Caching proxy server setup

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The caching proxy server stores cacheable content in a local cache before delivering it to the requester. You can configure the caching proxy server to handle protocols such as HTTP, FTP, and Gopher.

It does not store all content, only specific cacheable content that meets its rules. Examples of cacheable content include static Web pages and whole dynamic Web pages. Caching enables the caching proxy server to satisfy subsequent requests for the same content by delivering it directly from the local cache, which is much quicker than retrieving it again from the content host. Our caching proxy server was configured to use memory.

There are two basic types of caching content:
  • Static content

    Static content does not change over long periods of time. The content type can be HTML, JSP rendering less dynamic data, GIF, JPG, or others. Static content is characterized by content that is not generated on the fly and has predictable expiration values. Such content typically resides on the file system of the Web server or application server and is served unchanged to the client. To a large extent this content can be declared to be cacheable. This type of content is typically cached at a caching proxy. See Figure 1.

  • Dynamic content

    Dynamic content includes frequently updated content (such as exchange rates), as well as personalized and customized content. Although it is changing content, at the same time it must be stable over a long enough period for meaningful reuse to occur. However, if some content is very frequently accessed, such as requests for pricing information of a popular stock, even a short period of stability may be long enough to benefit from caching. This type of content is typically cached in the dynamic cache services of the application server or the ESI cache of the Web server plug-in (note that in our tests we did not use ESI caching). See Figure 1.

Figure 1. Caching content types
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Because the Trade application does not contain content that meets the static content criteria (Trade has only one page, the login page, that meets the requirements for external caching), the caching proxy server did not cache any content during our tests (WebSphere® Application Server V6 Scalability and Performance Handbook). Trade's dynamic content was cached in the application server's dynamic cache servers for tests in which Trade caching was enabled.

The following screen shots (Figure 2) from the caching proxy administrator panels show the activity statistics (top screen shot) and caching statistics (bottom screen shot) for the caching proxy during one of the Trade runs.

Figure 2. Caching proxy activity and cache statistics
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These screen shots show that no Trade application pages were being cached at the caching proxy. The activity statistics show that there are a high number of requests while the cache statistics show no cache hits.

The caching proxy server can also be configured as a reverse or forward proxy server.

The Edge Server caching proxy functions as a reverse proxy when it is located between a client browser on the Internet and Web servers that are located behind a firewall. In this role, the caching proxy intercepts user requests arriving from the Internet, forwards them to the appropriate host Web server, caches the returned data, and delivers that data to the client user across the Internet.

For more information on the caching proxy, see the caching proxy manuals at: 
https://www.ibm.com/software/webservers/appserv/doc/v602/ec/infocenter/index.html