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
272 with_deferred_fk_checks
281 relname_to_table_alias
284 _default_dbi_connect_attributes
286 _dbic_connect_attributes
289 bind_attribute_by_data_type
296 _per_row_update_delete
298 _dbh_execute_inserts_with_no_binds
299 _select_args_to_query
301 _multipk_update_delete
302 source_bind_attributes
303 _normalize_connect_info
315 _adjust_select_args_for_complex_prefetch
316 _resolve_ident_sources
319 _strip_cond_qualifiers
320 _strip_cond_qualifiers_from_array
321 _resolve_aliastypes_from_select_args
332 _dbh_columns_info_for
335 unimplemented => [qw/
336 _arm_global_destructor
339 get_use_dbms_capability
340 set_use_dbms_capability
351 _group_over_selection
352 _extract_order_criteria
363 # the capability framework
364 # not sure if CMOP->initialize does evil things to DBIC::S::DBI, fix if a problem
366 { $_ =~ /^ _ (?: use | supports | determine_supports ) _ /x }
367 ( Class::MOP::Class->initialize('DBIx::Class::Storage::DBI')->get_all_method_names )
371 if (DBIx::Class::_ENV_::DBICTEST) {
374 for my $type (keys %$method_dispatch) {
375 for (@{$method_dispatch->{$type}}) {
376 push @{$seen->{$_}}, $type;
380 if (my @dupes = grep { @{$seen->{$_}} > 1 } keys %$seen) {
382 'The following methods show up multiple times in ::Storage::DBI::Replicated handlers:',
383 (map { "$_: " . (join ', ', @{$seen->{$_}}) } sort @dupes),
388 if (my @cant = grep { ! DBIx::Class::Storage::DBI->can($_) } keys %$seen) {
390 '::Storage::DBI::Replicated specifies handling of the following *NON EXISTING* ::Storage::DBI methods:',
397 for my $method (@{$method_dispatch->{unimplemented}}) {
398 __PACKAGE__->meta->add_method($method, sub {
400 $self->throw_exception("$method must not be called on ".(blessed $self).' objects');
406 Defines an object that implements the read side of L<BIx::Class::Storage::DBI>.
410 has 'read_handler' => (
414 handles=>$method_dispatch->{reader},
419 Defines an object that implements the write side of L<BIx::Class::Storage::DBI>,
420 as well as methods that don't write or read that can be called on only one
421 storage, methods that return a C<$dbh>, and any methods that don't make sense to
426 has 'write_handler' => (
430 handles=>$method_dispatch->{writer},
435 has _master_connect_info_opts =>
436 (is => 'rw', isa => HashRef, default => sub { {} });
438 =head2 around: connect_info
440 Preserves master's C<connect_info> options (for merging with replicants.)
441 Also sets any Replicated-related options from connect_info, such as
442 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
446 around connect_info => sub {
447 my ($next, $self, $info, @extra) = @_;
449 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
452 for my $arg (@$info) {
453 next unless (reftype($arg)||'') eq 'HASH';
454 %opts = %{ $merge->merge($arg, \%opts) };
458 if (@opts{qw/pool_type pool_args/}) {
459 $self->pool_type(delete $opts{pool_type})
463 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
466 ## Since we possibly changed the pool_args, we need to clear the current
467 ## pool object so that next time it is used it will be rebuilt.
471 if (@opts{qw/balancer_type balancer_args/}) {
472 $self->balancer_type(delete $opts{balancer_type})
473 if $opts{balancer_type};
475 $self->balancer_args(
476 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
479 $self->balancer($self->_build_balancer)
483 $self->_master_connect_info_opts(\%opts);
487 @res = $self->$next($info, @extra);
489 $res[0] = $self->$next($info, @extra);
492 # Make sure master is blessed into the correct class and apply role to it.
493 my $master = $self->master;
494 $master->_determine_driver;
495 Moose::Meta::Class->initialize(ref $master);
497 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
499 # link pool back to master
500 $self->pool->master($master);
502 wantarray ? @res : $res[0];
507 This class defines the following methods.
511 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
512 first argument. So we need to massage the arguments a bit so that all the
513 bits get put into the correct places.
518 my ($class, $schema, $storage_type_args, @args) = @_;
529 Lazy builder for the L</master> attribute.
535 my $master = DBIx::Class::Storage::DBI->new($self->schema);
541 Lazy builder for the L</pool> attribute.
547 $self->create_pool(%{$self->pool_args});
550 =head2 _build_balancer
552 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
553 the balancer knows which pool it's balancing.
