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
317 _straight_join_to_node
320 _default_dbi_connect_attributes
322 _dbic_connect_attributes
326 bind_attribute_by_data_type
335 _per_row_update_delete
337 _dbh_execute_inserts_with_no_binds
338 _select_args_to_query
340 _multipk_update_delete
341 source_bind_attributes
342 _normalize_connect_info
347 _sqlt_minimum_version
356 _adjust_select_args_for_complex_prefetch
357 _resolve_ident_sources
360 _strip_cond_qualifiers
362 _resolve_aliastypes_from_select_args
367 _prefetch_insert_auto_nextvals
371 my @unimplemented = qw(
372 _arm_global_destructor
373 _preserve_foreign_dbh
377 get_use_dbms_capability
378 set_use_dbms_capability
384 _use_insert_returning
385 _supports_insert_returning
388 _supports_placeholders
389 _determine_supports_placeholders
391 _use_typeless_placeholders
392 _supports_typeless_placeholders
393 _determine_supports_typeless_placeholders
396 for my $method (@unimplemented) {
397 __PACKAGE__->meta->add_method($method, sub {
398 croak "$method must not be called on ".(blessed shift).' objects';
402 has _master_connect_info_opts =>
403 (is => 'rw', isa => HashRef, default => sub { {} });
405 =head2 around: connect_info
407 Preserves master's C<connect_info> options (for merging with replicants.)
408 Also sets any Replicated-related options from connect_info, such as
409 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
413 around connect_info => sub {
414 my ($next, $self, $info, @extra) = @_;
416 my $wantarray = wantarray;
418 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
421 for my $arg (@$info) {
422 next unless (reftype($arg)||'') eq 'HASH';
423 %opts = %{ $merge->merge($arg, \%opts) };
427 if (@opts{qw/pool_type pool_args/}) {
428 $self->pool_type(delete $opts{pool_type})
432 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
435 $self->pool($self->_build_pool)
439 if (@opts{qw/balancer_type balancer_args/}) {
440 $self->balancer_type(delete $opts{balancer_type})
441 if $opts{balancer_type};
443 $self->balancer_args(
444 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
447 $self->balancer($self->_build_balancer)
451 $self->_master_connect_info_opts(\%opts);
455 @res = $self->$next($info, @extra);
457 $res = $self->$next($info, @extra);
460 # Make sure master is blessed into the correct class and apply role to it.
461 my $master = $self->master;
462 $master->_determine_driver;
463 Moose::Meta::Class->initialize(ref $master);
465 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
467 # link pool back to master
468 $self->pool->master($master);
470 $wantarray ? @res : $res;
475 This class defines the following methods.
479 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
480 first argument. So we need to massage the arguments a bit so that all the
481 bits get put into the correct places.
486 my ($class, $schema, $storage_type_args, @args) = @_;
497 Lazy builder for the L</master> attribute.
503 my $master = DBIx::Class::Storage::DBI->new($self->schema);
509 Lazy builder for the L</pool> attribute.
515 $self->create_pool(%{$self->pool_args});
518 =head2 _build_balancer
520 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
521 the balancer knows which pool it's balancing.
525 sub _build_balancer {
527 $self->create_balancer(
529 master=>$self->master,
530 %{$self->balancer_args},
534 =head2 _build_write_handler
536 Lazy builder for the L</write_handler> attribute. The default is to set this to
541 sub _build_write_handler {
542 return shift->master;
545 =head2 _build_read_handler
547 Lazy builder for the L</read_handler> attribute. The default is to set this to
552 sub _build_read_handler {
553 return shift->balancer;
556 =head2 around: connect_replicants
558 All calls to connect_replicants needs to have an existing $schema tacked onto
559 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
560 options merged with the master, with replicant opts having higher priority.
564 around connect_replicants => sub {
565 my ($next, $self, @args) = @_;
568 $r = [ $r ] unless reftype $r eq 'ARRAY';
570 $self->throw_exception('coderef replicant connect_info not supported')
571 if ref $r->[0] && reftype $r->[0] eq 'CODE';
573 # any connect_info options?
