on the “http” section of the config, is done for each and every request arriving to your server. Say you have a virtual server with 10 domains and you only need this on one particular location of one of them. The lowercase URL is going to be calculated for every request of every domain.

I guess that by defining a perl function the URL calculation could be restricted to a particular location, have to look into it further. Another option is writing a C module.

And why would anybody want to rewrite every URL to lowercase? We’re migrating a legacy Tomcat-based application from Windows to Linux, and it seems the original developers were not “case-aware” at all, they mixed upper and lowercase in the filenames without regarding how the actual files were named. On Windows this is not a problem but when moving the app to Linux it is. So we have renamed every file and directory to lowercase and used the previous configuration on the nginx servers that load-balance our Tomcat farm. Some corner-cases remain (includes in JSP files, which don’t route back to the nginx server and are dealt internally by Tomcat) and have been dealt with one by one, but the bulk of wrongly addressed images, videos, links to HTML files, etc. now works.