CHI::Driver::Memory(3pm) User Contributed Perl Documentation CHI::Driver::Memory(3pm)NAME
CHI::Driver::Memory - In-process memory based cache
VERSION
version 0.54
SYNOPSIS
use CHI;
my $hash = {};
my $cache = CHI->new( driver => 'Memory', datastore => $hash );
my $cache = CHI->new( driver => 'Memory', global => 1 );
DESCRIPTION
This cache driver stores data on a per-process basis. This is the fastest of the cache implementations, but data can not be shared between
processes. Data will remain in the cache until cleared, expired, or the process dies.
To maintain the same semantics as other caches, references to data structures are deep-copied on set and get. Thus, modifications to the
original data structure will not affect the data structure stored in the cache, and vica versa. See CHI::Driver::RawMemory for a faster
memory cache that sacrifices this behavior.
CONSTRUCTOR OPTIONS
When using this driver, the following options can be passed to CHI->new() in addition to the CHI. One of datastore or global must be
specified, or else a warning (possibly an error eventually) will be thrown.
datastore [HASHREF]
A reference to a hash to be used for storage. Within the hash, each namespace is used as a key to a second-level hash. This hash may
be passed to multiple CHI::Driver::Memory constructors.
global [BOOL]
Use a standard global datastore. Multiple caches created with this flag will see the same data. Before 0.21, this was the default
behavior; now it must be specified explicitly (to avoid accidentally sharing the same datastore in unrelated code).
DISCARD POLICY
For CHI/SIZE AWARENESS caches, this driver implements an 'LRU' policy, which discards the least recently used items first. This is the
default policy.
SEE ALSO
CHI::Driver::RawMemory, CHI
AUTHOR
Jonathan Swartz <swartz@pobox.com>
COPYRIGHT AND LICENSE
This software is copyright (c) 2011 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.
perl v5.14.2 2012-05-30 CHI::Driver::Memory(3pm)
Check Out this Related Man Page
CHI::Driver::Development(3pm) User Contributed Perl Documentation CHI::Driver::Development(3pm)NAME
CHI::Driver::Development -- Manual for developing new CHI drivers
VERSION
version 0.54
SYNOPSIS
package CHI::Driver::MyDriver;
use Moose;
use strict;
use warnings;
extends 'CHI::Driver';
has ...;
__PACKAGE__->meta->make_immutable();
sub fetch {
my ( $self, $key ) = @_;
}
sub store {
my ( $self, $key, $data[, $expires_in] ) = @_;
}
sub remove {
my ( $self, $key ) = @_;
}
sub clear {
my ($self) = @_;
}
sub get_keys {
my ($self) = @_;
}
sub get_namespaces {
my ($self) = @_;
}
DESCRIPTION
This document describes how to implement a new CHI driver.
The easiest way to start is to look at existing drivers, such as CHI::Driver::Memory and CHI::Driver::FastMmap.
NAMING
If you are going to publicly release your driver, call it 'CHI::Driver::something' so that users can create it with
CHI->new(driver => 'I<something>');
If it's an internal driver, you can call it whatever you like and create it like
CHI->new(driver => '+My::Internal::CHI::Driver');
MOOSE
CHI driver classes must be Moose based to be fully functional, since we use Moose roles to implement various features. For backward
compatibility, non-Moose drivers will still work at a basic level, but you will see an error if using any feature requiring a role.
All drivers must directly or indirectly extend CHI::Driver.
NAMESPACE
All cache handles have an assigned namespace that you can access with "$self->namespace". You should use the namespace to partition your
data store. That is, two cache objects with different namespaces should be able to access the same key without any collision.
Examples:
o The Memory driver uses a separate sub-hash inside its main memory hash for each namespace.
o The File driver uses a separate top-level directory for each namespace.
o The FastMmap driver uses a separate Cache::FastMmap file for each namespace.
METHODS
Required methods
The following methods have no default implementation, and MUST be defined by your subclass:
store ( $self, $key, $data[, $expires_in] )
Associate $data with $key in the namespace, overwriting any existing entry. Called by "set". $data will contain any necessary
metadata, including expiration options, so you can just store it as a single block.
