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Direktori : C:/xampp/perl/vendor/lib/DBIx/Class/Storage/DBI/Replicated/ |
Current File : C:/xampp/perl/vendor/lib/DBIx/Class/Storage/DBI/Replicated/Balancer.pm |
package DBIx::Class::Storage::DBI::Replicated::Balancer; use Moose::Role; requires 'next_storage'; use MooseX::Types::Moose qw/Int/; use DBIx::Class::Storage::DBI::Replicated::Pool; use DBIx::Class::Storage::DBI::Replicated::Types qw/DBICStorageDBI/; use namespace::clean -except => 'meta'; =head1 NAME DBIx::Class::Storage::DBI::Replicated::Balancer - A Software Load Balancer =head1 SYNOPSIS This role is used internally by L<DBIx::Class::Storage::DBI::Replicated>. =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. =head1 ATTRIBUTES This class defines the following attributes. =head2 auto_validate_every ($seconds) If auto_validate has some sort of value, run L<DBIx::Class::Storage::DBI::Replicated::Pool/validate_replicants> every $seconds. Be careful with this, because if you set it to 0 you will end up validating every query. =cut has 'auto_validate_every' => ( is=>'rw', isa=>Int, predicate=>'has_auto_validate_every', ); =head2 master The L<DBIx::Class::Storage::DBI> object that is the master database all the replicants are trying to follow. The balancer needs to know it since it's the ultimate fallback. =cut has 'master' => ( is=>'ro', isa=>DBICStorageDBI, required=>1, ); =head2 pool The L<DBIx::Class::Storage::DBI::Replicated::Pool> object that we are trying to balance. =cut has 'pool' => ( is=>'ro', isa=>'DBIx::Class::Storage::DBI::Replicated::Pool', required=>1, ); =head2 current_replicant Replicant storages (slaves) handle all read only traffic. The assumption is that your database will become readbound well before it becomes write bound and that being able to spread your read only traffic around to multiple databases is going to help you to scale traffic. This attribute returns the next slave to handle a read request. Your L</pool> attribute has methods to help you shuffle through all the available replicants via its balancer object. =cut has 'current_replicant' => ( is=> 'rw', isa=>DBICStorageDBI, lazy_build=>1, handles=>[qw/ select select_single columns_info_for /], ); =head1 METHODS This class defines the following methods. =head2 _build_current_replicant Lazy builder for the L</current_replicant> attribute. =cut sub _build_current_replicant { my $self = shift @_; $self->next_storage; } =head2 next_storage This method should be defined in the class which consumes this role. Given a pool object, return the next replicant that will serve queries. The default behavior is to grab the first replicant it finds but you can write your own subclasses of L<DBIx::Class::Storage::DBI::Replicated::Balancer> to support other balance systems. This returns from the pool of active replicants. If there are no active replicants, then you should have it return the master as an ultimate fallback. =head2 around: next_storage Advice on next storage to add the autovalidation. We have this broken out so that it's easier to break out the auto validation into a role. This also returns the master in the case that none of the replicants are active or just forgot to create them :) =cut my $on_master; around 'next_storage' => sub { my ($next_storage, $self, @args) = @_; my $now = time; ## Do we need to validate the replicants? if( $self->has_auto_validate_every && ($self->auto_validate_every + $self->pool->last_validated) <= $now ) { $self->pool->validate_replicants; } ## Get a replicant, or the master if none if(my $next = $self->$next_storage(@args)) { $self->master->debugobj->print("Moved back to slave\n") if $on_master; $on_master = 0; return $next; } else { $self->master->debugobj->print("No Replicants validate, falling back to master reads.\n") unless $on_master++; return $self->master; } }; =head2 increment_storage Rolls the Storage to whatever is next in the queue, as defined by the Balancer. =cut sub increment_storage { my $self = shift @_; my $next_replicant = $self->next_storage; $self->current_replicant($next_replicant); } =head2 around: select Advice on the select attribute. Each time we use a replicant we need to change it via the storage pool algorithm. That way we are spreading the load evenly (hopefully) across existing capacity. =cut around 'select' => sub { my ($select, $self, @args) = @_; if (my $forced_pool = $args[-1]->{force_pool}) { delete $args[-1]->{force_pool}; return $self->_get_forced_pool($forced_pool)->select(@args); } elsif($self->master->{transaction_depth}) { return $self->master->select(@args); } else { $self->increment_storage; return $self->$select(@args); } }; =head2 around: select_single Advice on the select_single attribute. Each time we use a replicant we need to change it via the storage pool algorithm. That way we are spreading the load evenly (hopefully) across existing capacity. =cut around 'select_single' => sub { my ($select_single, $self, @args) = @_; if (my $forced_pool = $args[-1]->{force_pool}) { delete $args[-1]->{force_pool}; return $self->_get_forced_pool($forced_pool)->select_single(@args); } elsif($self->master->{transaction_depth}) { return $self->master->select_single(@args); } else { $self->increment_storage; return $self->$select_single(@args); } }; =head2 before: columns_info_for Advice on the current_replicant_storage attribute. Each time we use a replicant we need to change it via the storage pool algorithm. That way we are spreading the load evenly (hopefully) across existing capacity. =cut before 'columns_info_for' => sub { my $self = shift @_; $self->increment_storage; }; =head2 _get_forced_pool ($name) Given an identifier, find the most correct storage object to handle the query. =cut sub _get_forced_pool { my ($self, $forced_pool) = @_; if(blessed $forced_pool) { return $forced_pool; } elsif($forced_pool eq 'master') { return $self->master; } elsif(my $replicant = $self->pool->replicants->{$forced_pool}) { return $replicant; } else { $self->master->throw_exception("'$forced_pool' is not a named replicant."); } } =head1 FURTHER QUESTIONS? Check the list of L<additional DBIC resources|DBIx::Class/GETTING HELP/SUPPORT>. =head1 COPYRIGHT AND LICENSE This module is free software L<copyright|DBIx::Class/COPYRIGHT AND LICENSE> by the L<DBIx::Class (DBIC) authors|DBIx::Class/AUTHORS>. You can redistribute it and/or modify it under the same terms as the L<DBIx::Class library|DBIx::Class/COPYRIGHT AND LICENSE>. =cut 1;