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
283 _default_dbi_connect_attributes
285 _dbic_connect_attributes
291 bind_attribute_by_data_type
297 _per_row_update_delete
299 _dbh_execute_inserts_with_no_binds
300 _select_args_to_query
302 _multipk_update_delete
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 source_bind_attributes
341 get_use_dbms_capability
342 set_use_dbms_capability
353 _group_over_selection
354 _extract_order_criteria
365 # the capability framework
366 # not sure if CMOP->initialize does evil things to DBIC::S::DBI, fix if a problem
368 { $_ =~ /^ _ (?: use | supports | determine_supports ) _ /x }
369 ( Class::MOP::Class->initialize('DBIx::Class::Storage::DBI')->get_all_method_names )
373 if (DBIx::Class::_ENV_::DBICTEST) {
376 for my $type (keys %$method_dispatch) {
377 for (@{$method_dispatch->{$type}}) {
378 push @{$seen->{$_}}, $type;
382 if (my @dupes = grep { @{$seen->{$_}} > 1 } keys %$seen) {
384 'The following methods show up multiple times in ::Storage::DBI::Replicated handlers:',
385 (map { "$_: " . (join ', ', @{$seen->{$_}}) } sort @dupes),
390 if (my @cant = grep { ! DBIx::Class::Storage::DBI->can($_) } keys %$seen) {
392 '::Storage::DBI::Replicated specifies handling of the following *NON EXISTING* ::Storage::DBI methods:',
399 for my $method (@{$method_dispatch->{unimplemented}}) {
400 __PACKAGE__->meta->add_method($method, sub {
402 $self->throw_exception("$method must not be called on ".(blessed $self).' objects');
408 Defines an object that implements the read side of L<BIx::Class::Storage::DBI>.
412 has 'read_handler' => (
416 handles=>$method_dispatch->{reader},
421 Defines an object that implements the write side of L<BIx::Class::Storage::DBI>,
422 as well as methods that don't write or read that can be called on only one
423 storage, methods that return a C<$dbh>, and any methods that don't make sense to
428 has 'write_handler' => (
432 handles=>$method_dispatch->{writer},
437 has _master_connect_info_opts =>
438 (is => 'rw', isa => HashRef, default => sub { {} });
440 =head2 around: connect_info
442 Preserves master's C<connect_info> options (for merging with replicants.)
443 Also sets any Replicated-related options from connect_info, such as
444 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
448 around connect_info => sub {
449 my ($next, $self, $info, @extra) = @_;
451 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
454 for my $arg (@$info) {
455 next unless (reftype($arg)||'') eq 'HASH';
456 %opts = %{ $merge->merge($arg, \%opts) };
460 if (@opts{qw/pool_type pool_args/}) {
461 $self->pool_type(delete $opts{pool_type})
465 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
468 ## Since we possibly changed the pool_args, we need to clear the current
469 ## pool object so that next time it is used it will be rebuilt.
473 if (@opts{qw/balancer_type balancer_args/}) {
474 $self->balancer_type(delete $opts{balancer_type})
475 if $opts{balancer_type};
477 $self->balancer_args(
478 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
481 $self->balancer($self->_build_balancer)
485 $self->_master_connect_info_opts(\%opts);
489 @res = $self->$next($info, @extra);
491 $res[0] = $self->$next($info, @extra);
494 # Make sure master is blessed into the correct class and apply role to it.
495 my $master = $self->master;
496 $master->_determine_driver;
497 Moose::Meta::Class->initialize(ref $master);
499 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
501 # link pool back to master
502 $self->pool->master($master);
504 wantarray ? @res : $res[0];
509 This class defines the following methods.
513 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
514 first argument. So we need to massage the arguments a bit so that all the
515 bits get put into the correct places.
520 my ($class, $schema, $storage_type_args, @args) = @_;
531 Lazy builder for the L</master> attribute.
537 my $master = DBIx::Class::Storage::DBI->new($self->schema);
543 Lazy builder for the L</pool> attribute.
549 $self->create_pool(%{$self->pool_args});
552 =head2 _build_balancer
554 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
555 the balancer knows which pool it's balancing.
559 sub _build_balancer {
561 $self->create_balancer(
563 master=>$self->master,
564 %{$self->balancer_args},
568 =head2 _build_write_handler
570 Lazy builder for the L</write_handler> attribute. The default is to set this to
575 sub _build_write_handler {
576 return shift->master;
579 =head2 _build_read_handler
581 Lazy builder for the L</read_handler> attribute. The default is to set this to
586 sub _build_read_handler {
587 return shift->balancer;
590 =head2 around: connect_replicants
592 All calls to connect_replicants needs to have an existing $schema tacked onto
593 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
594 options merged with the master, with replicant opts having higher priority.