575 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
578 $r->[$i] = {} unless $r->[$i];
580 # merge if two hashes
581 my @hashes = @$r[$i .. $#{$r}];
583 $self->throw_exception('invalid connect_info options')
584 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
586 $self->throw_exception('too many hashrefs in connect_info')
589 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
590 my %opts = %{ $merge->merge(reverse @hashes) };
593 splice @$r, $i+1, ($#{$r} - $i), ();
595 # make sure master/replicants opts don't clash
596 my %master_opts = %{ $self->_master_connect_info_opts };
597 if (exists $opts{dbh_maker}) {
598 delete @master_opts{qw/dsn user password/};
600 delete $master_opts{dbh_maker};
603 %opts = %{ $merge->merge(\%opts, \%master_opts) };
609 $self->$next($self->schema, @args);
614 Returns an array of of all the connected storage backends. The first element
615 in the returned array is the master, and the remainings are each of the
622 return grep {defined $_ && blessed $_} (
624 values %{ $self->replicants },
628 =head2 execute_reliably ($coderef, ?@args)
630 Given a coderef, saves the current state of the L</read_handler>, forces it to
631 use reliable storage (e.g. sets it to the master), executes a coderef and then
632 restores the original state.
638 $schema->resultset('User')->create({name=>$name});
639 my $user_rs = $schema->resultset('User')->find({name=>$name});
643 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
645 Use this when you must be certain of your database state, such as when you just
646 inserted something and need to get a resultset including it, etc.
650 sub execute_reliably {
651 my ($self, $coderef, @args) = @_;
653 unless( ref $coderef eq 'CODE') {
654 $self->throw_exception('Second argument must be a coderef');
657 ##Get copy of master storage
658 my $master = $self->master;
660 ##Get whatever the current read hander is
661 my $current = $self->read_handler;
663 ##Set the read handler to master
664 $self->read_handler($master);
666 ## do whatever the caller needs
668 my $want_array = wantarray;
672 @result = $coderef->(@args);
673 } elsif(defined $want_array) {
674 ($result[0]) = ($coderef->(@args));
679 $self->throw_exception("coderef returned an error: $_");
681 ##Reset to the original state
682 $self->read_handler($current);
685 return $want_array ? @result : $result[0];
688 =head2 set_reliable_storage
690 Sets the current $schema to be 'reliable', that is all queries, both read and
691 write are sent to the master
695 sub set_reliable_storage {
697 my $schema = $self->schema;
698 my $write_handler = $self->schema->storage->write_handler;
700 $schema->storage->read_handler($write_handler);
703 =head2 set_balanced_storage
705 Sets the current $schema to be use the </balancer> for all reads, while all
706 writes are sent to the master only
710 sub set_balanced_storage {
712 my $schema = $self->schema;
713 my $balanced_handler = $self->schema->storage->balancer;
715 $schema->storage->read_handler($balanced_handler);
720 Check that the master and at least one of the replicants is connected.
727 $self->master->connected &&
728 $self->pool->connected_replicants;
731 =head2 ensure_connected
733 Make sure all the storages are connected.
737 sub ensure_connected {
739 foreach my $source ($self->all_storages) {
740 $source->ensure_connected(@_);
746 Set the limit_dialect for all existing storages
752 foreach my $source ($self->all_storages) {
753 $source->limit_dialect(@_);
755 return $self->master->quote_char;
760 Set the quote_char for all existing storages
766 foreach my $source ($self->all_storages) {
767 $source->quote_char(@_);
769 return $self->master->quote_char;
774 Set the name_sep for all existing storages
780 foreach my $source ($self->all_storages) {
781 $source->name_sep(@_);
783 return $self->master->name_sep;
788 Set the schema object for all existing storages
794 foreach my $source ($self->all_storages) {
795 $source->set_schema(@_);
801 set a debug flag across all storages
808 foreach my $source ($self->all_storages) {
812 return $self->master->debug;
823 return $self->master->debugobj(@_);
834 return $self->master->debugfh(@_);
845 return $self->master->debugcb(@_);
850 disconnect everything
856 foreach my $source ($self->all_storages) {
857 $source->disconnect(@_);
863 set cursor class on all storages, or return master's
868 my ($self, $cursor_class) = @_;
871 $_->cursor_class($cursor_class) for $self->all_storages;
873 $self->master->cursor_class;
878 set cursor class on all storages, or return master's, alias for L</cursor_class>
884 my ($self, $cursor_class) = @_;
