1package DBIx::Class::Storage::DBI::Replicated::Balancer::Random; 2 3use Moose; 4with 'DBIx::Class::Storage::DBI::Replicated::Balancer'; 5use DBIx::Class::Storage::DBI::Replicated::Types 'Weight'; 6use namespace::clean -except => 'meta'; 7 8=head1 NAME 9 10DBIx::Class::Storage::DBI::Replicated::Balancer::Random - A 'random' Balancer 11 12=head1 SYNOPSIS 13 14This class is used internally by L<DBIx::Class::Storage::DBI::Replicated>. You 15shouldn't need to create instances of this class. 16 17=head1 DESCRIPTION 18 19Given a pool (L<DBIx::Class::Storage::DBI::Replicated::Pool>) of replicated 20database's (L<DBIx::Class::Storage::DBI::Replicated::Replicant>), defines a 21method by which query load can be spread out across each replicant in the pool. 22 23This Balancer uses L<List::Util> keyword 'shuffle' to randomly pick an active 24replicant from the associated pool. This may or may not be random enough for 25you, patches welcome. 26 27=head1 ATTRIBUTES 28 29This class defines the following attributes. 30 31=head2 master_read_weight 32 33A number greater than 0 that specifies what weight to give the master when 34choosing which backend to execute a read query on. A value of 0, which is the 35default, does no reads from master, while a value of 1 gives it the same 36priority as any single replicant. 37 38For example: if you have 2 replicants, and a L</master_read_weight> of C<0.5>, 39the chance of reading from master will be C<20%>. 40 41You can set it to a value higher than 1, making master have higher weight than 42any single replicant, if for example you have a very powerful master. 43 44=cut 45 46has master_read_weight => (is => 'rw', isa => Weight, default => sub { 0 }); 47 48=head1 METHODS 49 50This class defines the following methods. 51 52=head2 next_storage 53 54Returns an active replicant at random. Please note that due to the nature of 55the word 'random' this means it's possible for a particular active replicant to 56be requested several times in a row. 57 58=cut 59 60sub next_storage { 61 my $self = shift @_; 62 63 my @replicants = $self->pool->active_replicants; 64 65 if (not @replicants) { 66 # will fall back to master anyway 67 return; 68 } 69 70 my $master = $self->master; 71 72 my $rnd = $self->_random_number(@replicants + $self->master_read_weight); 73 74 return $rnd >= @replicants ? $master : $replicants[int $rnd]; 75} 76 77sub _random_number { 78 rand($_[1]) 79} 80 81=head1 AUTHOR 82 83John Napiorkowski <john.napiorkowski@takkle.com> 84 85=head1 LICENSE 86 87You may distribute this code under the same terms as Perl itself. 88 89=cut 90 91__PACKAGE__->meta->make_immutable; 92 931; 94