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/;
20 use namespace::clean -except => 'meta';
24 DBIx::Class::Storage::DBI::Replicated - BETA Replicated database support
28 The Following example shows how to change an existing $schema to a replicated
29 storage type, add some replicated (read-only) databases, and perform reporting
32 You should set the 'storage_type attribute to a replicated type. You should
33 also define your arguments, such as which balancer you want and any arguments
34 that the Pool object should get.
36 my $schema = Schema::Class->clone;
37 $schema->storage_type( ['::DBI::Replicated', {balancer=>'::Random'}] );
38 $schema->connection(...);
40 Next, you need to add in the Replicants. Basically this is an array of
41 arrayrefs, where each arrayref is database connect information. Think of these
42 arguments as what you'd pass to the 'normal' $schema->connect method.
44 $schema->storage->connect_replicants(
45 [$dsn1, $user, $pass, \%opts],
46 [$dsn2, $user, $pass, \%opts],
47 [$dsn3, $user, $pass, \%opts],
50 Now, just use the $schema as you normally would. Automatically all reads will
51 be delegated to the replicants, while writes to the master.
53 $schema->resultset('Source')->search({name=>'etc'});
55 You can force a given query to use a particular storage using the search
56 attribute 'force_pool'. For example:
58 my $RS = $schema->resultset('Source')->search(undef, {force_pool=>'master'});
60 Now $RS will force everything (both reads and writes) to use whatever was setup
61 as the master storage. 'master' is hardcoded to always point to the Master,
62 but you can also use any Replicant name. Please see:
63 L<DBIx::Class::Storage::DBI::Replicated::Pool> and the replicants attribute for more.
65 Also see transactions and L</execute_reliably> for alternative ways to
66 force read traffic to the master. In general, you should wrap your statements
67 in a transaction when you are reading and writing to the same tables at the
68 same time, since your replicants will often lag a bit behind the master.
70 See L<DBIx::Class::Storage::DBI::Replicated::Instructions> for more help and
75 Warning: This class is marked BETA. This has been running a production
76 website using MySQL native replication as its backend and we have some decent
77 test coverage but the code hasn't yet been stressed by a variety of databases.
78 Individual DBs may have quirks we are not aware of. Please use this in first
79 development and pass along your experiences/bug fixes.
81 This class implements replicated data store for DBI. Currently you can define
82 one master and numerous slave database connections. All write-type queries
83 (INSERT, UPDATE, DELETE and even LAST_INSERT_ID) are routed to master
84 database, all read-type queries (SELECTs) go to the slave database.
86 Basically, any method request that L<DBIx::Class::Storage::DBI> would normally
87 handle gets delegated to one of the two attributes: L</read_handler> or to
88 L</write_handler>. Additionally, some methods need to be distributed
89 to all existing storages. This way our storage class is a drop in replacement
90 for L<DBIx::Class::Storage::DBI>.
92 Read traffic is spread across the replicants (slaves) occurring to a user
93 selected algorithm. The default algorithm is random weighted.
97 The consistency between master and replicants is database specific. The Pool
98 gives you a method to validate its replicants, removing and replacing them
99 when they fail/pass predefined criteria. Please make careful use of the ways
100 to force a query to run against Master when needed.
104 Replicated Storage has additional requirements not currently part of
105 L<DBIx::Class>. See L<DBIx::Class::Optional::Dependencies> for more details.
109 This class defines the following attributes.
113 The underlying L<DBIx::Class::Schema> object this storage is attaching
126 Contains the classname which will instantiate the L</pool> object. Defaults
127 to: L<DBIx::Class::Storage::DBI::Replicated::Pool>.
134 default=>'DBIx::Class::Storage::DBI::Replicated::Pool',
136 'create_pool' => 'new',
142 Contains a hashref of initialized information to pass to the Balancer object.
143 See L<DBIx::Class::Storage::DBI::Replicated::Pool> for available arguments.
157 The replication pool requires a balance class to provider the methods for
158 choose how to spread the query load across each replicant in the pool.
162 has 'balancer_type' => (
164 isa=>BalancerClassNamePart,
167 default=> 'DBIx::Class::Storage::DBI::Replicated::Balancer::First',
169 'create_balancer' => 'new',
175 Contains a hashref of initialized information to pass to the Balancer object.
176 See L<DBIx::Class::Storage::DBI::Replicated::Balancer> for available arguments.
180 has 'balancer_args' => (
190 Is a <DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a
191 container class for one or more replicated databases.
