Types of Caching

Caching can be passive as well as active. In passive caching the cache proxy server stores the web resources each time the client requests it. First of all, the cache server looks into its own database to check whether the requested resource is there or not. If it founds the desired data then there is no need to contact the web server and the data is delivered to the client instantly. If the proxy server doesn’t get the requested resource in its own database then it retrieves it from the relevant location on the internet and saves it for the future reference.

In active caching the cache proxy server stores and updates its database during its idle time. Whenever the cache server is not accessed by the clients for a set duration it learns the most frequently used resources, downloads them via internet and finally saves them in its cache for future reference. During the process of active caching the proxy server also checks for any updates regarding those resources which are already there in its database.

Challenges in Caching Process

No doubt that the cache servers incredibly reduce the latency periods and facilitate smooth data transactions, but the file caching process faces great challenges. This is not at all an easy task because the resources that have been saved in the cache server are static in nature but the web is highly dynamic and unpredictable. Sometimes a web page remains same for a long period and suddenly changes and sometimes changes are made every day. In case of real time applications such as sports and news web sites the updates are being done every second. So the cache server gets really into trouble while keeping all its records up to date so that the client doesn’t miss any single bit of information.

A large number of heuristic methods have been evolved till now and are being improved continuously in order to make the file caching more reliable and efficient. Sophisticated technologies are being implemented so that the cache server can keep its database up to date by updating the web documents and deleting the stale/expired records.

Load Balancing the Caching work

The caching can be done by implementing more than one cache proxy server and operating the whole array simultaneously. This benefits the organization in the way that the work load of caching can be shared among all the proxy servers. Thus, the caching can be done more effectively and speedily. This also increases the storage space to be used for storing HTML documents and other web applications. The whole array of cache servers can also be configured in such a way that if one cache server fails, then the remaining ones provide fault tolerance just like the Redundant Array of Inexpensive Disks (RAID).