mod_cdn: cdn-ify a website
Kris Beevers <kbeevers@voxel.net>
http://agile.internap.com/mod-cdn


Overview
----------------------------------------------------------------------
mod_cdn is an apache2 module developed at Voxel dot Net that makes
VoxCAST and other CDNs easier to use by automatically "CDNifying" some
HTML content and "originifying" the origin apache server to send
proper headers, validate authentication tokens, etc.  mod_cdn is meant
to be installed and configured on a CDN customer's origin server.

Some parts of mod_cdn are based on code from mod_proxy_html
(http://apache.webthing.com/mod_proxy_html/).

In addition to apache2, mod_cdn currently requires libxml2 to be
installed.


Features
----------------------------------------------------------------------
mod_cdn currently has the following features:

* Find links to content (e.g. img src tags) in HTML and rewrite the
  URLs to point to a different server (e.g., a VoxCAST host)
* Automatically add authentication token query string
  arguments to links in HTML that are being CDNified
* Automatically add query string ignore tokens in the query strings of
  URLs being CDNified, relative to some other query string argument
* Add proper Expires headers to static content for which the server is
  the CDN origin
* Add "Vox-Authorization: required" headers to static content for
  which the server is the CDN origin, and which requires
  authentication
* Verify the authentication tokens in query string arguments of static
  content requests for which the server is the CDN origin

Most sites probably don't need all of these features; they can each be
turned on and off and configured at a fairly high granularity.

A major coming-soon feature is dynamic threshold based switching
between CDN and non-CDN that takes into account server load metrics.


Documentation
----------------------------------------------------------------------
Some documentation for mod_cdn is available in the accompanying MANUAL
file or at http://agile.internap.com/mod-cdn.  This includes
documentation about installing and configuring the module.