598 around connect_replicants => sub {
599 my ($next, $self, @args) = @_;
602 $r = [ $r ] unless reftype $r eq 'ARRAY';
604 $self->throw_exception('coderef replicant connect_info not supported')
605 if ref $r->[0] && reftype $r->[0] eq 'CODE';
607 # any connect_info options?
609 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
612 $r->[$i] = {} unless $r->[$i];
614 # merge if two hashes
615 my @hashes = @$r[$i .. $#{$r}];
617 $self->throw_exception('invalid connect_info options')
618 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
620 $self->throw_exception('too many hashrefs in connect_info')
623 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
624 my %opts = %{ $merge->merge(reverse @hashes) };
627 splice @$r, $i+1, ($#{$r} - $i), ();
629 # make sure master/replicants opts don't clash
630 my %master_opts = %{ $self->_master_connect_info_opts };
631 if (exists $opts{dbh_maker}) {
632 delete @master_opts{qw/dsn user password/};
634 delete $master_opts{dbh_maker};
637 %opts = %{ $merge->merge(\%opts, \%master_opts) };
643 $self->$next($self->schema, @args);
648 Returns an array of of all the connected storage backends. The first element
649 in the returned array is the master, and the remainings are each of the
656 return grep {defined $_ && blessed $_} (
658 values %{ $self->replicants },
662 =head2 execute_reliably ($coderef, ?@args)
664 Given a coderef, saves the current state of the L</read_handler>, forces it to
665 use reliable storage (e.g. sets it to the master), executes a coderef and then
666 restores the original state.
672 $schema->resultset('User')->create({name=>$name});
673 my $user_rs = $schema->resultset('User')->find({name=>$name});
677 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
679 Use this when you must be certain of your database state, such as when you just
680 inserted something and need to get a resultset including it, etc.
684 sub execute_reliably {
685 my ($self, $coderef, @args) = @_;
687 unless( ref $coderef eq 'CODE') {
688 $self->throw_exception('Second argument must be a coderef');
691 ##Get copy of master storage
692 my $master = $self->master;
694 ##Get whatever the current read hander is
695 my $current = $self->read_handler;
697 ##Set the read handler to master
698 $self->read_handler($master);
700 ## do whatever the caller needs
702 my $want_array = wantarray;
706 @result = $coderef->(@args);
707 } elsif(defined $want_array) {
708 ($result[0]) = ($coderef->(@args));
713 $self->throw_exception("coderef returned an error: $_");
715 ##Reset to the original state
716 $self->read_handler($current);
719 return wantarray ? @result : $result[0];
722 =head2 set_reliable_storage
724 Sets the current $schema to be 'reliable', that is all queries, both read and
725 write are sent to the master
729 sub set_reliable_storage {
731 my $schema = $self->schema;
732 my $write_handler = $self->schema->storage->write_handler;
734 $schema->storage->read_handler($write_handler);
737 =head2 set_balanced_storage
739 Sets the current $schema to be use the </balancer> for all reads, while all
740 writes are sent to the master only
744 sub set_balanced_storage {
746 my $schema = $self->schema;
747 my $balanced_handler = $self->schema->storage->balancer;
749 $schema->storage->read_handler($balanced_handler);
754 Check that the master and at least one of the replicants is connected.
761 $self->master->connected &&
762 $self->pool->connected_replicants;
