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 If you have a multi-statement read only transaction you can force it to select
72 a random server in the pool by:
74 my $rs = $schema->resultset('Source')->search( undef,
75 { force_pool => $db->storage->read_handler->next_storage }
80 Warning: This class is marked BETA. This has been running a production
81 website using MySQL native replication as its backend and we have some decent
82 test coverage but the code hasn't yet been stressed by a variety of databases.
83 Individual DBs may have quirks we are not aware of. Please use this in first
84 development and pass along your experiences/bug fixes.
86 This class implements replicated data store for DBI. Currently you can define
87 one master and numerous slave database connections. All write-type queries
88 (INSERT, UPDATE, DELETE and even LAST_INSERT_ID) are routed to master
89 database, all read-type queries (SELECTs) go to the slave database.
91 Basically, any method request that L<DBIx::Class::Storage::DBI> would normally
92 handle gets delegated to one of the two attributes: L</read_handler> or to
93 L</write_handler>. Additionally, some methods need to be distributed
94 to all existing storages. This way our storage class is a drop in replacement
95 for L<DBIx::Class::Storage::DBI>.
97 Read traffic is spread across the replicants (slaves) occurring to a user
98 selected algorithm. The default algorithm is random weighted.
102 The consistency between master and replicants is database specific. The Pool
103 gives you a method to validate its replicants, removing and replacing them
104 when they fail/pass predefined criteria. Please make careful use of the ways
105 to force a query to run against Master when needed.
109 Replicated Storage has additional requirements not currently part of
110 L<DBIx::Class>. See L<DBIx::Class::Optional::Dependencies> for more details.
114 This class defines the following attributes.
118 The underlying L<DBIx::Class::Schema> object this storage is attaching
131 Contains the classname which will instantiate the L</pool> object. Defaults
132 to: L<DBIx::Class::Storage::DBI::Replicated::Pool>.
139 default=>'DBIx::Class::Storage::DBI::Replicated::Pool',
141 'create_pool' => 'new',
147 Contains a hashref of initialized information to pass to the Balancer object.
148 See L<DBIx::Class::Storage::DBI::Replicated::Pool> for available arguments.
162 The replication pool requires a balance class to provider the methods for
163 choose how to spread the query load across each replicant in the pool.
167 has 'balancer_type' => (
169 isa=>BalancerClassNamePart,
172 default=> 'DBIx::Class::Storage::DBI::Replicated::Balancer::First',
174 'create_balancer' => 'new',
180 Contains a hashref of initialized information to pass to the Balancer object.
181 See L<DBIx::Class::Storage::DBI::Replicated::Balancer> for available arguments.
185 has 'balancer_args' => (
195 Is a L<DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a
196 container class for one or more replicated databases.
202 isa=>'DBIx::Class::Storage::DBI::Replicated::Pool',
213 Is a L<DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This
214 is a class that takes a pool (L<DBIx::Class::Storage::DBI::Replicated::Pool>)
220 isa=>'DBIx::Class::Storage::DBI::Replicated::Balancer',
222 handles=>[qw/auto_validate_every/],
227 The master defines the canonical state for a pool of connected databases. All
228 the replicants are expected to match this databases state. Thus, in a classic
229 Master / Slaves distributed system, all the slaves are expected to replicate
230 the Master's state as quick as possible. This is the only database in the
231 pool of databases that is allowed to handle write traffic.
