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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.
CACHE::CACHE VERSUS CHI
Cache::Cache is in wide use and very stable, but has not changed in
years and is no longer actively developed.
CHI is the successor to Cache::Cache. It adheres to the basic
Cache::Cache API but adds new features and drivers (e.g. FastMmap and
Memcached), improves performance, and addresses limitations in the
Cache::Cache implementation. The authors recommend the use of CHI going
forward.
Questions about Cache::Cache and CHI may be directed to the perl-cache
mailing list at http://groups.google.com/group/perl-cache-discuss.
USAGE
First, choose the best type of cache implementation for your needs. The
simplest cache is the MemoryCache, which is suitable for applications
that are serving multiple sequential requests, and wish to avoid making
redundant expensive queries, such as an Apache/mod_perl application
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 acceptable, 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 SizeAwareSharedMemoryCache 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
section 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 particular
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.
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
particular 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
CHI - the successor to Cache::Cache
Cache::Object, Cache::MemoryCache, Cache::FileCache,
Cache::SharedMemoryCache, and Cache::SizeAwareFileCache
AUTHOR
Original author: DeWitt Clinton <dewitt AT unto.net>
Last author: $Author: dclinton $
Copyright (C) 2001-2003 DeWitt Clinton
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