765 =head2 ensure_connected
767 Make sure all the storages are connected.
771 sub ensure_connected {
773 foreach my $source ($self->all_storages) {
774 $source->ensure_connected(@_);
780 Set the limit_dialect for all existing storages
786 foreach my $source ($self->all_storages) {
787 $source->limit_dialect(@_);
789 return $self->master->limit_dialect;
794 Set the quote_char for all existing storages
800 foreach my $source ($self->all_storages) {
801 $source->quote_char(@_);
803 return $self->master->quote_char;
808 Set the name_sep for all existing storages
814 foreach my $source ($self->all_storages) {
815 $source->name_sep(@_);
817 return $self->master->name_sep;
822 Set the schema object for all existing storages
828 foreach my $source ($self->all_storages) {
829 $source->set_schema(@_);
835 set a debug flag across all storages
842 foreach my $source ($self->all_storages) {
846 return $self->master->debug;
857 return $self->master->debugobj(@_);
868 return $self->master->debugfh(@_);
879 return $self->master->debugcb(@_);
884 disconnect everything
890 foreach my $source ($self->all_storages) {
891 $source->disconnect(@_);
897 set cursor class on all storages, or return master's
902 my ($self, $cursor_class) = @_;
905 $_->cursor_class($cursor_class) for $self->all_storages;
907 $self->master->cursor_class;
912 set cursor class on all storages, or return master's, alias for L</cursor_class>
918 my ($self, $cursor_class) = @_;
921 $_->cursor($cursor_class) for $self->all_storages;
923 $self->master->cursor;
928 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
929 master's current setting
937 $_->unsafe(@_) for $self->all_storages;
940 return $self->master->unsafe;
943 =head2 disable_sth_caching
945 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
946 or returns master's current setting
950 sub disable_sth_caching {
954 $_->disable_sth_caching(@_) for $self->all_storages;
957 return $self->master->disable_sth_caching;
960 =head2 lag_behind_master
962 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
967 sub lag_behind_master {
970 return max map $_->lag_behind_master, $self->replicants;
973 =head2 is_replicating
975 returns true if all replicants return true for
976 L<DBIx::Class::Storage::DBI/is_replicating>
983 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
986 =head2 connect_call_datetime_setup
988 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
992 sub connect_call_datetime_setup {
994 $_->connect_call_datetime_setup for $self->all_storages;
999 $_->_populate_dbh for $self->all_storages;
1004 $_->_connect for $self->all_storages;
1009 $_->_rebless for $self->all_storages;
1012 sub _determine_driver {
1014 $_->_determine_driver for $self->all_storages;
1017 sub _driver_determined {
1021 $_->_driver_determined(@_) for $self->all_storages;
1024 return $self->master->_driver_determined;
1030 $_->_init for $self->all_storages;
1033 sub _run_connection_actions {
1036 $_->_run_connection_actions for $self->all_storages;
1039 sub _do_connection_actions {
1043 $_->_do_connection_actions(@_) for $self->all_storages;
1047 sub connect_call_do_sql {
1049 $_->connect_call_do_sql(@_) for $self->all_storages;
1052 sub disconnect_call_do_sql {
1054 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1057 sub _seems_connected {
1060 return min map $_->_seems_connected, $self->all_storages;
1066 return min map $_->_ping, $self->all_storages;
1069 # not using the normalized_version, because we want to preserve
1070 # version numbers much longer than the conventional xxx.yyyzzz
1071 my $numify_ver = sub {
1073 my @numparts = split /\D+/, $ver;
1074 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1076 return sprintf $format, @numparts;
1081 if (not $self->_dbh_details->{info}) {
1082 $self->_dbh_details->{info} = (
1083 reduce { $a->[0] < $b->[0] ? $a : $b }
1084 map [ $numify_ver->($_->{dbms_version}), $_ ],
1085 map $_->_server_info, $self->all_storages
1089 return $self->next::method;
1092 sub _get_server_version {
1095 return $self->_server_info->{dbms_version};
1100 Due to the fact that replicants can lag behind a master, you must take care to
1101 make sure you use one of the methods to force read queries to a master should
1102 you need realtime data integrity. For example, if you insert a row, and then
1103 immediately re-read it from the database (say, by doing $row->discard_changes)
1104 or you insert a row and then immediately build a query that expects that row
1105 to be an item, you should force the master to handle reads. Otherwise, due to
1106 the lag, there is no certainty your data will be in the expected state.
1108 For data integrity, all transactions automatically use the master storage for
1109 all read and write queries. Using a transaction is the preferred and recommended
1110 method to force the master to handle all read queries.
1112 Otherwise, you can force a single query to use the master with the 'force_pool'
1115 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1117 This attribute will safely be ignore by non replicated storages, so you can use
1118 the same code for both types of systems.
1120 Lastly, you can use the L</execute_reliably> method, which works very much like
1123 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1124 and L</set_balanced_storage>, however this operates at a global level and is not
1125 suitable if you have a shared Schema object being used by multiple processes,
1126 such as on a web application server. You can get around this limitation by
1127 using the Schema clone method.
1129 my $new_schema = $schema->clone;
1130 $new_schema->set_reliable_storage;
1132 ## $new_schema will use only the Master storage for all reads/writes while
1133 ## the $schema object will use replicated storage.
1137 John Napiorkowski <john.napiorkowski@takkle.com>
1139 Based on code originated by:
1141 Norbert Csongrádi <bert@cpan.org>
1142 Peter Siklósi <einon@einon.hu>
1146 You may distribute this code under the same terms as Perl itself.
1150 __PACKAGE__->meta->make_immutable;