-package DBIx::Class::Storage::DBI::Replication;
-
-use strict;
-use warnings;
+package DBIx::Class::Storage::DBI::Replicated;
+use Moose;
+use Class::MOP;
+use Moose::Util::TypeConstraints;
use DBIx::Class::Storage::DBI;
-use DBD::Multi;
-use base qw/Class::Accessor::Fast/;
-
-__PACKAGE__->mk_accessors( qw/read_source write_source/ );
+use DBIx::Class::Storage::DBI::Replicated::Pool;
+use DBIx::Class::Storage::DBI::Replicated::Balancer;
=head1 NAME
-DBIx::Class::Storage::DBI::Replication - EXPERIMENTAL Replicated database support
+DBIx::Class::Storage::DBI::Replicated - ALPHA Replicated database support
=head1 SYNOPSIS
- # change storage_type in your schema class
- $schema->storage_type( '::DBI::Replication' );
- $schema->connect_info( [
- [ "dbi:mysql:database=test;hostname=master", "username", "password", { AutoCommit => 1 } ], # master
- [ "dbi:mysql:database=test;hostname=slave1", "username", "password", { priority => 10 } ], # slave1
- [ "dbi:mysql:database=test;hostname=slave2", "username", "password", { priority => 10 } ], # slave2
- [ $dbh, '','', {priority=>10}], # add in a preexisting database handle
- [ sub { DBI->connect }, '', '', {priority=>10}], # DBD::Multi will call this coderef for connects
- <...>,
- { limit_dialect => 'LimitXY' } # If needed, see below
- ] );
-
+The Following example shows how to change an existing $schema to a replicated
+storage type, add some replicated (readonly) databases, and perform reporting
+tasks.
+
+ ## Change storage_type in your schema class
+ $schema->storage_type( ['::DBI::Replicated', {balancer=>'::Random'}] );
+
+ ## Add some slaves. Basically this is an array of arrayrefs, where each
+ ## arrayref is database connect information
+
+ $schema->storage->connect_replicants(
+ [$dsn1, $user, $pass, \%opts],
+ [$dsn2, $user, $pass, \%opts],
+ [$dsn3, $user, $pass, \%opts],
+ );
+
+ ## Now, just use the $schema as normal
+ $schema->resultset('Source')->search({name=>'etc'});
+
+ ## You can force a given query to use a particular storage using the search
+ ### attribute 'force_pool'. For example:
+
+ my $RS = $schema->resultset('Source')->search(undef, {force_pool=>'master'});
+
+ ## Now $RS will force everything (both reads and writes) to use whatever was
+ ## setup as the master storage. 'master' is hardcoded to always point to the
+ ## Master, but you can also use any Replicant name. Please see:
+ ## L<DBIx::Class::Storage::Replicated::Pool> and the replicants attribute for
+ ## More. Also see transactions and L</execute_reliably> for alternative ways
+ ## to force read traffic to the master.
+
=head1 DESCRIPTION
-Warning: This class is marked EXPERIMENTAL. It works for the authors but does
-not currently have automated tests so your mileage may vary.
+Warning: This class is marked BETA. This has been running a production
+website using MySQL native replication as it's backend and we have some decent
+test coverage but the code hasn't yet been stressed by a variety of databases.
+Individual DB's may have quirks we are not aware of. Please use this in first
+development and pass along your experiences/bug fixes.
This class implements replicated data store for DBI. Currently you can define
one master and numerous slave database connections. All write-type queries
(INSERT, UPDATE, DELETE and even LAST_INSERT_ID) are routed to master
database, all read-type queries (SELECTs) go to the slave database.
-For every slave database you can define a priority value, which controls data
-source usage pattern. It uses L<DBD::Multi>, so first the lower priority data
-sources used (if they have the same priority, the are used randomized), than
-if all low priority data sources fail, higher ones tried in order.
+Basically, any method request that L<DBIx::Class::Storage::DBI> would normally
+handle gets delegated to one of the two attributes: L</read_handler> or to
+L</write_handler>. Additionally, some methods need to be distributed
+to all existing storages. This way our storage class is a drop in replacement
+for L<DBIx::Class::Storage::DBI>.
