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
353 _adjust_select_args_for_complex_prefetch
354 _resolve_ident_sources
357 _strip_cond_qualifiers
358 _resolve_aliastypes_from_select_args
366 my @unimplemented = qw(
367 _arm_global_destructor
370 get_use_dbms_capability
371 set_use_dbms_capability
382 _group_over_selection
383 _extract_order_criteria
391 # the capability framework
392 # not sure if CMOP->initialize does evil things to DBIC::S::DBI, fix if a problem
393 push @unimplemented, ( grep
394 { $_ =~ /^ _ (?: use | supports | determine_supports ) _ /x }
395 ( Class::MOP::Class->initialize('DBIx::Class::Storage::DBI')->get_all_method_names )
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 $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 ## Since we possibly changed the pool_args, we need to clear the current
436 ## pool object so that next time it is used it will be rebuilt.
440 if (@opts{qw/balancer_type balancer_args/}) {
441 $self->balancer_type(delete $opts{balancer_type})
442 if $opts{balancer_type};
444 $self->balancer_args(
445 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
448 $self->balancer($self->_build_balancer)
452 $self->_master_connect_info_opts(\%opts);
456 @res = $self->$next($info, @extra);
458 $res[0] = $self->$next($info, @extra);
461 # Make sure master is blessed into the correct class and apply role to it.
462 my $master = $self->master;
463 $master->_determine_driver;
464 Moose::Meta::Class->initialize(ref $master);
466 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
468 # link pool back to master
469 $self->pool->master($master);
471 wantarray ? @res : $res[0];
476 This class defines the following methods.
480 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
481 first argument. So we need to massage the arguments a bit so that all the
482 bits get put into the correct places.
487 my ($class, $schema, $storage_type_args, @args) = @_;
498 Lazy builder for the L</master> attribute.
504 my $master = DBIx::Class::Storage::DBI->new($self->schema);
510 Lazy builder for the L</pool> attribute.
516 $self->create_pool(%{$self->pool_args});
519 =head2 _build_balancer
521 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
522 the balancer knows which pool it's balancing.
526 sub _build_balancer {
528 $self->create_balancer(
530 master=>$self->master,
531 %{$self->balancer_args},
535 =head2 _build_write_handler
537 Lazy builder for the L</write_handler> attribute. The default is to set this to
542 sub _build_write_handler {
543 return shift->master;
546 =head2 _build_read_handler
548 Lazy builder for the L</read_handler> attribute. The default is to set this to
553 sub _build_read_handler {
554 return shift->balancer;
557 =head2 around: connect_replicants
559 All calls to connect_replicants needs to have an existing $schema tacked onto
560 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
561 options merged with the master, with replicant opts having higher priority.
565 around connect_replicants => sub {
566 my ($next, $self, @args) = @_;
569 $r = [ $r ] unless reftype $r eq 'ARRAY';
571 $self->throw_exception('coderef replicant connect_info not supported')
572 if ref $r->[0] && reftype $r->[0] eq 'CODE';
574 # any connect_info options?
576 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
579 $r->[$i] = {} unless $r->[$i];
581 # merge if two hashes
582 my @hashes = @$r[$i .. $#{$r}];
584 $self->throw_exception('invalid connect_info options')
585 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
587 $self->throw_exception('too many hashrefs in connect_info')
590 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
591 my %opts = %{ $merge->merge(reverse @hashes) };
594 splice @$r, $i+1, ($#{$r} - $i), ();
596 # make sure master/replicants opts don't clash
597 my %master_opts = %{ $self->_master_connect_info_opts };
598 if (exists $opts{dbh_maker}) {
599 delete @master_opts{qw/dsn user password/};
601 delete $master_opts{dbh_maker};
604 %opts = %{ $merge->merge(\%opts, \%master_opts) };
610 $self->$next($self->schema, @args);
615 Returns an array of of all the connected storage backends. The first element
616 in the returned array is the master, and the remainings are each of the
623 return grep {defined $_ && blessed $_} (
625 values %{ $self->replicants },
629 =head2 execute_reliably ($coderef, ?@args)
631 Given a coderef, saves the current state of the L</read_handler>, forces it to
632 use reliable storage (e.g. sets it to the master), executes a coderef and then
633 restores the original state.
