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
354 _adjust_select_args_for_complex_prefetch
355 _resolve_ident_sources
358 _strip_cond_qualifiers
359 _extract_order_columns
360 _resolve_aliastypes_from_select_args
365 _prefetch_insert_auto_nextvals
369 my @unimplemented = qw(
370 _arm_global_destructor
371 _preserve_foreign_dbh
375 get_use_dbms_capability
376 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
398 for my $method (@unimplemented) {
399 __PACKAGE__->meta->add_method($method, sub {
400 croak "$method must not be called on ".(blessed shift).' objects';
404 has _master_connect_info_opts =>
405 (is => 'rw', isa => HashRef, default => sub { {} });
407 =head2 around: connect_info
409 Preserves master's C<connect_info> options (for merging with replicants.)
410 Also sets any Replicated-related options from connect_info, such as
411 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
415 around connect_info => sub {
416 my ($next, $self, $info, @extra) = @_;
418 my $wantarray = wantarray;
420 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
423 for my $arg (@$info) {
424 next unless (reftype($arg)||'') eq 'HASH';
425 %opts = %{ $merge->merge($arg, \%opts) };
429 if (@opts{qw/pool_type pool_args/}) {
430 $self->pool_type(delete $opts{pool_type})
434 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
437 $self->pool($self->_build_pool)
441 if (@opts{qw/balancer_type balancer_args/}) {
442 $self->balancer_type(delete $opts{balancer_type})
443 if $opts{balancer_type};
445 $self->balancer_args(
446 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
449 $self->balancer($self->_build_balancer)
453 $self->_master_connect_info_opts(\%opts);
457 @res = $self->$next($info, @extra);
459 $res = $self->$next($info, @extra);
462 # Make sure master is blessed into the correct class and apply role to it.
463 my $master = $self->master;
464 $master->_determine_driver;
465 Moose::Meta::Class->initialize(ref $master);
467 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
469 # link pool back to master
470 $self->pool->master($master);
472 $wantarray ? @res : $res;
477 This class defines the following methods.
481 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
482 first argument. So we need to massage the arguments a bit so that all the
483 bits get put into the correct places.
488 my ($class, $schema, $storage_type_args, @args) = @_;
499 Lazy builder for the L</master> attribute.
505 my $master = DBIx::Class::Storage::DBI->new($self->schema);
511 Lazy builder for the L</pool> attribute.
517 $self->create_pool(%{$self->pool_args});
520 =head2 _build_balancer
522 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
523 the balancer knows which pool it's balancing.
527 sub _build_balancer {
529 $self->create_balancer(
531 master=>$self->master,
532 %{$self->balancer_args},
536 =head2 _build_write_handler
538 Lazy builder for the L</write_handler> attribute. The default is to set this to
543 sub _build_write_handler {
544 return shift->master;
547 =head2 _build_read_handler
549 Lazy builder for the L</read_handler> attribute. The default is to set this to
554 sub _build_read_handler {
555 return shift->balancer;
558 =head2 around: connect_replicants
560 All calls to connect_replicants needs to have an existing $schema tacked onto
561 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
562 options merged with the master, with replicant opts having higher priority.
566 around connect_replicants => sub {
567 my ($next, $self, @args) = @_;
570 $r = [ $r ] unless reftype $r eq 'ARRAY';
572 $self->throw_exception('coderef replicant connect_info not supported')
573 if ref $r->[0] && reftype $r->[0] eq 'CODE';
575 # any connect_info options?