+
+Read traffic is spread across the replicants (slaves) occuring to a user
+selected algorithm. The default algorithm is random weighted.
+
+=head1 NOTES
+
+The consistancy betweeen master and replicants is database specific. The Pool
+gives you a method to validate it's replicants, removing and replacing them
+when they fail/pass predefined criteria. Please make careful use of the ways
+to force a query to run against Master when needed.
-=head1 CONFIGURATION
+=head1 ATTRIBUTES
-=head2 Limit dialect
+This class defines the following attributes.
-If you use LIMIT in your queries (effectively, if you use
-SQL::Abstract::Limit), do not forget to set up limit_dialect (perldoc
-SQL::Abstract::Limit) by passing it as an option in the (optional) hash
-reference to connect_info. DBIC can not set it up automatically, since it can
-not guess DBD::Multi connection types.
+=head2 schema
+
+The underlying L<DBIx::Class::Schema> object this storage is attaching
=cut
-sub new {
- my $proto = shift;
- my $class = ref( $proto ) || $proto;
- my $self = {};
+has 'schema' => (
+ is=>'rw',
+ isa=>'DBIx::Class::Schema',
+ weak_ref=>1,
+ required=>1,
+);
- bless( $self, $class );
+=head2 pool_type
- $self->write_source( DBIx::Class::Storage::DBI->new );
- $self->read_source( DBIx::Class::Storage::DBI->new );
+Contains the classname which will instantiate the L</pool> object. Defaults
+to: L<DBIx::Class::Storage::DBI::Replicated::Pool>.
- return $self;
-}
+=cut
-sub all_sources {
- my $self = shift;
+has 'pool_type' => (
+ is=>'ro',
+ isa=>'ClassName',
+ required=>1,
+ default=>'DBIx::Class::Storage::DBI::Replicated::Pool',
+ handles=>{
+ 'create_pool' => 'new',
+ },
+);
- my @sources = ($self->read_source, $self->write_source);
+=head2 pool_args
- return wantarray ? @sources : \@sources;
-}
+Contains a hashref of initialized information to pass to the Balancer object.
+See L<DBIx::Class::Storage::Replicated::Pool> for available arguments.
+
+=cut
-sub connect_info {
- my( $self, $source_info ) = @_;
+has 'pool_args' => (
+ is=>'ro',
+ isa=>'HashRef',
+ lazy=>1,
+ required=>1,
+ default=>sub { {} },
+);
- my( $info, $global_options, $options, @dsns );
- $info = [ @$source_info ];
+=head2 balancer_type
- $global_options = ref $info->[-1] eq 'HASH' ? pop( @$info ) : {};
- if( ref( $options = $info->[0]->[-1] ) eq 'HASH' ) {
- # Local options present in dsn, merge them with global options
- map { $global_options->{$_} = $options->{$_} } keys %$options;
- pop @{$info->[0]};
- }
+The replication pool requires a balance class to provider the methods for
+choose how to spread the query load across each replicant in the pool.
- # We need to copy-pass $global_options, since connect_info clears it while
- # processing options
- $self->write_source->connect_info( @{$info->[0]}, { %$global_options } );
+=cut
- ## allow either a DSN string or an already connect $dbh. Just remember if
- ## you use the $dbh option then DBD::Multi has no idea how to reconnect in
- ## the event of a failure.
-
- @dsns = map {
- ## if the first element in the arrayhash is a ref, make that the value
- my $db = ref $_->[0] ? $_->[0] : $_;
- ($_->[3]->{priority} || 10) => $db;
- } @{$info->[0]}[1..@{$info->[0]}-1];
+subtype 'DBIx::Class::Storage::DBI::Replicated::BalancerClassNamePart',
+ as 'ClassName';
- $global_options->{dsns} = \@dsns;
+coerce 'DBIx::Class::Storage::DBI::Replicated::BalancerClassNamePart',
+ from 'Str',
+ via {
+ my $type = $_;
+ if($type=~m/^::/) {
+ $type = 'DBIx::Class::Storage::DBI::Replicated::Balancer'.$type;
+ }
+ Class::MOP::load_class($type);
+ $type;
+ };
+
+has 'balancer_type' => (
+ is=>'ro',
+ isa=>'DBIx::Class::Storage::DBI::Replicated::BalancerClassNamePart',
+ coerce=>1,
+ required=>1,
+ default=> 'DBIx::Class::Storage::DBI::Replicated::Balancer::First',
+ handles=>{
+ 'create_balancer' => 'new',
+ },
+);
+
+=head2 balancer_args
+
+Contains a hashref of initialized information to pass to the Balancer object.
