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