== An Apache trick: using directories to create redirections

Suppose, not entirely hypothetically, that you're using Apache
ProxyPass directives as a reverse proxy to map _/someurl/_ on your
website to another web server. [[You generally have to redirect the
URL with the trailing slash ApacheProxyPass]], but of course you
would like a request for a plain '_/someurl_' to also work right
instead of just getting a 404 status response. Here, 'work right'
means that you'll generate a redirection from '_/someurl_' to
'_/someurl/_'.

It's certainly possible to do this with one of the various Apache
directives for explicit redirections (I'd use _RedirectMatch_).
But often there's an easier way: use a real filesystem directory.
If _somedir_ is a directory in the Apache document root and you
send a request for '_/somedir_', Apache's default behavior is to
send exactly the redirection we want. And Apache doesn't care if
the '_/somedir/_' URL is being diverted somewhere other than the
filesystem (via ProxyPass or other directives); it will still send
that redirection regardless.

So we can just do '_mkdir /docroot/someurl_' and everything will
work. The directory contents don't matter; I tend to put a README
file there with a note about how the directory is just there for
the redirection and actual contents in it will be ignored.

(This redirection trick happens automatically if you're using
_.htaccess_ files in a directory to control, say, [[internal
redirections ApacheRedirectHtaccess]]. However there are various
reasons for not using _.htaccess_ files, including centralizing
your configuration in one easily visible place instead of spraying
it all over the filesystem in a bunch of nominally invisible files.)

Back when I wrote [[my entry on ProxyPass ApacheProxyPass]], I
theorized about using this trick. I can now say that we've actually
done this in our configuration and it works fine.

(This trick is a very old one, of course; I'm sure people have been
doing it in Apache for ages. I just feel like writing it down
explicitly for various reasons.)