NAME

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 <[email protected]>

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