887 $_->cursor($cursor_class) for $self->all_storages;
889 $self->master->cursor;
894 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
895 master's current setting
903 $_->unsafe(@_) for $self->all_storages;
906 return $self->master->unsafe;
909 =head2 disable_sth_caching
911 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
912 or returns master's current setting
916 sub disable_sth_caching {
920 $_->disable_sth_caching(@_) for $self->all_storages;
923 return $self->master->disable_sth_caching;
926 =head2 lag_behind_master
928 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
933 sub lag_behind_master {
936 return max map $_->lag_behind_master, $self->replicants;
939 =head2 is_replicating
941 returns true if all replicants return true for
942 L<DBIx::Class::Storage::DBI/is_replicating>
949 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
952 =head2 connect_call_datetime_setup
954 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
958 sub connect_call_datetime_setup {
960 $_->connect_call_datetime_setup for $self->all_storages;
965 $_->_populate_dbh for $self->all_storages;
970 $_->_connect for $self->all_storages;
975 $_->_rebless for $self->all_storages;
978 sub _determine_driver {
980 $_->_determine_driver for $self->all_storages;
983 sub _driver_determined {
987 $_->_driver_determined(@_) for $self->all_storages;
990 return $self->master->_driver_determined;
996 $_->_init for $self->all_storages;
999 sub _run_connection_actions {
1002 $_->_run_connection_actions for $self->all_storages;
1005 sub _do_connection_actions {
1009 $_->_do_connection_actions(@_) for $self->all_storages;
1013 sub connect_call_do_sql {
1015 $_->connect_call_do_sql(@_) for $self->all_storages;
1018 sub disconnect_call_do_sql {
1020 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1023 sub _seems_connected {
1026 return min map $_->_seems_connected, $self->all_storages;
1032 return min map $_->_ping, $self->all_storages;
1035 # not using the normalized_version, because we want to preserve
1036 # version numbers much longer than the conventional xxx.yyyzzz
1037 my $numify_ver = sub {
1039 my @numparts = split /\D+/, $ver;
1040 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1042 return sprintf $format, @numparts;
1047 if (not $self->_dbh_details->{info}) {
1048 $self->_dbh_details->{info} = (
1049 reduce { $a->[0] < $b->[0] ? $a : $b }
1050 map [ $numify_ver->($_->{dbms_version}), $_ ],
1051 map $_->_server_info, $self->all_storages
1055 return $self->next::method;
1058 sub _get_server_version {
1061 return $self->_server_info->{dbms_version};
1066 Due to the fact that replicants can lag behind a master, you must take care to
1067 make sure you use one of the methods to force read queries to a master should
1068 you need realtime data integrity. For example, if you insert a row, and then
1069 immediately re-read it from the database (say, by doing $row->discard_changes)
1070 or you insert a row and then immediately build a query that expects that row
1071 to be an item, you should force the master to handle reads. Otherwise, due to
1072 the lag, there is no certainty your data will be in the expected state.
1074 For data integrity, all transactions automatically use the master storage for
1075 all read and write queries. Using a transaction is the preferred and recommended
1076 method to force the master to handle all read queries.
1078 Otherwise, you can force a single query to use the master with the 'force_pool'
1081 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1083 This attribute will safely be ignore by non replicated storages, so you can use
1084 the same code for both types of systems.
1086 Lastly, you can use the L</execute_reliably> method, which works very much like
1089 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1090 and L</set_balanced_storage>, however this operates at a global level and is not
1091 suitable if you have a shared Schema object being used by multiple processes,
1092 such as on a web application server. You can get around this limitation by
1093 using the Schema clone method.
1095 my $new_schema = $schema->clone;
1096 $new_schema->set_reliable_storage;
1098 ## $new_schema will use only the Master storage for all reads/writes while
1099 ## the $schema object will use replicated storage.
1103 John Napiorkowski <john.napiorkowski@takkle.com>
1105 Based on code originated by:
1107 Norbert Csongrádi <bert@cpan.org>
1108 Peter Siklósi <einon@einon.hu>
1112 You may distribute this code under the same terms as Perl itself.
1116 __PACKAGE__->meta->make_immutable;