1 package DBIx::Class::Storage::DBI::Replicated;
7 require DBIx::Class::Optional::Dependencies;
8 if ( my $missing = DBIx::Class::Optional::Dependencies->req_missing_for('replicated') ) {
9 die "The following modules are required for Replicated storage support: $missing\n";
14 use DBIx::Class::Storage::DBI;
15 use DBIx::Class::Storage::DBI::Replicated::Pool;
16 use DBIx::Class::Storage::DBI::Replicated::Balancer;
17 use DBIx::Class::Storage::DBI::Replicated::Types qw/BalancerClassNamePart DBICSchema DBICStorageDBI/;
18 use MooseX::Types::Moose qw/ClassName HashRef Object/;
19 use Scalar::Util 'reftype';
21 use List::Util qw/min max reduce/;
22 use Context::Preserve 'preserve_context';
25 use namespace::clean -except => 'meta';
29 DBIx::Class::Storage::DBI::Replicated - BETA Replicated database support
33 The Following example shows how to change an existing $schema to a replicated
34 storage type, add some replicated (read-only) databases, and perform reporting
37 You should set the 'storage_type attribute to a replicated type. You should
38 also define your arguments, such as which balancer you want and any arguments
39 that the Pool object should get.
41 my $schema = Schema::Class->clone;
42 $schema->storage_type(['::DBI::Replicated', { balancer_type => '::Random' }]);
43 $schema->connection(...);
45 Next, you need to add in the Replicants. Basically this is an array of
46 arrayrefs, where each arrayref is database connect information. Think of these
47 arguments as what you'd pass to the 'normal' $schema->connect method.
49 $schema->storage->connect_replicants(
50 [$dsn1, $user, $pass, \%opts],
51 [$dsn2, $user, $pass, \%opts],
52 [$dsn3, $user, $pass, \%opts],
55 Now, just use the $schema as you normally would. Automatically all reads will
56 be delegated to the replicants, while writes to the master.
58 $schema->resultset('Source')->search({name=>'etc'});
60 You can force a given query to use a particular storage using the search
61 attribute 'force_pool'. For example:
63 my $rs = $schema->resultset('Source')->search(undef, {force_pool=>'master'});
65 Now $rs will force everything (both reads and writes) to use whatever was setup
66 as the master storage. 'master' is hardcoded to always point to the Master,
67 but you can also use any Replicant name. Please see:
68 L<DBIx::Class::Storage::DBI::Replicated::Pool> and the replicants attribute for more.
70 Also see transactions and L</execute_reliably> for alternative ways to
71 force read traffic to the master. In general, you should wrap your statements
72 in a transaction when you are reading and writing to the same tables at the
73 same time, since your replicants will often lag a bit behind the master.
75 If you have a multi-statement read only transaction you can force it to select
76 a random server in the pool by:
78 my $rs = $schema->resultset('Source')->search( undef,
79 { force_pool => $db->storage->read_handler->next_storage }
84 Warning: This class is marked BETA. This has been running a production
85 website using MySQL native replication as its backend and we have some decent
86 test coverage but the code hasn't yet been stressed by a variety of databases.
87 Individual DBs may have quirks we are not aware of. Please use this in first
88 development and pass along your experiences/bug fixes.
90 This class implements replicated data store for DBI. Currently you can define
91 one master and numerous slave database connections. All write-type queries
92 (INSERT, UPDATE, DELETE and even LAST_INSERT_ID) are routed to master
93 database, all read-type queries (SELECTs) go to the slave database.
95 Basically, any method request that L<DBIx::Class::Storage::DBI> would normally
96 handle gets delegated to one of the two attributes: L</read_handler> or to
97 L</write_handler>. Additionally, some methods need to be distributed
98 to all existing storages. This way our storage class is a drop in replacement
99 for L<DBIx::Class::Storage::DBI>.
101 Read traffic is spread across the replicants (slaves) occurring to a user
102 selected algorithm. The default algorithm is random weighted.
106 The consistency between master and replicants is database specific. The Pool
107 gives you a method to validate its replicants, removing and replacing them
108 when they fail/pass predefined criteria. Please make careful use of the ways
109 to force a query to run against Master when needed.
