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Cache::Cache(3)	      User Contributed Perl Documentation      Cache::Cache(3)

NAME
       Cache::Cache -- the Cache interface.

DESCRIPTION
       The Cache modules are designed to assist a developer in persisting data
       for a specified period of time.	Often these modules are used in web
       applications to store data locally to save repeated and redundant
       expensive calls to remote machines or databases.	 People have also been
       known to use Cache::Cache for its straightforward interface in sharing
       data between runs of an application or invocations of a CGI-style
       script or simply as an easy to use abstraction of the filesystem or
       shared memory.

       The Cache::Cache interface is implemented by classes that support the
       get, set, remove, size, purge, and clear instance methods and their
       corresponding static methods for persisting data across method calls.

USAGE
       First, choose the best type of cache implementation for your needs.
       The simplest cache is the MemoryCache, which is suitable for applica-
       tions that are serving multiple sequential requests, and wish to avoid
       making redundant expensive queries, such as an Apache/mod_perl applica-
       tion talking to a database.  If you wish to share that data between
       processes, then perhaps the SharedMemoryCache is appropriate, although
       its behavior is tightly bound to the underlying IPC mechanism, which
       varies from system to system, and is unsuitable for large objects or
       large numbers of objects.  When the SharedMemoryCache is not accept-
       able, then FileCache offers all of the same functionality with similar
       performance metrics, and it is not limited in terms of the number of
       objects or their size.  If you wish to maintain a strict limit on the
       size of a file system based cache, then the SizeAwareFileCache is the
       way to go.  Similarly, the SizeAwareMemoryCache and the SizeAware-
       SharedMemoryCache add size management functionality to the MemoryCache
       and SharedMemoryCache classes respectively.

       Using a cache is simple.	 Here is some sample code for instantiating
       and using a file system based cache.

	 use Cache::FileCache;

	 my $cache = new Cache::FileCache( );

	 my $customer = $cache->get( $name );

	 if ( not defined $customer )
	 {
	   $customer = get_customer_from_db( $name );
	   $cache->set( $name, $customer, "10 minutes" );
	 }

	 return $customer;

CONSTANTS
       $EXPIRES_NEVER
	   The item being set in the cache will never expire.

       $EXPIRES_NOW
	   The item being set in the cache will expire immediately.

METHODS
       Clear( )
	   Remove all objects from all caches of this type.

       Purge( )
	   Remove all objects that have expired from all caches of this type.

       Size( )
	   Returns the total size of all objects in all caches of this type.

       new( $options_hash_ref )
	   Construct a new instance of a Cache::Cache. $options_hash_ref is a
	   reference to a hash containing configuration options; see the sec-
	   tion OPTIONS below.

       clear(  )
	   Remove all objects from the namespace associated with this cache
	   instance.

       get( $key )
	   Returns the data associated with $key.

       get_object( $key )
	   Returns the underlying Cache::Object object used to store the
	   cached data associated with $key.  This will not trigger a removal
	   of the cached object even if the object has expired.

       purge(  )
	   Remove all objects that have expired from the namespace associated
	   with this cache instance.

       remove( $key )
	   Delete the data associated with the $key from the cache.

       set( $key, $data, [$expires_in] )
	   Associates $data with $key in the cache. $expires_in indicates the
	   time in seconds until this data should be erased, or the constant
	   $EXPIRES_NOW, or the constant $EXPIRES_NEVER.  Defaults to
	   $EXPIRES_NEVER.  This variable can also be in the extended format
	   of "[number] [unit]", e.g., "10 minutes".  The valid units are s,
	   second, seconds, sec, m, minute, minutes, min, h, hour, hours, d,
	   day, days, w, week, weeks, M, month, months, y, year, and years.
	   Additionally, $EXPIRES_NOW can be represented as "now" and
	   $EXPIRES_NEVER can be represented as "never".

       set_object( $key, $object )
	   Associates $key with Cache::Object $object.	Using set_object (as
	   opposed to set) does not trigger an automatic removal of expired
	   objects.

       size(  )
	   Returns the total size of all objects in the namespace associated
	   with this cache instance.

       get_namespaces( )
	   Returns all the namespaces associated with this type of cache.

OPTIONS
       The options are set by passing in a reference to a hash containing any
       of the following keys:

       namespace
	   The namespace associated with this cache.  Defaults to "Default" if
	   not explicitly set.

       default_expires_in
	   The default expiration time for objects place in the cache.
	   Defaults to $EXPIRES_NEVER if not explicitly set.

       auto_purge_interval
	   Sets the auto purge interval.  If this option is set to a particu-
	   lar time ( in the same format as the expires_in ), then the purge(
	   ) routine will be called during the first set after the interval
	   expires.  The interval will then be reset.

       auto_purge_on_set
	   If this option is true, then the auto purge interval routine will
	   be checked on every set.

       auto_purge_on_get
	   If this option is true, then the auto purge interval routine will
	   be checked on every get.  This is probably not the desired behav-
	   ior, as the purge could be a very expensive operation.

PROPERTIES
       (get|set)_namespace( )
	   The namespace of this cache instance

       get_default_expires_in( )
	   The default expiration time for objects placed in this cache
	   instance

       get_keys( )
	   The list of keys specifying objects in the namespace associated
	   with this cache instance

       get_identifiers( )
	   This method has been deprecated in favor of get_keys( ).

       (get|set)_auto_purge_interval( )
	   Accesses the auto purge interval.  If this option is set to a par-
	   ticular time ( in the same format as the expires_in ), then the
	   purge( ) routine will be called during the first get after the
	   interval expires.  The interval will then be reset.

       (get|set)_auto_purge_on_set( )
	   If this property is true, then the auto purge interval routine will
	   be checked on every set.

       (get|set)_auto_purge_on_get( )
	   If this property is true, then the auto purge interval routine will
	   be checked on every get.

SEE ALSO
       Cache::Object, Cache::MemoryCache, Cache::FileCache, Cache::SharedMemo-
       ryCache, and Cache::SizeAwareFileCache

AUTHOR
       Original author: DeWitt Clinton <dewitt@unto.net>

       Last author:	$Author: dclinton $

       Copyright (C) 2001-2003 DeWitt Clinton

perl v5.8.8			  2003-04-15		       Cache::Cache(3)
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