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/;
21 use namespace::clean -except => 'meta';
25 DBIx::Class::Storage::DBI::Replicated - BETA Replicated database support
29 The Following example shows how to change an existing $schema to a replicated
30 storage type, add some replicated (read-only) databases, and perform reporting
33 You should set the 'storage_type attribute to a replicated type. You should
34 also define your arguments, such as which balancer you want and any arguments
35 that the Pool object should get.
37 my $schema = Schema::Class->clone;
38 $schema->storage_type( ['::DBI::Replicated', {balancer=>'::Random'}] );
39 $schema->connection(...);
41 Next, you need to add in the Replicants. Basically this is an array of
42 arrayrefs, where each arrayref is database connect information. Think of these
43 arguments as what you'd pass to the 'normal' $schema->connect method.
45 $schema->storage->connect_replicants(
46 [$dsn1, $user, $pass, \%opts],
47 [$dsn2, $user, $pass, \%opts],
48 [$dsn3, $user, $pass, \%opts],
51 Now, just use the $schema as you normally would. Automatically all reads will
52 be delegated to the replicants, while writes to the master.
54 $schema->resultset('Source')->search({name=>'etc'});
56 You can force a given query to use a particular storage using the search
57 attribute 'force_pool'. For example:
59 my $RS = $schema->resultset('Source')->search(undef, {force_pool=>'master'});
61 Now $RS will force everything (both reads and writes) to use whatever was setup
62 as the master storage. 'master' is hardcoded to always point to the Master,
63 but you can also use any Replicant name. Please see:
64 L<DBIx::Class::Storage::DBI::Replicated::Pool> and the replicants attribute for more.
66 Also see transactions and L</execute_reliably> for alternative ways to
67 force read traffic to the master. In general, you should wrap your statements
68 in a transaction when you are reading and writing to the same tables at the
69 same time, since your replicants will often lag a bit behind the master.
71 See L<DBIx::Class::Storage::DBI::Replicated::Instructions> for more help and
76 Warning: This class is marked BETA. This has been running a production
77 website using MySQL native replication as its backend and we have some decent
78 test coverage but the code hasn't yet been stressed by a variety of databases.
79 Individual DBs may have quirks we are not aware of. Please use this in first
80 development and pass along your experiences/bug fixes.
82 This class implements replicated data store for DBI. Currently you can define
83 one master and numerous slave database connections. All write-type queries
84 (INSERT, UPDATE, DELETE and even LAST_INSERT_ID) are routed to master
85 database, all read-type queries (SELECTs) go to the slave database.
87 Basically, any method request that L<DBIx::Class::Storage::DBI> would normally
88 handle gets delegated to one of the two attributes: L</read_handler> or to
89 L</write_handler>. Additionally, some methods need to be distributed
90 to all existing storages. This way our storage class is a drop in replacement
91 for L<DBIx::Class::Storage::DBI>.
93 Read traffic is spread across the replicants (slaves) occurring to a user
94 selected algorithm. The default algorithm is random weighted.
98 The consistency between master and replicants is database specific. The Pool
99 gives you a method to validate its replicants, removing and replacing them
100 when they fail/pass predefined criteria. Please make careful use of the ways
101 to force a query to run against Master when needed.
105 Replicated Storage has additional requirements not currently part of
106 L<DBIx::Class>. See L<DBIx::Class::Optional::Dependencies> for more details.
110 This class defines the following attributes.
114 The underlying L<DBIx::Class::Schema> object this storage is attaching
127 Contains the classname which will instantiate the L</pool> object. Defaults
128 to: L<DBIx::Class::Storage::DBI::Replicated::Pool>.
135 default=>'DBIx::Class::Storage::DBI::Replicated::Pool',
137 'create_pool' => 'new',
143 Contains a hashref of initialized information to pass to the Balancer object.
144 See L<DBIx::Class::Storage::DBI::Replicated::Pool> for available arguments.
158 The replication pool requires a balance class to provider the methods for
159 choose how to spread the query load across each replicant in the pool.