113 Replicated Storage has additional requirements not currently part of
114 L<DBIx::Class>. See L<DBIx::Class::Optional::Dependencies> for more details.
118 This class defines the following attributes.
122 The underlying L<DBIx::Class::Schema> object this storage is attaching
135 Contains the classname which will instantiate the L</pool> object. Defaults
136 to: L<DBIx::Class::Storage::DBI::Replicated::Pool>.
143 default=>'DBIx::Class::Storage::DBI::Replicated::Pool',
145 'create_pool' => 'new',
151 Contains a hashref of initialized information to pass to the Balancer object.
152 See L<DBIx::Class::Storage::DBI::Replicated::Pool> for available arguments.
166 The replication pool requires a balance class to provider the methods for
167 choose how to spread the query load across each replicant in the pool.
171 has 'balancer_type' => (
173 isa=>BalancerClassNamePart,
176 default=> 'DBIx::Class::Storage::DBI::Replicated::Balancer::First',
178 'create_balancer' => 'new',
184 Contains a hashref of initialized information to pass to the Balancer object.
185 See L<DBIx::Class::Storage::DBI::Replicated::Balancer> for available arguments.
189 has 'balancer_args' => (
199 Is a L<DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a
200 container class for one or more replicated databases.
206 isa=>'DBIx::Class::Storage::DBI::Replicated::Pool',
217 Is a L<DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This
218 is a class that takes a pool (L<DBIx::Class::Storage::DBI::Replicated::Pool>)
224 isa=>'DBIx::Class::Storage::DBI::Replicated::Balancer',
226 handles=>[qw/auto_validate_every/],
231 The master defines the canonical state for a pool of connected databases. All
232 the replicants are expected to match this databases state. Thus, in a classic
233 Master / Slaves distributed system, all the slaves are expected to replicate
234 the Master's state as quick as possible. This is the only database in the
235 pool of databases that is allowed to handle write traffic.
245 =head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE
247 The following methods are delegated all the methods required for the
248 L<DBIx::Class::Storage::DBI> interface.
252 my $method_dispatch = {
264 deployment_statements
267 build_datetime_parser
282 with_deferred_fk_checks
290 relname_to_table_alias
292 _default_dbi_connect_attributes
294 _dbic_connect_attributes
300 bind_attribute_by_data_type
304 _dbh_execute_for_fetch
306 _dbh_execute_inserts_with_no_binds
307 _select_args_to_query
310 _normalize_connect_info
325 /, Class::MOP::Class->initialize('DBIx::Class::Storage::DBIHacks')->get_method_list ],
330 _dbh_columns_info_for
333 unimplemented => [qw/
334 _arm_global_destructor
338 get_use_dbms_capability
339 set_use_dbms_capability
346 _determine_connector_driver
347 _extract_driver_from_connect_info
349 _warn_undetermined_driver
356 _perform_autoinc_retrieval
357 _autoinc_supplied_for_op
370 # the capability framework
371 # not sure if CMOP->initialize does evil things to DBIC::S::DBI, fix if a problem
373 { $_ =~ /^ _ (?: use | supports | determine_supports ) _ /x and $_ ne '_use_multicolumn_in' }
374 ( Class::MOP::Class->initialize('DBIx::Class::Storage::DBI')->get_all_method_names )
378 if (DBIx::Class::_ENV_::DBICTEST) {
381 for my $type (keys %$method_dispatch) {
382 for (@{$method_dispatch->{$type}}) {
383 push @{$seen->{$_}}, $type;
387 if (my @dupes = grep { @{$seen->{$_}} > 1 } keys %$seen) {
389 'The following methods show up multiple times in ::Storage::DBI::Replicated handlers:',
390 (map { "$_: " . (join ', ', @{$seen->{$_}}) } sort @dupes),
395 if (my @cant = grep { ! DBIx::Class::Storage::DBI->can($_) } keys %$seen) {
397 '::Storage::DBI::Replicated specifies handling of the following *NON EXISTING* ::Storage::DBI methods:',
404 for my $method (@{$method_dispatch->{unimplemented}}) {
405 __PACKAGE__->meta->add_method($method, sub {
407 $self->throw_exception("$method() must not be called on ".(blessed $self).' objects');
