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
337 get_use_dbms_capability
338 set_use_dbms_capability
345 _determine_connector_driver
346 _extract_driver_from_connect_info
348 _warn_undetermined_driver
355 _perform_autoinc_retrieval
356 _autoinc_supplied_for_op
369 # the capability framework
370 # not sure if CMOP->initialize does evil things to DBIC::S::DBI, fix if a problem
372 { $_ =~ /^ _ (?: use | supports | determine_supports ) _ /x and $_ ne '_use_multicolumn_in' }
373 ( Class::MOP::Class->initialize('DBIx::Class::Storage::DBI')->get_all_method_names )
377 if (DBIx::Class::_ENV_::DBICTEST) {
380 for my $type (keys %$method_dispatch) {
381 for (@{$method_dispatch->{$type}}) {
382 push @{$seen->{$_}}, $type;
386 if (my @dupes = grep { @{$seen->{$_}} > 1 } keys %$seen) {
388 'The following methods show up multiple times in ::Storage::DBI::Replicated handlers:',
389 (map { "$_: " . (join ', ', @{$seen->{$_}}) } sort @dupes),
394 if (my @cant = grep { ! DBIx::Class::Storage::DBI->can($_) } keys %$seen) {
396 '::Storage::DBI::Replicated specifies handling of the following *NON EXISTING* ::Storage::DBI methods:',
403 for my $method (@{$method_dispatch->{unimplemented}}) {
404 __PACKAGE__->meta->add_method($method, sub {
406 $self->throw_exception("$method() must not be called on ".(blessed $self).' objects');
412 Defines an object that implements the read side of L<DBIx::Class::Storage::DBI>.
416 has 'read_handler' => (
420 handles=>$method_dispatch->{reader},
425 Defines an object that implements the write side of L<DBIx::Class::Storage::DBI>,
426 as well as methods that don't write or read that can be called on only one
427 storage, methods that return a C<$dbh>, and any methods that don't make sense to
432 has 'write_handler' => (
436 handles=>$method_dispatch->{writer},
441 has _master_connect_info_opts =>
442 (is => 'rw', isa => HashRef, default => sub { {} });
444 =head2 around: connect_info
446 Preserves master's C<connect_info> options (for merging with replicants.)
447 Also sets any Replicated-related options from connect_info, such as
448 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
452 around connect_info => sub {
453 my ($next, $self, $info, @extra) = @_;
455 $self->throw_exception(
456 'connect_info can not be retrieved from a replicated storage - '
457 . 'accessor must be called on a specific pool instance'
458 ) unless defined $info;
460 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
463 for my $arg (@$info) {
464 next unless (reftype($arg)||'') eq 'HASH';
465 %opts = %{ $merge->merge($arg, \%opts) };
469 if (@opts{qw/pool_type pool_args/}) {
470 $self->pool_type(delete $opts{pool_type})
474 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
477 ## Since we possibly changed the pool_args, we need to clear the current
478 ## pool object so that next time it is used it will be rebuilt.
482 if (@opts{qw/balancer_type balancer_args/}) {
483 $self->balancer_type(delete $opts{balancer_type})
484 if $opts{balancer_type};
486 $self->balancer_args(
487 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
490 $self->balancer($self->_build_balancer)
494 $self->_master_connect_info_opts(\%opts);
496 return preserve_context {
497 $self->$next($info, @extra);
499 # Make sure master is blessed into the correct class and apply role to it.
500 my $master = $self->master;
501 $master->_determine_driver;
502 Moose::Meta::Class->initialize(ref $master);
504 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
506 # link pool back to master
507 $self->pool->master($master);
513 This class defines the following methods.
517 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
518 first argument. So we need to massage the arguments a bit so that all the
519 bits get put into the correct places.
524 my ($class, $schema, $storage_type_args, @args) = @_;
535 Lazy builder for the L</master> attribute.
541 my $master = DBIx::Class::Storage::DBI->new($self->schema);
547 Lazy builder for the L</pool> attribute.
553 $self->create_pool(%{$self->pool_args});
556 =head2 _build_balancer
558 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
559 the balancer knows which pool it's balancing.
563 sub _build_balancer {
565 $self->create_balancer(
567 master=>$self->master,
568 %{$self->balancer_args},
572 =head2 _build_write_handler
574 Lazy builder for the L</write_handler> attribute. The default is to set this to
579 sub _build_write_handler {
580 return shift->master;
583 =head2 _build_read_handler
585 Lazy builder for the L</read_handler> attribute. The default is to set this to
590 sub _build_read_handler {
591 return shift->balancer;
594 =head2 around: connect_replicants
596 All calls to connect_replicants needs to have an existing $schema tacked onto
597 top of the args, since L<DBIx::Class::Storage::DBI> needs it, and any
598 L<connect_info|DBIx::Class::Storage::DBI/connect_info>
599 options merged with the master, with replicant opts having higher priority.