163 has 'balancer_type' => (
165 isa=>BalancerClassNamePart,
168 default=> 'DBIx::Class::Storage::DBI::Replicated::Balancer::First',
170 'create_balancer' => 'new',
176 Contains a hashref of initialized information to pass to the Balancer object.
177 See L<DBIx::Class::Storage::DBI::Replicated::Balancer> for available arguments.
181 has 'balancer_args' => (
191 Is a L<DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a
192 container class for one or more replicated databases.
198 isa=>'DBIx::Class::Storage::DBI::Replicated::Pool',
209 Is a L<DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This
210 is a class that takes a pool (L<DBIx::Class::Storage::DBI::Replicated::Pool>)
216 isa=>'DBIx::Class::Storage::DBI::Replicated::Balancer',
218 handles=>[qw/auto_validate_every/],
223 The master defines the canonical state for a pool of connected databases. All
224 the replicants are expected to match this databases state. Thus, in a classic
225 Master / Slaves distributed system, all the slaves are expected to replicate
226 the Master's state as quick as possible. This is the only database in the
227 pool of databases that is allowed to handle write traffic.
237 =head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE
239 The following methods are delegated all the methods required for the
240 L<DBIx::Class::Storage::DBI> interface.
244 my $method_dispatch = {
256 deployment_statements
259 build_datetime_parser
275 with_deferred_fk_checks
284 relname_to_table_alias
286 _default_dbi_connect_attributes
288 _dbic_connect_attributes
294 bind_attribute_by_data_type
300 _per_row_update_delete
301 _dbh_execute_inserts_with_no_binds
302 _select_args_to_query
305 _multipk_update_delete
306 _normalize_connect_info
316 _adjust_select_args_for_complex_prefetch
317 _resolve_ident_sources
320 _strip_cond_qualifiers
321 _strip_cond_qualifiers_from_array
322 _resolve_aliastypes_from_select_args
333 _dbh_columns_info_for
336 unimplemented => [qw/
337 _arm_global_destructor
340 source_bind_attributes
342 get_use_dbms_capability
343 set_use_dbms_capability
354 _group_over_selection
355 _extract_order_criteria
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);
490 @res = $self->$next($info, @extra);
492 $res[0] = $self->$next($info, @extra);
495 # Make sure master is blessed into the correct class and apply role to it.
496 my $master = $self->master;
497 $master->_determine_driver;
498 Moose::Meta::Class->initialize(ref $master);
500 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
502 # link pool back to master
503 $self->pool->master($master);
505 wantarray ? @res : $res[0];
510 This class defines the following methods.
514 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
515 first argument. So we need to massage the arguments a bit so that all the
516 bits get put into the correct places.
521 my ($class, $schema, $storage_type_args, @args) = @_;
532 Lazy builder for the L</master> attribute.
538 my $master = DBIx::Class::Storage::DBI->new($self->schema);
544 Lazy builder for the L</pool> attribute.
550 $self->create_pool(%{$self->pool_args});
553 =head2 _build_balancer
555 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
556 the balancer knows which pool it's balancing.
560 sub _build_balancer {
562 $self->create_balancer(
564 master=>$self->master,
565 %{$self->balancer_args},
569 =head2 _build_write_handler
571 Lazy builder for the L</write_handler> attribute. The default is to set this to
576 sub _build_write_handler {
577 return shift->master;
580 =head2 _build_read_handler
582 Lazy builder for the L</read_handler> attribute. The default is to set this to
587 sub _build_read_handler {
588 return shift->balancer;
591 =head2 around: connect_replicants
593 All calls to connect_replicants needs to have an existing $schema tacked onto
594 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
595 options merged with the master, with replicant opts having higher priority.
599 around connect_replicants => sub {
600 my ($next, $self, @args) = @_;
603 $r = [ $r ] unless reftype $r eq 'ARRAY';
605 $self->throw_exception('coderef replicant connect_info not supported')
606 if ref $r->[0] && reftype $r->[0] eq 'CODE';
608 # any connect_info options?