+See L<DBIx::Class::Storage::Replicated::Balancer> for available arguments.
- $self->read_source->connect_info( [ 'dbi:Multi:', undef, undef, { %$global_options } ] );
-}
+=cut
-sub select {
- shift->read_source->select( @_ );
-}
-sub select_single {
- shift->read_source->select_single( @_ );
-}
-sub throw_exception {
- shift->read_source->throw_exception( @_ );
-}
-sub sql_maker {
- shift->read_source->sql_maker( @_ );
-}
-sub columns_info_for {
- shift->read_source->columns_info_for( @_ );
-}
-sub sqlt_type {
- shift->read_source->sqlt_type( @_ );
-}
-sub create_ddl_dir {
- shift->read_source->create_ddl_dir( @_ );
-}
-sub deployment_statements {
- shift->read_source->deployment_statements( @_ );
-}
-sub datetime_parser {
- shift->read_source->datetime_parser( @_ );
-}
-sub datetime_parser_type {
- shift->read_source->datetime_parser_type( @_ );
-}
-sub build_datetime_parser {
- shift->read_source->build_datetime_parser( @_ );
-}
+has 'balancer_args' => (
+ is=>'ro',
+ isa=>'HashRef',
+ lazy=>1,
+ required=>1,
+ default=>sub { {} },
+);
-sub limit_dialect { $_->limit_dialect( @_ ) for( shift->all_sources ) }
-sub quote_char { $_->quote_char( @_ ) for( shift->all_sources ) }
-sub name_sep { $_->quote_char( @_ ) for( shift->all_sources ) }
-sub disconnect { $_->disconnect( @_ ) for( shift->all_sources ) }
-sub set_schema { $_->set_schema( @_ ) for( shift->all_sources ) }
+=head2 pool
-sub DESTROY {
- my $self = shift;
+Is a <DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a
+container class for one or more replicated databases.
- undef $self->{write_source};
- undef $self->{read_sources};
-}
+=cut
+
+has 'pool' => (
+ is=>'ro',
+ isa=>'DBIx::Class::Storage::DBI::Replicated::Pool',
+ lazy_build=>1,
+ handles=>[qw/
+ connect_replicants
+ replicants
+ has_replicants
+ /],
+);
+
+=head2 balancer
+
+Is a <DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This
+is a class that takes a pool (<DBIx::Class::Storage::DBI::Replicated::Pool>)
+
+=cut
+
+has 'balancer' => (
+ is=>'ro',
+ isa=>'DBIx::Class::Storage::DBI::Replicated::Balancer',
+ lazy_build=>1,
+ handles=>[qw/auto_validate_every/],
+);
+
+=head2 master
+
+The master defines the canonical state for a pool of connected databases. All
+the replicants are expected to match this databases state. Thus, in a classic
+Master / Slaves distributed system, all the slaves are expected to replicate
+the Master's state as quick as possible. This is the only database in the
+pool of databases that is allowed to handle write traffic.
+
+=cut
+
+has 'master' => (
+ is=> 'ro',
+ isa=>'DBIx::Class::Storage::DBI',
+ lazy_build=>1,
+);
+
+=head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE
+
+The following methods are delegated all the methods required for the
+L<DBIx::Class::Storage::DBI> interface.
+
+=head2 read_handler
+
+Defines an object that implements the read side of L<BIx::Class::Storage::DBI>.
