WA and Yahoo's exceptional performance rules

The battle with creative folks exists in many organizations which is why WebAccelerator has been designed to give you the best of both worlds. The creative folks are able to modify an existing object without changing the name and you can still utilize caching on WebAccelerator and the browser. This is accomplished through 2 methods - intelligent browser referencing and invalidations. From the WebAccelerator cache perspective invalidation triggers can be written into the policy or through a stand alone application. These invalidations are triggered when a certain page is hit in the application or an item is published to the database or the content managemetn system, the invalidation can be for a specific item, for an entire directory or for the entire site. This invalidation message tells WebAccelerator that content that matches the invalidation trigger is no longer valid and needs to be refreshed from the origin server on the next request.

 

 

The Intelligent Browser Referencing is re-writing the uri for the image with a very specific hash, when the object changes the hash will be different. For example the browser receives an image with the uri 'image1.gif;abcdefghijkl' this is written to the browsers cache for a period of time. When the object is upadted the hash value that is created will be different as the object has a new size, last modified date, etc. The uri for the image will now be 'image1.gif;zyxwvu' this is an object that does not exist in the browser cache so a full GET request will be issued for this new object.

 

 

The combination of invalidating content and Intelligent Browser Referncing allows the creative folks to change items and instantly see their changes when they next visit the page instead of the old cached version.