1 package DBIx::Class::Storage::DBI::Replicated;
5 die('The following modules are required for Replication ' . DBIx::Class::Optional::Dependencies->req_missing_for ('replicated') . "\n" )
6 unless DBIx::Class::Optional::Dependencies->req_ok_for ('replicated');
10 use DBIx::Class::Storage::DBI;
11 use DBIx::Class::Storage::DBI::Replicated::Pool;
12 use DBIx::Class::Storage::DBI::Replicated::Balancer;
13 use DBIx::Class::Storage::DBI::Replicated::Types qw/BalancerClassNamePart DBICSchema DBICStorageDBI/;
14 use MooseX::Types::Moose qw/ClassName HashRef Object/;
15 use Scalar::Util 'reftype';
17 use List::Util qw/min max reduce/;
18 use Context::Preserve 'preserve_context';
21 use namespace::clean -except => 'meta';
27 DBIx::Class::Storage::DBI::Replicated - BETA Replicated database support
31 The Following example shows how to change an existing $schema to a replicated
32 storage type, add some replicated (read-only) databases, and perform reporting
35 You should set the 'storage_type attribute to a replicated type. You should
36 also define your arguments, such as which balancer you want and any arguments
37 that the Pool object should get.
39 my $schema = Schema::Class->clone;
40 $schema->storage_type( ['::DBI::Replicated', {balancer=>'::Random'}] );
41 $schema->connection(...);
43 Next, you need to add in the Replicants. Basically this is an array of
44 arrayrefs, where each arrayref is database connect information. Think of these
45 arguments as what you'd pass to the 'normal' $schema->connect method.
47 $schema->storage->connect_replicants(
48 [$dsn1, $user, $pass, \%opts],
49 [$dsn2, $user, $pass, \%opts],
50 [$dsn3, $user, $pass, \%opts],
53 Now, just use the $schema as you normally would. Automatically all reads will
54 be delegated to the replicants, while writes to the master.
56 $schema->resultset('Source')->search({name=>'etc'});
58 You can force a given query to use a particular storage using the search
59 attribute 'force_pool'. For example:
61 my $rs = $schema->resultset('Source')->search(undef, {force_pool=>'master'});
63 Now $rs will force everything (both reads and writes) to use whatever was setup
64 as the master storage. 'master' is hardcoded to always point to the Master,
65 but you can also use any Replicant name. Please see:
66 L<DBIx::Class::Storage::DBI::Replicated::Pool> and the replicants attribute for more.
68 Also see transactions and L</execute_reliably> for alternative ways to
69 force read traffic to the master. In general, you should wrap your statements
70 in a transaction when you are reading and writing to the same tables at the
71 same time, since your replicants will often lag a bit behind the master.
73 If you have a multi-statement read only transaction you can force it to select
74 a random server in the pool by:
76 my $rs = $schema->resultset('Source')->search( undef,
77 { force_pool => $db->storage->read_handler->next_storage }
82 Warning: This class is marked BETA. This has been running a production
83 website using MySQL native replication as its backend and we have some decent
84 test coverage but the code hasn't yet been stressed by a variety of databases.
85 Individual DBs may have quirks we are not aware of. Please use this in first
86 development and pass along your experiences/bug fixes.
88 This class implements replicated data store for DBI. Currently you can define
89 one master and numerous slave database connections. All write-type queries
90 (INSERT, UPDATE, DELETE and even LAST_INSERT_ID) are routed to master
91 database, all read-type queries (SELECTs) go to the slave database.
93 Basically, any method request that L<DBIx::Class::Storage::DBI> would normally
94 handle gets delegated to one of the two attributes: L</read_handler> or to
95 L</write_handler>. Additionally, some methods need to be distributed
96 to all existing storages. This way our storage class is a drop in replacement
97 for L<DBIx::Class::Storage::DBI>.
99 Read traffic is spread across the replicants (slaves) occurring to a user
100 selected algorithm. The default algorithm is random weighted.