+
+=cut
+
+has 'read_handler' => (
+ is=>'rw',
+ isa=>'Object',
+ lazy_build=>1,
+ handles=>[qw/
+ select
+ select_single
+ columns_info_for
+ /],
+);
+
+=head2 write_handler
+
+Defines an object that implements the write side of L<BIx::Class::Storage::DBI>.
+
+=cut
+
+has 'write_handler' => (
+ is=>'ro',
+ isa=>'Object',
+ lazy_build=>1,
+ lazy_build=>1,
+ handles=>[qw/
+ on_connect_do
+ on_disconnect_do
+ connect_info
+ throw_exception
+ sql_maker
+ sqlt_type
+ create_ddl_dir
+ deployment_statements
+ datetime_parser
+ datetime_parser_type
+ last_insert_id
+ insert
+ insert_bulk
+ update
+ delete
+ dbh
+ txn_begin
+ txn_do
+ txn_commit
+ txn_rollback
+ txn_scope_guard
+ sth
+ deploy
+
+ reload_row
+ _prep_for_execute
+ configure_sqlt
+
+ /],
+);
+
+=head1 METHODS
+
+This class defines the following methods.
+
+=head2 BUILDARGS
-sub last_insert_id {
- shift->write_source->last_insert_id( @_ );
+L<DBIx::Class::Schema> when instantiating it's storage passed itself as the
+first argument. So we need to massage the arguments a bit so that all the
+bits get put into the correct places.
+
+=cut
+
+sub BUILDARGS {
+ my ($class, $schema, $storage_type_args, @args) = @_;
+
+ return {
+ schema=>$schema,
+ %$storage_type_args,
+ @args
+ }
}
-sub insert {
- shift->write_source->insert( @_ );
+
+=head2 _build_master
+
+Lazy builder for the L</master> attribute.
+
+=cut
+
+sub _build_master {
+ my $self = shift @_;
+ DBIx::Class::Storage::DBI->new($self->schema);
}
-sub update {
- shift->write_source->update( @_ );
+
+=head2 _build_pool
+
+Lazy builder for the L</pool> attribute.
+
+=cut
+
+sub _build_pool {
+ my $self = shift @_;
+ $self->create_pool(%{$self->pool_args});
}
-sub update_all {
- shift->write_source->update_all( @_ );
+
+=head2 _build_balancer
+
+Lazy builder for the L</balancer> attribute. This takes a Pool object so that
+the balancer knows which pool it's balancing.
+
+=cut
+
+sub _build_balancer {
+ my $self = shift @_;
+ $self->create_balancer(
+ pool=>$self->pool,
+ master=>$self->master,
+ %{$self->balancer_args},
+ );
}
-sub delete {
- shift->write_source->delete( @_ );
+
+=head2 _build_write_handler
+
+Lazy builder for the L</write_handler> attribute. The default is to set this to
+the L</master>.
+
+=cut
+
+sub _build_write_handler {
+ return shift->master;
}
-sub delete_all {
- shift->write_source->delete_all( @_ );
+
+=head2 _build_read_handler
+
+Lazy builder for the L</read_handler> attribute. The default is to set this to
+the L</balancer>.
+
+=cut
+
+sub _build_read_handler {
+ return shift->balancer;
}
-sub create {
- shift->write_source->create( @_ );
+
+=head2 around: connect_replicants
+
+All calls to connect_replicants needs to have an existing $schema tacked onto
+top of the args, since L<DBIx::Storage::DBI> needs it.
+
+=cut
+
+around 'connect_replicants' => sub {
+ my ($method, $self, @args) = @_;
+ $self->$method($self->schema, @args);
+};
+
+=head2 all_storages
+
+Returns an array of of all the connected storage backends. The first element
+in the returned array is the master, and the remainings are each of the
+replicants.
+
+=cut
+
+sub all_storages {
+ my $self = shift @_;
+ return grep {defined $_ && blessed $_} (
+ $self->master,
+ $self->replicants,
+ );
}
-sub find_or_create {
- shift->write_source->find_or_create( @_ );
+
+=head2 execute_reliably ($coderef, ?@args)
+
+Given a coderef, saves the current state of the L</read_handler>, forces it to
+use reliable storage (ie sets it to the master), executes a coderef and then
+restores the original state.