241 =head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE
243 The following methods are delegated all the methods required for the
244 L<DBIx::Class::Storage::DBI> interface.
248 my $method_dispatch = {
260 deployment_statements
263 build_datetime_parser
279 with_deferred_fk_checks
288 relname_to_table_alias
290 _default_dbi_connect_attributes
292 _dbic_connect_attributes
298 bind_attribute_by_data_type
302 _dbh_execute_for_fetch
304 _per_row_update_delete
305 _dbh_execute_inserts_with_no_binds
306 _select_args_to_query
309 _multipk_update_delete
310 _normalize_connect_info
324 /, Class::MOP::Class->initialize('DBIx::Class::Storage::DBIHacks')->get_method_list ],
329 _dbh_columns_info_for
332 unimplemented => [qw/
333 _arm_global_destructor
336 source_bind_attributes
338 get_use_dbms_capability
339 set_use_dbms_capability
360 # the capability framework
361 # not sure if CMOP->initialize does evil things to DBIC::S::DBI, fix if a problem
363 { $_ =~ /^ _ (?: use | supports | determine_supports ) _ /x }
364 ( Class::MOP::Class->initialize('DBIx::Class::Storage::DBI')->get_all_method_names )
368 if (DBIx::Class::_ENV_::DBICTEST) {
371 for my $type (keys %$method_dispatch) {
372 for (@{$method_dispatch->{$type}}) {
373 push @{$seen->{$_}}, $type;
377 if (my @dupes = grep { @{$seen->{$_}} > 1 } keys %$seen) {
379 'The following methods show up multiple times in ::Storage::DBI::Replicated handlers:',
380 (map { "$_: " . (join ', ', @{$seen->{$_}}) } sort @dupes),
385 if (my @cant = grep { ! DBIx::Class::Storage::DBI->can($_) } keys %$seen) {
387 '::Storage::DBI::Replicated specifies handling of the following *NON EXISTING* ::Storage::DBI methods:',
394 for my $method (@{$method_dispatch->{unimplemented}}) {
395 __PACKAGE__->meta->add_method($method, sub {
397 $self->throw_exception("$method must not be called on ".(blessed $self).' objects');
403 Defines an object that implements the read side of L<BIx::Class::Storage::DBI>.
407 has 'read_handler' => (
411 handles=>$method_dispatch->{reader},
416 Defines an object that implements the write side of L<BIx::Class::Storage::DBI>,
417 as well as methods that don't write or read that can be called on only one
418 storage, methods that return a C<$dbh>, and any methods that don't make sense to
423 has 'write_handler' => (
427 handles=>$method_dispatch->{writer},
432 has _master_connect_info_opts =>
433 (is => 'rw', isa => HashRef, default => sub { {} });
435 =head2 around: connect_info
437 Preserves master's C<connect_info> options (for merging with replicants.)
438 Also sets any Replicated-related options from connect_info, such as
439 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
443 around connect_info => sub {
444 my ($next, $self, $info, @extra) = @_;
446 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
449 for my $arg (@$info) {
450 next unless (reftype($arg)||'') eq 'HASH';
451 %opts = %{ $merge->merge($arg, \%opts) };
455 if (@opts{qw/pool_type pool_args/}) {
456 $self->pool_type(delete $opts{pool_type})
460 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
463 ## Since we possibly changed the pool_args, we need to clear the current
464 ## pool object so that next time it is used it will be rebuilt.
468 if (@opts{qw/balancer_type balancer_args/}) {
469 $self->balancer_type(delete $opts{balancer_type})
470 if $opts{balancer_type};
472 $self->balancer_args(
473 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
476 $self->balancer($self->_build_balancer)
480 $self->_master_connect_info_opts(\%opts);
484 @res = $self->$next($info, @extra);
486 $res[0] = $self->$next($info, @extra);
489 # Make sure master is blessed into the correct class and apply role to it.
490 my $master = $self->master;
491 $master->_determine_driver;
492 Moose::Meta::Class->initialize(ref $master);
494 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
496 # link pool back to master
497 $self->pool->master($master);
499 wantarray ? @res : $res[0];
504 This class defines the following methods.
508 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
509 first argument. So we need to massage the arguments a bit so that all the
510 bits get put into the correct places.
515 my ($class, $schema, $storage_type_args, @args) = @_;
526 Lazy builder for the L</master> attribute.
532 my $master = DBIx::Class::Storage::DBI->new($self->schema);
538 Lazy builder for the L</pool> attribute.
544 $self->create_pool(%{$self->pool_args});
547 =head2 _build_balancer
549 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
550 the balancer knows which pool it's balancing.
554 sub _build_balancer {
556 $self->create_balancer(
558 master=>$self->master,
559 %{$self->balancer_args},
563 =head2 _build_write_handler
565 Lazy builder for the L</write_handler> attribute. The default is to set this to
570 sub _build_write_handler {
571 return shift->master;
574 =head2 _build_read_handler
576 Lazy builder for the L</read_handler> attribute. The default is to set this to
581 sub _build_read_handler {
582 return shift->balancer;
585 =head2 around: connect_replicants
587 All calls to connect_replicants needs to have an existing $schema tacked onto
588 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
589 options merged with the master, with replicant opts having higher priority.
593 around connect_replicants => sub {
594 my ($next, $self, @args) = @_;
597 $r = [ $r ] unless reftype $r eq 'ARRAY';
599 $self->throw_exception('coderef replicant connect_info not supported')
600 if ref $r->[0] && reftype $r->[0] eq 'CODE';
602 # any connect_info options?