603 around connect_replicants => sub {
604 my ($next, $self, @args) = @_;
607 $r = [ $r ] unless reftype $r eq 'ARRAY';
609 $self->throw_exception('coderef replicant connect_info not supported')
610 if ref $r->[0] && reftype $r->[0] eq 'CODE';
612 # any connect_info options?
614 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
617 $r->[$i] = {} unless $r->[$i];
619 # merge if two hashes
620 my @hashes = @$r[$i .. $#{$r}];
622 $self->throw_exception('invalid connect_info options')
623 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
625 $self->throw_exception('too many hashrefs in connect_info')
628 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
629 my %opts = %{ $merge->merge(reverse @hashes) };
632 splice @$r, $i+1, ($#{$r} - $i), ();
634 # make sure master/replicants opts don't clash
635 my %master_opts = %{ $self->_master_connect_info_opts };
636 if (exists $opts{dbh_maker}) {
637 delete @master_opts{qw/dsn user password/};
639 delete $master_opts{dbh_maker};
642 %opts = %{ $merge->merge(\%opts, \%master_opts) };
648 $self->$next($self->schema, @args);
653 Returns an array of all the connected storage backends. The first element
654 in the returned array is the master, and the rest are each of the
661 return grep {defined $_ && blessed $_} (
663 values %{ $self->replicants },
667 =head2 execute_reliably ($coderef, ?@args)
669 Given a coderef, saves the current state of the L</read_handler>, forces it to
670 use reliable storage (e.g. sets it to the master), executes a coderef and then
671 restores the original state.
677 $schema->resultset('User')->create({name=>$name});
678 my $user_rs = $schema->resultset('User')->find({name=>$name});
682 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
684 Use this when you must be certain of your database state, such as when you just
685 inserted something and need to get a resultset including it, etc.
689 sub execute_reliably {
693 unless( ref $coderef eq 'CODE') {
694 $self->throw_exception('Second argument must be a coderef');
697 ## replace the current read handler for the remainder of the scope
698 local $self->{read_handler} = $self->master;
704 $self->throw_exception("coderef returned an error: $_");
708 =head2 set_reliable_storage
710 Sets the current $schema to be 'reliable', that is all queries, both read and
711 write are sent to the master
715 sub set_reliable_storage {
717 my $schema = $self->schema;
718 my $write_handler = $self->schema->storage->write_handler;
720 $schema->storage->read_handler($write_handler);
723 =head2 set_balanced_storage
725 Sets the current $schema to be use the </balancer> for all reads, while all
726 writes are sent to the master only
730 sub set_balanced_storage {
732 my $schema = $self->schema;
733 my $balanced_handler = $self->schema->storage->balancer;
735 $schema->storage->read_handler($balanced_handler);
740 Check that the master and at least one of the replicants is connected.
747 $self->master->connected &&
748 $self->pool->connected_replicants;