639 $schema->resultset('User')->create({name=>$name});
640 my $user_rs = $schema->resultset('User')->find({name=>$name});
644 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
646 Use this when you must be certain of your database state, such as when you just
647 inserted something and need to get a resultset including it, etc.
651 sub execute_reliably {
652 my ($self, $coderef, @args) = @_;
654 unless( ref $coderef eq 'CODE') {
655 $self->throw_exception('Second argument must be a coderef');
658 ##Get copy of master storage
659 my $master = $self->master;
661 ##Get whatever the current read hander is
662 my $current = $self->read_handler;
664 ##Set the read handler to master
665 $self->read_handler($master);
667 ## do whatever the caller needs
669 my $want_array = wantarray;
673 @result = $coderef->(@args);
674 } elsif(defined $want_array) {
675 ($result[0]) = ($coderef->(@args));
680 $self->throw_exception("coderef returned an error: $_");
682 ##Reset to the original state
683 $self->read_handler($current);
686 return wantarray ? @result : $result[0];
689 =head2 set_reliable_storage
691 Sets the current $schema to be 'reliable', that is all queries, both read and
692 write are sent to the master
696 sub set_reliable_storage {
698 my $schema = $self->schema;
699 my $write_handler = $self->schema->storage->write_handler;
701 $schema->storage->read_handler($write_handler);
704 =head2 set_balanced_storage
706 Sets the current $schema to be use the </balancer> for all reads, while all
707 writes are sent to the master only
711 sub set_balanced_storage {
713 my $schema = $self->schema;
714 my $balanced_handler = $self->schema->storage->balancer;
716 $schema->storage->read_handler($balanced_handler);
721 Check that the master and at least one of the replicants is connected.
728 $self->master->connected &&
729 $self->pool->connected_replicants;
732 =head2 ensure_connected
734 Make sure all the storages are connected.
738 sub ensure_connected {
740 foreach my $source ($self->all_storages) {
741 $source->ensure_connected(@_);
747 Set the limit_dialect for all existing storages
753 foreach my $source ($self->all_storages) {
754 $source->limit_dialect(@_);
756 return $self->master->limit_dialect;
761 Set the quote_char for all existing storages
767 foreach my $source ($self->all_storages) {
768 $source->quote_char(@_);
770 return $self->master->quote_char;
775 Set the name_sep for all existing storages
781 foreach my $source ($self->all_storages) {
782 $source->name_sep(@_);
784 return $self->master->name_sep;
789 Set the schema object for all existing storages
795 foreach my $source ($self->all_storages) {
796 $source->set_schema(@_);
802 set a debug flag across all storages
809 foreach my $source ($self->all_storages) {
813 return $self->master->debug;
824 return $self->master->debugobj(@_);
835 return $self->master->debugfh(@_);
846 return $self->master->debugcb(@_);
851 disconnect everything
857 foreach my $source ($self->all_storages) {
858 $source->disconnect(@_);
864 set cursor class on all storages, or return master's
869 my ($self, $cursor_class) = @_;
872 $_->cursor_class($cursor_class) for $self->all_storages;
874 $self->master->cursor_class;
879 set cursor class on all storages, or return master's, alias for L</cursor_class>
885 my ($self, $cursor_class) = @_;
888 $_->cursor($cursor_class) for $self->all_storages;
890 $self->master->cursor;
895 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
896 master's current setting
904 $_->unsafe(@_) for $self->all_storages;
907 return $self->master->unsafe;
910 =head2 disable_sth_caching
912 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
913 or returns master's current setting
917 sub disable_sth_caching {
921 $_->disable_sth_caching(@_) for $self->all_storages;
924 return $self->master->disable_sth_caching;
927 =head2 lag_behind_master
929 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
934 sub lag_behind_master {
