Variable Cache Plugin

This Plugin caches Foswiki macros in selected topics for faster page rendering.

Most topics in a typical Foswiki 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 Macros, 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 An outdated cache gets refreshed when a user is looking at a topic; in which case it will take longer to render the page.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 Foswiki topic 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:

    Parameter	Description	Default
    refresh="24"	Cache refresh period in hours, e.g. maximum age of cache	REFRESH Plugin setting
    cachemsg="..."	Message shown when looking at a cached topic Note: Use $age to indicate the age of cache, $link to indicate the refresh URL	CACHEMSG Plugin setting
    updatemsg="..."	Message shown after a cache refresh Note: Use $link to indicate the refresh URL	UPDATEMSG Plugin setting

• 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 then the cache refresh period (unless refresh if set to 0)
  • the cache is older then 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 then 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 values. You can override the defaults for these preferences in SitePreferences, the WebPreferences topic of the current web, or in individual topics that use the plugin. Changing them here will have no effect! This allows you to upgrade the plugin without having to worry about losing your settings.

• One line description, is shown in the TextFormattingRules topic:
  • Set VARCACHEPLUGIN_SHORTDESCRIPTION = Cache Foswiki macros in selected topics for faster page rendering

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

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

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

Installation Instructions

%$INSTALL_INSTRUCTIONS%

Plugin Info

Plugin Author:	Original: TWiki:Main/PeterThoeny, In Foswiki context Foswiki:Main.KennethLavrsen
Copyright:	© 2004-2007, TWIKI.NET, © 2008-2011 Foswiki Contributors
License:	GPL (GNU General Public License)
Plugin Release:	%$RELEASE%
Plugin Version:	%$VERSION%
Change History:
1.1 (28 Jul 2011)	Minor bugfix -- Foswiki:Main.CrawfordCurrie
05 May 2011:	Foswikitask:Item10713: cache is now stored in the plugins work area, not under pub; Foswikitask:Item10712: No longer read preferences from plugin topic -- Foswiki:Main.AndrewJones
29 Jan 2009:	Foswiki version
06 Jan 2006:	Small fix for TWiki 4.0
16 Jul 2004:	Doc improvements (no code change)
15 Jul 2004:	Initial version
Plugin Home:	http://foswiki.org/Extensions/VarCachePlugin
Support:	http://foswiki.org/Support/VarCachePlugin

Related Topics: Plugins, DeveloperDocumentationCategory, AdminDocumentationCategory, DefaultPreferences, SitePreferences