197 isa=>'DBIx::Class::Storage::DBI::Replicated::Pool',
208 Is a <DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This
209 is a class that takes a pool (<DBIx::Class::Storage::DBI::Replicated::Pool>)
215 isa=>'DBIx::Class::Storage::DBI::Replicated::Balancer',
217 handles=>[qw/auto_validate_every/],
222 The master defines the canonical state for a pool of connected databases. All
223 the replicants are expected to match this databases state. Thus, in a classic
224 Master / Slaves distributed system, all the slaves are expected to replicate
225 the Master's state as quick as possible. This is the only database in the
226 pool of databases that is allowed to handle write traffic.
236 =head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE
238 The following methods are delegated all the methods required for the
239 L<DBIx::Class::Storage::DBI> interface.
243 Defines an object that implements the read side of L<BIx::Class::Storage::DBI>.
247 has 'read_handler' => (
255 _dbh_columns_info_for
262 Defines an object that implements the write side of L<BIx::Class::Storage::DBI>,
263 as well as methods that don't write or read that can be called on only one
264 storage, methods that return a C<$dbh>, and any methods that don't make sense to
269 has 'write_handler' => (
284 deployment_statements
287 build_datetime_parser
301 with_deferred_fk_checks
304 with_deferred_fk_checks
309 _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
348 _sqlt_minimum_version
351 _typeless_placeholders_supported
358 _adjust_select_args_for_complex_prefetch
359 _resolve_ident_sources
362 _strip_cond_qualifiers
364 _resolve_aliastypes_from_select_args
369 _prefetch_insert_auto_nextvals
375 has _master_connect_info_opts =>
376 (is => 'rw', isa => HashRef, default => sub { {} });
378 =head2 around: connect_info
380 Preserves master's C<connect_info> options (for merging with replicants.)
381 Also sets any Replicated-related options from connect_info, such as
382 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
386 around connect_info => sub {
387 my ($next, $self, $info, @extra) = @_;
389 my $wantarray = wantarray;
391 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
394 for my $arg (@$info) {
395 next unless (reftype($arg)||'') eq 'HASH';
396 %opts = %{ $merge->merge($arg, \%opts) };
400 if (@opts{qw/pool_type pool_args/}) {
401 $self->pool_type(delete $opts{pool_type})
405 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
408 $self->pool($self->_build_pool)
412 if (@opts{qw/balancer_type balancer_args/}) {
413 $self->balancer_type(delete $opts{balancer_type})
414 if $opts{balancer_type};
416 $self->balancer_args(
417 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
420 $self->balancer($self->_build_balancer)
424 $self->_master_connect_info_opts(\%opts);
428 @res = $self->$next($info, @extra);
430 $res = $self->$next($info, @extra);
433 # Make sure master is blessed into the correct class and apply role to it.
434 my $master = $self->master;
435 $master->_determine_driver;
436 Moose::Meta::Class->initialize(ref $master);
438 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
440 # link pool back to master
441 $self->pool->master($master);
443 $wantarray ? @res : $res;
448 This class defines the following methods.
452 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
453 first argument. So we need to massage the arguments a bit so that all the
454 bits get put into the correct places.
459 my ($class, $schema, $storage_type_args, @args) = @_;
470 Lazy builder for the L</master> attribute.
476 my $master = DBIx::Class::Storage::DBI->new($self->schema);
482 Lazy builder for the L</pool> attribute.
488 $self->create_pool(%{$self->pool_args});
491 =head2 _build_balancer
493 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
494 the balancer knows which pool it's balancing.
498 sub _build_balancer {
500 $self->create_balancer(
502 master=>$self->master,
503 %{$self->balancer_args},
507 =head2 _build_write_handler
509 Lazy builder for the L</write_handler> attribute. The default is to set this to
514 sub _build_write_handler {
515 return shift->master;
518 =head2 _build_read_handler
520 Lazy builder for the L</read_handler> attribute. The default is to set this to
525 sub _build_read_handler {
526 return shift->balancer;
529 =head2 around: connect_replicants
531 All calls to connect_replicants needs to have an existing $schema tacked onto
532 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
533 options merged with the master, with replicant opts having higher priority.
