URI redirection (2)

0.1.0 Location
0.2.0 Description
0.3.0 Redirection loop

2006/08/23 Update

Location

	$web/etc/rewrite

Description

This file is used to redirect a requested URI to other URI.
URI redirection takes two steps. The first is by "/sys/lib/httpd.rewrite" and the second is by "$web/etc/rewrite". The former is managed by the server administrator and the latter, by the document administrator.

The first field is a path from document root, therefore

first field begins with "/"
first field cannot begin with "/~"

The format allowed in second field is one of:

scheme://hostdom[:port][/path][;params][?query]
/path[;params][?query]

where [ ] is meta symbol that denotes inside of these symbol can be omitted and

scheme :: any scheme
hostdom :: full name of host (pegasus.goodwill.com for example)
port :: port number
path :: path to document
params :: argument list for CGI
query :: query string

The matched portion is replaced by the string of second field. See also path matching.

Redirection loop

Let's consider about

/private		https://pegasus.goodwill.com/private

that appeared in case study of "/sys/lib/httpd.rewrite".
Why bob wrote such a line? He wanted to use "https" for "/private".
Request will come at first time with "http://pegasus.goodwill.com/private". The request will then be redirected to "https://pegasus.goodwill.com/private". The client will make a second request "https://pegasus.goodwill.com/private". What will happen then?
If server redirects the request to "https://pegasus.goodwill.com/private", then the redirection will fall into infinite loop! Therefore Pegasus does not redirect the request and simply accept as a request of this URI.
The expression of redirection loop is allowed only in "$web/etc/rewrite", not in "/sys/lib/httpd.rewrite". And the loop must be closed in a single line.