Configuring ALI Portlet Caching Settings

In ALI , the HTTP Configuration page of the Web Service editor allows portal administrators to set minimum and maximum validation times for cached portlet content.

Note: Using HTTP headers to control caching is always preferable. Administrators can override some programmatic caching, but they cannot be relied upon to set caching correctly. If your portlet requires specific editor settings for its caching strategy, you must include this information in your Installation Guide.

The default cache settings are a minimum of 0 seconds and a maximum of 20 days.

The minimum and maximum caching settings in the Portlet editor affect caching as follows.

The Portal Server never makes a request to the remote server before the Minimum Cache Time if there is content in the cache. (In version 6.0, the portlet cache is limited to 15 minutes, so a request will always be made after 15 minutes.) Multiple requests made for the same portlet with identical cachekeys within this minimum time always receive cached content. As noted earlier, setting the Cache-Control header to “no-cache” overrides editor caching settings; content will not be cached.
The Portal Server always makes a request to the remote server after the Maximum Cache Time. Cached content might or might not be returned, based on other information (for example, the Last-Modified header).
The Portal Server might or might not make a request to the remote server if content has been cached in between the Minimum and Maximum Cache Time. The Portal Server observes programmatic caching (for example, the Expires header) in the window between the minimum and maximum times.

Setting the Cache-Control header to “no-cache” overrides editor settings; content will never be cached.

For example, the minimum caching time for a particular portlet is set to ten minutes, and the maximum caching time is set to one hour. Client A requests the portlet content. Five minutes later, Client B, with an identical set of preferences, requests the same content. Five minutes is under the minimum caching time set in the Portlet editor, so cached content is returned, no matter what type of programmatic caching has been implemented by the portlet. (Remember, the Portal Server only abides by headers if cached content was generated between the minimum and maximum caching times set in the editor. An Expires header set to two minutes does not refresh the cache in this example.) If no copies of the content existed for Client B’s particular collection of settings or no content was cached, the remote server would be called to generate content that matched that group of settings.

To continue the example, Client A requests the portlet content again, and there is a matching copy of the content in the cache that is 15 minutes old. This is over the minimum caching time and under the maximum. In this case, whether or not new content is generated depends on the HTTP headers sent by the portlet. If the portlet has not specified any caching programmatically, the Portal Server asks the remote server for fresh content. If the portlet set the Expires header to 30 minutes, new content is not generated. If ETag or Last-Modified caching was implemented, new content is only returned if content has changed.

Finally, Client A requests the same content two hours later, and the matching copy was generated more than an hour before. Since this is over the maximum caching time set in the Portlet editor, the Portal Server requests new content from the remote server, regardless of the caching specified programmatically by the portlet. Of course, if the portlet has implemented ETag or Last-Modified caching, new content is only returned if content has changed.

Parent topic: About Pagelet Caching

AquaLogic User Interaction Development Guide

Configuring ALI Portlet Caching Settings