537 around connect_replicants => sub {
538 my ($next, $self, @args) = @_;
541 $r = [ $r ] unless reftype $r eq 'ARRAY';
543 $self->throw_exception('coderef replicant connect_info not supported')
544 if ref $r->[0] && reftype $r->[0] eq 'CODE';
546 # any connect_info options?
548 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
551 $r->[$i] = {} unless $r->[$i];
553 # merge if two hashes
554 my @hashes = @$r[$i .. $#{$r}];
556 $self->throw_exception('invalid connect_info options')
557 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
559 $self->throw_exception('too many hashrefs in connect_info')
562 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
563 my %opts = %{ $merge->merge(reverse @hashes) };
566 splice @$r, $i+1, ($#{$r} - $i), ();
568 # make sure master/replicants opts don't clash
569 my %master_opts = %{ $self->_master_connect_info_opts };
570 if (exists $opts{dbh_maker}) {
571 delete @master_opts{qw/dsn user password/};
573 delete $master_opts{dbh_maker};
576 %opts = %{ $merge->merge(\%opts, \%master_opts) };
582 $self->$next($self->schema, @args);
587 Returns an array of of all the connected storage backends. The first element
588 in the returned array is the master, and the remainings are each of the
595 return grep {defined $_ && blessed $_} (
597 values %{ $self->replicants },
601 =head2 execute_reliably ($coderef, ?@args)
603 Given a coderef, saves the current state of the L</read_handler>, forces it to
604 use reliable storage (e.g. sets it to the master), executes a coderef and then
605 restores the original state.
611 $schema->resultset('User')->create({name=>$name});
612 my $user_rs = $schema->resultset('User')->find({name=>$name});
616 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
618 Use this when you must be certain of your database state, such as when you just
619 inserted something and need to get a resultset including it, etc.
623 sub execute_reliably {
624 my ($self, $coderef, @args) = @_;
626 unless( ref $coderef eq 'CODE') {
627 $self->throw_exception('Second argument must be a coderef');
630 ##Get copy of master storage
631 my $master = $self->master;
633 ##Get whatever the current read hander is
634 my $current = $self->read_handler;
636 ##Set the read handler to master
637 $self->read_handler($master);
639 ## do whatever the caller needs
641 my $want_array = wantarray;
645 @result = $coderef->(@args);
646 } elsif(defined $want_array) {
647 ($result[0]) = ($coderef->(@args));
653 ##Reset to the original state
654 $self->read_handler($current);
656 ##Exception testing has to come last, otherwise you might leave the
657 ##read_handler set to master.
660 $self->throw_exception("coderef returned an error: $@");
662 return $want_array ? @result : $result[0];
666 =head2 set_reliable_storage
668 Sets the current $schema to be 'reliable', that is all queries, both read and
669 write are sent to the master
673 sub set_reliable_storage {
675 my $schema = $self->schema;
676 my $write_handler = $self->schema->storage->write_handler;
678 $schema->storage->read_handler($write_handler);
681 =head2 set_balanced_storage
683 Sets the current $schema to be use the </balancer> for all reads, while all
684 writes are sent to the master only
688 sub set_balanced_storage {
690 my $schema = $self->schema;
691 my $balanced_handler = $self->schema->storage->balancer;
693 $schema->storage->read_handler($balanced_handler);
698 Check that the master and at least one of the replicants is connected.
705 $self->master->connected &&
706 $self->pool->connected_replicants;