413 Defines an object that implements the read side of L<DBIx::Class::Storage::DBI>.
417 has 'read_handler' => (
421 handles=>$method_dispatch->{reader},
426 Defines an object that implements the write side of L<DBIx::Class::Storage::DBI>,
427 as well as methods that don't write or read that can be called on only one
428 storage, methods that return a C<$dbh>, and any methods that don't make sense to
433 has 'write_handler' => (
437 handles=>$method_dispatch->{writer},
442 has _master_connect_info_opts =>
443 (is => 'rw', isa => HashRef, default => sub { {} });
445 =head2 around: connect_info
447 Preserves master's C<connect_info> options (for merging with replicants.)
448 Also sets any Replicated-related options from connect_info, such as
449 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
453 around connect_info => sub {
454 my ($next, $self, $info, @extra) = @_;
456 $self->throw_exception(
457 'connect_info can not be retrieved from a replicated storage - '
458 . 'accessor must be called on a specific pool instance'
459 ) unless defined $info;
461 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
464 for my $arg (@$info) {
465 next unless (reftype($arg)||'') eq 'HASH';
466 %opts = %{ $merge->merge($arg, \%opts) };
470 if (@opts{qw/pool_type pool_args/}) {
471 $self->pool_type(delete $opts{pool_type})
475 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
478 ## Since we possibly changed the pool_args, we need to clear the current
479 ## pool object so that next time it is used it will be rebuilt.
483 if (@opts{qw/balancer_type balancer_args/}) {
484 $self->balancer_type(delete $opts{balancer_type})
485 if $opts{balancer_type};
487 $self->balancer_args(
488 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
491 $self->balancer($self->_build_balancer)
495 $self->_master_connect_info_opts(\%opts);
497 return preserve_context {
498 $self->$next($info, @extra);
500 # Make sure master is blessed into the correct class and apply role to it.
501 my $master = $self->master;
502 $master->_determine_driver;
503 Moose::Meta::Class->initialize(ref $master);
505 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
507 # link pool back to master
508 $self->pool->master($master);
514 This class defines the following methods.
518 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
519 first argument. So we need to massage the arguments a bit so that all the
520 bits get put into the correct places.
525 my ($class, $schema, $storage_type_args, @args) = @_;
536 Lazy builder for the L</master> attribute.
542 my $master = DBIx::Class::Storage::DBI->new($self->schema);
548 Lazy builder for the L</pool> attribute.
554 $self->create_pool(%{$self->pool_args});
557 =head2 _build_balancer
559 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
560 the balancer knows which pool it's balancing.
564 sub _build_balancer {
566 $self->create_balancer(
568 master=>$self->master,
569 %{$self->balancer_args},
573 =head2 _build_write_handler
575 Lazy builder for the L</write_handler> attribute. The default is to set this to
580 sub _build_write_handler {
581 return shift->master;
584 =head2 _build_read_handler
586 Lazy builder for the L</read_handler> attribute. The default is to set this to
591 sub _build_read_handler {
592 return shift->balancer;
595 =head2 around: connect_replicants
597 All calls to connect_replicants needs to have an existing $schema tacked onto
598 top of the args, since L<DBIx::Class::Storage::DBI> needs it, and any
599 L<connect_info|DBIx::Class::Storage::DBI/connect_info>
600 options merged with the master, with replicant opts having higher priority.
604 around connect_replicants => sub {
605 my ($next, $self, @args) = @_;
608 $r = [ $r ] unless reftype $r eq 'ARRAY';
610 $self->throw_exception('coderef replicant connect_info not supported')
611 if ref $r->[0] && reftype $r->[0] eq 'CODE';
613 # any connect_info options?
