Variable Cache Plugin

This Plugin caches TWiki variables in selected topics for faster page rendering.

Most topics in a typical TWiki installation are rendered within a small deviation in terms of speed. Exceptions are topics that contain a lot of dynamic content. This is mainly caused by CPU or I/O intensive TWikiVariables, such as %SEARCH{}% and %INCLUDE{}%.

This Plugin caches all %VARIABLES% located in a topic so that the topic can get rendered as quickly as one without variables. An outdated cache gets refreshed when a user is looking at a topic; in which case it will take longer to render the page. Time-based refresh can also be disabled in favor of an on-demand cache update.

The rendering of TWiki markup to HTML is not cached. That is, user specific HTML rendering based on skin settings is not affected by the caching.

Syntax Rules and Cache Update Rules

• Add a %VARCACHE{}% variable to the topic you want to cache
  • It supports these parameters:

• The %VARCACHE{}% variable gets:
  • replaced with the cachemsg message when looking at a cached topic
  • replaced with the updatemsg message if the cache has just been updated
  • removed if caching is not active, e.g. when the topic gets rendered dynamically
• The cache gets updated on topic view if:
  • the cache does not exist (e.g. after adding the %VARCACHE{}% variable)
  • the cache is older than the cache refresh period (unless refresh if set to 0)
  • the cache is older than the topic (e.g. the topic has been updated)
  • the topic is accessed with a ?varcache=refresh URL parameter (usually by following the refresh link in the cache message)
• The topic is rendered dynamically without caching when:
  • the topic has URL parameters other than varcache (e.g. to show dynamic content properly, such as table sorting, filtering, searching)
  • the topic is previewed after editing
• Limitations:
  • The cache is not user specific. For example, all users see the expanded %WIKIUSERNAME% of the person who refreshed the cache (on demand or by looking at a topic with an exired cache)

Plugin Settings

Plugin settings are stored as preferences variables. To reference a plugin setting write %<plugin>_<setting>%, i.e. %VARCACHEPLUGIN_SHORTDESCRIPTION%

• One line description, is shown in the TextFormattingRules topic:
  • Set SHORTDESCRIPTION = Cache TWiki variables in selected topics for faster page rendering

• Debug plugin: (See output in data/debug.txt)
  • Set DEBUG = 0

• Default refresh period in hours. No automatic refresh: 0, default: 24
  • Set REFRESH = 24

• Cache help messages. Use $age to indicate age of cache, $link to indicate the refresh URL
  • Set CACHEMSG = This topic was cached $age ago ([[$link][refresh]])
  • Set UDATEMSG = This topic is now cached ([[$link][refresh]])
  • #Set CACHEMSG =
  • #Set UDATEMSG =

Plugin Installation Instructions

Note: You do not need to install anything on the browser to use this plugin. The following instructions are for the administrator who installs the Plugin on the TWiki server.

• Download the ZIP file from the Plugin web (see below)
• Unzip VarCachePlugin.zip in your twiki installation directory. Content:

• TWiki 4.0 and up: Run the configure script to enable the Plugin
• Test if the installation was successful:
  • Visit the VarCachePluginTest topic, it contains a nested search
  • Click on the refresh link or append a ?varcache=refresh parameter to the URL

Plugin Info

Related Topics: TWikiPlugins, DeveloperDocumentationCategory, AdminDocumentationCategory, TWikiPreferences

-- TWiki:Main/PeterThoeny - 06 Jan 2006