709 =head2 ensure_connected
711 Make sure all the storages are connected.
715 sub ensure_connected {
717 foreach my $source ($self->all_storages) {
718 $source->ensure_connected(@_);
724 Set the limit_dialect for all existing storages
730 foreach my $source ($self->all_storages) {
731 $source->limit_dialect(@_);
733 return $self->master->quote_char;
738 Set the quote_char for all existing storages
744 foreach my $source ($self->all_storages) {
745 $source->quote_char(@_);
747 return $self->master->quote_char;
752 Set the name_sep for all existing storages
758 foreach my $source ($self->all_storages) {
759 $source->name_sep(@_);
761 return $self->master->name_sep;
766 Set the schema object for all existing storages
772 foreach my $source ($self->all_storages) {
773 $source->set_schema(@_);
779 set a debug flag across all storages
786 foreach my $source ($self->all_storages) {
790 return $self->master->debug;
801 return $self->master->debugobj(@_);
812 return $self->master->debugfh(@_);
823 return $self->master->debugcb(@_);
828 disconnect everything
834 foreach my $source ($self->all_storages) {
835 $source->disconnect(@_);
841 set cursor class on all storages, or return master's
846 my ($self, $cursor_class) = @_;
849 $_->cursor_class($cursor_class) for $self->all_storages;
851 $self->master->cursor_class;
856 set cursor class on all storages, or return master's, alias for L</cursor_class>
862 my ($self, $cursor_class) = @_;
865 $_->cursor($cursor_class) for $self->all_storages;
867 $self->master->cursor;
872 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
873 master's current setting
881 $_->unsafe(@_) for $self->all_storages;
884 return $self->master->unsafe;
887 =head2 disable_sth_caching
889 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
890 or returns master's current setting
894 sub disable_sth_caching {
898 $_->disable_sth_caching(@_) for $self->all_storages;
901 return $self->master->disable_sth_caching;
904 =head2 lag_behind_master
906 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
911 sub lag_behind_master {
914 return max map $_->lag_behind_master, $self->replicants;
917 =head2 is_replicating
919 returns true if all replicants return true for
920 L<DBIx::Class::Storage::DBI/is_replicating>
927 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
930 =head2 connect_call_datetime_setup
932 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
936 sub connect_call_datetime_setup {
938 $_->connect_call_datetime_setup for $self->all_storages;
943 $_->_populate_dbh for $self->all_storages;
948 $_->_connect for $self->all_storages;
953 $_->_rebless for $self->all_storages;
956 sub _determine_driver {
958 $_->_determine_driver for $self->all_storages;
961 sub _driver_determined {
965 $_->_driver_determined(@_) for $self->all_storages;
968 return $self->master->_driver_determined;
974 $_->_init for $self->all_storages;
977 sub _run_connection_actions {
980 $_->_run_connection_actions for $self->all_storages;
983 sub _do_connection_actions {
987 $_->_do_connection_actions(@_) for $self->all_storages;
991 sub connect_call_do_sql {
993 $_->connect_call_do_sql(@_) for $self->all_storages;
996 sub disconnect_call_do_sql {
998 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1001 sub _seems_connected {
1004 return min map $_->_seems_connected, $self->all_storages;
1010 return min map $_->_ping, $self->all_storages;
1016 if (not $self->_server_info_hash) {
1017 no warnings 'numeric'; # in case dbms_version doesn't normalize
1021 sort { $a->[0] <=> $b->[0] }
1022 map [ (defined $_->{normalized_dbms_version} ? $_->{normalized_dbms_version}
1023 : $_->{dbms_version}), $_ ],
1024 map $_->_server_info, $self->all_storages;
1026 my $min_version_info = $infos[0];
1028 $self->_server_info_hash($min_version_info); # on master
1031 return $self->_server_info_hash;
1034 sub _get_server_version {
1037 return $self->_server_info->{dbms_version};
1042 Due to the fact that replicants can lag behind a master, you must take care to
1043 make sure you use one of the methods to force read queries to a master should
1044 you need realtime data integrity. For example, if you insert a row, and then
1045 immediately re-read it from the database (say, by doing $row->discard_changes)
1046 or you insert a row and then immediately build a query that expects that row
1047 to be an item, you should force the master to handle reads. Otherwise, due to
1048 the lag, there is no certainty your data will be in the expected state.
1050 For data integrity, all transactions automatically use the master storage for
1051 all read and write queries. Using a transaction is the preferred and recommended
1052 method to force the master to handle all read queries.
1054 Otherwise, you can force a single query to use the master with the 'force_pool'
1057 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1059 This attribute will safely be ignore by non replicated storages, so you can use
1060 the same code for both types of systems.
1062 Lastly, you can use the L</execute_reliably> method, which works very much like
1065 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1066 and L</set_balanced_storage>, however this operates at a global level and is not
1067 suitable if you have a shared Schema object being used by multiple processes,
1068 such as on a web application server. You can get around this limitation by
1069 using the Schema clone method.
1071 my $new_schema = $schema->clone;
1072 $new_schema->set_reliable_storage;
1074 ## $new_schema will use only the Master storage for all reads/writes while
1075 ## the $schema object will use replicated storage.
1079 John Napiorkowski <john.napiorkowski@takkle.com>
1081 Based on code originated by:
1083 Norbert Csongrádi <bert@cpan.org>
1084 Peter Siklósi <einon@einon.hu>
1088 You may distribute this code under the same terms as Perl itself.
1092 __PACKAGE__->meta->make_immutable;