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RIBASUSHI / DBIx-Class-0.08260_01 / lib / DBIx / Class / Storage / DBI / Replicated / Balancer / Random.pm 

            

              
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package DBIx::Class::Storage::DBI::Replicated::Balancer::Random;
use Moose;
with 'DBIx::Class::Storage::DBI::Replicated::Balancer';
use DBIx::Class::Storage::DBI::Replicated::Types 'Weight';
use namespace::clean -except => 'meta';
=head1 NAME
DBIx::Class::Storage::DBI::Replicated::Balancer::Random - A 'random' Balancer
=head1 SYNOPSIS
This class is used internally by L<DBIx::Class::Storage::DBI::Replicated>.  You
shouldn't need to create instances of this class.
=head1 DESCRIPTION
Given a pool (L<DBIx::Class::Storage::DBI::Replicated::Pool>) of replicated
database's (L<DBIx::Class::Storage::DBI::Replicated::Replicant>), defines a
method by which query load can be spread out across each replicant in the pool.
This Balancer uses L<List::Util> keyword 'shuffle' to randomly pick an active
replicant from the associated pool.  This may or may not be random enough for
you, patches welcome.
=head1 ATTRIBUTES
This class defines the following attributes.
=head2 master_read_weight
A number greater than 0 that specifies what weight to give the master when
choosing which backend to execute a read query on. A value of 0, which is the
default, does no reads from master, while a value of 1 gives it the same
priority as any single replicant.
For example: if you have 2 replicants, and a L</master_read_weight> of C<0.5>,
the chance of reading from master will be C<20%>.
You can set it to a value higher than 1, making master have higher weight than
any single replicant, if for example you have a very powerful master.
=cut
has master_read_weight => (is => 'rw', isa => Weight, default => sub { 0 });
=head1 METHODS
This class defines the following methods.
=head2 next_storage
Returns an active replicant at random.  Please note that due to the nature of
the word 'random' this means it's possible for a particular active replicant to
be requested several times in a row.
=cut
sub next_storage {
  my $self = shift @_;
  my @replicants = $self->pool->active_replicants;
  if (not @replicants) {
    # will fall back to master anyway
    return;
  }
  my $master     = $self->master;
  my $rnd = $self->_random_number(@replicants + $self->master_read_weight);
  return $rnd >= @replicants ? $master : $replicants[int $rnd];
}
sub _random_number {
  rand($_[1])
}
=head1 AUTHOR
John Napiorkowski <john.napiorkowski@takkle.com>
=head1 LICENSE
You may distribute this code under the same terms as Perl itself.
=cut
__PACKAGE__->meta->make_immutable;
1;