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 Defines an object that implements the read side of L<BIx::Class::Storage::DBI>.
249 has 'read_handler' => (
257 _dbh_columns_info_for
264 Defines an object that implements the write side of L<BIx::Class::Storage::DBI>,
265 as well as methods that don't write or read that can be called on only one
266 storage, methods that return a C<$dbh>, and any methods that don't make sense to
271 has 'write_handler' => (
286 deployment_statements
289 build_datetime_parser
303 with_deferred_fk_checks
306 with_deferred_fk_checks
316 relname_to_table_alias
319 _default_dbi_connect_attributes
321 _dbic_connect_attributes
325 bind_attribute_by_data_type
333 _per_row_update_delete
335 _dbh_execute_inserts_with_no_binds
336 _select_args_to_query
338 _multipk_update_delete
339 source_bind_attributes
340 _normalize_connect_info
345 _sqlt_minimum_version
353 _adjust_select_args_for_complex_prefetch
354 _resolve_ident_sources
357 _strip_cond_qualifiers
358 _resolve_aliastypes_from_select_args
366 my @unimplemented = qw(
367 _arm_global_destructor
370 get_use_dbms_capability
371 set_use_dbms_capability
379 _group_over_selection
381 _extract_order_criteria
386 # the capability framework
387 # not sure if CMOP->initialize does evil things to DBIC::S::DBI, fix if a problem
388 push @unimplemented, ( grep
389 { $_ =~ /^ _ (?: use | supports | determine_supports ) _ /x }
390 ( Class::MOP::Class->initialize('DBIx::Class::Storage::DBI')->get_all_method_names )
393 for my $method (@unimplemented) {
394 __PACKAGE__->meta->add_method($method, sub {
395 croak "$method must not be called on ".(blessed shift).' objects';
399 has _master_connect_info_opts =>
400 (is => 'rw', isa => HashRef, default => sub { {} });
402 =head2 around: connect_info
404 Preserves master's C<connect_info> options (for merging with replicants.)
405 Also sets any Replicated-related options from connect_info, such as
406 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
410 around connect_info => sub {
411 my ($next, $self, $info, @extra) = @_;
413 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
416 for my $arg (@$info) {
417 next unless (reftype($arg)||'') eq 'HASH';
418 %opts = %{ $merge->merge($arg, \%opts) };
422 if (@opts{qw/pool_type pool_args/}) {
423 $self->pool_type(delete $opts{pool_type})
427 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
430 ## Since we possibly changed the pool_args, we need to clear the current
431 ## pool object so that next time it is used it will be rebuilt.
435 if (@opts{qw/balancer_type balancer_args/}) {
436 $self->balancer_type(delete $opts{balancer_type})
437 if $opts{balancer_type};
439 $self->balancer_args(
440 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
443 $self->balancer($self->_build_balancer)
447 $self->_master_connect_info_opts(\%opts);
451 @res = $self->$next($info, @extra);
453 $res[0] = $self->$next($info, @extra);
456 # Make sure master is blessed into the correct class and apply role to it.
457 my $master = $self->master;
458 $master->_determine_driver;
459 Moose::Meta::Class->initialize(ref $master);
461 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
463 # link pool back to master
464 $self->pool->master($master);
466 wantarray ? @res : $res[0];
471 This class defines the following methods.
475 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
476 first argument. So we need to massage the arguments a bit so that all the
477 bits get put into the correct places.
482 my ($class, $schema, $storage_type_args, @args) = @_;
493 Lazy builder for the L</master> attribute.
499 my $master = DBIx::Class::Storage::DBI->new($self->schema);
505 Lazy builder for the L</pool> attribute.
511 $self->create_pool(%{$self->pool_args});
514 =head2 _build_balancer
516 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
517 the balancer knows which pool it's balancing.
521 sub _build_balancer {
523 $self->create_balancer(
525 master=>$self->master,
526 %{$self->balancer_args},
530 =head2 _build_write_handler
532 Lazy builder for the L</write_handler> attribute. The default is to set this to
537 sub _build_write_handler {
538 return shift->master;
541 =head2 _build_read_handler
543 Lazy builder for the L</read_handler> attribute. The default is to set this to
548 sub _build_read_handler {
549 return shift->balancer;
552 =head2 around: connect_replicants
554 All calls to connect_replicants needs to have an existing $schema tacked onto
555 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
556 options merged with the master, with replicant opts having higher priority.