610 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
613 $r->[$i] = {} unless $r->[$i];
615 # merge if two hashes
616 my @hashes = @$r[$i .. $#{$r}];
618 $self->throw_exception('invalid connect_info options')
619 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
621 $self->throw_exception('too many hashrefs in connect_info')
624 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
625 my %opts = %{ $merge->merge(reverse @hashes) };
628 splice @$r, $i+1, ($#{$r} - $i), ();
630 # make sure master/replicants opts don't clash
631 my %master_opts = %{ $self->_master_connect_info_opts };
632 if (exists $opts{dbh_maker}) {
633 delete @master_opts{qw/dsn user password/};
635 delete $master_opts{dbh_maker};
638 %opts = %{ $merge->merge(\%opts, \%master_opts) };
644 $self->$next($self->schema, @args);
649 Returns an array of of all the connected storage backends. The first element
650 in the returned array is the master, and the remainings are each of the
657 return grep {defined $_ && blessed $_} (
659 values %{ $self->replicants },
663 =head2 execute_reliably ($coderef, ?@args)
665 Given a coderef, saves the current state of the L</read_handler>, forces it to
666 use reliable storage (e.g. sets it to the master), executes a coderef and then
667 restores the original state.
673 $schema->resultset('User')->create({name=>$name});
674 my $user_rs = $schema->resultset('User')->find({name=>$name});
678 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
680 Use this when you must be certain of your database state, such as when you just
681 inserted something and need to get a resultset including it, etc.
685 sub execute_reliably {
686 my ($self, $coderef, @args) = @_;
688 unless( ref $coderef eq 'CODE') {
689 $self->throw_exception('Second argument must be a coderef');
692 ##Get copy of master storage
693 my $master = $self->master;
695 ##Get whatever the current read hander is
696 my $current = $self->read_handler;
698 ##Set the read handler to master
699 $self->read_handler($master);
701 ## do whatever the caller needs
703 my $want_array = wantarray;
707 @result = $coderef->(@args);
708 } elsif(defined $want_array) {
709 ($result[0]) = ($coderef->(@args));
714 $self->throw_exception("coderef returned an error: $_");
716 ##Reset to the original state
717 $self->read_handler($current);
720 return wantarray ? @result : $result[0];
723 =head2 set_reliable_storage
725 Sets the current $schema to be 'reliable', that is all queries, both read and
726 write are sent to the master
730 sub set_reliable_storage {
732 my $schema = $self->schema;
733 my $write_handler = $self->schema->storage->write_handler;
735 $schema->storage->read_handler($write_handler);
738 =head2 set_balanced_storage
740 Sets the current $schema to be use the </balancer> for all reads, while all
741 writes are sent to the master only
745 sub set_balanced_storage {
747 my $schema = $self->schema;
748 my $balanced_handler = $self->schema->storage->balancer;
750 $schema->storage->read_handler($balanced_handler);
755 Check that the master and at least one of the replicants is connected.
762 $self->master->connected &&
763 $self->pool->connected_replicants;
766 =head2 ensure_connected
768 Make sure all the storages are connected.
772 sub ensure_connected {
774 foreach my $source ($self->all_storages) {
775 $source->ensure_connected(@_);
781 Set the limit_dialect for all existing storages
787 foreach my $source ($self->all_storages) {
788 $source->limit_dialect(@_);
790 return $self->master->limit_dialect;
795 Set the quote_char for all existing storages
801 foreach my $source ($self->all_storages) {
802 $source->quote_char(@_);
804 return $self->master->quote_char;
809 Set the name_sep for all existing storages
815 foreach my $source ($self->all_storages) {
816 $source->name_sep(@_);
818 return $self->master->name_sep;
823 Set the schema object for all existing storages
829 foreach my $source ($self->all_storages) {
830 $source->set_schema(@_);
836 set a debug flag across all storages
843 foreach my $source ($self->all_storages) {
847 return $self->master->debug;
858 return $self->master->debugobj(@_);
869 return $self->master->debugfh(@_);
880 return $self->master->debugcb(@_);
885 disconnect everything
891 foreach my $source ($self->all_storages) {
892 $source->disconnect(@_);
898 set cursor class on all storages, or return master's
903 my ($self, $cursor_class) = @_;
906 $_->cursor_class($cursor_class) for $self->all_storages;
908 $self->master->cursor_class;
913 set cursor class on all storages, or return master's, alias for L</cursor_class>
919 my ($self, $cursor_class) = @_;