104 The consistency between master and replicants is database specific. The Pool
105 gives you a method to validate its replicants, removing and replacing them
106 when they fail/pass predefined criteria. Please make careful use of the ways
107 to force a query to run against Master when needed.
111 Replicated Storage has additional requirements not currently part of
112 L<DBIx::Class>. See L<DBIx::Class::Optional::Dependencies> for more details.
116 This class defines the following attributes.
120 The underlying L<DBIx::Class::Schema> object this storage is attaching
133 Contains the classname which will instantiate the L</pool> object. Defaults
134 to: L<DBIx::Class::Storage::DBI::Replicated::Pool>.
141 default=>'DBIx::Class::Storage::DBI::Replicated::Pool',
143 'create_pool' => 'new',
149 Contains a hashref of initialized information to pass to the Balancer object.
150 See L<DBIx::Class::Storage::DBI::Replicated::Pool> for available arguments.
164 The replication pool requires a balance class to provider the methods for
165 choose how to spread the query load across each replicant in the pool.
169 has 'balancer_type' => (
171 isa=>BalancerClassNamePart,
174 default=> 'DBIx::Class::Storage::DBI::Replicated::Balancer::First',
176 'create_balancer' => 'new',
182 Contains a hashref of initialized information to pass to the Balancer object.
183 See L<DBIx::Class::Storage::DBI::Replicated::Balancer> for available arguments.
187 has 'balancer_args' => (
197 Is a L<DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a
198 container class for one or more replicated databases.
204 isa=>'DBIx::Class::Storage::DBI::Replicated::Pool',
215 Is a L<DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This
216 is a class that takes a pool (L<DBIx::Class::Storage::DBI::Replicated::Pool>)
222 isa=>'DBIx::Class::Storage::DBI::Replicated::Balancer',
224 handles=>[qw/auto_validate_every/],
229 The master defines the canonical state for a pool of connected databases. All
230 the replicants are expected to match this databases state. Thus, in a classic
231 Master / Slaves distributed system, all the slaves are expected to replicate
232 the Master's state as quick as possible. This is the only database in the
233 pool of databases that is allowed to handle write traffic.
243 =head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE
245 The following methods are delegated all the methods required for the
246 L<DBIx::Class::Storage::DBI> interface.
250 my $method_dispatch = {
262 deployment_statements
265 build_datetime_parser
281 with_deferred_fk_checks
289 relname_to_table_alias
291 _default_dbi_connect_attributes
293 _dbic_connect_attributes
299 bind_attribute_by_data_type
303 _dbh_execute_for_fetch
305 _dbh_execute_inserts_with_no_binds
306 _select_args_to_query
309 _normalize_connect_info
323 /, Class::MOP::Class->initialize('DBIx::Class::Storage::DBIHacks')->get_method_list ],
328 _dbh_columns_info_for
331 unimplemented => [qw/
332 _arm_global_destructor
335 source_bind_attributes
337 get_use_dbms_capability
338 set_use_dbms_capability
344 _determine_connector_driver
346 _warn_undetermined_driver
353 _perform_autoinc_retrieval
354 _autoinc_supplied_for_op
366 # the capability framework
367 # not sure if CMOP->initialize does evil things to DBIC::S::DBI, fix if a problem
369 { $_ =~ /^ _ (?: use | supports | determine_supports ) _ /x }
370 ( Class::MOP::Class->initialize('DBIx::Class::Storage::DBI')->get_all_method_names )
374 if (DBIx::Class::_ENV_::DBICTEST) {
377 for my $type (keys %$method_dispatch) {
378 for (@{$method_dispatch->{$type}}) {
379 push @{$seen->{$_}}, $type;
383 if (my @dupes = grep { @{$seen->{$_}} > 1 } keys %$seen) {
385 'The following methods show up multiple times in ::Storage::DBI::Replicated handlers:',
386 (map { "$_: " . (join ', ', @{$seen->{$_}}) } sort @dupes),
391 if (my @cant = grep { ! DBIx::Class::Storage::DBI->can($_) } keys %$seen) {
393 '::Storage::DBI::Replicated specifies handling of the following *NON EXISTING* ::Storage::DBI methods:',
400 for my $method (@{$method_dispatch->{unimplemented}}) {
401 __PACKAGE__->meta->add_method($method, sub {
403 $self->throw_exception("$method must not be called on ".(blessed $self).' objects');
