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Local YUI combo loader

Quite a while ago I had users complaining they could not use my application from another secure network zone. It appeared the root cause was in using Yahoo CDN for serving YUI resources while there was no internet access in that specific network zone. Also living behind a proxy, our regular users used to suffer from longer delays from time to time due to proxying. An obvious solution turned out to be using a locally served YUI. For this a combo loader is required if you care about efficiency on Production.

Installation
To start with, there are several alternative open-source tools that can be used for combo loading:
The Node.js combo handler is supplied with rather self-contained README file at github. Nevertheless, I'll outline main steps here that worked for me:
  1. Install Node.js and npm package manager.
  2. Run npm install combohandler.
  3. Choose a location for the local YUI files, e.g. /opt/combohandler/yui.
  4. Download YUI3 release zip and YUI 2in3 release zip if needed.
  5. Place sources at the chosen location. Besides I've renamed the top directories, so I've got the following:
  6. ls /opt/combohandler/yui/
    2in3/  3.17.2/
    
    ls /opt/combohandler/yui/2in3/
    2.2.2/  2.3.1/  2.4.1/  2.5.2/  2.6.0/  2.7.0/  2.8.0/  2.8.0r4  2.8.1/  2.8.2/  2.8.2r1  2.9.0/  2.9.0pr1.2725/  build/  meta/
    
    ls /opt/combohandler/yui/3.17.2/
    align-plugin/  cssbase-context/  editor-para/  model-sync-rest/  series-marker/
    --- and many more here ---
    
  7. Create JSON routes config /opt/combohandler/yui/root.json:
  8. {
      "/yui/combo": "/opt/combohandler/yui"
    }
    
  9. Start combohandler now: combohandler -p 8555 -b /yui/public -f /opt/combohandler/yui/root.json
Now it's time for some comments on the steps above. First, you can see I use both YUI3 and YUI 2in3 releases but I do not use YUI gallery modules though. If you need gallery modules as well, I hope you'll be able to make them working yourself although I'll give some useful links in the configuration section. Second, I've configured the port 8555 above and the base URL path /yui/public that is used for rewriting relative URLs. This base URL should provide direct access to any YUI resource. To give a better idea here is our Apache HTTP server virtual host configuration:
<VirtualHost *:80>
    Alias /yui/public "/opt/combohandler/yui"
    <Directory "/opt/combohandler/yui">
        Options None
        AllowOverride None
        Order allow,deny
        Allow from all
    </Directory>
    ProxyPass /yui/combo http://localhost:8555/yui/combo
</VirtualHost>
Finally the following should be working:

Application configuration
Configuring the application is much easier, you only need to fix yui.js location and provide a custom YUI config to enable local combo loader. Here is the javascript I've used:
YUI_config = {
  comboBase: 'http://domain.com/yui/combo?',
  combine:   true,
  groups: {
    yui2: {
      combine:   true,
      root:      '2in3/2.9.0/build/',
      patterns:  {
        "yui2-": {
          configFn: function (me) {
            if(/-skin|reset|fonts|grids|base/.test(me.name)) {
              me.type = "css";
              me.path = me.path.replace(/\.js/, ".css");
              me.path = me.path.replace(/\/yui2-skin/, "/assets/skins/sam/yui2-skin");
            }
          }
        }
      }
    }
  }
};
You can see here a separate yui2 group configuration. If you are going to use YUI gallery modules, they can be configured using groups as well. For some examples you can refer to the related blog article and YUI forum topic.

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