+
+Example:
+
+ my $reliably = sub {
+ my $name = shift @_;
+ $schema->resultset('User')->create({name=>$name});
+ my $user_rs = $schema->resultset('User')->find({name=>$name});
+ return $user_rs;
+ };
+
+ my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
+
+Use this when you must be certain of your database state, such as when you just
+inserted something and need to get a resultset including it, etc.
+
+=cut
+
+use Benchmark;
+
+sub execute_reliably {
+ my ($self, $coderef, @args) = @_;
+
+ unless( ref $coderef eq 'CODE') {
+ $self->throw_exception('Second argument must be a coderef');
+ }
+
+ ##Get copy of master storage
+ my $master = $self->master;
+
+ ##Get whatever the current read hander is
+ my $current = $self->read_handler;
+
+ ##Set the read handler to master
+ $self->read_handler($master);
+
+ ## do whatever the caller needs
+ my @result;
+ my $want_array = wantarray;
+
+ eval {
+ if($want_array) {
+ @result = $coderef->(@args);
+ } elsif(defined $want_array) {
+ ($result[0]) = ($coderef->(@args));
+ } else {
+ $coderef->(@args);
+ }
+ };
+
+ ##Reset to the original state
+ $self->read_handler($current);
+
+ ##Exception testing has to come last, otherwise you might leave the
+ ##read_handler set to master.
+
+ if($@) {
+ $self->throw_exception("coderef returned an error: $@");
+ } else {
+ return $want_array ? @result : $result[0];
+ }
+}
+
+=head2 set_reliable_storage
+
+Sets the current $schema to be 'reliable', that is all queries, both read and
+write are sent to the master
+
+=cut
+
+sub set_reliable_storage {
+ my $self = shift @_;
+ my $schema = $self->schema;
+ my $write_handler = $self->schema->storage->write_handler;
+
+ $schema->storage->read_handler($write_handler);
}
-sub update_or_create {
- shift->write_source->update_or_create( @_ );
+
+=head2 set_balanced_storage
+
+Sets the current $schema to be use the </balancer> for all reads, while all
+writea are sent to the master only
+
+=cut
+
+sub set_balanced_storage {
+ my $self = shift @_;
+ my $schema = $self->schema;
+ my $write_handler = $self->schema->storage->balancer;
+
+ $schema->storage->read_handler($write_handler);
}
+
+=head2 around: txn_do ($coderef)
+
+Overload to the txn_do method, which is delegated to whatever the
+L<write_handler> is set to. We overload this in order to wrap in inside a
+L</execute_reliably> method.
+
+=cut
+
+around 'txn_do' => sub {
+ my($txn_do, $self, $coderef, @args) = @_;
+ $self->execute_reliably(sub {$self->$txn_do($coderef, @args)});
+};
+
+=head2 connected
+
+Check that the master and at least one of the replicants is connected.
+
+=cut
+
sub connected {
- shift->write_source->connected( @_ );
+ my $self = shift @_;
+ return
+ $self->master->connected &&
+ $self->pool->connected_replicants;
}
+
+=head2 ensure_connected
+
+Make sure all the storages are connected.
