NAME

CHI::Cascade - the cache dependencies (cache and like 'make' utility concept)

SYNOPSIS

    use CHI;
    use CHI::Cascade;

    $cascade = CHI::Cascade->new(chi => CHI->new(...));

    $cascade->rule(
	target	=> 'unique_name',
	depends	=> ['unique_name_other1', 'unique_name_other2'],
	code	=> sub {
	    my ($target_name, $values_of_depends) = @_;

	    # $values_of_depends == {
	    #     unique_name_other1 => $value_1,
	    #     unique_name_other2 => $value_2
	    # }

	    # Now we can calcualte $value
	    return $value;
	}
    );

    $cascade->rule(
	target	=> 'unique_name_other1',
	depends	=> 'unique_name_other3',
	code	=> sub {
	    my ($target_name, $values_of_depends) = @_;

	    # $values_of_depends == {
	    #     unique_name_other3 => $value_3
	    # }

	    # computing here
	    return $value;
	}
    );

    $value_of_this_target = $cascade->run('unique_name');

DESCRIPTION

This module is the attempt to use a benefits of caching and 'make' concept. If we have many an expensive tasks and want to cache it we can split its to small expsnsive tasks and to describe dependencies for cache items.

This module is experimental yet. I plan to improve it near time but some things already work. You can take a look for t/* tests as examples.

STATUS

This module is experimental and not finished for new features ;-) Please send me issues through https://github.com/Perlover/CHI-Cascade page

CHI::Cascade & make

Here simple example how it works. Here is a direct analogy to Unix make utility:

In CHI::Cascade:		In make:

rule			rule
depends			prerequisites
code			commands
run( rule_name )		make target_name

FEATURES

The features of this module are following:

Computing inside process

If module needs to compute item for cache we compute inside process (no forks) For web applications it means that one process for one request could take a some time for computing. But other processes will not wait and will get either old previous computed value or undef value.

Non-blocking computing for concurrent processes

If other process want to get data from cache we should not block it. So concurrent process can get an old data if new computing is run or can get undef value. A concurrent process should decide itself what it should do after it - try again after few time or print some message like 'Please wait and try again' to user.

Each target is splitted is two items in cache

For optimization this module keeps target's info by separately from value item. A target item has lock & timestamp fields. A value item has a computed value.

EXAMPLE

For example please to see the SYNOPSIS

When we prepared a rules and a depends we can:

If unique_name_other1 and/or unique_name_other2 are(is) more newer than unique_name the unique_name will be recomputed. If in this example unique_name_other1 and unique_name_other2 are older than unique_name but the unique_name_other3 is newer than unique_name_other1 then unique_name_other1 will be recomputed and after the unique_name will be recomputed.

And even we can have a same rule:

    $cascade->rule(
	target	=> qr/unique_name_(.*)/,
	depends	=> sub { 'unique_name_other_' . $_[0] },
	code	=> sub {
	    my ($target_name, $values_of_depends) = @_;

	    # $this_name == 'unique_name_3' if $cascade->run('unique_name_3') was
	    # $values_of_depends == {
	    #     unique_name_other3 => $value_ref_3
	    # }
	}
    );

    $cascade->rule(
	target	=> qr/unique_name_other_(.*)/,
	code	=> sub {
	    my ($target_name, $values_of_depends) = @_;
	    ...
	}
    );

When we will do:

$cascade->run('unique_name_52');

$cascade will find rule with qr/unique_name_(.*)/, will make =~ and will find a depend as unique_name_other_52

AUTHOR

This module has been written by Perlover <perlover@perlover.com>

LICENSE

This module is free software and is published under the same terms as Perl itself.

SEE ALSO

CHI					- mandatory
CHI::Driver::Memcached::Fast	- recommended
CHI::Driver::File			- file caching