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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. |
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16 | |
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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 | |
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23 | =head1 ATTRIBUTES |
24 | |
25 | This class defines the following attributes. |
26 | |
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27 | =head2 master_read_weight |
28 | |
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29 | A number greater than 0 that specifies what weight to give the master when |
30 | choosing which backend to execute a read query on. A value of 0, which is the |
31 | default, does no reads from master, while a value of 1 gives it the same |
32 | priority as any single replicant. |
33 | |
34 | For example: if you have 2 replicants, and a L</master_read_weight> of C<0.5>, |
35 | the chance of reading from master will be C<20%>. |
36 | |
37 | You can set it to a value higher than 1, making master have higher weight than |
38 | any single replicant, if for example you have a very powerful master. |
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39 | |
40 | =cut |
41 | |
42 | has master_read_weight => (is => 'rw', isa => Weight, default => sub { 0 }); |
43 | |
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44 | =head1 METHODS |
45 | |
46 | This class defines the following methods. |
47 | |
48 | =head2 next_storage |
49 | |
50 | Returns an active replicant at random. Please note that due to the nature of |
51 | the word 'random' this means it's possible for a particular active replicant to |
52 | be requested several times in a row. |
53 | |
54 | =cut |
55 | |
56 | sub next_storage { |
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57 | my $self = shift @_; |
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58 | |
59 | my @replicants = $self->pool->active_replicants; |
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60 | |
61 | if (not @replicants) { |
62 | # will fall back to master anyway |
63 | return; |
64 | } |
65 | |
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66 | my $master = $self->master; |
67 | |
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68 | my $rnd = $self->_random_number(@replicants + $self->master_read_weight); |
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69 | |
70 | return $rnd >= @replicants ? $master : $replicants[int $rnd]; |
71 | } |
72 | |
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73 | sub _random_number { |
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74 | rand($_[1]) |
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75 | } |
76 | |
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77 | =head1 FURTHER QUESTIONS? |
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78 | |
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79 | Check the list of L<additional DBIC resources|DBIx::Class/GETTING HELP/SUPPORT>. |
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80 | |
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81 | =head1 COPYRIGHT AND LICENSE |
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82 | |
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83 | This module is free software L<copyright|DBIx::Class/COPYRIGHT AND LICENSE> |
84 | by the L<DBIx::Class (DBIC) authors|DBIx::Class/AUTHORS>. You can |
85 | redistribute it and/or modify it under the same terms as the |
86 | L<DBIx::Class library|DBIx::Class/COPYRIGHT AND LICENSE>. |
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87 | |
88 | =cut |
89 | |
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90 | __PACKAGE__->meta->make_immutable; |
91 | |
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92 | 1; |