+
+=cut
+
sub ensure_connected {
- shift->write_source->ensure_connected( @_ );
+ my $self = shift @_;
+ foreach my $source ($self->all_storages) {
+ $source->ensure_connected(@_);
+ }
}
-sub dbh {
- shift->write_source->dbh( @_ );
+
+=head2 limit_dialect
+
+Set the limit_dialect for all existing storages
+
+=cut
+
+sub limit_dialect {
+ my $self = shift @_;
+ foreach my $source ($self->all_storages) {
+ $source->limit_dialect(@_);
+ }
}
-sub txn_begin {
- shift->write_source->txn_begin( @_ );
+
+=head2 quote_char
+
+Set the quote_char for all existing storages
+
+=cut
+
+sub quote_char {
+ my $self = shift @_;
+ foreach my $source ($self->all_storages) {
+ $source->quote_char(@_);
+ }
}
-sub txn_commit {
- shift->write_source->txn_commit( @_ );
+
+=head2 name_sep
+
+Set the name_sep for all existing storages
+
+=cut
+
+sub name_sep {
+ my $self = shift @_;
+ foreach my $source ($self->all_storages) {
+ $source->name_sep(@_);
+ }
}
-sub txn_rollback {
- shift->write_source->txn_rollback( @_ );
+
+=head2 set_schema
+
+Set the schema object for all existing storages
+
+=cut
+
+sub set_schema {
+ my $self = shift @_;
+ foreach my $source ($self->all_storages) {
+ $source->set_schema(@_);
+ }
}
-sub sth {
- shift->write_source->sth( @_ );
+
+=head2 debug
+
+set a debug flag across all storages
+
+=cut
+
+sub debug {
+ my $self = shift @_;
+ foreach my $source ($self->all_storages) {
+ $source->debug(@_);
+ }
}
-sub deploy {
- shift->write_source->deploy( @_ );
+
+=head2 debugobj
+
+set a debug object across all storages
+
+=cut
+
+sub debugobj {
+ my $self = shift @_;
+ foreach my $source ($self->all_storages) {
+ $source->debugobj(@_);
+ }
}
+=head2 debugfh
-sub debugfh { shift->_not_supported( 'debugfh' ) };
-sub debugcb { shift->_not_supported( 'debugcb' ) };
+set a debugfh object across all storages
-sub _not_supported {
- my( $self, $method ) = @_;
+=cut
- die "This Storage does not support $method method.";
+sub debugfh {
+ my $self = shift @_;
+ foreach my $source ($self->all_storages) {
+ $source->debugfh(@_);
+ }
}
-=head1 SEE ALSO
+=head2 debugcb
-L<DBI::Class::Storage::DBI>, L<DBD::Multi>, L<DBI>
+set a debug callback across all storages
+
+=cut
+
+sub debugcb {
+ my $self = shift @_;
+ foreach my $source ($self->all_storages) {
+ $source->debugcb(@_);
+ }
+}
+
+=head2 disconnect
+
+disconnect everything
+
+=cut
+
+sub disconnect {
+ my $self = shift @_;
+ foreach my $source ($self->all_storages) {
+ $source->disconnect(@_);
+ }
+}
+
+=head1 GOTCHAS
+
+Due to the fact that replicants can lag behind a master, you must take care to
+make sure you use one of the methods to force read queries to a master should
+you need realtime data integrity. For example, if you insert a row, and then
+immediately re-read it from the database (say, by doing $row->discard_changes)
+or you insert a row and then immediately build a query that expects that row
+to be an item, you should force the master to handle reads. Otherwise, due to
+the lag, there is no certainty your data will be in the expected state.
+
+For data integrity, all transactions automatically use the master storage for
+all read and write queries. Using a transaction is the preferred and recommended
+method to force the master to handle all read queries.
+
+Otherwise, you can force a single query to use the master with the 'force_pool'
+attribute:
+
+ my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
+
+This attribute will safely be ignore by non replicated storages, so you can use
+the same code for both types of systems.
+
+Lastly, you can use the L</execute_reliably> method, which works very much like
+a transaction.
+
+For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
+and L</set_balanced_storage>, however this operates at a global level and is not
+suitable if you have a shared Schema object being used by multiple processes,
+such as on a web application server. You can get around this limitation by
+using the Schema clone method.
+
+ my $new_schema = $schema->clone;
+ $new_schema->set_reliable_storage;
+
+ ## $new_schema will use only the Master storage for all reads/writes while
+ ## the $schema object will use replicated storage.
=head1 AUTHOR
-Norbert Csongrádi <bert@cpan.org>
+ John Napiorkowski <john.napiorkowski@takkle.com>
-Peter Siklósi <einon@einon.hu>
+Based on code originated by:
+
+ Norbert Csongrádi <bert@cpan.org>
+ Peter Siklósi <einon@einon.hu>
=head1 LICENSE
=cut
+__PACKAGE__->meta->make_immutable;
+
1;
projects / dbsrgits/DBIx-Class.git / blobdiff