NSCCN/perl-cache-cache：Perl模块，提供缓存框架，支持多级缓存和多种后端存储

You may distribute under the terms of either the GNU General Public License or the Artistic License, as specified in the Perl README file.

NAME

Cache::Cache

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 package provides Cache::Cache, a generic interface for creating persistent data stores. This interface is implemented by the Cache::MemoryCache, Cache::SharedMemoryCache, Cache::FileCache, Cache::SizeAwareFileCache, Cache::SizeAwareMemoryCache, and Cache::SizeAwareSharedMemoryCache classes.

This work aggregates and extends the obsolete File::Cache and IPC::Cache projects.

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.

L<CHI|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.

REQUIREMENTS

Digest::SHA1 Error File::Spec File::Path Storable

OPTIONAL

IPC::ShareLite

INSTALLATION

perl Makefile.PL make make test make install

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;

Please refer to the perldoc for Cache::Cache and the related implementations for complete documentation.

INCOMPATIBLE CHANGES

Cache::Cache 0.99 contains the following incompatible changes:

* Error::Simple is thrown on exceptions

* the get_identifiers method has been deprecated in favor of the
  get_keys method

* the internal format of object in a FileCache has been modified,
  necessitating a clearing of the cache while upgrading (make test 
  does this for the standard cache root)

Also note that Storable is not forward compatible between all releases. That is, older versions of the Cache will not always be able to read objects written by newer versions. This is unlikely to ever be an issue in production scenarios.

ON LOCKING:

The FileCache backend uses an temp file and an atomic rename to avoid requiring a lock during the write. This has been demonstrated to be safe across all platforms to date.

The MemoryCache backend relies on Perl’s atomic write to a hash to ensure that a lock is not required.

The SharedMemoryCache backend uses ShareLite’s locking mechanism for safety during the write.