560 around connect_replicants => sub {
561 my ($next, $self, @args) = @_;
564 $r = [ $r ] unless reftype $r eq 'ARRAY';
566 $self->throw_exception('coderef replicant connect_info not supported')
567 if ref $r->[0] && reftype $r->[0] eq 'CODE';
569 # any connect_info options?
571 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
574 $r->[$i] = {} unless $r->[$i];
576 # merge if two hashes
577 my @hashes = @$r[$i .. $#{$r}];
579 $self->throw_exception('invalid connect_info options')
580 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
582 $self->throw_exception('too many hashrefs in connect_info')
585 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
586 my %opts = %{ $merge->merge(reverse @hashes) };
589 splice @$r, $i+1, ($#{$r} - $i), ();
591 # make sure master/replicants opts don't clash
592 my %master_opts = %{ $self->_master_connect_info_opts };
593 if (exists $opts{dbh_maker}) {
594 delete @master_opts{qw/dsn user password/};
596 delete $master_opts{dbh_maker};
599 %opts = %{ $merge->merge(\%opts, \%master_opts) };
605 $self->$next($self->schema, @args);
610 Returns an array of of all the connected storage backends. The first element
611 in the returned array is the master, and the remainings are each of the
618 return grep {defined $_ && blessed $_} (
620 values %{ $self->replicants },
624 =head2 execute_reliably ($coderef, ?@args)
626 Given a coderef, saves the current state of the L</read_handler>, forces it to
627 use reliable storage (e.g. sets it to the master), executes a coderef and then
628 restores the original state.
634 $schema->resultset('User')->create({name=>$name});
635 my $user_rs = $schema->resultset('User')->find({name=>$name});
639 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
641 Use this when you must be certain of your database state, such as when you just
642 inserted something and need to get a resultset including it, etc.
646 sub execute_reliably {
647 my ($self, $coderef, @args) = @_;
649 unless( ref $coderef eq 'CODE') {
650 $self->throw_exception('Second argument must be a coderef');
653 ##Get copy of master storage
654 my $master = $self->master;
656 ##Get whatever the current read hander is
657 my $current = $self->read_handler;
659 ##Set the read handler to master
660 $self->read_handler($master);
662 ## do whatever the caller needs
664 my $want_array = wantarray;
668 @result = $coderef->(@args);
669 } elsif(defined $want_array) {
670 ($result[0]) = ($coderef->(@args));
675 $self->throw_exception("coderef returned an error: $_");
677 ##Reset to the original state
678 $self->read_handler($current);
681 return wantarray ? @result : $result[0];
684 =head2 set_reliable_storage
686 Sets the current $schema to be 'reliable', that is all queries, both read and
687 write are sent to the master
691 sub set_reliable_storage {
693 my $schema = $self->schema;
694 my $write_handler = $self->schema->storage->write_handler;
696 $schema->storage->read_handler($write_handler);
699 =head2 set_balanced_storage
701 Sets the current $schema to be use the </balancer> for all reads, while all
702 writes are sent to the master only
706 sub set_balanced_storage {
708 my $schema = $self->schema;
709 my $balanced_handler = $self->schema->storage->balancer;
711 $schema->storage->read_handler($balanced_handler);
716 Check that the master and at least one of the replicants is connected.
723 $self->master->connected &&
724 $self->pool->connected_replicants;