409 Defines an object that implements the read side of L<BIx::Class::Storage::DBI>.
413 has 'read_handler' => (
417 handles=>$method_dispatch->{reader},
422 Defines an object that implements the write side of L<BIx::Class::Storage::DBI>,
423 as well as methods that don't write or read that can be called on only one
424 storage, methods that return a C<$dbh>, and any methods that don't make sense to
429 has 'write_handler' => (
433 handles=>$method_dispatch->{writer},
438 has _master_connect_info_opts =>
439 (is => 'rw', isa => HashRef, default => sub { {} });
441 =head2 around: connect_info
443 Preserves master's C<connect_info> options (for merging with replicants.)
444 Also sets any Replicated-related options from connect_info, such as
445 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
449 around connect_info => sub {
450 my ($next, $self, $info, @extra) = @_;
452 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
455 for my $arg (@$info) {
456 next unless (reftype($arg)||'') eq 'HASH';
457 %opts = %{ $merge->merge($arg, \%opts) };
461 if (@opts{qw/pool_type pool_args/}) {
462 $self->pool_type(delete $opts{pool_type})
466 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
469 ## Since we possibly changed the pool_args, we need to clear the current
470 ## pool object so that next time it is used it will be rebuilt.
474 if (@opts{qw/balancer_type balancer_args/}) {
475 $self->balancer_type(delete $opts{balancer_type})
476 if $opts{balancer_type};
478 $self->balancer_args(
479 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
482 $self->balancer($self->_build_balancer)
486 $self->_master_connect_info_opts(\%opts);
488 return preserve_context {
489 $self->$next($info, @extra);
491 # Make sure master is blessed into the correct class and apply role to it.
492 my $master = $self->master;
493 $master->_determine_driver;
494 Moose::Meta::Class->initialize(ref $master);
496 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
498 # link pool back to master
499 $self->pool->master($master);
505 This class defines the following methods.
509 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
510 first argument. So we need to massage the arguments a bit so that all the
511 bits get put into the correct places.
516 my ($class, $schema, $storage_type_args, @args) = @_;
527 Lazy builder for the L</master> attribute.
533 my $master = DBIx::Class::Storage::DBI->new($self->schema);
539 Lazy builder for the L</pool> attribute.
545 $self->create_pool(%{$self->pool_args});
548 =head2 _build_balancer
550 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
551 the balancer knows which pool it's balancing.
555 sub _build_balancer {
557 $self->create_balancer(
559 master=>$self->master,
560 %{$self->balancer_args},
564 =head2 _build_write_handler
566 Lazy builder for the L</write_handler> attribute. The default is to set this to
571 sub _build_write_handler {
572 return shift->master;
575 =head2 _build_read_handler
577 Lazy builder for the L</read_handler> attribute. The default is to set this to
582 sub _build_read_handler {
583 return shift->balancer;
586 =head2 around: connect_replicants
588 All calls to connect_replicants needs to have an existing $schema tacked onto
589 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
590 options merged with the master, with replicant opts having higher priority.
594 around connect_replicants => sub {
595 my ($next, $self, @args) = @_;
598 $r = [ $r ] unless reftype $r eq 'ARRAY';
600 $self->throw_exception('coderef replicant connect_info not supported')
601 if ref $r->[0] && reftype $r->[0] eq 'CODE';
603 # any connect_info options?