$expires_in is optionally the number of seconds from now when the entry will expire. This will only be passed if "expires_on_backend"
in CHI is set. If your driver does not support expiration, or if you'd rather just let CHI manage expiration, you can ignore this.
fetch ( $self, $key )
Returns the data associated with $key in the namespace. Called by "get". The main CHI::Driver superclass will take care of extracting
out metadata like expiration options and determining if the value has expired.
remove ( $self, $key )
Remove the data associated with the $key in the namespace.
clear ( $self )
Remove all data associated with the namespace. (Technically not required, but the default implementation, which iterates over all keys
and calls "remove" for each, is very inefficient).
Overridable methods
The following methods have a default implementation, but MAY be overridden by your subclass:
BUILD ( $self, $options )
Define the Moose BUILD method if you want to process any options specific to your driver.
fetch_multi_hashref ( $keys )
Override this if you want to efficiently process multiple fetches. Return a hash reference from keys to fetched data. If a key is not
available, it may be left out of the hash or paired with undef. The default method will iterate over $keys and call fetch for each.
This method is called by get_multi_arrayref and get_multi_hashref.
store_multi ( $key_data, $options )
Override this if you want to efficiently process multiple stores. $key_data is a hash of keys and data that should be stored. The
default will iterate over $key_data and call store for each pair.
This method is called by set_multi.
Optional methods
The following methods have no default implementation, and MAY be defined by your subclass, but are not required for basic cache operations.
get_keys ( $self )
Return all keys in the namespace. It is acceptable to either include or omit expired keys.
get_namespaces ( $self )
Return namespaces associated with the cache. It is acceptable to either include or omit namespaces with no valid keys.
DISCARD POLICIES
You can create new discard policies for CHI/SIZE AWARENESS caches, to choose items to discard when the cache gets full. For example, the
Memory driver implements an LRU policy.
To implement a discard policy foo, define a subroutine discard_policy_foo, which takes a driver object and returns a closure that returns
one key each time it is called. The closure should maintain state so that each key is only returned once.
For example, here's the Memory driver's LRU implementation. It utilizes a hash containing the last used time for each key.
sub discard_policy_lru {
my ($self) = @_;
my $last_used_time = $self->{metadata_for_namespace}->{last_used_time};
my @keys_in_lru_order =
sort { $last_used_time->{$a} <=> $last_used_time->{$b} } $self->get_keys;
return sub {
shift(@keys_in_lru_order);
};
}
You can set the default discard policy for your driver by overriding default_discard_policy; otherwise the default is 'arbitrary'.
sub default_discard_policy { 'lru' }
TESTING
CHI has a standard set of unit tests that should be used to ensure your driver is fully implementing the CHI API.
To use CHI's tests (replacing MyDriver with the name of your driver):
o Install Test::Class, and add Test::Class to the build dependencies for your distribution.
o Add a module called CHI::Driver::MyDriver::t::CHIDriverTests to your distribution containing:
package CHI::Driver::MyDriver::t::CHIDriverTests;
use strict;
use warnings;
use CHI::Test;
use base qw(CHI::t::Driver);
sub new_cache_options {
my $self = shift;
return (
$self->SUPER::new_cache_options(),
driver => '+CHI::Driver::MyDriver',
# Any other CHI->new parameters for your test driver
);
}
1;
o Add a test script called t/CHI-driver-tests.t to your distribution containing:
#!perl -w
use strict;
use warnings;
use CHI::Driver::MyDriver::t::CHIDriverTests;
CHI::Driver::MyDriver::t::CHIDriverTests->runtests;
o You may need to override other methods in CHI::Driver::MyDriver::t::CHIDriverTests, e.g. to skip tests that do not apply to your
driver. See CHI::t::Driver::Memory and CHI::t::Driver::File in this distribution for examples.
AUTHOR
Jonathan Swartz
SEE ALSO
CHI, CHI::Driver
COPYRIGHT &; LICENSE
Copyright (C) 2007 Jonathan Swartz.
CHI is provided "as is" and without any express or implied warranties, including, without limitation, the implied warranties of
merchantibility and fitness for a particular purpose.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
AUTHOR
Jonathan Swartz <swartz@pobox.com>
COPYRIGHT AND LICENSE
This software is copyright (c) 2011 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.
perl v5.14.2 2012-05-30 CHI::Driver::Development(3pm)