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/;
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 See L<DBIx::Class::Storage::DBI::Replicated::Instructions> for more help and
76 Warning: This class is marked BETA. This has been running a production
77 website using MySQL native replication as its backend and we have some decent
78 test coverage but the code hasn't yet been stressed by a variety of databases.
79 Individual DBs may have quirks we are not aware of. Please use this in first
80 development and pass along your experiences/bug fixes.
82 This class implements replicated data store for DBI. Currently you can define
83 one master and numerous slave database connections. All write-type queries
84 (INSERT, UPDATE, DELETE and even LAST_INSERT_ID) are routed to master
85 database, all read-type queries (SELECTs) go to the slave database.
87 Basically, any method request that L<DBIx::Class::Storage::DBI> would normally
88 handle gets delegated to one of the two attributes: L</read_handler> or to
89 L</write_handler>. Additionally, some methods need to be distributed
90 to all existing storages. This way our storage class is a drop in replacement
91 for L<DBIx::Class::Storage::DBI>.
93 Read traffic is spread across the replicants (slaves) occurring to a user
94 selected algorithm. The default algorithm is random weighted.
98 The consistency between master and replicants is database specific. The Pool
99 gives you a method to validate its replicants, removing and replacing them
100 when they fail/pass predefined criteria. Please make careful use of the ways
101 to force a query to run against Master when needed.
105 Replicated Storage has additional requirements not currently part of
106 L<DBIx::Class>. See L<DBIx::Class::Optional::Dependencies> for more details.
110 This class defines the following attributes.
114 The underlying L<DBIx::Class::Schema> object this storage is attaching
127 Contains the classname which will instantiate the L</pool> object. Defaults
128 to: L<DBIx::Class::Storage::DBI::Replicated::Pool>.
135 default=>'DBIx::Class::Storage::DBI::Replicated::Pool',
137 'create_pool' => 'new',
143 Contains a hashref of initialized information to pass to the Balancer object.
144 See L<DBIx::Class::Storage::DBI::Replicated::Pool> for available arguments.
158 The replication pool requires a balance class to provider the methods for
159 choose how to spread the query load across each replicant in the pool.
163 has 'balancer_type' => (
165 isa=>BalancerClassNamePart,
168 default=> 'DBIx::Class::Storage::DBI::Replicated::Balancer::First',
170 'create_balancer' => 'new',
176 Contains a hashref of initialized information to pass to the Balancer object.
177 See L<DBIx::Class::Storage::DBI::Replicated::Balancer> for available arguments.
181 has 'balancer_args' => (
191 Is a <DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a
192 container class for one or more replicated databases.
198 isa=>'DBIx::Class::Storage::DBI::Replicated::Pool',
209 Is a <DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This
210 is a class that takes a pool (<DBIx::Class::Storage::DBI::Replicated::Pool>)
216 isa=>'DBIx::Class::Storage::DBI::Replicated::Balancer',
218 handles=>[qw/auto_validate_every/],
223 The master defines the canonical state for a pool of connected databases. All
224 the replicants are expected to match this databases state. Thus, in a classic
225 Master / Slaves distributed system, all the slaves are expected to replicate
226 the Master's state as quick as possible. This is the only database in the
227 pool of databases that is allowed to handle write traffic.