751 =head2 ensure_connected
753 Make sure all the storages are connected.
757 sub ensure_connected {
759 foreach my $source ($self->all_storages) {
760 $source->ensure_connected(@_);
766 Set the limit_dialect for all existing storages
772 foreach my $source ($self->all_storages) {
773 $source->limit_dialect(@_);
775 return $self->master->limit_dialect;
780 Set the quote_char for all existing storages
786 foreach my $source ($self->all_storages) {
787 $source->quote_char(@_);
789 return $self->master->quote_char;
794 Set the name_sep for all existing storages
800 foreach my $source ($self->all_storages) {
801 $source->name_sep(@_);
803 return $self->master->name_sep;
808 Set the schema object for all existing storages
814 foreach my $source ($self->all_storages) {
815 $source->set_schema(@_);
821 set a debug flag across all storages
828 foreach my $source ($self->all_storages) {
832 return $self->master->debug;
843 return $self->master->debugobj(@_);
854 return $self->master->debugfh(@_);
865 return $self->master->debugcb(@_);
870 disconnect everything
876 foreach my $source ($self->all_storages) {
877 $source->disconnect(@_);
883 set cursor class on all storages, or return master's
888 my ($self, $cursor_class) = @_;
891 $_->cursor_class($cursor_class) for $self->all_storages;
893 $self->master->cursor_class;
898 set cursor class on all storages, or return master's, alias for L</cursor_class>
904 my ($self, $cursor_class) = @_;
907 $_->cursor($cursor_class) for $self->all_storages;
909 $self->master->cursor;
914 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
915 master's current setting
923 $_->unsafe(@_) for $self->all_storages;
926 return $self->master->unsafe;
929 =head2 disable_sth_caching
931 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
932 or returns master's current setting
936 sub disable_sth_caching {
940 $_->disable_sth_caching(@_) for $self->all_storages;
943 return $self->master->disable_sth_caching;
946 =head2 lag_behind_master
948 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
953 sub lag_behind_master {
956 return max map $_->lag_behind_master, $self->replicants;
959 =head2 is_replicating
961 returns true if all replicants return true for
962 L<DBIx::Class::Storage::DBI/is_replicating>
969 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
972 =head2 connect_call_datetime_setup
974 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
978 sub connect_call_datetime_setup {
980 $_->connect_call_datetime_setup for $self->all_storages;
985 $_->_populate_dbh for $self->all_storages;
990 $_->_connect for $self->all_storages;
995 $_->_rebless for $self->all_storages;
998 sub _determine_driver {
1000 $_->_determine_driver for $self->all_storages;
1003 sub _driver_determined {
1007 $_->_driver_determined(@_) for $self->all_storages;
1010 return $self->master->_driver_determined;
1016 $_->_init for $self->all_storages;
1019 sub _run_connection_actions {
1022 $_->_run_connection_actions for $self->all_storages;
1025 sub _do_connection_actions {
1029 $_->_do_connection_actions(@_) for $self->all_storages;
1033 sub connect_call_do_sql {
1035 $_->connect_call_do_sql(@_) for $self->all_storages;
1038 sub disconnect_call_do_sql {
1040 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1043 sub _seems_connected {
1046 return min map $_->_seems_connected, $self->all_storages;
1052 return min map $_->_ping, $self->all_storages;
1055 # not using the normalized_version, because we want to preserve
1056 # version numbers much longer than the conventional xxx.yyyzzz
1057 my $numify_ver = sub {
1059 my @numparts = split /\D+/, $ver;
1060 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1062 return sprintf $format, @numparts;
1067 if (not $self->_dbh_details->{info}) {
1068 $self->_dbh_details->{info} = (
1069 reduce { $a->[0] < $b->[0] ? $a : $b }
1070 map [ $numify_ver->($_->{dbms_version}), $_ ],
1071 map $_->_server_info, $self->all_storages
1075 return $self->next::method;
1078 sub _get_server_version {
1081 return $self->_server_info->{dbms_version};
1086 Due to the fact that replicants can lag behind a master, you must take care to
1087 make sure you use one of the methods to force read queries to a master should
1088 you need realtime data integrity. For example, if you insert a row, and then
1089 immediately re-read it from the database (say, by doing
1090 L<< $result->discard_changes|DBIx::Class::Row/discard_changes >>)
1091 or you insert a row and then immediately build a query that expects that row
1092 to be an item, you should force the master to handle reads. Otherwise, due to
1093 the lag, there is no certainty your data will be in the expected state.
1095 For data integrity, all transactions automatically use the master storage for
1096 all read and write queries. Using a transaction is the preferred and recommended
1097 method to force the master to handle all read queries.
1099 Otherwise, you can force a single query to use the master with the 'force_pool'
1102 my $result = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1104 This attribute will safely be ignored by non replicated storages, so you can use
1105 the same code for both types of systems.
1107 Lastly, you can use the L</execute_reliably> method, which works very much like
1110 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1111 and L</set_balanced_storage>, however this operates at a global level and is not
1112 suitable if you have a shared Schema object being used by multiple processes,
1113 such as on a web application server. You can get around this limitation by
1114 using the Schema clone method.
1116 my $new_schema = $schema->clone;
1117 $new_schema->set_reliable_storage;
1119 ## $new_schema will use only the Master storage for all reads/writes while
1120 ## the $schema object will use replicated storage.
1122 =head1 FURTHER QUESTIONS?
1124 Check the list of L<additional DBIC resources|DBIx::Class/GETTING HELP/SUPPORT>.
1126 =head1 COPYRIGHT AND LICENSE
1128 This module is free software L<copyright|DBIx::Class/COPYRIGHT AND LICENSE>
1129 by the L<DBIx::Class (DBIC) authors|DBIx::Class/AUTHORS>. You can
1130 redistribute it and/or modify it under the same terms as the
1131 L<DBIx::Class library|DBIx::Class/COPYRIGHT AND LICENSE>.
1135 __PACKAGE__->meta->make_immutable;