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');
12 use DBIx::Class::Storage::DBI;
13 use Scalar::Util qw(reftype blessed);
14 use List::Util qw(min max reduce);
16 use Sub::Name 'subname';
18 use DBIx::Class::Storage::DBI::Replicated::Types
19 qw(DBICSchema DBICStorageDBI ClassName HashRef Object
20 DoesDBICStorageReplicatedBalancer DBICStorageDBIReplicatedPool Defined);
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=> sub { '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' => (
165 default=>sub { 'DBIx::Class::Storage::DBI::Replicated::Balancer::First' },
168 sub create_balancer {
169 my ($self, @args) = @_;
170 my $type = $self->balancer_type;
171 $type = 'DBIx::Class::Storage::DBI::Replicated::Balancer'.$type
173 $self->schema->ensure_class_loaded($type);
174 return $type->new(@args);
179 Contains a hashref of initialized information to pass to the Balancer object.
180 See L<DBIx::Class::Storage::DBI::Replicated::Balancer> for available arguments.
184 has 'balancer_args' => (
188 default=>sub { +{} },
193 Is a L<DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a
194 container class for one or more replicated databases.
200 isa =>DBICStorageDBIReplicatedPool,
202 builder=>'_build_pool',
203 clearer=>'clear_pool',
212 Is a L<DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This
213 is a class that takes a pool (L<DBIx::Class::Storage::DBI::Replicated::Pool>)
219 isa => DoesDBICStorageReplicatedBalancer,
221 builder=>'_build_balancer',
222 handles=>[qw/auto_validate_every/],
227 The master defines the canonical state for a pool of connected databases. All
228 the replicants are expected to match this databases state. Thus, in a classic
229 Master / Slaves distributed system, all the slaves are expected to replicate
230 the Master's state as quick as possible. This is the only database in the
231 pool of databases that is allowed to handle write traffic.
237 isa => DBICStorageDBI,
239 builder=>'_build_master',
242 =head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE
244 The following methods are delegated all the methods required for the
245 L<DBIx::Class::Storage::DBI> interface.
249 Defines an object that implements the read side of L<BIx::Class::Storage::DBI>.
253 has 'read_handler' => (
257 builder=>'_build_read_handler',
262 _dbh_columns_info_for
269 Defines an object that implements the write side of L<BIx::Class::Storage::DBI>,
270 as well as methods that don't write or read that can be called on only one
271 storage, methods that return a C<$dbh>, and any methods that don't make sense to
276 has 'write_handler' => (
280 builder=>'_build_write_handler',
292 deployment_statements
295 build_datetime_parser
309 with_deferred_fk_checks
321 relname_to_table_alias
324 _default_dbi_connect_attributes
326 _dbic_connect_attributes
330 bind_attribute_by_data_type
338 _per_row_update_delete
340 _dbh_execute_inserts_with_no_binds
341 _select_args_to_query
343 _multipk_update_delete
344 source_bind_attributes
345 _normalize_connect_info
350 _sqlt_minimum_version
358 _adjust_select_args_for_complex_prefetch
359 _resolve_ident_sources
362 _strip_cond_qualifiers
363 _resolve_aliastypes_from_select_args
371 my @unimplemented = qw(
372 _arm_global_destructor
373 _preserve_foreign_dbh
377 get_use_dbms_capability
378 set_use_dbms_capability
386 _group_over_selection
387 _extract_order_criteria
393 # the capability framework
394 push @unimplemented, ( grep
395 { $_ =~ /^ _ (?: use | supports | determine_supports ) _ /x }
396 @{Class::Inspector->methods('DBIx::Class::Storage::DBI')||[]}
399 for my $method (@unimplemented) {
402 *{__PACKAGE__ ."::$method"} = subname $method => sub {
403 croak "$method must not be called on ".(blessed shift).' objects';
408 has _master_connect_info_opts => (
411 default => sub { +{} },
414 =head2 around: connect_info
416 Preserves master's C<connect_info> options (for merging with replicants.)
417 Also sets any Replicated-related options from connect_info, such as
418 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
422 around connect_info => sub {
423 my ($next, $self, $info, @extra) = @_;
425 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
428 for my $arg (@$info) {
429 next unless (reftype($arg)||'') eq 'HASH';
430 %opts = %{ $merge->merge($arg, \%opts) };
434 if (@opts{qw/pool_type pool_args/}) {
435 $self->pool_type(delete $opts{pool_type})
439 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
442 ## Since we possibly changed the pool_args, we need to clear the current
443 ## pool object so that next time it is used it will be rebuilt.
447 if (@opts{qw/balancer_type balancer_args/}) {
448 $self->balancer_type(delete $opts{balancer_type})
449 if $opts{balancer_type};
451 $self->balancer_args(
452 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
455 $self->balancer($self->_build_balancer)
459 $self->_master_connect_info_opts(\%opts);
463 @res = $self->$next($info, @extra);
465 $res[0] = $self->$next($info, @extra);
468 # Make sure master is blessed into the correct class and apply role to it.