557 sub _build_balancer {
559 $self->create_balancer(
561 master=>$self->master,
562 %{$self->balancer_args},
566 =head2 _build_write_handler
568 Lazy builder for the L</write_handler> attribute. The default is to set this to
573 sub _build_write_handler {
574 return shift->master;
577 =head2 _build_read_handler
579 Lazy builder for the L</read_handler> attribute. The default is to set this to
584 sub _build_read_handler {
585 return shift->balancer;
588 =head2 around: connect_replicants
590 All calls to connect_replicants needs to have an existing $schema tacked onto
591 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
592 options merged with the master, with replicant opts having higher priority.
596 around connect_replicants => sub {
597 my ($next, $self, @args) = @_;
600 $r = [ $r ] unless reftype $r eq 'ARRAY';
602 $self->throw_exception('coderef replicant connect_info not supported')
603 if ref $r->[0] && reftype $r->[0] eq 'CODE';
605 # any connect_info options?
607 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
610 $r->[$i] = {} unless $r->[$i];
612 # merge if two hashes
613 my @hashes = @$r[$i .. $#{$r}];
615 $self->throw_exception('invalid connect_info options')
616 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
618 $self->throw_exception('too many hashrefs in connect_info')
621 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
622 my %opts = %{ $merge->merge(reverse @hashes) };
625 splice @$r, $i+1, ($#{$r} - $i), ();
627 # make sure master/replicants opts don't clash
628 my %master_opts = %{ $self->_master_connect_info_opts };
629 if (exists $opts{dbh_maker}) {
630 delete @master_opts{qw/dsn user password/};
632 delete $master_opts{dbh_maker};
635 %opts = %{ $merge->merge(\%opts, \%master_opts) };
641 $self->$next($self->schema, @args);
646 Returns an array of of all the connected storage backends. The first element
647 in the returned array is the master, and the remainings are each of the
654 return grep {defined $_ && blessed $_} (
656 values %{ $self->replicants },
660 =head2 execute_reliably ($coderef, ?@args)
662 Given a coderef, saves the current state of the L</read_handler>, forces it to
663 use reliable storage (e.g. sets it to the master), executes a coderef and then
664 restores the original state.
670 $schema->resultset('User')->create({name=>$name});
671 my $user_rs = $schema->resultset('User')->find({name=>$name});
675 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
677 Use this when you must be certain of your database state, such as when you just
678 inserted something and need to get a resultset including it, etc.
682 sub execute_reliably {
683 my ($self, $coderef, @args) = @_;
685 unless( ref $coderef eq 'CODE') {
686 $self->throw_exception('Second argument must be a coderef');
689 ##Get copy of master storage
690 my $master = $self->master;
692 ##Get whatever the current read hander is
693 my $current = $self->read_handler;
695 ##Set the read handler to master
696 $self->read_handler($master);
698 ## do whatever the caller needs
700 my $want_array = wantarray;
704 @result = $coderef->(@args);
705 } elsif(defined $want_array) {
706 ($result[0]) = ($coderef->(@args));
711 $self->throw_exception("coderef returned an error: $_");
713 ##Reset to the original state
714 $self->read_handler($current);
717 return wantarray ? @result : $result[0];
720 =head2 set_reliable_storage
722 Sets the current $schema to be 'reliable', that is all queries, both read and
723 write are sent to the master
727 sub set_reliable_storage {
729 my $schema = $self->schema;
730 my $write_handler = $self->schema->storage->write_handler;
732 $schema->storage->read_handler($write_handler);
735 =head2 set_balanced_storage
737 Sets the current $schema to be use the </balancer> for all reads, while all
738 writes are sent to the master only
742 sub set_balanced_storage {
744 my $schema = $self->schema;
745 my $balanced_handler = $self->schema->storage->balancer;
747 $schema->storage->read_handler($balanced_handler);
752 Check that the master and at least one of the replicants is connected.
759 $self->master->connected &&
760 $self->pool->connected_replicants;
