David Kitchen

So I have a piece of .htaccess magic on one of the sites that I run.

What this particular set of instructions do is allow me to run a second web server of a different version behind my Apache 1.3 installation, and still have it appear to the end user as if I only run one web server, basically it’s a proxy. I like this, this is good.

The .htaccess rule I setup is for Trac and specifically the tracd daemon, and my rules look like this:
RewriteEngine On
RewriteRule ^trac_common/(.*)$ http://127.0.0.1:8080/trac_common/$1 [P]
RewriteRule ^projects/?(.*)$ http://127.0.0.1:8080/$1 [P]
RewriteRule ^trac(.*)$ http://127.0.0.1:8080/trac$1 [P]


The [P] at the end of those mod_rewrite lines is telling mod_rewrite to use mod_proxy to handle the request and forward the request internally to the web server running on the high port.

Nice and simple, if a request comes in which has the url /projects/ go to the top Trac page.
If a request comes in for the project named trac with the url /trac/ go to that projects’ Trac site.

This works OK, except that the code browser within Trac is accessing the Subversion repository, and within SVN some of the directory paths and files have spaces in them.

What happens is that under the hood a request ends up looking like this:
GET /trac/browser/root/path with spaces in HTTP/1.1

That’s wrong as only two spaces can exist in a GET request, and those spaces delimit the request type, request URI and the protocol.

So somewhere within mod_rewrite and mod_proxy the spaces are not being escaped as they should, because the request should look like this:
GET /trac/browser/root/path%20with%20spaces%20in HTTP/1.1

So, how do you go about replacing spaces using mod_rewrite?

Much googling will tell you that mod_rewrite does not allow you to perform regexp or string replacements.

However, you don’t need to. mod_rewrite already has a RewriteMap feature and we can use that.

If we take our rewrite rules out of the .htaccess file and place them in our httpd.conf file we can use the built-in escape function:
RewriteMap escape int:escape
RewriteEngine On
RewriteRule ^/trac_common/(.*)$ http://127.0.0.1:8080/trac_common/${escape:$1} [P]
RewriteRule ^/projects/?(.*)$ http://127.0.0.1:8080/${escape:$1} [P]
RewriteRule ^/trac(.*)$ http://127.0.0.1:8080/trac${escape:$1} [P]

That now correctly escapes spaces in the matched URL’s and the source browser connected to SVN now works perfectly.

Hope this saves someone else some time.