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

