$Id: README.txt,v 1.23 2010-02-02 23:33:39 wimleers Exp $ Description ----------- The aim of this module to provide easy Content Delivery Network integration for Drupal sites. Obviously it has to patch Drupal core to rewrite the URLs. URLs must be rewritten to be able to actually serve the files from a CDN. It provides two modes: basic and advanced. In basic mode, only "Origin Pull" CDNs are supported. These are CDNs that only require you to replace the domain name (and possibly base path) with another domain name. The CDN will then automatically fetch (pull) the files from your server (the origin). In advanced mode, you must install and configure the daemon I wrote as part of my bachelor thesis: File Conveyor [1]. This allows for much more advanced setups: files can be processed before they are synced and your CDN doesn't *have* to support Origin Pull, any push method is fine. Push always uses transfer protocols, either well-established ones (e.g. FTP) or custom ones (e.g. Amazon S3 and Mosso CloudFiles). It is thanks to this abstraction layer that it can be used for *any* CDN, thereby avoiding vendor lock-in. - File Conveyor includes "transporters" for FTP, Amazon S3, Amazon CloudFront and Mosso CloudFiles. - File Conveyor also allows for any kind of automatic file processing. It includes "processors" for: image optimization (using a combination of ImageMagick, pngcrush, jpegtran and gifsicle), CSS minification (YUI Compressor), JS minification (YUI Compressor and/or Google Closure Compiler), and so on. It's also very easy to add your own processors. To serve images generated by the ImageCache module from a CDN, you must apply a patch to the ImageCache module, because it uses its own custom function to generate file URLs. Note: "Origin Pull" means the CDN pulls files from the origin server (i.e. the Drupal web server). That's where its name comes from. Amazon S3, CloudFiles and CacheFly are all examples of Push CDNs. The first two have custom protocols, the latter uses FTP. These don't automatically pull files from your server (the origin server), but you have to push the files manually (or using a script of some sort, or my daemon) to the CDN. Other CDNs, such as SimpleCDN, offer both pull- and push-functionality. This module was written as part of the bachelor thesis [1] of Wim Leers at Hasselt University [3]. [1] http://fileconveyor.org/ [2] http://wimleers.com/tags/bachelor-thesis [3] http://uhasselt.be/ Supported CDNs -------------- - Basic mode: any Origin Pull CDN. - Advanced mode: any Origin Pull CDN and any push CDN that supports FTP. Support for other transfer protocols is welcomed and encouraged: your patches are welcome! Amazon S3, Amazon CloudFront and Mosso CloudFiles are also supported. Installation ------------ 1) Apply the Drupal core patch (patches/drupal6.patch). Instructions can be found at http://drupal.org/patch/apply. This patch effectively backports hook_file_url_alter() from Drupal 7 to Drupal 6. See the notes about this backport if you're interested in the details or want to use it in your own module. 2) Apply the ImageCache patch (patches/imagecache.patch), if you want to serve images generated by the ImageCache module from a CDN. This is a separate patch because it uses its own custom function to generate file URLs. 3) Place this module directory in your "modules" folder (this will usually be "sites/all/modules/"). Don't install your module in Drupal core's "modules" folder, since that will cause problems and is bad practice in general. If "sites/all/modules" doesn't exist yet, just create it. 4) Enable the module. 5) Visit "admin/settings/cdn" to learn about the various settings. 6) If you want to use advanced mode, install and configure the daemon first. You can install it by performing an svn checkout from svn://wimleers.com/school/bachelor-thesis/code/daemon Then follow the instructions in the included INSTALL.txt and README.txt. Use the config.xml file that is included in this module and modify it to comply with your setup and to suit your needs. 7) Go to admin/reports/status. The CDN integration module will report its status here. If you've enabled advanced mode and have set up the daemon, you will see some basic stats here as well, and you can check here to see if the daemon is currently running. You can also see here if you've applied the patches correctly! Notes on the backport of hook_file_url_alter() for Drupal 6 ----------------------------------------------------------- An identical backport is impossible because in Drupal 7, there's the new File API which uses PHP stream wrappers. It doesn't make sense to backport the entire new File API. - Issue for Drupal 7 core patch: http://drupal.org/node/499156 - The backport of hook_file_url_alter() is based on the patch *before* stream wrapper support went in, i.e. the patch in this comment: http://drupal.org/node/499156#comment-1866878 http://drupal.org/files/issues/cdn-integration-499156-62.patch - Documentation for hook_file_url_alter() for Drupal 7: http://api.drupal.org/api/function/hook_file_url_alter/7 - For analogous documentation for the Drupal 6 backport, see the included patches/hook_file_url_alter.php When using multiple servers: picking a specific one based on some criteria -------------------------------------------------------------------------- For this purpose, you can implement the cdn_advanced_pick_server() function: /** * Implementation of cdn_advanced_pick_server(). */ function cdn_advanced_pick_server($servers_for_file) { // The data that you get - one nested array per server from which the file // can be served: // $servers_for_file[0] = array('url' => 'http://cdn1.com/image.jpg', 'server' => 'cdn1.com') // $servers_for_file[1] = array('url' => 'http://cdn2.net/image.jpg', 'server' => 'cdn2.net') $which = your_logic_to_pick_a_server(); // Return one of the nested arrays. return $servers_for_file[$which]; } So to get the default behavior (pick the first server found), one would write: /** * Implementation of cdn_advanced_pick_server(). */ function cdn_advanced_pick_server($servers_for_file) { return $servers_for_file[0]; } Supporting the CDN integration module in your modules ----------------------------------------------------- It's very easy to support the CDN integration module in your module. Simply create a variable function, e.g.: $file_create_url = (module_exists('cdn')) ? 'file_create_url' : 'url'; Then create all file URLs using this variable function. E.g. $file_url = $file_create_url(drupal_get_path('module', 'episodes') .'/lib/episodes.js'); Author ------ Wim Leers ~ http://wimleers.com/ This module was written as part of the bachelor thesis of Wim Leers at Hasselt University.