469 my $master = $self->master;
470 $master->_determine_driver;
472 ## Moose::Meta::Class->initialize(ref $master);
473 Role::Tiny->apply_roles_to_object($master, 'DBIx::Class::Storage::DBI::Replicated::WithDSN');
474 ## DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
476 # link pool back to master
477 $self->pool->master($master);
479 wantarray ? @res : $res[0];
484 This class defines the following methods.
488 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
489 first argument. So we need to massage the arguments a bit so that all the
490 bits get put into the correct places.
495 my ($orig, $class, $schema, $storage_type_args, @args) = @_;
506 Lazy builder for the L</master> attribute.
512 my $master = DBIx::Class::Storage::DBI->new($self->schema);
518 Lazy builder for the L</pool> attribute.
524 $self->create_pool(%{$self->pool_args});
527 =head2 _build_balancer
529 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
530 the balancer knows which pool it's balancing.
534 sub _build_balancer {
536 $self->create_balancer(
538 master=>$self->master,
539 %{$self->balancer_args},
543 =head2 _build_write_handler
545 Lazy builder for the L</write_handler> attribute. The default is to set this to
550 sub _build_write_handler {
551 return shift->master;
554 =head2 _build_read_handler
556 Lazy builder for the L</read_handler> attribute. The default is to set this to
561 sub _build_read_handler {
562 return shift->balancer;
565 =head2 around: connect_replicants
567 All calls to connect_replicants needs to have an existing $schema tacked onto
568 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
569 options merged with the master, with replicant opts having higher priority.
573 around connect_replicants => sub {
574 my ($next, $self, @args) = @_;
577 $r = [ $r ] unless reftype $r eq 'ARRAY';
579 $self->throw_exception('coderef replicant connect_info not supported')
580 if ref $r->[0] && reftype $r->[0] eq 'CODE';
582 # any connect_info options?
584 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
587 $r->[$i] = {} unless $r->[$i];
589 # merge if two hashes
590 my @hashes = @$r[$i .. $#{$r}];
592 $self->throw_exception('invalid connect_info options')
593 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
595 $self->throw_exception('too many hashrefs in connect_info')
598 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
599 my %opts = %{ $merge->merge(reverse @hashes) };
602 splice @$r, $i+1, ($#{$r} - $i), ();
604 # make sure master/replicants opts don't clash
605 my %master_opts = %{ $self->_master_connect_info_opts };
606 if (exists $opts{dbh_maker}) {
607 delete @master_opts{qw/dsn user password/};
609 delete $master_opts{dbh_maker};
612 %opts = %{ $merge->merge(\%opts, \%master_opts) };
618 $self->$next($self->schema, @args);
623 Returns an array of of all the connected storage backends. The first element
624 in the returned array is the master, and the remainings are each of the
631 return grep {defined $_ && blessed $_} (
633 values %{ $self->replicants },
637 =head2 execute_reliably ($coderef, ?@args)
639 Given a coderef, saves the current state of the L</read_handler>, forces it to
640 use reliable storage (e.g. sets it to the master), executes a coderef and then
641 restores the original state.
647 $schema->resultset('User')->create({name=>$name});
648 my $user_rs = $schema->resultset('User')->find({name=>$name});
652 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
654 Use this when you must be certain of your database state, such as when you just
655 inserted something and need to get a resultset including it, etc.
659 sub execute_reliably {
660 my ($self, $coderef, @args) = @_;
662 unless( ref $coderef eq 'CODE') {
663 $self->throw_exception('Second argument must be a coderef');
666 ##Get copy of master storage
667 my $master = $self->master;
669 ##Get whatever the current read hander is
670 my $current = $self->read_handler;
672 ##Set the read handler to master
673 $self->read_handler($master);
675 ## do whatever the caller needs
677 my $want_array = wantarray;
681 @result = $coderef->(@args);
682 } elsif(defined $want_array) {
683 ($result[0]) = ($coderef->(@args));
688 $self->throw_exception("coderef returned an error: $_");
690 ##Reset to the original state
691 $self->read_handler($current);
694 return wantarray ? @result : $result[0];
697 =head2 set_reliable_storage
699 Sets the current $schema to be 'reliable', that is all queries, both read and
700 write are sent to the master
704 sub set_reliable_storage {
706 my $schema = $self->schema;
707 my $write_handler = $self->schema->storage->write_handler;
709 $schema->storage->read_handler($write_handler);
712 =head2 set_balanced_storage
714 Sets the current $schema to be use the </balancer> for all reads, while all
715 writes are sent to the master only
719 sub set_balanced_storage {
721 my $schema = $self->schema;
722 my $balanced_handler = $self->schema->storage->balancer;
724 $schema->storage->read_handler($balanced_handler);
729 Check that the master and at least one of the replicants is connected.
736 $self->master->connected &&
737 $self->pool->connected_replicants;
