Web Caching

Cache Busting and Server Busting

Cache busting is a technique that content providers use to prevent their pages from being served as hits from caches. Often this means making every response uncachable. This issue is difficult to assess for a number of reasons. First and foremost, owners and publishers have legal rights to control the distribution of their information. Whether or not we agree with their decision to defeat caching, the choice is theirs to make. Usually, their reasons are unknown to us, but the reasons might include the copyright issues discussed previously or the desire to increase the number and accuracy of their hit counts. Second, some content providers, by the very nature of their business, might serve only uncachable content. We should not be surprised to find that sites that exist only to count advertisement impressions do not allow their responses to be cached. Issues relating to advertising are explored further in the next section.

How would someone be able to claim that an origin server is cache busting? Cache users and administrators sometimes expect certain types of objects to be cachable by default. When users visit a page for the first time and then access it again a short while later, they expect the page to load very quickly because it should be in the cache. When the page loads slowly, they wonder why. If a user is curious and savvy enough, she might find a way to examine the reply headers firsthand. With access to the cache log files, administrators ...