237 =head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE
239 The following methods are delegated all the methods required for the
240 L<DBIx::Class::Storage::DBI> interface.
244 Defines an object that implements the read side of L<BIx::Class::Storage::DBI>.
248 has 'read_handler' => (
256 _dbh_columns_info_for
263 Defines an object that implements the write side of L<BIx::Class::Storage::DBI>,
264 as well as methods that don't write or read that can be called on only one
265 storage, methods that return a C<$dbh>, and any methods that don't make sense to
270 has 'write_handler' => (
285 deployment_statements
288 build_datetime_parser
302 with_deferred_fk_checks
305 with_deferred_fk_checks
310 _supports_insert_returning
316 relname_to_table_alias
317 _straight_join_to_node
320 _default_dbi_connect_attributes
325 bind_attribute_by_data_type
334 _per_row_update_delete
336 _dbh_execute_inserts_with_no_binds
337 _select_args_to_query
339 _multipk_update_delete
340 source_bind_attributes
341 _normalize_connect_info
345 _placeholders_supported
347 _sqlt_minimum_version
350 _typeless_placeholders_supported
357 _adjust_select_args_for_complex_prefetch
358 _resolve_ident_sources
361 _strip_cond_qualifiers
363 _resolve_aliastypes_from_select_args
368 _prefetch_insert_auto_nextvals
373 my @unimplemented = qw(
374 _arm_global_destructor
375 _preserve_foreign_dbh
380 for my $method (@unimplemented) {
381 __PACKAGE__->meta->add_method($method, sub {
382 croak "$method must not be called on ".(blessed shift).' objects';
386 has _master_connect_info_opts =>
387 (is => 'rw', isa => HashRef, default => sub { {} });
389 =head2 around: connect_info
391 Preserves master's C<connect_info> options (for merging with replicants.)
392 Also sets any Replicated-related options from connect_info, such as
393 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
397 around connect_info => sub {
398 my ($next, $self, $info, @extra) = @_;
400 my $wantarray = wantarray;
402 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
405 for my $arg (@$info) {
406 next unless (reftype($arg)||'') eq 'HASH';
407 %opts = %{ $merge->merge($arg, \%opts) };
411 if (@opts{qw/pool_type pool_args/}) {
412 $self->pool_type(delete $opts{pool_type})
416 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
419 $self->pool($self->_build_pool)
423 if (@opts{qw/balancer_type balancer_args/}) {
424 $self->balancer_type(delete $opts{balancer_type})
425 if $opts{balancer_type};
427 $self->balancer_args(
428 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
431 $self->balancer($self->_build_balancer)
435 $self->_master_connect_info_opts(\%opts);
439 @res = $self->$next($info, @extra);
441 $res = $self->$next($info, @extra);
444 # Make sure master is blessed into the correct class and apply role to it.
445 my $master = $self->master;
446 $master->_determine_driver;
447 Moose::Meta::Class->initialize(ref $master);
449 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
451 # link pool back to master
452 $self->pool->master($master);
454 $wantarray ? @res : $res;
459 This class defines the following methods.
463 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
464 first argument. So we need to massage the arguments a bit so that all the
465 bits get put into the correct places.
470 my ($class, $schema, $storage_type_args, @args) = @_;
481 Lazy builder for the L</master> attribute.
487 my $master = DBIx::Class::Storage::DBI->new($self->schema);
493 Lazy builder for the L</pool> attribute.
499 $self->create_pool(%{$self->pool_args});
502 =head2 _build_balancer
504 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
505 the balancer knows which pool it's balancing.
509 sub _build_balancer {
511 $self->create_balancer(
513 master=>$self->master,
514 %{$self->balancer_args},
518 =head2 _build_write_handler
520 Lazy builder for the L</write_handler> attribute. The default is to set this to
525 sub _build_write_handler {
526 return shift->master;
529 =head2 _build_read_handler
531 Lazy builder for the L</read_handler> attribute. The default is to set this to
536 sub _build_read_handler {
537 return shift->balancer;
540 =head2 around: connect_replicants
542 All calls to connect_replicants needs to have an existing $schema tacked onto
543 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
544 options merged with the master, with replicant opts having higher priority.
548 around connect_replicants => sub {
549 my ($next, $self, @args) = @_;
552 $r = [ $r ] unless reftype $r eq 'ARRAY';
554 $self->throw_exception('coderef replicant connect_info not supported')
555 if ref $r->[0] && reftype $r->[0] eq 'CODE';
557 # any connect_info options?