604 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
607 $r->[$i] = {} unless $r->[$i];
609 # merge if two hashes
610 my @hashes = @$r[$i .. $#{$r}];
612 $self->throw_exception('invalid connect_info options')
613 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
615 $self->throw_exception('too many hashrefs in connect_info')
618 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
619 my %opts = %{ $merge->merge(reverse @hashes) };
622 splice @$r, $i+1, ($#{$r} - $i), ();
624 # make sure master/replicants opts don't clash
625 my %master_opts = %{ $self->_master_connect_info_opts };
626 if (exists $opts{dbh_maker}) {
627 delete @master_opts{qw/dsn user password/};
629 delete $master_opts{dbh_maker};
632 %opts = %{ $merge->merge(\%opts, \%master_opts) };
638 $self->$next($self->schema, @args);
643 Returns an array of of all the connected storage backends. The first element
644 in the returned array is the master, and the remainings are each of the
651 return grep {defined $_ && blessed $_} (
653 values %{ $self->replicants },
657 =head2 execute_reliably ($coderef, ?@args)
659 Given a coderef, saves the current state of the L</read_handler>, forces it to
660 use reliable storage (e.g. sets it to the master), executes a coderef and then
661 restores the original state.
667 $schema->resultset('User')->create({name=>$name});
668 my $user_rs = $schema->resultset('User')->find({name=>$name});
672 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
674 Use this when you must be certain of your database state, such as when you just
675 inserted something and need to get a resultset including it, etc.
679 sub execute_reliably {
680 my ($self, $coderef, @args) = @_;
682 unless( ref $coderef eq 'CODE') {
683 $self->throw_exception('Second argument must be a coderef');
686 ##Get copy of master storage
687 my $master = $self->master;
689 ##Get whatever the current read hander is
690 my $current = $self->read_handler;
692 ##Set the read handler to master
693 $self->read_handler($master);
695 ## do whatever the caller needs
697 my $want_array = wantarray;
701 @result = $coderef->(@args);
702 } elsif(defined $want_array) {
703 ($result[0]) = ($coderef->(@args));
708 $self->throw_exception("coderef returned an error: $_");
710 ##Reset to the original state
711 $self->read_handler($current);
714 return wantarray ? @result : $result[0];
717 =head2 set_reliable_storage
719 Sets the current $schema to be 'reliable', that is all queries, both read and
720 write are sent to the master
724 sub set_reliable_storage {
726 my $schema = $self->schema;
727 my $write_handler = $self->schema->storage->write_handler;
729 $schema->storage->read_handler($write_handler);
732 =head2 set_balanced_storage
734 Sets the current $schema to be use the </balancer> for all reads, while all
735 writes are sent to the master only
739 sub set_balanced_storage {
741 my $schema = $self->schema;
742 my $balanced_handler = $self->schema->storage->balancer;
744 $schema->storage->read_handler($balanced_handler);
749 Check that the master and at least one of the replicants is connected.
756 $self->master->connected &&
757 $self->pool->connected_replicants;
