1 package DBIx::Class::Storage::DBI::Replicated::Balancer::Random;
4 with 'DBIx::Class::Storage::DBI::Replicated::Balancer';
5 use DBIx::Class::Storage::DBI::Replicated::Types 'Weight';
6 use namespace::clean -except => 'meta';
10 DBIx::Class::Storage::DBI::Replicated::Balancer::Random - A 'random' Balancer
14 This class is used internally by L<DBIx::Class::Storage::DBI::Replicated>. You
15 shouldn't need to create instances of this class.
19 Given a pool (L<DBIx::Class::Storage::DBI::Replicated::Pool>) of replicated
20 database's (L<DBIx::Class::Storage::DBI::Replicated::Replicant>), defines a
21 method by which query load can be spread out across each replicant in the pool.
23 This Balancer uses L<List::Util> keyword 'shuffle' to randomly pick an active
24 replicant from the associated pool. This may or may not be random enough for
29 This class defines the following attributes.
31 =head2 master_read_weight
33 A number greater than 0 that specifies what weight to give the master when
34 choosing which backend to execute a read query on. A value of 0, which is the
35 default, does no reads from master, while a value of 1 gives it the same
36 priority as any single replicant.
38 For example: if you have 2 replicants, and a L</master_read_weight> of C<0.5>,
39 the chance of reading from master will be C<20%>.
41 You can set it to a value higher than 1, making master have higher weight than
42 any single replicant, if for example you have a very powerful master.
46 has master_read_weight => (is => 'rw', isa => Weight, default => sub { 0 });
50 This class defines the following methods.
54 Returns an active replicant at random. Please note that due to the nature of
55 the word 'random' this means it's possible for a particular active replicant to
56 be requested several times in a row.
63 my @replicants = $self->pool->active_replicants;
65 if (not @replicants) {
66 # will fall back to master anyway
70 my $master = $self->master;
72 my $rnd = $self->_random_number(@replicants + $self->master_read_weight);
74 return $rnd >= @replicants ? $master : $replicants[int $rnd];
83 John Napiorkowski <john.napiorkowski@takkle.com>
87 You may distribute this code under the same terms as Perl itself.
91 __PACKAGE__->meta->make_immutable;