559 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
562 $r->[$i] = {} unless $r->[$i];
564 # merge if two hashes
565 my @hashes = @$r[$i .. $#{$r}];
567 $self->throw_exception('invalid connect_info options')
568 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
570 $self->throw_exception('too many hashrefs in connect_info')
573 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
574 my %opts = %{ $merge->merge(reverse @hashes) };
577 splice @$r, $i+1, ($#{$r} - $i), ();
579 # make sure master/replicants opts don't clash
580 my %master_opts = %{ $self->_master_connect_info_opts };
581 if (exists $opts{dbh_maker}) {
582 delete @master_opts{qw/dsn user password/};
584 delete $master_opts{dbh_maker};
587 %opts = %{ $merge->merge(\%opts, \%master_opts) };
593 $self->$next($self->schema, @args);
598 Returns an array of of all the connected storage backends. The first element
599 in the returned array is the master, and the remainings are each of the
606 return grep {defined $_ && blessed $_} (
608 values %{ $self->replicants },
612 =head2 execute_reliably ($coderef, ?@args)
614 Given a coderef, saves the current state of the L</read_handler>, forces it to
615 use reliable storage (e.g. sets it to the master), executes a coderef and then
616 restores the original state.
622 $schema->resultset('User')->create({name=>$name});
623 my $user_rs = $schema->resultset('User')->find({name=>$name});
627 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
629 Use this when you must be certain of your database state, such as when you just
630 inserted something and need to get a resultset including it, etc.
634 sub execute_reliably {
635 my ($self, $coderef, @args) = @_;
637 unless( ref $coderef eq 'CODE') {
638 $self->throw_exception('Second argument must be a coderef');
641 ##Get copy of master storage
642 my $master = $self->master;
644 ##Get whatever the current read hander is
645 my $current = $self->read_handler;
647 ##Set the read handler to master
648 $self->read_handler($master);
650 ## do whatever the caller needs
652 my $want_array = wantarray;
656 @result = $coderef->(@args);
657 } elsif(defined $want_array) {
658 ($result[0]) = ($coderef->(@args));
663 $self->throw_exception("coderef returned an error: $_");
665 ##Reset to the original state
666 $self->read_handler($current);
669 return $want_array ? @result : $result[0];
672 =head2 set_reliable_storage
674 Sets the current $schema to be 'reliable', that is all queries, both read and
675 write are sent to the master
679 sub set_reliable_storage {
681 my $schema = $self->schema;
682 my $write_handler = $self->schema->storage->write_handler;
684 $schema->storage->read_handler($write_handler);
687 =head2 set_balanced_storage
689 Sets the current $schema to be use the </balancer> for all reads, while all
690 writes are sent to the master only
694 sub set_balanced_storage {
696 my $schema = $self->schema;
697 my $balanced_handler = $self->schema->storage->balancer;
699 $schema->storage->read_handler($balanced_handler);
704 Check that the master and at least one of the replicants is connected.
711 $self->master->connected &&
712 $self->pool->connected_replicants;
715 =head2 ensure_connected
717 Make sure all the storages are connected.
721 sub ensure_connected {
723 foreach my $source ($self->all_storages) {
724 $source->ensure_connected(@_);
730 Set the limit_dialect for all existing storages
736 foreach my $source ($self->all_storages) {
737 $source->limit_dialect(@_);
739 return $self->master->quote_char;
744 Set the quote_char for all existing storages
750 foreach my $source ($self->all_storages) {
751 $source->quote_char(@_);
753 return $self->master->quote_char;
758 Set the name_sep for all existing storages
764 foreach my $source ($self->all_storages) {
765 $source->name_sep(@_);
767 return $self->master->name_sep;
772 Set the schema object for all existing storages
778 foreach my $source ($self->all_storages) {
779 $source->set_schema(@_);
785 set a debug flag across all storages
792 foreach my $source ($self->all_storages) {
796 return $self->master->debug;
807 return $self->master->debugobj(@_);
818 return $self->master->debugfh(@_);
829 return $self->master->debugcb(@_);
834 disconnect everything
840 foreach my $source ($self->all_storages) {
841 $source->disconnect(@_);
847 set cursor class on all storages, or return master's
852 my ($self, $cursor_class) = @_;
855 $_->cursor_class($cursor_class) for $self->all_storages;
857 $self->master->cursor_class;
862 set cursor class on all storages, or return master's, alias for L</cursor_class>