615 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
618 $r->[$i] = {} unless $r->[$i];
620 # merge if two hashes
621 my @hashes = @$r[$i .. $#{$r}];
623 $self->throw_exception('invalid connect_info options')
624 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
626 $self->throw_exception('too many hashrefs in connect_info')
629 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
630 my %opts = %{ $merge->merge(reverse @hashes) };
633 splice @$r, $i+1, ($#{$r} - $i), ();
635 # make sure master/replicants opts don't clash
636 my %master_opts = %{ $self->_master_connect_info_opts };
637 if (exists $opts{dbh_maker}) {
638 delete @master_opts{qw/dsn user password/};
640 delete $master_opts{dbh_maker};
643 %opts = %{ $merge->merge(\%opts, \%master_opts) };
649 $self->$next($self->schema, @args);
654 Returns an array of all the connected storage backends. The first element
655 in the returned array is the master, and the rest are each of the
662 return grep {defined $_ && blessed $_} (
664 values %{ $self->replicants },
668 =head2 execute_reliably ($coderef, ?@args)
670 Given a coderef, saves the current state of the L</read_handler>, forces it to
671 use reliable storage (e.g. sets it to the master), executes a coderef and then
672 restores the original state.
678 $schema->resultset('User')->create({name=>$name});
679 my $user_rs = $schema->resultset('User')->find({name=>$name});
683 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
685 Use this when you must be certain of your database state, such as when you just
686 inserted something and need to get a resultset including it, etc.
690 sub execute_reliably {
694 unless( ref $coderef eq 'CODE') {
695 $self->throw_exception('Second argument must be a coderef');
698 ## replace the current read handler for the remainder of the scope
699 local $self->{read_handler} = $self->master;
705 $self->throw_exception("coderef returned an error: $_");
709 =head2 set_reliable_storage
711 Sets the current $schema to be 'reliable', that is all queries, both read and
712 write are sent to the master
716 sub set_reliable_storage {
718 my $schema = $self->schema;
719 my $write_handler = $self->schema->storage->write_handler;
721 $schema->storage->read_handler($write_handler);
724 =head2 set_balanced_storage
726 Sets the current $schema to be use the </balancer> for all reads, while all
727 writes are sent to the master only
731 sub set_balanced_storage {
733 my $schema = $self->schema;
734 my $balanced_handler = $self->schema->storage->balancer;
736 $schema->storage->read_handler($balanced_handler);
741 Check that the master and at least one of the replicants is connected.
748 $self->master->connected &&
749 $self->pool->connected_replicants;
752 =head2 ensure_connected
754 Make sure all the storages are connected.
758 sub ensure_connected {
760 foreach my $source ($self->all_storages) {
761 $source->ensure_connected(@_);
767 Set the limit_dialect for all existing storages
773 foreach my $source ($self->all_storages) {
774 $source->limit_dialect(@_);
776 return $self->master->limit_dialect;
781 Set the quote_char for all existing storages
787 foreach my $source ($self->all_storages) {
788 $source->quote_char(@_);
790 return $self->master->quote_char;
795 Set the name_sep for all existing storages
801 foreach my $source ($self->all_storages) {
802 $source->name_sep(@_);
804 return $self->master->name_sep;
809 Set the schema object for all existing storages
815 foreach my $source ($self->all_storages) {
816 $source->set_schema(@_);
822 set a debug flag across all storages
829 foreach my $source ($self->all_storages) {
833 return $self->master->debug;
844 return $self->master->debugobj(@_);
855 return $self->master->debugfh(@_);
866 return $self->master->debugcb(@_);
871 disconnect everything
877 foreach my $source ($self->all_storages) {
878 $source->disconnect(@_);
884 set cursor class on all storages, or return master's
889 my ($self, $cursor_class) = @_;
892 $_->cursor_class($cursor_class) for $self->all_storages;
894 $self->master->cursor_class;
899 set cursor class on all storages, or return master's, alias for L</cursor_class>
905 my ($self, $cursor_class) = @_;
908 $_->cursor($cursor_class) for $self->all_storages;
910 $self->master->cursor;
915 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
916 master's current setting
924 $_->unsafe(@_) for $self->all_storages;
927 return $self->master->unsafe;
930 =head2 disable_sth_caching
932 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