740 =head2 ensure_connected
742 Make sure all the storages are connected.
746 sub ensure_connected {
748 foreach my $source ($self->all_storages) {
749 $source->ensure_connected(@_);
755 Set the limit_dialect for all existing storages
761 foreach my $source ($self->all_storages) {
762 $source->limit_dialect(@_);
764 return $self->master->limit_dialect;
769 Set the quote_char for all existing storages
775 foreach my $source ($self->all_storages) {
776 $source->quote_char(@_);
778 return $self->master->quote_char;
783 Set the name_sep for all existing storages
789 foreach my $source ($self->all_storages) {
790 $source->name_sep(@_);
792 return $self->master->name_sep;
797 Set the schema object for all existing storages
803 foreach my $source ($self->all_storages) {
804 $source->set_schema(@_);
810 set a debug flag across all storages
817 foreach my $source ($self->all_storages) {
821 return $self->master->debug;
832 return $self->master->debugobj(@_);
843 return $self->master->debugfh(@_);
854 return $self->master->debugcb(@_);
859 disconnect everything
865 foreach my $source ($self->all_storages) {
866 $source->disconnect(@_);
872 set cursor class on all storages, or return master's
877 my ($self, $cursor_class) = @_;
880 $_->cursor_class($cursor_class) for $self->all_storages;
882 $self->master->cursor_class;
887 set cursor class on all storages, or return master's, alias for L</cursor_class>
893 my ($self, $cursor_class) = @_;
896 $_->cursor($cursor_class) for $self->all_storages;
898 $self->master->cursor;
903 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
904 master's current setting
912 $_->unsafe(@_) for $self->all_storages;
915 return $self->master->unsafe;
918 =head2 disable_sth_caching
920 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
921 or returns master's current setting
925 sub disable_sth_caching {
929 $_->disable_sth_caching(@_) for $self->all_storages;
932 return $self->master->disable_sth_caching;
935 =head2 lag_behind_master
937 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
942 sub lag_behind_master {
945 return max map $_->lag_behind_master, $self->replicants;
948 =head2 is_replicating
950 returns true if all replicants return true for
951 L<DBIx::Class::Storage::DBI/is_replicating>
958 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
961 =head2 connect_call_datetime_setup
963 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
967 sub connect_call_datetime_setup {
969 $_->connect_call_datetime_setup for $self->all_storages;
974 $_->_populate_dbh for $self->all_storages;
979 $_->_connect for $self->all_storages;
984 $_->_rebless for $self->all_storages;
987 sub _determine_driver {
989 $_->_determine_driver for $self->all_storages;
992 sub _driver_determined {
996 $_->_driver_determined(@_) for $self->all_storages;
999 return $self->master->_driver_determined;
1005 $_->_init for $self->all_storages;
1008 sub _run_connection_actions {
1011 $_->_run_connection_actions for $self->all_storages;
1014 sub _do_connection_actions {
1018 $_->_do_connection_actions(@_) for $self->all_storages;
1022 sub connect_call_do_sql {
1024 $_->connect_call_do_sql(@_) for $self->all_storages;
1027 sub disconnect_call_do_sql {
1029 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1032 sub _seems_connected {
1035 return min map $_->_seems_connected, $self->all_storages;
1041 return min map $_->_ping, $self->all_storages;
1044 # not using the normalized_version, because we want to preserve
1045 # version numbers much longer than the conventional xxx.yyyzzz
1046 my $numify_ver = sub {
1048 my @numparts = split /\D+/, $ver;
1049 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1051 return sprintf $format, @numparts;
1056 if (not $self->_dbh_details->{info}) {
1057 $self->_dbh_details->{info} = (
1058 reduce { $a->[0] < $b->[0] ? $a : $b }
1059 map [ $numify_ver->($_->{dbms_version}), $_ ],
1060 map $_->_server_info, $self->all_storages
1064 return $self->next::method;
1067 sub _get_server_version {
1070 return $self->_server_info->{dbms_version};
1075 Due to the fact that replicants can lag behind a master, you must take care to
1076 make sure you use one of the methods to force read queries to a master should
1077 you need realtime data integrity. For example, if you insert a row, and then
1078 immediately re-read it from the database (say, by doing $row->discard_changes)
1079 or you insert a row and then immediately build a query that expects that row
1080 to be an item, you should force the master to handle reads. Otherwise, due to
1081 the lag, there is no certainty your data will be in the expected state.
1083 For data integrity, all transactions automatically use the master storage for
1084 all read and write queries. Using a transaction is the preferred and recommended
1085 method to force the master to handle all read queries.
1087 Otherwise, you can force a single query to use the master with the 'force_pool'
1090 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1092 This attribute will safely be ignore by non replicated storages, so you can use
1093 the same code for both types of systems.
1095 Lastly, you can use the L</execute_reliably> method, which works very much like
1098 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1099 and L</set_balanced_storage>, however this operates at a global level and is not
1100 suitable if you have a shared Schema object being used by multiple processes,
1101 such as on a web application server. You can get around this limitation by
1102 using the Schema clone method.
1104 my $new_schema = $schema->clone;
1105 $new_schema->set_reliable_storage;
1107 ## $new_schema will use only the Master storage for all reads/writes while
1108 ## the $schema object will use replicated storage.
1112 John Napiorkowski <jjnapiork@cpan.org>
1114 Based on code originated by:
1116 Norbert Csongrádi <bert@cpan.org>
1117 Peter Siklósi <einon@einon.hu>
1121 You may distribute this code under the same terms as Perl itself.