868 my ($self, $cursor_class) = @_;
871 $_->cursor($cursor_class) for $self->all_storages;
873 $self->master->cursor;
878 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
879 master's current setting
887 $_->unsafe(@_) for $self->all_storages;
890 return $self->master->unsafe;
893 =head2 disable_sth_caching
895 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
896 or returns master's current setting
900 sub disable_sth_caching {
904 $_->disable_sth_caching(@_) for $self->all_storages;
907 return $self->master->disable_sth_caching;
910 =head2 lag_behind_master
912 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
917 sub lag_behind_master {
920 return max map $_->lag_behind_master, $self->replicants;
923 =head2 is_replicating
925 returns true if all replicants return true for
926 L<DBIx::Class::Storage::DBI/is_replicating>
933 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
936 =head2 connect_call_datetime_setup
938 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
942 sub connect_call_datetime_setup {
944 $_->connect_call_datetime_setup for $self->all_storages;
949 $_->_populate_dbh for $self->all_storages;
954 $_->_connect for $self->all_storages;
959 $_->_rebless for $self->all_storages;
962 sub _determine_driver {
964 $_->_determine_driver for $self->all_storages;
967 sub _driver_determined {
971 $_->_driver_determined(@_) for $self->all_storages;
974 return $self->master->_driver_determined;
980 $_->_init for $self->all_storages;
983 sub _run_connection_actions {
986 $_->_run_connection_actions for $self->all_storages;
989 sub _do_connection_actions {
993 $_->_do_connection_actions(@_) for $self->all_storages;
997 sub connect_call_do_sql {
999 $_->connect_call_do_sql(@_) for $self->all_storages;
1002 sub disconnect_call_do_sql {
1004 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1007 sub _seems_connected {
1010 return min map $_->_seems_connected, $self->all_storages;
1016 return min map $_->_ping, $self->all_storages;
1019 my $numify_ver = sub {
1021 my @numparts = split /\D+/, $ver;
1022 my $format = '%d.' . (join '', ('%05d') x (@numparts - 1));
1024 return sprintf $format, @numparts;
1030 if (not $self->_server_info_hash) {
1031 my $min_version_info = (
1032 reduce { $a->[0] < $b->[0] ? $a : $b }
1033 map [ $numify_ver->($_->{dbms_version}), $_ ],
1034 map $_->_server_info, $self->all_storages
1037 $self->_server_info_hash($min_version_info); # on master
1040 return $self->_server_info_hash;
1043 sub _get_server_version {
1046 return $self->_server_info->{dbms_version};
1051 Due to the fact that replicants can lag behind a master, you must take care to
1052 make sure you use one of the methods to force read queries to a master should
1053 you need realtime data integrity. For example, if you insert a row, and then
1054 immediately re-read it from the database (say, by doing $row->discard_changes)
1055 or you insert a row and then immediately build a query that expects that row
1056 to be an item, you should force the master to handle reads. Otherwise, due to
1057 the lag, there is no certainty your data will be in the expected state.
1059 For data integrity, all transactions automatically use the master storage for
1060 all read and write queries. Using a transaction is the preferred and recommended
1061 method to force the master to handle all read queries.
1063 Otherwise, you can force a single query to use the master with the 'force_pool'
1066 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1068 This attribute will safely be ignore by non replicated storages, so you can use
1069 the same code for both types of systems.
1071 Lastly, you can use the L</execute_reliably> method, which works very much like
1074 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1075 and L</set_balanced_storage>, however this operates at a global level and is not
1076 suitable if you have a shared Schema object being used by multiple processes,
1077 such as on a web application server. You can get around this limitation by
1078 using the Schema clone method.
1080 my $new_schema = $schema->clone;
1081 $new_schema->set_reliable_storage;
1083 ## $new_schema will use only the Master storage for all reads/writes while
1084 ## the $schema object will use replicated storage.
1088 John Napiorkowski <john.napiorkowski@takkle.com>
1090 Based on code originated by:
1092 Norbert Csongrádi <bert@cpan.org>
1093 Peter Siklósi <einon@einon.hu>
1097 You may distribute this code under the same terms as Perl itself.
1101 __PACKAGE__->meta->make_immutable;