605 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
608 $r->[$i] = {} unless $r->[$i];
610 # merge if two hashes
611 my @hashes = @$r[$i .. $#{$r}];
613 $self->throw_exception('invalid connect_info options')
614 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
616 $self->throw_exception('too many hashrefs in connect_info')
619 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
620 my %opts = %{ $merge->merge(reverse @hashes) };
623 splice @$r, $i+1, ($#{$r} - $i), ();
625 # make sure master/replicants opts don't clash
626 my %master_opts = %{ $self->_master_connect_info_opts };
627 if (exists $opts{dbh_maker}) {
628 delete @master_opts{qw/dsn user password/};
630 delete $master_opts{dbh_maker};
633 %opts = %{ $merge->merge(\%opts, \%master_opts) };
639 $self->$next($self->schema, @args);
644 Returns an array of of all the connected storage backends. The first element
645 in the returned array is the master, and the remainings are each of the
652 return grep {defined $_ && blessed $_} (
654 values %{ $self->replicants },
658 =head2 execute_reliably ($coderef, ?@args)
660 Given a coderef, saves the current state of the L</read_handler>, forces it to
661 use reliable storage (e.g. sets it to the master), executes a coderef and then
662 restores the original state.
668 $schema->resultset('User')->create({name=>$name});
669 my $user_rs = $schema->resultset('User')->find({name=>$name});
673 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
675 Use this when you must be certain of your database state, such as when you just
676 inserted something and need to get a resultset including it, etc.
680 sub execute_reliably {
684 unless( ref $coderef eq 'CODE') {
685 $self->throw_exception('Second argument must be a coderef');
688 ## replace the current read handler for the remainder of the scope
689 local $self->{read_handler} = $self->master;
695 $self->throw_exception("coderef returned an error: $_");
699 =head2 set_reliable_storage
701 Sets the current $schema to be 'reliable', that is all queries, both read and
702 write are sent to the master
706 sub set_reliable_storage {
708 my $schema = $self->schema;
709 my $write_handler = $self->schema->storage->write_handler;
711 $schema->storage->read_handler($write_handler);
714 =head2 set_balanced_storage
716 Sets the current $schema to be use the </balancer> for all reads, while all
717 writes are sent to the master only
721 sub set_balanced_storage {
723 my $schema = $self->schema;
724 my $balanced_handler = $self->schema->storage->balancer;
726 $schema->storage->read_handler($balanced_handler);
731 Check that the master and at least one of the replicants is connected.
738 $self->master->connected &&
739 $self->pool->connected_replicants;
742 =head2 ensure_connected
744 Make sure all the storages are connected.
748 sub ensure_connected {
750 foreach my $source ($self->all_storages) {
751 $source->ensure_connected(@_);
757 Set the limit_dialect for all existing storages
763 foreach my $source ($self->all_storages) {
764 $source->limit_dialect(@_);
766 return $self->master->limit_dialect;
771 Set the quote_char for all existing storages
777 foreach my $source ($self->all_storages) {
778 $source->quote_char(@_);
780 return $self->master->quote_char;
785 Set the name_sep for all existing storages
791 foreach my $source ($self->all_storages) {
792 $source->name_sep(@_);
794 return $self->master->name_sep;
799 Set the schema object for all existing storages
805 foreach my $source ($self->all_storages) {
806 $source->set_schema(@_);
812 set a debug flag across all storages
819 foreach my $source ($self->all_storages) {
823 return $self->master->debug;
834 return $self->master->debugobj(@_);
845 return $self->master->debugfh(@_);
856 return $self->master->debugcb(@_);
861 disconnect everything
867 foreach my $source ($self->all_storages) {
868 $source->disconnect(@_);
874 set cursor class on all storages, or return master's
879 my ($self, $cursor_class) = @_;
882 $_->cursor_class($cursor_class) for $self->all_storages;
884 $self->master->cursor_class;
889 set cursor class on all storages, or return master's, alias for L</cursor_class>
895 my ($self, $cursor_class) = @_;
898 $_->cursor($cursor_class) for $self->all_storages;
900 $self->master->cursor;
905 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
906 master's current setting
914 $_->unsafe(@_) for $self->all_storages;