937 return max map $_->lag_behind_master, $self->replicants;
940 =head2 is_replicating
942 returns true if all replicants return true for
943 L<DBIx::Class::Storage::DBI/is_replicating>
950 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
953 =head2 connect_call_datetime_setup
955 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
959 sub connect_call_datetime_setup {
961 $_->connect_call_datetime_setup for $self->all_storages;
966 $_->_populate_dbh for $self->all_storages;
971 $_->_connect for $self->all_storages;
976 $_->_rebless for $self->all_storages;
979 sub _determine_driver {
981 $_->_determine_driver for $self->all_storages;
984 sub _driver_determined {
988 $_->_driver_determined(@_) for $self->all_storages;
991 return $self->master->_driver_determined;
997 $_->_init for $self->all_storages;
1000 sub _run_connection_actions {
1003 $_->_run_connection_actions for $self->all_storages;
1006 sub _do_connection_actions {
1010 $_->_do_connection_actions(@_) for $self->all_storages;
1014 sub connect_call_do_sql {
1016 $_->connect_call_do_sql(@_) for $self->all_storages;
1019 sub disconnect_call_do_sql {
1021 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1024 sub _seems_connected {
1027 return min map $_->_seems_connected, $self->all_storages;
1033 return min map $_->_ping, $self->all_storages;
1036 # not using the normalized_version, because we want to preserve
1037 # version numbers much longer than the conventional xxx.yyyzzz
1038 my $numify_ver = sub {
1040 my @numparts = split /\D+/, $ver;
1041 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1043 return sprintf $format, @numparts;
1048 if (not $self->_dbh_details->{info}) {
1049 $self->_dbh_details->{info} = (
1050 reduce { $a->[0] < $b->[0] ? $a : $b }
1051 map [ $numify_ver->($_->{dbms_version}), $_ ],
1052 map $_->_server_info, $self->all_storages
1056 return $self->next::method;
1059 sub _get_server_version {
1062 return $self->_server_info->{dbms_version};
1067 Due to the fact that replicants can lag behind a master, you must take care to
1068 make sure you use one of the methods to force read queries to a master should
1069 you need realtime data integrity. For example, if you insert a row, and then
1070 immediately re-read it from the database (say, by doing $row->discard_changes)
1071 or you insert a row and then immediately build a query that expects that row
1072 to be an item, you should force the master to handle reads. Otherwise, due to
1073 the lag, there is no certainty your data will be in the expected state.
1075 For data integrity, all transactions automatically use the master storage for
1076 all read and write queries. Using a transaction is the preferred and recommended
1077 method to force the master to handle all read queries.
1079 Otherwise, you can force a single query to use the master with the 'force_pool'
1082 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1084 This attribute will safely be ignore by non replicated storages, so you can use
1085 the same code for both types of systems.
1087 Lastly, you can use the L</execute_reliably> method, which works very much like
1090 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1091 and L</set_balanced_storage>, however this operates at a global level and is not
1092 suitable if you have a shared Schema object being used by multiple processes,
1093 such as on a web application server. You can get around this limitation by
1094 using the Schema clone method.
1096 my $new_schema = $schema->clone;
1097 $new_schema->set_reliable_storage;
1099 ## $new_schema will use only the Master storage for all reads/writes while
1100 ## the $schema object will use replicated storage.
1104 John Napiorkowski <john.napiorkowski@takkle.com>
1106 Based on code originated by:
1108 Norbert Csongrádi <bert@cpan.org>
1109 Peter Siklósi <einon@einon.hu>
1113 You may distribute this code under the same terms as Perl itself.
1117 __PACKAGE__->meta->make_immutable;