1 package DBIx::Class::Storage::DBI::Replicated;
4 use Carp::Clan qw/^DBIx::Class/;
6 croak('The following modules are required for Replication ' . DBIx::Class::Optional::Dependencies->req_missing_for ('replicated') )
7 unless DBIx::Class::Optional::Dependencies->req_ok_for ('replicated');
11 use DBIx::Class::Storage::DBI;
12 use DBIx::Class::Storage::DBI::Replicated::Pool;
13 use DBIx::Class::Storage::DBI::Replicated::Balancer;
14 use DBIx::Class::Storage::DBI::Replicated::Types qw/BalancerClassNamePart DBICSchema DBICStorageDBI/;
15 use MooseX::Types::Moose qw/ClassName HashRef Object/;
16 use Scalar::Util 'reftype';
18 use List::Util qw/min max reduce/;
22 use namespace::clean -except => 'meta';
26 DBIx::Class::Storage::DBI::Replicated - BETA Replicated database support
30 The Following example shows how to change an existing $schema to a replicated
31 storage type, add some replicated (read-only) databases, and perform reporting
34 You should set the 'storage_type attribute to a replicated type. You should
35 also define your arguments, such as which balancer you want and any arguments
36 that the Pool object should get.
38 my $schema = Schema::Class->clone;
39 $schema->storage_type( ['::DBI::Replicated', {balancer=>'::Random'}] );
40 $schema->connection(...);
42 Next, you need to add in the Replicants. Basically this is an array of
43 arrayrefs, where each arrayref is database connect information. Think of these
44 arguments as what you'd pass to the 'normal' $schema->connect method.
46 $schema->storage->connect_replicants(
47 [$dsn1, $user, $pass, \%opts],
48 [$dsn2, $user, $pass, \%opts],
49 [$dsn3, $user, $pass, \%opts],
52 Now, just use the $schema as you normally would. Automatically all reads will
53 be delegated to the replicants, while writes to the master.
55 $schema->resultset('Source')->search({name=>'etc'});
57 You can force a given query to use a particular storage using the search
58 attribute 'force_pool'. For example:
60 my $RS = $schema->resultset('Source')->search(undef, {force_pool=>'master'});
62 Now $RS will force everything (both reads and writes) to use whatever was setup
63 as the master storage. 'master' is hardcoded to always point to the Master,
64 but you can also use any Replicant name. Please see:
65 L<DBIx::Class::Storage::DBI::Replicated::Pool> and the replicants attribute for more.
67 Also see transactions and L</execute_reliably> for alternative ways to
68 force read traffic to the master. In general, you should wrap your statements
69 in a transaction when you are reading and writing to the same tables at the
70 same time, since your replicants will often lag a bit behind the master.
72 See L<DBIx::Class::Storage::DBI::Replicated::Instructions> for more help and
77 Warning: This class is marked BETA. This has been running a production
78 website using MySQL native replication as its backend and we have some decent
79 test coverage but the code hasn't yet been stressed by a variety of databases.
80 Individual DBs may have quirks we are not aware of. Please use this in first
81 development and pass along your experiences/bug fixes.
83 This class implements replicated data store for DBI. Currently you can define
84 one master and numerous slave database connections. All write-type queries
85 (INSERT, UPDATE, DELETE and even LAST_INSERT_ID) are routed to master
86 database, all read-type queries (SELECTs) go to the slave database.
88 Basically, any method request that L<DBIx::Class::Storage::DBI> would normally
89 handle gets delegated to one of the two attributes: L</read_handler> or to
90 L</write_handler>. Additionally, some methods need to be distributed
91 to all existing storages. This way our storage class is a drop in replacement
92 for L<DBIx::Class::Storage::DBI>.
94 Read traffic is spread across the replicants (slaves) occurring to a user
95 selected algorithm. The default algorithm is random weighted.
99 The consistency between master and replicants is database specific. The Pool
100 gives you a method to validate its replicants, removing and replacing them
101 when they fail/pass predefined criteria. Please make careful use of the ways
102 to force a query to run against Master when needed.
106 Replicated Storage has additional requirements not currently part of
107 L<DBIx::Class>. See L<DBIx::Class::Optional::Dependencies> for more details.
111 This class defines the following attributes.
115 The underlying L<DBIx::Class::Schema> object this storage is attaching
128 Contains the classname which will instantiate the L</pool> object. Defaults
129 to: L<DBIx::Class::Storage::DBI::Replicated::Pool>.
136 default=>'DBIx::Class::Storage::DBI::Replicated::Pool',
138 'create_pool' => 'new',
144 Contains a hashref of initialized information to pass to the Balancer object.
145 See L<DBIx::Class::Storage::DBI::Replicated::Pool> for available arguments.
159 The replication pool requires a balance class to provider the methods for
160 choose how to spread the query load across each replicant in the pool.
164 has 'balancer_type' => (
166 isa=>BalancerClassNamePart,
169 default=> 'DBIx::Class::Storage::DBI::Replicated::Balancer::First',
171 'create_balancer' => 'new',
177 Contains a hashref of initialized information to pass to the Balancer object.
178 See L<DBIx::Class::Storage::DBI::Replicated::Balancer> for available arguments.
182 has 'balancer_args' => (
192 Is a L<DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a
193 container class for one or more replicated databases.
199 isa=>'DBIx::Class::Storage::DBI::Replicated::Pool',
210 Is a L<DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This
211 is a class that takes a pool (L<DBIx::Class::Storage::DBI::Replicated::Pool>)
217 isa=>'DBIx::Class::Storage::DBI::Replicated::Balancer',
219 handles=>[qw/auto_validate_every/],
224 The master defines the canonical state for a pool of connected databases. All
225 the replicants are expected to match this databases state. Thus, in a classic
226 Master / Slaves distributed system, all the slaves are expected to replicate
227 the Master's state as quick as possible. This is the only database in the
228 pool of databases that is allowed to handle write traffic.
238 =head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE
240 The following methods are delegated all the methods required for the
241 L<DBIx::Class::Storage::DBI> interface.
245 my $method_dispatch = {
257 deployment_statements
260 build_datetime_parser
274 with_deferred_fk_checks
283 relname_to_table_alias
286 _default_dbi_connect_attributes
288 _dbic_connect_attributes
291 bind_attribute_by_data_type
298 _per_row_update_delete
300 _dbh_execute_inserts_with_no_binds
301 _select_args_to_query
303 _multipk_update_delete
304 source_bind_attributes
305 _normalize_connect_info
317 _adjust_select_args_for_complex_prefetch
318 _resolve_ident_sources
321 _strip_cond_qualifiers
322 _strip_cond_qualifiers_from_array
323 _resolve_aliastypes_from_select_args
333 _dbh_columns_info_for
336 unimplemented => [qw/
337 _arm_global_destructor
340 get_use_dbms_capability
341 set_use_dbms_capability
352 _group_over_selection
353 _extract_order_criteria
362 # the capability framework
363 # not sure if CMOP->initialize does evil things to DBIC::S::DBI, fix if a problem
365 { $_ =~ /^ _ (?: use | supports | determine_supports ) _ /x }
366 ( Class::MOP::Class->initialize('DBIx::Class::Storage::DBI')->get_all_method_names )
370 if (DBIx::Class::_ENV_::DBICTEST) {
373 for my $type (keys %$method_dispatch) {
374 for (@{$method_dispatch->{$type}}) {
375 push @{$seen->{$_}}, $type;
379 if (my @dupes = grep { @{$seen->{$_}} > 1 } keys %$seen) {
381 'The following methods show up multiple times in ::Storage::DBI::Replicated handlers:',
382 (map { "$_: " . (join ', ', @{$seen->{$_}}) } sort @dupes),
387 if (my @cant = grep { ! DBIx::Class::Storage::DBI->can($_) } keys %$seen) {
389 '::Storage::DBI::Replicated specifies handling of the following *NON EXISTING* ::Storage::DBI methods:',
396 for my $method (@{$method_dispatch->{unimplemented}}) {
397 __PACKAGE__->meta->add_method($method, sub {
398 croak "$method must not be called on ".(blessed shift).' objects';
404 Defines an object that implements the read side of L<BIx::Class::Storage::DBI>.
408 has 'read_handler' => (
412 handles=>$method_dispatch->{reader},
417 Defines an object that implements the write side of L<BIx::Class::Storage::DBI>,
418 as well as methods that don't write or read that can be called on only one
419 storage, methods that return a C<$dbh>, and any methods that don't make sense to
424 has 'write_handler' => (
428 handles=>$method_dispatch->{writer},
433 has _master_connect_info_opts =>
434 (is => 'rw', isa => HashRef, default => sub { {} });
436 =head2 around: connect_info
438 Preserves master's C<connect_info> options (for merging with replicants.)
439 Also sets any Replicated-related options from connect_info, such as
440 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
444 around connect_info => sub {
445 my ($next, $self, $info, @extra) = @_;
447 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
450 for my $arg (@$info) {
451 next unless (reftype($arg)||'') eq 'HASH';
452 %opts = %{ $merge->merge($arg, \%opts) };
456 if (@opts{qw/pool_type pool_args/}) {
457 $self->pool_type(delete $opts{pool_type})
461 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
464 ## Since we possibly changed the pool_args, we need to clear the current
465 ## pool object so that next time it is used it will be rebuilt.
469 if (@opts{qw/balancer_type balancer_args/}) {
470 $self->balancer_type(delete $opts{balancer_type})
471 if $opts{balancer_type};
473 $self->balancer_args(
474 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
477 $self->balancer($self->_build_balancer)
481 $self->_master_connect_info_opts(\%opts);
485 @res = $self->$next($info, @extra);
487 $res[0] = $self->$next($info, @extra);
490 # Make sure master is blessed into the correct class and apply role to it.
491 my $master = $self->master;
492 $master->_determine_driver;
493 Moose::Meta::Class->initialize(ref $master);
495 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
497 # link pool back to master
498 $self->pool->master($master);
500 wantarray ? @res : $res[0];
505 This class defines the following methods.
509 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
510 first argument. So we need to massage the arguments a bit so that all the
511 bits get put into the correct places.
516 my ($class, $schema, $storage_type_args, @args) = @_;
527 Lazy builder for the L</master> attribute.
533 my $master = DBIx::Class::Storage::DBI->new($self->schema);
539 Lazy builder for the L</pool> attribute.
545 $self->create_pool(%{$self->pool_args});
548 =head2 _build_balancer
550 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
551 the balancer knows which pool it's balancing.
555 sub _build_balancer {
557 $self->create_balancer(
559 master=>$self->master,
560 %{$self->balancer_args},
564 =head2 _build_write_handler
566 Lazy builder for the L</write_handler> attribute. The default is to set this to
571 sub _build_write_handler {
572 return shift->master;
575 =head2 _build_read_handler
577 Lazy builder for the L</read_handler> attribute. The default is to set this to
582 sub _build_read_handler {
583 return shift->balancer;
586 =head2 around: connect_replicants
588 All calls to connect_replicants needs to have an existing $schema tacked onto
589 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
590 options merged with the master, with replicant opts having higher priority.
594 around connect_replicants => sub {
595 my ($next, $self, @args) = @_;
598 $r = [ $r ] unless reftype $r eq 'ARRAY';
600 $self->throw_exception('coderef replicant connect_info not supported')
601 if ref $r->[0] && reftype $r->[0] eq 'CODE';
603 # any connect_info options?
605 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
608 $r->[$i] = {} unless $r->[$i];
610 # merge if two hashes
611 my @hashes = @$r[$i .. $#{$r}];
613 $self->throw_exception('invalid connect_info options')
614 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
616 $self->throw_exception('too many hashrefs in connect_info')
619 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
620 my %opts = %{ $merge->merge(reverse @hashes) };
623 splice @$r, $i+1, ($#{$r} - $i), ();
625 # make sure master/replicants opts don't clash
626 my %master_opts = %{ $self->_master_connect_info_opts };
627 if (exists $opts{dbh_maker}) {
628 delete @master_opts{qw/dsn user password/};
630 delete $master_opts{dbh_maker};
633 %opts = %{ $merge->merge(\%opts, \%master_opts) };
639 $self->$next($self->schema, @args);
644 Returns an array of of all the connected storage backends. The first element
645 in the returned array is the master, and the remainings are each of the
652 return grep {defined $_ && blessed $_} (
654 values %{ $self->replicants },
658 =head2 execute_reliably ($coderef, ?@args)
660 Given a coderef, saves the current state of the L</read_handler>, forces it to
661 use reliable storage (e.g. sets it to the master), executes a coderef and then
662 restores the original state.
668 $schema->resultset('User')->create({name=>$name});
669 my $user_rs = $schema->resultset('User')->find({name=>$name});
673 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
675 Use this when you must be certain of your database state, such as when you just
676 inserted something and need to get a resultset including it, etc.
680 sub execute_reliably {
681 my ($self, $coderef, @args) = @_;
683 unless( ref $coderef eq 'CODE') {
684 $self->throw_exception('Second argument must be a coderef');
687 ##Get copy of master storage
688 my $master = $self->master;
690 ##Get whatever the current read hander is
691 my $current = $self->read_handler;
693 ##Set the read handler to master
694 $self->read_handler($master);
696 ## do whatever the caller needs
698 my $want_array = wantarray;
702 @result = $coderef->(@args);
703 } elsif(defined $want_array) {
704 ($result[0]) = ($coderef->(@args));
709 $self->throw_exception("coderef returned an error: $_");
711 ##Reset to the original state
712 $self->read_handler($current);
715 return wantarray ? @result : $result[0];
718 =head2 set_reliable_storage
720 Sets the current $schema to be 'reliable', that is all queries, both read and
721 write are sent to the master
725 sub set_reliable_storage {
727 my $schema = $self->schema;
728 my $write_handler = $self->schema->storage->write_handler;
730 $schema->storage->read_handler($write_handler);
733 =head2 set_balanced_storage
735 Sets the current $schema to be use the </balancer> for all reads, while all
736 writes are sent to the master only
740 sub set_balanced_storage {
742 my $schema = $self->schema;
743 my $balanced_handler = $self->schema->storage->balancer;
745 $schema->storage->read_handler($balanced_handler);
750 Check that the master and at least one of the replicants is connected.
757 $self->master->connected &&
758 $self->pool->connected_replicants;
761 =head2 ensure_connected
763 Make sure all the storages are connected.
767 sub ensure_connected {
769 foreach my $source ($self->all_storages) {
770 $source->ensure_connected(@_);
776 Set the limit_dialect for all existing storages
782 foreach my $source ($self->all_storages) {
783 $source->limit_dialect(@_);
785 return $self->master->limit_dialect;
790 Set the quote_char for all existing storages
796 foreach my $source ($self->all_storages) {
797 $source->quote_char(@_);
799 return $self->master->quote_char;
804 Set the name_sep for all existing storages
810 foreach my $source ($self->all_storages) {
811 $source->name_sep(@_);
813 return $self->master->name_sep;
818 Set the schema object for all existing storages
824 foreach my $source ($self->all_storages) {
825 $source->set_schema(@_);
831 set a debug flag across all storages
838 foreach my $source ($self->all_storages) {
842 return $self->master->debug;
853 return $self->master->debugobj(@_);
864 return $self->master->debugfh(@_);
875 return $self->master->debugcb(@_);
880 disconnect everything
886 foreach my $source ($self->all_storages) {
887 $source->disconnect(@_);
893 set cursor class on all storages, or return master's
898 my ($self, $cursor_class) = @_;
901 $_->cursor_class($cursor_class) for $self->all_storages;
903 $self->master->cursor_class;
908 set cursor class on all storages, or return master's, alias for L</cursor_class>
914 my ($self, $cursor_class) = @_;
917 $_->cursor($cursor_class) for $self->all_storages;
919 $self->master->cursor;
924 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
925 master's current setting
933 $_->unsafe(@_) for $self->all_storages;
936 return $self->master->unsafe;
939 =head2 disable_sth_caching
941 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
942 or returns master's current setting
946 sub disable_sth_caching {
950 $_->disable_sth_caching(@_) for $self->all_storages;
953 return $self->master->disable_sth_caching;
956 =head2 lag_behind_master
958 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
963 sub lag_behind_master {
966 return max map $_->lag_behind_master, $self->replicants;
969 =head2 is_replicating
971 returns true if all replicants return true for
972 L<DBIx::Class::Storage::DBI/is_replicating>
979 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
982 =head2 connect_call_datetime_setup
984 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
988 sub connect_call_datetime_setup {
990 $_->connect_call_datetime_setup for $self->all_storages;
995 $_->_populate_dbh for $self->all_storages;
1000 $_->_connect for $self->all_storages;
1005 $_->_rebless for $self->all_storages;
1008 sub _determine_driver {
1010 $_->_determine_driver for $self->all_storages;
1013 sub _driver_determined {
1017 $_->_driver_determined(@_) for $self->all_storages;
1020 return $self->master->_driver_determined;
1026 $_->_init for $self->all_storages;
1029 sub _run_connection_actions {
1032 $_->_run_connection_actions for $self->all_storages;
1035 sub _do_connection_actions {
1039 $_->_do_connection_actions(@_) for $self->all_storages;
1043 sub connect_call_do_sql {
1045 $_->connect_call_do_sql(@_) for $self->all_storages;
1048 sub disconnect_call_do_sql {
1050 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1053 sub _seems_connected {
1056 return min map $_->_seems_connected, $self->all_storages;
1062 return min map $_->_ping, $self->all_storages;
1065 # not using the normalized_version, because we want to preserve
1066 # version numbers much longer than the conventional xxx.yyyzzz
1067 my $numify_ver = sub {
1069 my @numparts = split /\D+/, $ver;
1070 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1072 return sprintf $format, @numparts;
1077 if (not $self->_dbh_details->{info}) {
1078 $self->_dbh_details->{info} = (
1079 reduce { $a->[0] < $b->[0] ? $a : $b }
1080 map [ $numify_ver->($_->{dbms_version}), $_ ],
1081 map $_->_server_info, $self->all_storages
1085 return $self->next::method;
1088 sub _get_server_version {
1091 return $self->_server_info->{dbms_version};
1096 Due to the fact that replicants can lag behind a master, you must take care to
1097 make sure you use one of the methods to force read queries to a master should
1098 you need realtime data integrity. For example, if you insert a row, and then
1099 immediately re-read it from the database (say, by doing $row->discard_changes)
1100 or you insert a row and then immediately build a query that expects that row
1101 to be an item, you should force the master to handle reads. Otherwise, due to
1102 the lag, there is no certainty your data will be in the expected state.
1104 For data integrity, all transactions automatically use the master storage for
1105 all read and write queries. Using a transaction is the preferred and recommended
1106 method to force the master to handle all read queries.
1108 Otherwise, you can force a single query to use the master with the 'force_pool'
1111 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1113 This attribute will safely be ignore by non replicated storages, so you can use
1114 the same code for both types of systems.
1116 Lastly, you can use the L</execute_reliably> method, which works very much like
1119 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1120 and L</set_balanced_storage>, however this operates at a global level and is not
1121 suitable if you have a shared Schema object being used by multiple processes,
1122 such as on a web application server. You can get around this limitation by
1123 using the Schema clone method.
1125 my $new_schema = $schema->clone;
1126 $new_schema->set_reliable_storage;
1128 ## $new_schema will use only the Master storage for all reads/writes while
1129 ## the $schema object will use replicated storage.
1133 John Napiorkowski <john.napiorkowski@takkle.com>
1135 Based on code originated by:
1137 Norbert Csongrádi <bert@cpan.org>
1138 Peter Siklósi <einon@einon.hu>
1142 You may distribute this code under the same terms as Perl itself.
1146 __PACKAGE__->meta->make_immutable;