917 return $self->master->unsafe;
920 =head2 disable_sth_caching
922 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
923 or returns master's current setting
927 sub disable_sth_caching {
931 $_->disable_sth_caching(@_) for $self->all_storages;
934 return $self->master->disable_sth_caching;
937 =head2 lag_behind_master
939 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
944 sub lag_behind_master {
947 return max map $_->lag_behind_master, $self->replicants;
950 =head2 is_replicating
952 returns true if all replicants return true for
953 L<DBIx::Class::Storage::DBI/is_replicating>
960 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
963 =head2 connect_call_datetime_setup
965 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
969 sub connect_call_datetime_setup {
971 $_->connect_call_datetime_setup for $self->all_storages;
976 $_->_populate_dbh for $self->all_storages;
981 $_->_connect for $self->all_storages;
986 $_->_rebless for $self->all_storages;
989 sub _determine_driver {
991 $_->_determine_driver for $self->all_storages;
994 sub _driver_determined {
998 $_->_driver_determined(@_) for $self->all_storages;
1001 return $self->master->_driver_determined;
1007 $_->_init for $self->all_storages;
1010 sub _run_connection_actions {
1013 $_->_run_connection_actions for $self->all_storages;
1016 sub _do_connection_actions {
1020 $_->_do_connection_actions(@_) for $self->all_storages;
1024 sub connect_call_do_sql {
1026 $_->connect_call_do_sql(@_) for $self->all_storages;
1029 sub disconnect_call_do_sql {
1031 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1034 sub _seems_connected {
1037 return min map $_->_seems_connected, $self->all_storages;
1043 return min map $_->_ping, $self->all_storages;
1046 # not using the normalized_version, because we want to preserve
1047 # version numbers much longer than the conventional xxx.yyyzzz
1048 my $numify_ver = sub {
1050 my @numparts = split /\D+/, $ver;
1051 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1053 return sprintf $format, @numparts;
1058 if (not $self->_dbh_details->{info}) {
1059 $self->_dbh_details->{info} = (
1060 reduce { $a->[0] < $b->[0] ? $a : $b }
1061 map [ $numify_ver->($_->{dbms_version}), $_ ],
1062 map $_->_server_info, $self->all_storages
1066 return $self->next::method;
1069 sub _get_server_version {
1072 return $self->_server_info->{dbms_version};
1077 Due to the fact that replicants can lag behind a master, you must take care to
1078 make sure you use one of the methods to force read queries to a master should
1079 you need realtime data integrity. For example, if you insert a row, and then
1080 immediately re-read it from the database (say, by doing $row->discard_changes)
1081 or you insert a row and then immediately build a query that expects that row
1082 to be an item, you should force the master to handle reads. Otherwise, due to
1083 the lag, there is no certainty your data will be in the expected state.
1085 For data integrity, all transactions automatically use the master storage for
1086 all read and write queries. Using a transaction is the preferred and recommended
1087 method to force the master to handle all read queries.
1089 Otherwise, you can force a single query to use the master with the 'force_pool'
1092 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1094 This attribute will safely be ignore by non replicated storages, so you can use
1095 the same code for both types of systems.
1097 Lastly, you can use the L</execute_reliably> method, which works very much like
1100 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1101 and L</set_balanced_storage>, however this operates at a global level and is not
1102 suitable if you have a shared Schema object being used by multiple processes,
1103 such as on a web application server. You can get around this limitation by
1104 using the Schema clone method.
1106 my $new_schema = $schema->clone;
1107 $new_schema->set_reliable_storage;
1109 ## $new_schema will use only the Master storage for all reads/writes while
1110 ## the $schema object will use replicated storage.
1114 John Napiorkowski <john.napiorkowski@takkle.com>
1116 Based on code originated by:
1118 Norbert Csongrádi <bert@cpan.org>
1119 Peter Siklósi <einon@einon.hu>
1123 You may distribute this code under the same terms as Perl itself.
1127 __PACKAGE__->meta->make_immutable;