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
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
325 /, Class::MOP::Class->initialize('DBIx::Class::Storage::DBIHacks')->get_method_list ],
330 _dbh_columns_info_for
333 unimplemented => [qw/
334 _arm_global_destructor
337 source_bind_attributes
339 get_use_dbms_capability
340 set_use_dbms_capability
361 # the capability framework
362 # not sure if CMOP->initialize does evil things to DBIC::S::DBI, fix if a problem
364 { $_ =~ /^ _ (?: use | supports | determine_supports ) _ /x }
365 ( Class::MOP::Class->initialize('DBIx::Class::Storage::DBI')->get_all_method_names )
369 if (DBIx::Class::_ENV_::DBICTEST) {
372 for my $type (keys %$method_dispatch) {
373 for (@{$method_dispatch->{$type}}) {
374 push @{$seen->{$_}}, $type;
378 if (my @dupes = grep { @{$seen->{$_}} > 1 } keys %$seen) {
380 'The following methods show up multiple times in ::Storage::DBI::Replicated handlers:',
381 (map { "$_: " . (join ', ', @{$seen->{$_}}) } sort @dupes),
386 if (my @cant = grep { ! DBIx::Class::Storage::DBI->can($_) } keys %$seen) {
388 '::Storage::DBI::Replicated specifies handling of the following *NON EXISTING* ::Storage::DBI methods:',
395 for my $method (@{$method_dispatch->{unimplemented}}) {
396 __PACKAGE__->meta->add_method($method, sub {
398 $self->throw_exception("$method must not be called on ".(blessed $self).' objects');
404 Defines an object that implements the read side of L<BIx::Class::Storage::DBI>.
408 has 'read_handler' => (
412 handles=>$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;