NAME

Catalyst::Plugin::Cache - Flexible caching support for Catalyst.

SYNOPSIS

        use Catalyst qw/
        Cache
    /;

    # configure a backend or use a store plugin 
    __PACKAGE__->config->{'Plugin::Cache'}{backend} = {
        class => "Cache::Bounded",
        # ... params for Cache::Bounded...
    };

    # typical example for Cache::Memcached::libmemcached
    __PACKAGE__->config->{'Plugin::Cache'}{backend} = {
        class   => "Cache::Memcached::libmemcached",
        servers => ['127.0.0.1:11211'],
        debug   => 2,
    };


    # In a controller:

    sub foo : Local {
        my ( $self, $c, $id ) = @_;

        my $cache = $c->cache;

        my $result;

        unless ( $result = $cache->get( $id ) ) {
            # ... calculate result ...
            $c->cache->set( $id, $result );
        }
    };

DESCRIPTION

This plugin gives you access to a variety of systems for caching data. It allows you to use a very simple configuration API, while maintaining the possibility of flexibility when you need it later.

Among its features are support for multiple backends, segmentation based on component or controller, keyspace partitioning, and so more, in various subsidiary plugins.

METHODS

cache $profile_name

cache %meta

Return a curried object with metadata from $profile_name or as explicitly specified.

If a profile by the name $profile_name doesn't exist, but a backend object by that name does exist, the backend will be returned instead, since the interface for curried caches and backends is almost identical.

This method can also be called without arguments, in which case is treated as though the %meta hash was empty.

See "METADATA" for details.

curry_cache %meta

Return a Catalyst::Plugin::Cache::Curried object, curried with %meta.

See "METADATA" for details.

cache_set $key, $value, %meta

cache_get $key, %meta

cache_remove $key, %meta

cache_compute $key, $code, %meta

These cache operations will call choose_cache_backend with %meta, and then call "set", "get", "remove", or "compute" on the resulting backend object.

If the backend object does not support "compute" then we emulate it by calling cache_get, and if the returned value is undefined we call the passed code reference, stores the returned value with cache_set, and then returns the value. Inspired by CHI.

choose_cache_backend %meta

Select a backend object. This should return undef if no specific backend was selected - its caller will handle getting "default_cache_backend" on its own.

This method is typically used by plugins.

get_cache_backend $name

Get a backend object by name.

default_cache_backend

Return the default backend object.

temporary_cache_backend

When no default cache backend is configured this method might return a backend known to work well with the current Catalyst::Engine. This is a stub.

METADATA

Introduction

Whenever you set or retrieve a key you may specify additional metadata that will be used to select a specific backend.

This metadata is very freeform, and the only key that has any meaning by default is the "backend" key which can be used to explicitly choose a backend by name.

The "choose_cache_backend" method can be overridden in order to facilitate more intelligent backend selection. For example, Catalyst::Plugin::Cache::Choose::KeyRegexes overrides that method to select a backend based on key regexes.

Another example is a Catalyst::Plugin::Cache::ControllerNamespacing, which wraps backends in objects that perform key mangling, in order to keep caches namespaced per controller.

However, this is generally left as a hook for larger, more complex applications. Most configurations should make due XXXX

The simplest way to dynamically select a backend is based on the "Cache Profiles" configuration.

Meta Data Keys

"choose_cache_backend" is called with some default keys.

key: Supplied by "cache_get", "cache_set", and "cache_remove".
value: Supplied by "cache_set".
caller: The package name of the innermost caller that doesn't match "qr/Plugin::Cache/".
caller_frame: The entire "caller($i)" frame of "caller".
component: The package name of the innermost caller who "isa" Catalyst::Component.
component_frame: This entire "caller($i)" frame of "component".
controller: The package name of the innermost caller who "isa" Catalyst::Controller.
controller_frame: This entire "caller($i)" frame of "controller".

Metadata Currying

In order to avoid specifying %meta over and over again you may call "cache" or "curry_cache" with %meta once, and get back a curried cache object. This object responds to the methods "get", "set", and "remove", by appending its captured metadata and delegating them to "cache_get", "cache_set", and "cache_remove".

This is simpler than it sounds.

Here is an example using currying:

    my $cache = $c->cache( %meta ); # cache is curried

    $cache->set( $key, $value );

    $cache->get( $key );

And here is an example without using currying:

    $c->cache_set( $key, $value, %meta );

    $c->cache_get( $key, %meta );

See Catalyst::Plugin::Cache::Curried for details.

CONFIGURATION

    $c->config->{'Plugin::Cache'} = {
        ...
    };

All configuration parameters should be provided in a hash reference under the "Plugin::Cache" key in the "config" hash.

Backend Configuration

Configuring backend objects is done by adding hash entries under the "backends" key in the main config.

A special case is that the hash key under the "backend" (singular) key of the main config is assumed to be the backend named "default".

class

Instantiate a backend from a Cache compatible class. E.g.

    $c->config->{'Plugin::Cache'}{backends}{small_things} = {
        class    => "Cache::Bounded",
        interval => 1000,
        size     => 10000,
    };
    
    $c->config->{'Plugin::Cache'}{backends}{large_things} = {
        class => "Cache::Memcached",
        data  => '1.2.3.4:1234',
    };

The options in the hash are passed to the class's "new" method.

The class will be "required" as necessary during setup time.

store

Instantiate a backend using a store plugin, e.g.

    $c->config->{'Plugin::Cache'}{backend} = {
        store => "FastMmap",
    };

Store plugins typically require less configuration because they are specialized for Catalyst applications. For example Catalyst::Plugin::Cache::Store::FastMmap will specify a default "share_file", and additionally use a subclass of Cache::FastMmap that can also store non reference data.

The store plugin must be loaded.

Cache Profiles

profiles

Supply your own predefined profiles for cache metadata, when using the "cache" method.

For example when you specify

    $c->config->{'Plugin::Cache'}{profiles}{thumbnails} = {
        backend => "large_things",
    };

And then get a cache object like this:

    $c->cache("thumbnails");

It is the same as if you had done:

    $c->cache( backend => "large_things" );

Miscellaneous Configuration

default_store: When you do not specify a "store" parameter in the backend configuration this one will be used instead. This configuration parameter is not necessary if only one store plugin is loaded.

TERMINOLOGY

backend

An object that responds to the methods detailed in Catalyst::Plugin::Cache::Backend (or more).

store

A plugin that provides backends of a certain type. This is a bit like a factory.

cache

Stored key/value pairs of data for easy re-access.

metadata

"Extra" information about the item being stored, which can be used to locate an appropriate backend.

curried cache

  my $cache = $c->cache(type => 'thumbnails');
  $cache->set('pic01', $thumbnaildata);

A cache which has been pre-configured with a particular set of namespacing data. In the example the cache returned could be one specifically tuned for storing thumbnails.

An object that responds to "get", "set", and "remove", and will automatically add metadata to calls to "$c->cache_get", etc.

AUTHOR

Yuval Kogman, "nothingmuch@woobling.org"

Jos Boumans, "kane@cpan.org"

COPYRIGHT & LICENSE

This library is free software, you can redistribute it and/or modify it under the same terms as Perl itself, as well as under the terms of the MIT license.

POD ERRORS

Hey! The above document had some coding errors, which are explained below:

Around line 444:: Expected text after =item, not a bullet