922 $_->cursor($cursor_class) for $self->all_storages;
924 $self->master->cursor;
929 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
930 master's current setting
938 $_->unsafe(@_) for $self->all_storages;
941 return $self->master->unsafe;
944 =head2 disable_sth_caching
946 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
947 or returns master's current setting
951 sub disable_sth_caching {
955 $_->disable_sth_caching(@_) for $self->all_storages;
958 return $self->master->disable_sth_caching;
961 =head2 lag_behind_master
963 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
968 sub lag_behind_master {
971 return max map $_->lag_behind_master, $self->replicants;
974 =head2 is_replicating
976 returns true if all replicants return true for
977 L<DBIx::Class::Storage::DBI/is_replicating>
984 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
987 =head2 connect_call_datetime_setup
989 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
993 sub connect_call_datetime_setup {
995 $_->connect_call_datetime_setup for $self->all_storages;
1000 $_->_populate_dbh for $self->all_storages;
1005 $_->_connect for $self->all_storages;
1010 $_->_rebless for $self->all_storages;
1013 sub _determine_driver {
1015 $_->_determine_driver for $self->all_storages;
1018 sub _driver_determined {
1022 $_->_driver_determined(@_) for $self->all_storages;
1025 return $self->master->_driver_determined;
1031 $_->_init for $self->all_storages;
1034 sub _run_connection_actions {
1037 $_->_run_connection_actions for $self->all_storages;
1040 sub _do_connection_actions {
1044 $_->_do_connection_actions(@_) for $self->all_storages;
1048 sub connect_call_do_sql {
1050 $_->connect_call_do_sql(@_) for $self->all_storages;
1053 sub disconnect_call_do_sql {
1055 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1058 sub _seems_connected {
1061 return min map $_->_seems_connected, $self->all_storages;
1067 return min map $_->_ping, $self->all_storages;
1070 # not using the normalized_version, because we want to preserve
1071 # version numbers much longer than the conventional xxx.yyyzzz
1072 my $numify_ver = sub {
1074 my @numparts = split /\D+/, $ver;
1075 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1077 return sprintf $format, @numparts;
1082 if (not $self->_dbh_details->{info}) {
1083 $self->_dbh_details->{info} = (
1084 reduce { $a->[0] < $b->[0] ? $a : $b }
1085 map [ $numify_ver->($_->{dbms_version}), $_ ],
1086 map $_->_server_info, $self->all_storages
1090 return $self->next::method;
1093 sub _get_server_version {
1096 return $self->_server_info->{dbms_version};
1101 Due to the fact that replicants can lag behind a master, you must take care to
1102 make sure you use one of the methods to force read queries to a master should
1103 you need realtime data integrity. For example, if you insert a row, and then
1104 immediately re-read it from the database (say, by doing $row->discard_changes)
1105 or you insert a row and then immediately build a query that expects that row
1106 to be an item, you should force the master to handle reads. Otherwise, due to
1107 the lag, there is no certainty your data will be in the expected state.
1109 For data integrity, all transactions automatically use the master storage for
1110 all read and write queries. Using a transaction is the preferred and recommended
1111 method to force the master to handle all read queries.
1113 Otherwise, you can force a single query to use the master with the 'force_pool'
1116 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1118 This attribute will safely be ignore by non replicated storages, so you can use
1119 the same code for both types of systems.
1121 Lastly, you can use the L</execute_reliably> method, which works very much like
1124 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1125 and L</set_balanced_storage>, however this operates at a global level and is not
1126 suitable if you have a shared Schema object being used by multiple processes,
1127 such as on a web application server. You can get around this limitation by
1128 using the Schema clone method.
1130 my $new_schema = $schema->clone;
1131 $new_schema->set_reliable_storage;
1133 ## $new_schema will use only the Master storage for all reads/writes while
1134 ## the $schema object will use replicated storage.
1138 John Napiorkowski <john.napiorkowski@takkle.com>
1140 Based on code originated by:
1142 Norbert Csongrádi <bert@cpan.org>
1143 Peter Siklósi <einon@einon.hu>
1147 You may distribute this code under the same terms as Perl itself.
1151 __PACKAGE__->meta->make_immutable;