577 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
580 $r->[$i] = {} unless $r->[$i];
582 # merge if two hashes
583 my @hashes = @$r[$i .. $#{$r}];
585 $self->throw_exception('invalid connect_info options')
586 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
588 $self->throw_exception('too many hashrefs in connect_info')
591 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
592 my %opts = %{ $merge->merge(reverse @hashes) };
595 splice @$r, $i+1, ($#{$r} - $i), ();
597 # make sure master/replicants opts don't clash
598 my %master_opts = %{ $self->_master_connect_info_opts };
599 if (exists $opts{dbh_maker}) {
600 delete @master_opts{qw/dsn user password/};
602 delete $master_opts{dbh_maker};
605 %opts = %{ $merge->merge(\%opts, \%master_opts) };
611 $self->$next($self->schema, @args);
616 Returns an array of of all the connected storage backends. The first element
617 in the returned array is the master, and the remainings are each of the
624 return grep {defined $_ && blessed $_} (
626 values %{ $self->replicants },
630 =head2 execute_reliably ($coderef, ?@args)
632 Given a coderef, saves the current state of the L</read_handler>, forces it to
633 use reliable storage (e.g. sets it to the master), executes a coderef and then
634 restores the original state.
640 $schema->resultset('User')->create({name=>$name});
641 my $user_rs = $schema->resultset('User')->find({name=>$name});
645 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
647 Use this when you must be certain of your database state, such as when you just
648 inserted something and need to get a resultset including it, etc.
652 sub execute_reliably {
653 my ($self, $coderef, @args) = @_;
655 unless( ref $coderef eq 'CODE') {
656 $self->throw_exception('Second argument must be a coderef');
659 ##Get copy of master storage
660 my $master = $self->master;
662 ##Get whatever the current read hander is
663 my $current = $self->read_handler;
665 ##Set the read handler to master
666 $self->read_handler($master);
668 ## do whatever the caller needs
670 my $want_array = wantarray;
674 @result = $coderef->(@args);
675 } elsif(defined $want_array) {
676 ($result[0]) = ($coderef->(@args));
681 $self->throw_exception("coderef returned an error: $_");
683 ##Reset to the original state
684 $self->read_handler($current);
687 return $want_array ? @result : $result[0];
690 =head2 set_reliable_storage
692 Sets the current $schema to be 'reliable', that is all queries, both read and
693 write are sent to the master
697 sub set_reliable_storage {
699 my $schema = $self->schema;
700 my $write_handler = $self->schema->storage->write_handler;
702 $schema->storage->read_handler($write_handler);
705 =head2 set_balanced_storage
707 Sets the current $schema to be use the </balancer> for all reads, while all
708 writes are sent to the master only
712 sub set_balanced_storage {
714 my $schema = $self->schema;
715 my $balanced_handler = $self->schema->storage->balancer;
717 $schema->storage->read_handler($balanced_handler);
722 Check that the master and at least one of the replicants is connected.
729 $self->master->connected &&
730 $self->pool->connected_replicants;
733 =head2 ensure_connected
735 Make sure all the storages are connected.
739 sub ensure_connected {
741 foreach my $source ($self->all_storages) {
742 $source->ensure_connected(@_);
748 Set the limit_dialect for all existing storages
754 foreach my $source ($self->all_storages) {
755 $source->limit_dialect(@_);
757 return $self->master->quote_char;
762 Set the quote_char for all existing storages
768 foreach my $source ($self->all_storages) {
769 $source->quote_char(@_);
771 return $self->master->quote_char;
776 Set the name_sep for all existing storages
782 foreach my $source ($self->all_storages) {
783 $source->name_sep(@_);
785 return $self->master->name_sep;
790 Set the schema object for all existing storages
796 foreach my $source ($self->all_storages) {
797 $source->set_schema(@_);
803 set a debug flag across all storages
810 foreach my $source ($self->all_storages) {
814 return $self->master->debug;
825 return $self->master->debugobj(@_);
836 return $self->master->debugfh(@_);
847 return $self->master->debugcb(@_);
852 disconnect everything
858 foreach my $source ($self->all_storages) {
859 $source->disconnect(@_);
865 set cursor class on all storages, or return master's
870 my ($self, $cursor_class) = @_;
873 $_->cursor_class($cursor_class) for $self->all_storages;
875 $self->master->cursor_class;
880 set cursor class on all storages, or return master's, alias for L</cursor_class>
886 my ($self, $cursor_class) = @_;