760 =head2 ensure_connected
762 Make sure all the storages are connected.
766 sub ensure_connected {
768 foreach my $source ($self->all_storages) {
769 $source->ensure_connected(@_);
775 Set the limit_dialect for all existing storages
781 foreach my $source ($self->all_storages) {
782 $source->limit_dialect(@_);
784 return $self->master->limit_dialect;
789 Set the quote_char for all existing storages
795 foreach my $source ($self->all_storages) {
796 $source->quote_char(@_);
798 return $self->master->quote_char;
803 Set the name_sep for all existing storages
809 foreach my $source ($self->all_storages) {
810 $source->name_sep(@_);
812 return $self->master->name_sep;
817 Set the schema object for all existing storages
823 foreach my $source ($self->all_storages) {
824 $source->set_schema(@_);
830 set a debug flag across all storages
837 foreach my $source ($self->all_storages) {
841 return $self->master->debug;
852 return $self->master->debugobj(@_);
863 return $self->master->debugfh(@_);
874 return $self->master->debugcb(@_);
879 disconnect everything
885 foreach my $source ($self->all_storages) {
886 $source->disconnect(@_);
892 set cursor class on all storages, or return master's
897 my ($self, $cursor_class) = @_;
900 $_->cursor_class($cursor_class) for $self->all_storages;
902 $self->master->cursor_class;
907 set cursor class on all storages, or return master's, alias for L</cursor_class>
913 my ($self, $cursor_class) = @_;
916 $_->cursor($cursor_class) for $self->all_storages;
918 $self->master->cursor;
923 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
924 master's current setting
932 $_->unsafe(@_) for $self->all_storages;
935 return $self->master->unsafe;
938 =head2 disable_sth_caching
940 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
941 or returns master's current setting
945 sub disable_sth_caching {
949 $_->disable_sth_caching(@_) for $self->all_storages;
952 return $self->master->disable_sth_caching;
955 =head2 lag_behind_master
957 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
962 sub lag_behind_master {
965 return max map $_->lag_behind_master, $self->replicants;
968 =head2 is_replicating
970 returns true if all replicants return true for
971 L<DBIx::Class::Storage::DBI/is_replicating>
978 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
981 =head2 connect_call_datetime_setup
983 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
987 sub connect_call_datetime_setup {
989 $_->connect_call_datetime_setup for $self->all_storages;
994 $_->_populate_dbh for $self->all_storages;
999 $_->_connect for $self->all_storages;
1004 $_->_rebless for $self->all_storages;
1007 sub _determine_driver {
1009 $_->_determine_driver for $self->all_storages;
1012 sub _driver_determined {
1016 $_->_driver_determined(@_) for $self->all_storages;
1019 return $self->master->_driver_determined;
1025 $_->_init for $self->all_storages;
1028 sub _run_connection_actions {
1031 $_->_run_connection_actions for $self->all_storages;
1034 sub _do_connection_actions {
1038 $_->_do_connection_actions(@_) for $self->all_storages;
1042 sub connect_call_do_sql {
1044 $_->connect_call_do_sql(@_) for $self->all_storages;
1047 sub disconnect_call_do_sql {
1049 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1052 sub _seems_connected {
1055 return min map $_->_seems_connected, $self->all_storages;
1061 return min map $_->_ping, $self->all_storages;
1064 # not using the normalized_version, because we want to preserve
1065 # version numbers much longer than the conventional xxx.yyyzzz
1066 my $numify_ver = sub {
1068 my @numparts = split /\D+/, $ver;
1069 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1071 return sprintf $format, @numparts;
1076 if (not $self->_dbh_details->{info}) {
1077 $self->_dbh_details->{info} = (
1078 reduce { $a->[0] < $b->[0] ? $a : $b }
1079 map [ $numify_ver->($_->{dbms_version}), $_ ],
1080 map $_->_server_info, $self->all_storages
1084 return $self->next::method;
1087 sub _get_server_version {
1090 return $self->_server_info->{dbms_version};
1095 Due to the fact that replicants can lag behind a master, you must take care to
1096 make sure you use one of the methods to force read queries to a master should
1097 you need realtime data integrity. For example, if you insert a row, and then
1098 immediately re-read it from the database (say, by doing $row->discard_changes)
1099 or you insert a row and then immediately build a query that expects that row
1100 to be an item, you should force the master to handle reads. Otherwise, due to
1101 the lag, there is no certainty your data will be in the expected state.
1103 For data integrity, all transactions automatically use the master storage for
1104 all read and write queries. Using a transaction is the preferred and recommended
1105 method to force the master to handle all read queries.
1107 Otherwise, you can force a single query to use the master with the 'force_pool'
1110 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1112 This attribute will safely be ignore by non replicated storages, so you can use
1113 the same code for both types of systems.
1115 Lastly, you can use the L</execute_reliably> method, which works very much like
1118 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1119 and L</set_balanced_storage>, however this operates at a global level and is not
1120 suitable if you have a shared Schema object being used by multiple processes,
1121 such as on a web application server. You can get around this limitation by
1122 using the Schema clone method.
1124 my $new_schema = $schema->clone;
1125 $new_schema->set_reliable_storage;
1127 ## $new_schema will use only the Master storage for all reads/writes while
1128 ## the $schema object will use replicated storage.
1132 John Napiorkowski <john.napiorkowski@takkle.com>
1134 Based on code originated by:
1136 Norbert Csongrádi <bert@cpan.org>
1137 Peter Siklósi <einon@einon.hu>
1141 You may distribute this code under the same terms as Perl itself.
1145 __PACKAGE__->meta->make_immutable;