Web Cache

What is Cache? Cache is the storing of data temporarily to improve performance. Cache exist in a variety of areas such as your CPU, Hard Disk and DNS. CPU CacheHard Disk CacheDNS Cache

Our Focus Our focus on this tutorial will be web cache. Web cache is temporary storing of data that is used with delivering a webpage (html, php, javascript, etc).

Why and How Many sites today are dynamic websites that 1. Use a database connection 2. Written with a scripting language 3. Have changing content With the amount of technology behind making these sites work combined with larges volumes of traffic going to these sites, cache is very important to improve the user experience and lowering cost of your hardware.

Basic Flow Without Cache User Server Database 1. User request goes to server 2. Server request content from database 3. Database returns data 4. Server returns content

This Is Ok If….. 1. Not a lot of content 2. Small amount of users/pageviews This Is Bad If….. 1. Lots of contents 2. Lots of users/pageviews

Flow With Cache User Server Database 1. User request goes to server 2. Server gets content that is cached Database only needed to be called for new content 3. Server returns data

Cache Benefits CPU Cycle Billing: If you are billed by the CPU Cycle, cache can save you money because less of the cpu is used when reading a file rather than a complex database query. Bottleneck: If there is a bottleneck on your web service such as with your database, not calling the database as often and using cached database queries could help with that bottleneck Faster UI: Storing cached files, whether in a file in the browser or a location on the server, can lower the amount of time need to load a page. This can make a faster user experience.

Basic Caching Methods Headers: PHP has a cache option set in the headers. This can be useful for caching external files such as JavaScript and CSS files. Basic File Cache: Basic file cache is an easy to implement solution for writing and reading cache on a server. Memcache: A PHP extension for caching files on multiple servers. Cache Lite: A PHP extension installed through PEAR that caches whole pages or sections of pages. APC : APC, short for Alternative PHP Cache, is another php extension that cache’s PHP code. It is installed through PECL.

Higher Level Caching Varnish: A HTTP accelerator(reverse proxy) that caches data in virtual memory. Squid: A caching server that can cache DNS, FTP, HTTPS, HTTP, TSL, and SSL protocols. Apache Traffic Server: A reverse proxy and forward proxy caching server that despite its name, works with Nginx. XtraDB: If you are using a Mysql database, this caching solution can help optimize performance of your database better than the standard InnoDB.

Review As you can see, caching can occur at many levels. Database (ex: XtraDB) Server ( ex: Memcache) DNS/Networks ( ex: Squid) Client’s Browser (ex: Headers) Take the time to research these solutions further to see how can they improve your site’s performance.

ProdigyView and Caching Natively, ProdigyView offers two type of caching: file cache and memcache. Bot are easy to setup and use. Caching solutions can be extended by using a third party caching solution or writing an adapter that will change how the cache works.

API Reference For a better understanding of cache in ProdigyView, visit the api by clicking on the link below. PVCache More Tutorials For more tutorials, please visit: