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/;
18 use Context::Preserve 'preserve_context';
21 use namespace::clean -except => 'meta';
27 DBIx::Class::Storage::DBI::Replicated - BETA Replicated database support
31 The Following example shows how to change an existing $schema to a replicated
32 storage type, add some replicated (read-only) databases, and perform reporting
35 You should set the 'storage_type attribute to a replicated type. You should
36 also define your arguments, such as which balancer you want and any arguments
37 that the Pool object should get.
39 my $schema = Schema::Class->clone;
40 $schema->storage_type( ['::DBI::Replicated', {balancer=>'::Random'}] );
41 $schema->connection(...);
43 Next, you need to add in the Replicants. Basically this is an array of
44 arrayrefs, where each arrayref is database connect information. Think of these
45 arguments as what you'd pass to the 'normal' $schema->connect method.
47 $schema->storage->connect_replicants(
48 [$dsn1, $user, $pass, \%opts],
49 [$dsn2, $user, $pass, \%opts],
50 [$dsn3, $user, $pass, \%opts],
53 Now, just use the $schema as you normally would. Automatically all reads will
54 be delegated to the replicants, while writes to the master.
56 $schema->resultset('Source')->search({name=>'etc'});
58 You can force a given query to use a particular storage using the search
59 attribute 'force_pool'. For example:
61 my $rs = $schema->resultset('Source')->search(undef, {force_pool=>'master'});
63 Now $rs will force everything (both reads and writes) to use whatever was setup
64 as the master storage. 'master' is hardcoded to always point to the Master,
65 but you can also use any Replicant name. Please see:
66 L<DBIx::Class::Storage::DBI::Replicated::Pool> and the replicants attribute for more.
68 Also see transactions and L</execute_reliably> for alternative ways to
69 force read traffic to the master. In general, you should wrap your statements
70 in a transaction when you are reading and writing to the same tables at the
71 same time, since your replicants will often lag a bit behind the master.
73 If you have a multi-statement read only transaction you can force it to select
74 a random server in the pool by:
76 my $rs = $schema->resultset('Source')->search( undef,
77 { force_pool => $db->storage->read_handler->next_storage }
82 Warning: This class is marked BETA. This has been running a production
83 website using MySQL native replication as its backend and we have some decent
84 test coverage but the code hasn't yet been stressed by a variety of databases.
85 Individual DBs may have quirks we are not aware of. Please use this in first
86 development and pass along your experiences/bug fixes.
88 This class implements replicated data store for DBI. Currently you can define
89 one master and numerous slave database connections. All write-type queries
90 (INSERT, UPDATE, DELETE and even LAST_INSERT_ID) are routed to master
91 database, all read-type queries (SELECTs) go to the slave database.
93 Basically, any method request that L<DBIx::Class::Storage::DBI> would normally
94 handle gets delegated to one of the two attributes: L</read_handler> or to
95 L</write_handler>. Additionally, some methods need to be distributed
96 to all existing storages. This way our storage class is a drop in replacement
97 for L<DBIx::Class::Storage::DBI>.
99 Read traffic is spread across the replicants (slaves) occurring to a user
100 selected algorithm. The default algorithm is random weighted.
104 The consistency between master and replicants is database specific. The Pool
105 gives you a method to validate its replicants, removing and replacing them
106 when they fail/pass predefined criteria. Please make careful use of the ways
107 to force a query to run against Master when needed.
111 Replicated Storage has additional requirements not currently part of
112 L<DBIx::Class>. See L<DBIx::Class::Optional::Dependencies> for more details.
116 This class defines the following attributes.
120 The underlying L<DBIx::Class::Schema> object this storage is attaching
133 Contains the classname which will instantiate the L</pool> object. Defaults
134 to: L<DBIx::Class::Storage::DBI::Replicated::Pool>.
141 default=>'DBIx::Class::Storage::DBI::Replicated::Pool',
143 'create_pool' => 'new',
149 Contains a hashref of initialized information to pass to the Balancer object.
150 See L<DBIx::Class::Storage::DBI::Replicated::Pool> for available arguments.
164 The replication pool requires a balance class to provider the methods for
165 choose how to spread the query load across each replicant in the pool.
169 has 'balancer_type' => (
171 isa=>BalancerClassNamePart,
174 default=> 'DBIx::Class::Storage::DBI::Replicated::Balancer::First',
176 'create_balancer' => 'new',
182 Contains a hashref of initialized information to pass to the Balancer object.
183 See L<DBIx::Class::Storage::DBI::Replicated::Balancer> for available arguments.
187 has 'balancer_args' => (
197 Is a L<DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a
198 container class for one or more replicated databases.
204 isa=>'DBIx::Class::Storage::DBI::Replicated::Pool',
215 Is a L<DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This
216 is a class that takes a pool (L<DBIx::Class::Storage::DBI::Replicated::Pool>)
222 isa=>'DBIx::Class::Storage::DBI::Replicated::Balancer',
224 handles=>[qw/auto_validate_every/],
229 The master defines the canonical state for a pool of connected databases. All
230 the replicants are expected to match this databases state. Thus, in a classic
231 Master / Slaves distributed system, all the slaves are expected to replicate
232 the Master's state as quick as possible. This is the only database in the
233 pool of databases that is allowed to handle write traffic.
243 =head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE
245 The following methods are delegated all the methods required for the
246 L<DBIx::Class::Storage::DBI> interface.
250 my $method_dispatch = {
262 deployment_statements
265 build_datetime_parser
281 with_deferred_fk_checks
289 relname_to_table_alias
291 _default_dbi_connect_attributes
293 _dbic_connect_attributes
299 bind_attribute_by_data_type
303 _dbh_execute_for_fetch
305 _dbh_execute_inserts_with_no_binds
306 _select_args_to_query
309 _normalize_connect_info
323 /, Class::MOP::Class->initialize('DBIx::Class::Storage::DBIHacks')->get_method_list ],
328 _dbh_columns_info_for
331 unimplemented => [qw/
332 _arm_global_destructor
335 source_bind_attributes
337 get_use_dbms_capability
338 set_use_dbms_capability
349 _perform_autoinc_retrieval
350 _autoinc_supplied_for_op
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 {
399 $self->throw_exception("$method must not be called on ".(blessed $self).' objects');
405 Defines an object that implements the read side of L<BIx::Class::Storage::DBI>.
409 has 'read_handler' => (
413 handles=>$method_dispatch->{reader},
418 Defines an object that implements the write side of L<BIx::Class::Storage::DBI>,
419 as well as methods that don't write or read that can be called on only one
420 storage, methods that return a C<$dbh>, and any methods that don't make sense to
425 has 'write_handler' => (
429 handles=>$method_dispatch->{writer},
434 has _master_connect_info_opts =>
435 (is => 'rw', isa => HashRef, default => sub { {} });
437 =head2 around: connect_info
439 Preserves master's C<connect_info> options (for merging with replicants.)
440 Also sets any Replicated-related options from connect_info, such as
441 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
445 around connect_info => sub {
446 my ($next, $self, $info, @extra) = @_;
448 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
451 for my $arg (@$info) {
452 next unless (reftype($arg)||'') eq 'HASH';
453 %opts = %{ $merge->merge($arg, \%opts) };
457 if (@opts{qw/pool_type pool_args/}) {
458 $self->pool_type(delete $opts{pool_type})
462 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
465 ## Since we possibly changed the pool_args, we need to clear the current
466 ## pool object so that next time it is used it will be rebuilt.
470 if (@opts{qw/balancer_type balancer_args/}) {
471 $self->balancer_type(delete $opts{balancer_type})
472 if $opts{balancer_type};
474 $self->balancer_args(
475 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
478 $self->balancer($self->_build_balancer)
482 $self->_master_connect_info_opts(\%opts);
484 return preserve_context {
485 $self->$next($info, @extra);
487 # Make sure master is blessed into the correct class and apply role to it.
488 my $master = $self->master;
489 $master->_determine_driver;
490 Moose::Meta::Class->initialize(ref $master);
492 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
494 # link pool back to master
495 $self->pool->master($master);
501 This class defines the following methods.
505 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
506 first argument. So we need to massage the arguments a bit so that all the
507 bits get put into the correct places.
512 my ($class, $schema, $storage_type_args, @args) = @_;
523 Lazy builder for the L</master> attribute.
529 my $master = DBIx::Class::Storage::DBI->new($self->schema);
535 Lazy builder for the L</pool> attribute.
541 $self->create_pool(%{$self->pool_args});
544 =head2 _build_balancer
546 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
547 the balancer knows which pool it's balancing.
551 sub _build_balancer {
553 $self->create_balancer(
555 master=>$self->master,
556 %{$self->balancer_args},
560 =head2 _build_write_handler
562 Lazy builder for the L</write_handler> attribute. The default is to set this to
567 sub _build_write_handler {
568 return shift->master;
571 =head2 _build_read_handler
573 Lazy builder for the L</read_handler> attribute. The default is to set this to
578 sub _build_read_handler {
579 return shift->balancer;
582 =head2 around: connect_replicants
584 All calls to connect_replicants needs to have an existing $schema tacked onto
585 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
586 options merged with the master, with replicant opts having higher priority.
590 around connect_replicants => sub {
591 my ($next, $self, @args) = @_;
594 $r = [ $r ] unless reftype $r eq 'ARRAY';
596 $self->throw_exception('coderef replicant connect_info not supported')
597 if ref $r->[0] && reftype $r->[0] eq 'CODE';
599 # any connect_info options?
601 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
604 $r->[$i] = {} unless $r->[$i];
606 # merge if two hashes
607 my @hashes = @$r[$i .. $#{$r}];
609 $self->throw_exception('invalid connect_info options')
610 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
612 $self->throw_exception('too many hashrefs in connect_info')
615 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
616 my %opts = %{ $merge->merge(reverse @hashes) };
619 splice @$r, $i+1, ($#{$r} - $i), ();
621 # make sure master/replicants opts don't clash
622 my %master_opts = %{ $self->_master_connect_info_opts };
623 if (exists $opts{dbh_maker}) {
624 delete @master_opts{qw/dsn user password/};
626 delete $master_opts{dbh_maker};
629 %opts = %{ $merge->merge(\%opts, \%master_opts) };
635 $self->$next($self->schema, @args);
640 Returns an array of of all the connected storage backends. The first element
641 in the returned array is the master, and the remainings are each of the
648 return grep {defined $_ && blessed $_} (
650 values %{ $self->replicants },
654 =head2 execute_reliably ($coderef, ?@args)
656 Given a coderef, saves the current state of the L</read_handler>, forces it to
657 use reliable storage (e.g. sets it to the master), executes a coderef and then
658 restores the original state.
664 $schema->resultset('User')->create({name=>$name});
665 my $user_rs = $schema->resultset('User')->find({name=>$name});
669 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
671 Use this when you must be certain of your database state, such as when you just
672 inserted something and need to get a resultset including it, etc.
676 sub execute_reliably {
680 unless( ref $coderef eq 'CODE') {
681 $self->throw_exception('Second argument must be a coderef');
684 ## replace the current read handler for the remainder of the scope
685 local $self->{read_handler} = $self->master;
691 $self->throw_exception("coderef returned an error: $_");
695 =head2 set_reliable_storage
697 Sets the current $schema to be 'reliable', that is all queries, both read and
698 write are sent to the master
702 sub set_reliable_storage {
704 my $schema = $self->schema;
705 my $write_handler = $self->schema->storage->write_handler;
707 $schema->storage->read_handler($write_handler);
710 =head2 set_balanced_storage
712 Sets the current $schema to be use the </balancer> for all reads, while all
713 writes are sent to the master only
717 sub set_balanced_storage {
719 my $schema = $self->schema;
720 my $balanced_handler = $self->schema->storage->balancer;
722 $schema->storage->read_handler($balanced_handler);
727 Check that the master and at least one of the replicants is connected.
734 $self->master->connected &&
735 $self->pool->connected_replicants;
