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/;
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
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));
664 ##Reset to the original state
665 $self->read_handler($current);
667 ##Exception testing has to come last, otherwise you might leave the
668 ##read_handler set to master.
671 $self->throw_exception("coderef returned an error: $@");
673 return $want_array ? @result : $result[0];
677 =head2 set_reliable_storage
679 Sets the current $schema to be 'reliable', that is all queries, both read and
680 write are sent to the master
684 sub set_reliable_storage {
686 my $schema = $self->schema;
687 my $write_handler = $self->schema->storage->write_handler;
689 $schema->storage->read_handler($write_handler);
692 =head2 set_balanced_storage
694 Sets the current $schema to be use the </balancer> for all reads, while all
695 writes are sent to the master only
699 sub set_balanced_storage {
701 my $schema = $self->schema;
702 my $balanced_handler = $self->schema->storage->balancer;
704 $schema->storage->read_handler($balanced_handler);
709 Check that the master and at least one of the replicants is connected.
716 $self->master->connected &&
717 $self->pool->connected_replicants;
720 =head2 ensure_connected
722 Make sure all the storages are connected.
726 sub ensure_connected {
728 foreach my $source ($self->all_storages) {
729 $source->ensure_connected(@_);
735 Set the limit_dialect for all existing storages
741 foreach my $source ($self->all_storages) {
742 $source->limit_dialect(@_);
744 return $self->master->quote_char;
749 Set the quote_char for all existing storages
755 foreach my $source ($self->all_storages) {
756 $source->quote_char(@_);
758 return $self->master->quote_char;
763 Set the name_sep for all existing storages
769 foreach my $source ($self->all_storages) {
770 $source->name_sep(@_);
772 return $self->master->name_sep;
777 Set the schema object for all existing storages
783 foreach my $source ($self->all_storages) {
784 $source->set_schema(@_);
790 set a debug flag across all storages
797 foreach my $source ($self->all_storages) {
801 return $self->master->debug;
812 return $self->master->debugobj(@_);
823 return $self->master->debugfh(@_);
834 return $self->master->debugcb(@_);
839 disconnect everything
845 foreach my $source ($self->all_storages) {
846 $source->disconnect(@_);
852 set cursor class on all storages, or return master's
857 my ($self, $cursor_class) = @_;
860 $_->cursor_class($cursor_class) for $self->all_storages;
862 $self->master->cursor_class;
867 set cursor class on all storages, or return master's, alias for L</cursor_class>
873 my ($self, $cursor_class) = @_;
876 $_->cursor($cursor_class) for $self->all_storages;
878 $self->master->cursor;
883 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
884 master's current setting
892 $_->unsafe(@_) for $self->all_storages;
895 return $self->master->unsafe;
898 =head2 disable_sth_caching
900 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
901 or returns master's current setting
905 sub disable_sth_caching {
909 $_->disable_sth_caching(@_) for $self->all_storages;
912 return $self->master->disable_sth_caching;
915 =head2 lag_behind_master
917 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
922 sub lag_behind_master {
925 return max map $_->lag_behind_master, $self->replicants;
928 =head2 is_replicating
930 returns true if all replicants return true for
931 L<DBIx::Class::Storage::DBI/is_replicating>
938 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
941 =head2 connect_call_datetime_setup
943 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
947 sub connect_call_datetime_setup {
949 $_->connect_call_datetime_setup for $self->all_storages;
954 $_->_populate_dbh for $self->all_storages;
959 $_->_connect for $self->all_storages;
964 $_->_rebless for $self->all_storages;
967 sub _determine_driver {
969 $_->_determine_driver for $self->all_storages;
972 sub _driver_determined {
976 $_->_driver_determined(@_) for $self->all_storages;
979 return $self->master->_driver_determined;
985 $_->_init for $self->all_storages;
988 sub _run_connection_actions {
991 $_->_run_connection_actions for $self->all_storages;
994 sub _do_connection_actions {
998 $_->_do_connection_actions(@_) for $self->all_storages;
1002 sub connect_call_do_sql {
1004 $_->connect_call_do_sql(@_) for $self->all_storages;
1007 sub disconnect_call_do_sql {
1009 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1012 sub _seems_connected {
1015 return min map $_->_seems_connected, $self->all_storages;
1021 return min map $_->_ping, $self->all_storages;
1024 my $numify_ver = sub {
1026 my @numparts = split /\D+/, $ver;
1027 my $format = '%d.' . (join '', ('%05d') x (@numparts - 1));
1029 return sprintf $format, @numparts;
1035 if (not $self->_server_info_hash) {
1036 my $min_version_info = (
1037 reduce { $a->[0] < $b->[0] ? $a : $b }
1038 map [ $numify_ver->($_->{dbms_version}), $_ ],
1039 map $_->_server_info, $self->all_storages
1042 $self->_server_info_hash($min_version_info); # on master
1045 return $self->_server_info_hash;
1048 sub _get_server_version {
1051 return $self->_server_info->{dbms_version};
1056 Due to the fact that replicants can lag behind a master, you must take care to
1057 make sure you use one of the methods to force read queries to a master should
1058 you need realtime data integrity. For example, if you insert a row, and then
1059 immediately re-read it from the database (say, by doing $row->discard_changes)
1060 or you insert a row and then immediately build a query that expects that row
1061 to be an item, you should force the master to handle reads. Otherwise, due to
1062 the lag, there is no certainty your data will be in the expected state.
1064 For data integrity, all transactions automatically use the master storage for
1065 all read and write queries. Using a transaction is the preferred and recommended
1066 method to force the master to handle all read queries.
1068 Otherwise, you can force a single query to use the master with the 'force_pool'
1071 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1073 This attribute will safely be ignore by non replicated storages, so you can use
1074 the same code for both types of systems.
1076 Lastly, you can use the L</execute_reliably> method, which works very much like
1079 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1080 and L</set_balanced_storage>, however this operates at a global level and is not
1081 suitable if you have a shared Schema object being used by multiple processes,
1082 such as on a web application server. You can get around this limitation by
1083 using the Schema clone method.
1085 my $new_schema = $schema->clone;
1086 $new_schema->set_reliable_storage;
1088 ## $new_schema will use only the Master storage for all reads/writes while
1089 ## the $schema object will use replicated storage.
1093 John Napiorkowski <john.napiorkowski@takkle.com>
1095 Based on code originated by:
1097 Norbert Csongrádi <bert@cpan.org>
1098 Peter Siklósi <einon@einon.hu>
1102 You may distribute this code under the same terms as Perl itself.
1106 __PACKAGE__->meta->make_immutable;