933 or returns master's current setting
937 sub disable_sth_caching {
941 $_->disable_sth_caching(@_) for $self->all_storages;
944 return $self->master->disable_sth_caching;
947 =head2 lag_behind_master
949 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
954 sub lag_behind_master {
957 return max map $_->lag_behind_master, $self->replicants;
960 =head2 is_replicating
962 returns true if all replicants return true for
963 L<DBIx::Class::Storage::DBI/is_replicating>
970 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
973 =head2 connect_call_datetime_setup
975 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
979 sub connect_call_datetime_setup {
981 $_->connect_call_datetime_setup for $self->all_storages;
986 $_->_populate_dbh for $self->all_storages;
991 $_->_connect for $self->all_storages;
996 $_->_rebless for $self->all_storages;
999 sub _determine_driver {
1001 $_->_determine_driver for $self->all_storages;
1004 sub _driver_determined {
1008 $_->_driver_determined(@_) for $self->all_storages;
1011 return $self->master->_driver_determined;
1017 $_->_init for $self->all_storages;
1020 sub _run_connection_actions {
1023 $_->_run_connection_actions for $self->all_storages;
1026 sub _do_connection_actions {
1030 $_->_do_connection_actions(@_) for $self->all_storages;
1034 sub connect_call_do_sql {
1036 $_->connect_call_do_sql(@_) for $self->all_storages;
1039 sub disconnect_call_do_sql {
1041 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1044 sub _seems_connected {
1047 return min map $_->_seems_connected, $self->all_storages;
1053 return min map $_->_ping, $self->all_storages;
1056 # not using the normalized_version, because we want to preserve
1057 # version numbers much longer than the conventional xxx.yyyzzz
1058 my $numify_ver = sub {
1060 my @numparts = split /\D+/, $ver;
1061 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1063 return sprintf $format, @numparts;
1068 if (not $self->_dbh_details->{info}) {
1069 $self->_dbh_details->{info} = (
1070 reduce { $a->[0] < $b->[0] ? $a : $b }
1071 map [ $numify_ver->($_->{dbms_version}), $_ ],
1072 map $_->_server_info, $self->all_storages
1076 return $self->next::method;
1079 sub _get_server_version {
1082 return $self->_server_info->{dbms_version};
1087 Due to the fact that replicants can lag behind a master, you must take care to
1088 make sure you use one of the methods to force read queries to a master should
1089 you need realtime data integrity. For example, if you insert a row, and then
1090 immediately re-read it from the database (say, by doing
1091 L<< $result->discard_changes|DBIx::Class::Row/discard_changes >>)
1092 or you insert a row and then immediately build a query that expects that row
1093 to be an item, you should force the master to handle reads. Otherwise, due to
1094 the lag, there is no certainty your data will be in the expected state.
1096 For data integrity, all transactions automatically use the master storage for
1097 all read and write queries. Using a transaction is the preferred and recommended
1098 method to force the master to handle all read queries.
1100 Otherwise, you can force a single query to use the master with the 'force_pool'
1103 my $result = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1105 This attribute will safely be ignored by non replicated storages, so you can use
1106 the same code for both types of systems.
1108 Lastly, you can use the L</execute_reliably> method, which works very much like
1111 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1112 and L</set_balanced_storage>, however this operates at a global level and is not
1113 suitable if you have a shared Schema object being used by multiple processes,
1114 such as on a web application server. You can get around this limitation by
1115 using the Schema clone method.
1117 my $new_schema = $schema->clone;
1118 $new_schema->set_reliable_storage;
1120 ## $new_schema will use only the Master storage for all reads/writes while
1121 ## the $schema object will use replicated storage.
1123 =head1 FURTHER QUESTIONS?
1125 Check the list of L<additional DBIC resources|DBIx::Class/GETTING HELP/SUPPORT>.
1127 =head1 COPYRIGHT AND LICENSE
1129 This module is free software L<copyright|DBIx::Class/COPYRIGHT AND LICENSE>
1130 by the L<DBIx::Class (DBIC) authors|DBIx::Class/AUTHORS>. You can
1131 redistribute it and/or modify it under the same terms as the
1132 L<DBIx::Class library|DBIx::Class/COPYRIGHT AND LICENSE>.
1136 __PACKAGE__->meta->make_immutable;