738 =head2 ensure_connected
740 Make sure all the storages are connected.
744 sub ensure_connected {
746 foreach my $source ($self->all_storages) {
747 $source->ensure_connected(@_);
753 Set the limit_dialect for all existing storages
759 foreach my $source ($self->all_storages) {
760 $source->limit_dialect(@_);
762 return $self->master->limit_dialect;
767 Set the quote_char for all existing storages
773 foreach my $source ($self->all_storages) {
774 $source->quote_char(@_);
776 return $self->master->quote_char;
781 Set the name_sep for all existing storages
787 foreach my $source ($self->all_storages) {
788 $source->name_sep(@_);
790 return $self->master->name_sep;
795 Set the schema object for all existing storages
801 foreach my $source ($self->all_storages) {
802 $source->set_schema(@_);
808 set a debug flag across all storages
815 foreach my $source ($self->all_storages) {
819 return $self->master->debug;
830 return $self->master->debugobj(@_);
841 return $self->master->debugfh(@_);
852 return $self->master->debugcb(@_);
857 disconnect everything
863 foreach my $source ($self->all_storages) {
864 $source->disconnect(@_);
870 set cursor class on all storages, or return master's
875 my ($self, $cursor_class) = @_;
878 $_->cursor_class($cursor_class) for $self->all_storages;
880 $self->master->cursor_class;
885 set cursor class on all storages, or return master's, alias for L</cursor_class>
891 my ($self, $cursor_class) = @_;
894 $_->cursor($cursor_class) for $self->all_storages;
896 $self->master->cursor;
901 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
902 master's current setting
910 $_->unsafe(@_) for $self->all_storages;
913 return $self->master->unsafe;
916 =head2 disable_sth_caching
918 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
919 or returns master's current setting
923 sub disable_sth_caching {
927 $_->disable_sth_caching(@_) for $self->all_storages;
930 return $self->master->disable_sth_caching;
933 =head2 lag_behind_master
935 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
940 sub lag_behind_master {
943 return max map $_->lag_behind_master, $self->replicants;
946 =head2 is_replicating
948 returns true if all replicants return true for
949 L<DBIx::Class::Storage::DBI/is_replicating>
956 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
959 =head2 connect_call_datetime_setup
961 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
965 sub connect_call_datetime_setup {
967 $_->connect_call_datetime_setup for $self->all_storages;
972 $_->_populate_dbh for $self->all_storages;
977 $_->_connect for $self->all_storages;
982 $_->_rebless for $self->all_storages;
985 sub _determine_driver {
987 $_->_determine_driver for $self->all_storages;
990 sub _driver_determined {
994 $_->_driver_determined(@_) for $self->all_storages;
997 return $self->master->_driver_determined;
1003 $_->_init for $self->all_storages;
1006 sub _run_connection_actions {
1009 $_->_run_connection_actions for $self->all_storages;
1012 sub _do_connection_actions {
1016 $_->_do_connection_actions(@_) for $self->all_storages;
1020 sub connect_call_do_sql {
1022 $_->connect_call_do_sql(@_) for $self->all_storages;
1025 sub disconnect_call_do_sql {
1027 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1030 sub _seems_connected {
1033 return min map $_->_seems_connected, $self->all_storages;
1039 return min map $_->_ping, $self->all_storages;
1042 # not using the normalized_version, because we want to preserve
1043 # version numbers much longer than the conventional xxx.yyyzzz
1044 my $numify_ver = sub {
1046 my @numparts = split /\D+/, $ver;
1047 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1049 return sprintf $format, @numparts;
1054 if (not $self->_dbh_details->{info}) {
1055 $self->_dbh_details->{info} = (
1056 reduce { $a->[0] < $b->[0] ? $a : $b }
1057 map [ $numify_ver->($_->{dbms_version}), $_ ],
1058 map $_->_server_info, $self->all_storages
1062 return $self->next::method;
1065 sub _get_server_version {
1068 return $self->_server_info->{dbms_version};
1073 Due to the fact that replicants can lag behind a master, you must take care to
1074 make sure you use one of the methods to force read queries to a master should
1075 you need realtime data integrity. For example, if you insert a row, and then
1076 immediately re-read it from the database (say, by doing $row->discard_changes)
1077 or you insert a row and then immediately build a query that expects that row
1078 to be an item, you should force the master to handle reads. Otherwise, due to
1079 the lag, there is no certainty your data will be in the expected state.
1081 For data integrity, all transactions automatically use the master storage for
1082 all read and write queries. Using a transaction is the preferred and recommended
1083 method to force the master to handle all read queries.
1085 Otherwise, you can force a single query to use the master with the 'force_pool'
1088 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1090 This attribute will safely be ignore by non replicated storages, so you can use
1091 the same code for both types of systems.
1093 Lastly, you can use the L</execute_reliably> method, which works very much like
1096 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1097 and L</set_balanced_storage>, however this operates at a global level and is not
1098 suitable if you have a shared Schema object being used by multiple processes,
1099 such as on a web application server. You can get around this limitation by
1100 using the Schema clone method.
1102 my $new_schema = $schema->clone;
1103 $new_schema->set_reliable_storage;
1105 ## $new_schema will use only the Master storage for all reads/writes while
1106 ## the $schema object will use replicated storage.
1110 John Napiorkowski <john.napiorkowski@takkle.com>
1112 Based on code originated by:
1114 Norbert Csongrádi <bert@cpan.org>
1115 Peter Siklósi <einon@einon.hu>
1119 You may distribute this code under the same terms as Perl itself.
1123 __PACKAGE__->meta->make_immutable;