727 =head2 ensure_connected
729 Make sure all the storages are connected.
733 sub ensure_connected {
735 foreach my $source ($self->all_storages) {
736 $source->ensure_connected(@_);
742 Set the limit_dialect for all existing storages
748 foreach my $source ($self->all_storages) {
749 $source->limit_dialect(@_);
751 return $self->master->limit_dialect;
756 Set the quote_char for all existing storages
762 foreach my $source ($self->all_storages) {
763 $source->quote_char(@_);
765 return $self->master->quote_char;
770 Set the name_sep for all existing storages
776 foreach my $source ($self->all_storages) {
777 $source->name_sep(@_);
779 return $self->master->name_sep;
784 Set the schema object for all existing storages
790 foreach my $source ($self->all_storages) {
791 $source->set_schema(@_);
797 set a debug flag across all storages
804 foreach my $source ($self->all_storages) {
808 return $self->master->debug;
819 return $self->master->debugobj(@_);
830 return $self->master->debugfh(@_);
841 return $self->master->debugcb(@_);
846 disconnect everything
852 foreach my $source ($self->all_storages) {
853 $source->disconnect(@_);
859 set cursor class on all storages, or return master's
864 my ($self, $cursor_class) = @_;
867 $_->cursor_class($cursor_class) for $self->all_storages;
869 $self->master->cursor_class;
874 set cursor class on all storages, or return master's, alias for L</cursor_class>
880 my ($self, $cursor_class) = @_;
883 $_->cursor($cursor_class) for $self->all_storages;
885 $self->master->cursor;
890 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
891 master's current setting
899 $_->unsafe(@_) for $self->all_storages;
902 return $self->master->unsafe;
905 =head2 disable_sth_caching
907 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
908 or returns master's current setting
912 sub disable_sth_caching {
916 $_->disable_sth_caching(@_) for $self->all_storages;
919 return $self->master->disable_sth_caching;
922 =head2 lag_behind_master
924 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
929 sub lag_behind_master {
932 return max map $_->lag_behind_master, $self->replicants;
935 =head2 is_replicating
937 returns true if all replicants return true for
938 L<DBIx::Class::Storage::DBI/is_replicating>
945 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
948 =head2 connect_call_datetime_setup
950 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
954 sub connect_call_datetime_setup {
956 $_->connect_call_datetime_setup for $self->all_storages;
961 $_->_populate_dbh for $self->all_storages;
966 $_->_connect for $self->all_storages;
971 $_->_rebless for $self->all_storages;
974 sub _determine_driver {
976 $_->_determine_driver for $self->all_storages;
979 sub _driver_determined {
983 $_->_driver_determined(@_) for $self->all_storages;
986 return $self->master->_driver_determined;
992 $_->_init for $self->all_storages;
995 sub _run_connection_actions {
998 $_->_run_connection_actions for $self->all_storages;
1001 sub _do_connection_actions {
1005 $_->_do_connection_actions(@_) for $self->all_storages;
1009 sub connect_call_do_sql {
1011 $_->connect_call_do_sql(@_) for $self->all_storages;
1014 sub disconnect_call_do_sql {
1016 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1019 sub _seems_connected {
1022 return min map $_->_seems_connected, $self->all_storages;
1028 return min map $_->_ping, $self->all_storages;
1031 # not using the normalized_version, because we want to preserve
1032 # version numbers much longer than the conventional xxx.yyyzzz
1033 my $numify_ver = sub {
1035 my @numparts = split /\D+/, $ver;
1036 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1038 return sprintf $format, @numparts;
1043 if (not $self->_dbh_details->{info}) {
1044 $self->_dbh_details->{info} = (
1045 reduce { $a->[0] < $b->[0] ? $a : $b }
1046 map [ $numify_ver->($_->{dbms_version}), $_ ],
1047 map $_->_server_info, $self->all_storages
1051 return $self->next::method;
1054 sub _get_server_version {
1057 return $self->_server_info->{dbms_version};
1062 Due to the fact that replicants can lag behind a master, you must take care to
1063 make sure you use one of the methods to force read queries to a master should
1064 you need realtime data integrity. For example, if you insert a row, and then
1065 immediately re-read it from the database (say, by doing $row->discard_changes)
1066 or you insert a row and then immediately build a query that expects that row
1067 to be an item, you should force the master to handle reads. Otherwise, due to
1068 the lag, there is no certainty your data will be in the expected state.
1070 For data integrity, all transactions automatically use the master storage for
1071 all read and write queries. Using a transaction is the preferred and recommended
1072 method to force the master to handle all read queries.
1074 Otherwise, you can force a single query to use the master with the 'force_pool'
1077 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1079 This attribute will safely be ignore by non replicated storages, so you can use
1080 the same code for both types of systems.
1082 Lastly, you can use the L</execute_reliably> method, which works very much like
1085 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1086 and L</set_balanced_storage>, however this operates at a global level and is not
1087 suitable if you have a shared Schema object being used by multiple processes,
1088 such as on a web application server. You can get around this limitation by
1089 using the Schema clone method.
1091 my $new_schema = $schema->clone;
1092 $new_schema->set_reliable_storage;
1094 ## $new_schema will use only the Master storage for all reads/writes while
1095 ## the $schema object will use replicated storage.
1099 John Napiorkowski <john.napiorkowski@takkle.com>
1101 Based on code originated by:
1103 Norbert Csongrádi <bert@cpan.org>
1104 Peter Siklósi <einon@einon.hu>
1108 You may distribute this code under the same terms as Perl itself.
1112 __PACKAGE__->meta->make_immutable;