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Jonathan Swartz

NAME

Poet::Cache -- Poet caching with CHI

SYNOPSIS

    # In a conf file...
    cache:
       defaults:
          driver: Memcached
          servers: ["10.0.0.15:11211", "10.0.0.15:11212"]

    # In a script...
    use Poet::Script qw($cache);

    # In a module...
    use Poet qw($cache);

    # In a component...
    my $cache = $m->cache;

    # For an arbitrary namespace...
    my $cache = Poet::Cache->new(namespace => 'Some::Namespace')

    # then...
    my $customer = $cache->get($name);
    if ( !defined $customer ) {
        $customer = get_customer_from_db($name);
        $cache->set( $name, $customer, "10 minutes" );
    }
    my $customer2 = $cache->compute($name2, "10 minutes", sub {
        get_customer_from_db($name2)
    });

DESCRIPTION

Poet::Cache is a subclass of CHI. CHI provides a unified caching API over a variety of storage backends, such as memory, plain files, memory mapped files, memcached, and DBI.

Each package and Mason component uses its own CHI namespace so that caches remain separate.

CONFIGURATION

The Poet configuration entry 'cache', if any, will be passed to Poet::Cache->config(). This can go in any Poet conf file, e.g. local.cfg or global/cache.cfg.

Here's a simple configuration that caches everything to files under data/cache. This is also the default if no configuration is present.

   cache:
      defaults:
         driver: File
         root_dir: ${root}/data/cache

Here's a more involved configuration that defines several "storage types" and assigns each namespace a storage type.

   cache:
      defaults:
         expires_variance: 0.2
      storage:
         file:
            driver: File
            root_dir: ${root}/data/cache
         memcached:
            driver: Memcached
            servers: ["10.0.0.15:11211", "10.0.0.15:11212"]
            compress_threshold: 4096
      namespace:
         /some/component:       { storage: file, expires_in: 5min }
         /some/other/component: { storage: memcached, expires_in: 1h }
         Some::Library:         { storage: memcached, expires_in: 10min } 

Given the configuration above, and the code

    package Some::Library;
    use Poet qw($cache);

this $cache will be created with properties

    driver: Memcached
    servers: ["10.0.0.15:11211", "10.0.0.15:11212"]
    compress_threshold: 4096
    expires_in: 10min

USAGE

Obtaining cache handle

  • In a script (namespace will be 'main'):

        use Poet::Script qw($cache);
  • In a module MyApp::Foo (namespace will be 'MyApp::Foo'):

        use Poet qw($cache);
  • In a component /foo/bar (namespace will be '/foo/bar'):

        my $cache = $m->cache;
  • Manually for an arbitrary namespace:

        my $cache = Poet::Cache->new(namespace => 'Some::Namespace');
            
        # or
        
        my $cache = MyApp::Cache->new(category => 'Some::Namespace');

Using cache handle

    my $customer = $cache->get($name);
    if ( !defined $customer ) {
        $customer = get_customer_from_db($name);
        $cache->set( $name, $customer, "10 minutes" );
    }
    my $customer2 = $cache->compute($name2, "10 minutes", sub {
        get_customer_from_db($name2)
    });

See CHI and Mason::Plugin::Cache for more details.

MODIFIABLE METHODS

These methods are not intended to be called externally, but may be useful to override or modify with method modifiers in subclasses.

initialize_caching

Called once when the Poet environment is initialized. By default, calls __PACKAGE__->config with the configuration entry 'cache'.

SEE ALSO

Poet

AUTHOR

Jonathan Swartz <swartz@pobox.com>

COPYRIGHT AND LICENSE

This software is copyright (c) 2012 by Jonathan Swartz.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.




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