763 =head2 ensure_connected
765 Make sure all the storages are connected.
769 sub ensure_connected {
771 foreach my $source ($self->all_storages) {
772 $source->ensure_connected(@_);
778 Set the limit_dialect for all existing storages
784 foreach my $source ($self->all_storages) {
785 $source->limit_dialect(@_);
787 return $self->master->limit_dialect;
792 Set the quote_char for all existing storages
798 foreach my $source ($self->all_storages) {
799 $source->quote_char(@_);
801 return $self->master->quote_char;
806 Set the name_sep for all existing storages
812 foreach my $source ($self->all_storages) {
813 $source->name_sep(@_);
815 return $self->master->name_sep;
820 Set the schema object for all existing storages
826 foreach my $source ($self->all_storages) {
827 $source->set_schema(@_);
833 set a debug flag across all storages
840 foreach my $source ($self->all_storages) {
844 return $self->master->debug;
855 return $self->master->debugobj(@_);
866 return $self->master->debugfh(@_);
877 return $self->master->debugcb(@_);
882 disconnect everything
888 foreach my $source ($self->all_storages) {
889 $source->disconnect(@_);
895 set cursor class on all storages, or return master's
900 my ($self, $cursor_class) = @_;
903 $_->cursor_class($cursor_class) for $self->all_storages;
905 $self->master->cursor_class;
910 set cursor class on all storages, or return master's, alias for L</cursor_class>
916 my ($self, $cursor_class) = @_;
919 $_->cursor($cursor_class) for $self->all_storages;
921 $self->master->cursor;
926 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
927 master's current setting
935 $_->unsafe(@_) for $self->all_storages;
938 return $self->master->unsafe;
941 =head2 disable_sth_caching
943 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
944 or returns master's current setting
948 sub disable_sth_caching {
952 $_->disable_sth_caching(@_) for $self->all_storages;
955 return $self->master->disable_sth_caching;
958 =head2 lag_behind_master
960 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
965 sub lag_behind_master {
968 return max map $_->lag_behind_master, $self->replicants;
971 =head2 is_replicating
973 returns true if all replicants return true for
974 L<DBIx::Class::Storage::DBI/is_replicating>
981 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
984 =head2 connect_call_datetime_setup
986 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
990 sub connect_call_datetime_setup {
992 $_->connect_call_datetime_setup for $self->all_storages;
997 $_->_populate_dbh for $self->all_storages;
1002 $_->_connect for $self->all_storages;
1007 $_->_rebless for $self->all_storages;
1010 sub _determine_driver {
1012 $_->_determine_driver for $self->all_storages;
1015 sub _driver_determined {
1019 $_->_driver_determined(@_) for $self->all_storages;
1022 return $self->master->_driver_determined;
1028 $_->_init for $self->all_storages;
1031 sub _run_connection_actions {
1034 $_->_run_connection_actions for $self->all_storages;
1037 sub _do_connection_actions {
1041 $_->_do_connection_actions(@_) for $self->all_storages;
1045 sub connect_call_do_sql {
1047 $_->connect_call_do_sql(@_) for $self->all_storages;
1050 sub disconnect_call_do_sql {
1052 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1055 sub _seems_connected {
1058 return min map $_->_seems_connected, $self->all_storages;
1064 return min map $_->_ping, $self->all_storages;
1067 # not using the normalized_version, because we want to preserve
1068 # version numbers much longer than the conventional xxx.yyyzzz
1069 my $numify_ver = sub {
1071 my @numparts = split /\D+/, $ver;
1072 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1074 return sprintf $format, @numparts;
1079 if (not $self->_dbh_details->{info}) {
1080 $self->_dbh_details->{info} = (
1081 reduce { $a->[0] < $b->[0] ? $a : $b }
1082 map [ $numify_ver->($_->{dbms_version}), $_ ],
1083 map $_->_server_info, $self->all_storages
1087 return $self->next::method;
1090 sub _get_server_version {
1093 return $self->_server_info->{dbms_version};
1098 Due to the fact that replicants can lag behind a master, you must take care to
1099 make sure you use one of the methods to force read queries to a master should
1100 you need realtime data integrity. For example, if you insert a row, and then
1101 immediately re-read it from the database (say, by doing $row->discard_changes)
1102 or you insert a row and then immediately build a query that expects that row
1103 to be an item, you should force the master to handle reads. Otherwise, due to
1104 the lag, there is no certainty your data will be in the expected state.
1106 For data integrity, all transactions automatically use the master storage for
1107 all read and write queries. Using a transaction is the preferred and recommended
1108 method to force the master to handle all read queries.
1110 Otherwise, you can force a single query to use the master with the 'force_pool'
1113 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1115 This attribute will safely be ignore by non replicated storages, so you can use
1116 the same code for both types of systems.
1118 Lastly, you can use the L</execute_reliably> method, which works very much like
1121 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1122 and L</set_balanced_storage>, however this operates at a global level and is not
1123 suitable if you have a shared Schema object being used by multiple processes,
1124 such as on a web application server. You can get around this limitation by
1125 using the Schema clone method.
1127 my $new_schema = $schema->clone;
1128 $new_schema->set_reliable_storage;
1130 ## $new_schema will use only the Master storage for all reads/writes while
1131 ## the $schema object will use replicated storage.
1135 John Napiorkowski <john.napiorkowski@takkle.com>
1137 Based on code originated by:
1139 Norbert Csongrádi <bert@cpan.org>
1140 Peter Siklósi <einon@einon.hu>
1144 You may distribute this code under the same terms as Perl itself.
1148 __PACKAGE__->meta->make_immutable;