889 $_->cursor($cursor_class) for $self->all_storages;
891 $self->master->cursor;
896 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
897 master's current setting
905 $_->unsafe(@_) for $self->all_storages;
908 return $self->master->unsafe;
911 =head2 disable_sth_caching
913 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
914 or returns master's current setting
918 sub disable_sth_caching {
922 $_->disable_sth_caching(@_) for $self->all_storages;
925 return $self->master->disable_sth_caching;
928 =head2 lag_behind_master
930 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
935 sub lag_behind_master {
938 return max map $_->lag_behind_master, $self->replicants;
941 =head2 is_replicating
943 returns true if all replicants return true for
944 L<DBIx::Class::Storage::DBI/is_replicating>
951 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
954 =head2 connect_call_datetime_setup
956 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
960 sub connect_call_datetime_setup {
962 $_->connect_call_datetime_setup for $self->all_storages;
967 $_->_populate_dbh for $self->all_storages;
972 $_->_connect for $self->all_storages;
977 $_->_rebless for $self->all_storages;
980 sub _determine_driver {
982 $_->_determine_driver for $self->all_storages;
985 sub _driver_determined {
989 $_->_driver_determined(@_) for $self->all_storages;
992 return $self->master->_driver_determined;
998 $_->_init for $self->all_storages;
1001 sub _run_connection_actions {
1004 $_->_run_connection_actions for $self->all_storages;
1007 sub _do_connection_actions {
1011 $_->_do_connection_actions(@_) for $self->all_storages;
1015 sub connect_call_do_sql {
1017 $_->connect_call_do_sql(@_) for $self->all_storages;
1020 sub disconnect_call_do_sql {
1022 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1025 sub _seems_connected {
1028 return min map $_->_seems_connected, $self->all_storages;
1034 return min map $_->_ping, $self->all_storages;
1037 # not using the normalized_version, because we want to preserve
1038 # version numbers much longer than the conventional xxx.yyyzzz
1039 my $numify_ver = sub {
1041 my @numparts = split /\D+/, $ver;
1042 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1044 return sprintf $format, @numparts;
1049 if (not $self->_dbh_details->{info}) {
1050 $self->_dbh_details->{info} = (
1051 reduce { $a->[0] < $b->[0] ? $a : $b }
1052 map [ $numify_ver->($_->{dbms_version}), $_ ],
1053 map $_->_server_info, $self->all_storages
1057 return $self->next::method;
1060 sub _get_server_version {
1063 return $self->_server_info->{dbms_version};
1068 Due to the fact that replicants can lag behind a master, you must take care to
1069 make sure you use one of the methods to force read queries to a master should
1070 you need realtime data integrity. For example, if you insert a row, and then
1071 immediately re-read it from the database (say, by doing $row->discard_changes)
1072 or you insert a row and then immediately build a query that expects that row
1073 to be an item, you should force the master to handle reads. Otherwise, due to
1074 the lag, there is no certainty your data will be in the expected state.
1076 For data integrity, all transactions automatically use the master storage for
1077 all read and write queries. Using a transaction is the preferred and recommended
1078 method to force the master to handle all read queries.
1080 Otherwise, you can force a single query to use the master with the 'force_pool'
1083 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1085 This attribute will safely be ignore by non replicated storages, so you can use
1086 the same code for both types of systems.
1088 Lastly, you can use the L</execute_reliably> method, which works very much like
1091 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1092 and L</set_balanced_storage>, however this operates at a global level and is not
1093 suitable if you have a shared Schema object being used by multiple processes,
1094 such as on a web application server. You can get around this limitation by
1095 using the Schema clone method.
1097 my $new_schema = $schema->clone;
1098 $new_schema->set_reliable_storage;
1100 ## $new_schema will use only the Master storage for all reads/writes while
1101 ## the $schema object will use replicated storage.
1105 John Napiorkowski <john.napiorkowski@takkle.com>
1107 Based on code originated by:
1109 Norbert Csongrádi <bert@cpan.org>
1110 Peter Siklósi <einon@einon.hu>
1114 You may distribute this code under the same terms as Perl itself.
1118 __PACKAGE__->meta->make_immutable;