1 package DBIx::Class::Storage::DBI::Replicated;
7 require DBIx::Class::Optional::Dependencies;
8 if ( my $missing = DBIx::Class::Optional::Dependencies->req_missing_for('replicated') ) {
9 die "The following modules are required for Replicated storage support: $missing\n";
14 use DBIx::Class::Storage::DBI;
15 use DBIx::Class::Storage::DBI::Replicated::Pool;
16 use DBIx::Class::Storage::DBI::Replicated::Balancer;
17 use DBIx::Class::Storage::DBI::Replicated::Types qw/BalancerClassNamePart DBICSchema DBICStorageDBI/;
18 use MooseX::Types::Moose qw/ClassName HashRef Object/;
19 use Scalar::Util 'reftype';
21 use List::Util qw/min max reduce/;
22 use Context::Preserve 'preserve_context';
25 use namespace::clean -except => 'meta';
29 DBIx::Class::Storage::DBI::Replicated - BETA Replicated database support
33 The Following example shows how to change an existing $schema to a replicated
34 storage type, add some replicated (read-only) databases, and perform reporting
37 You should set the 'storage_type attribute to a replicated type. You should
38 also define your arguments, such as which balancer you want and any arguments
39 that the Pool object should get.
41 my $schema = Schema::Class->clone;
42 $schema->storage_type(['::DBI::Replicated', { balancer_type => '::Random' }]);
43 $schema->connection(...);
45 Next, you need to add in the Replicants. Basically this is an array of
46 arrayrefs, where each arrayref is database connect information. Think of these
47 arguments as what you'd pass to the 'normal' $schema->connect method.
49 $schema->storage->connect_replicants(
50 [$dsn1, $user, $pass, \%opts],
51 [$dsn2, $user, $pass, \%opts],
52 [$dsn3, $user, $pass, \%opts],
55 Now, just use the $schema as you normally would. Automatically all reads will
56 be delegated to the replicants, while writes to the master.
58 $schema->resultset('Source')->search({name=>'etc'});
60 You can force a given query to use a particular storage using the search
61 attribute 'force_pool'. For example:
63 my $rs = $schema->resultset('Source')->search(undef, {force_pool=>'master'});
65 Now $rs will force everything (both reads and writes) to use whatever was setup
66 as the master storage. 'master' is hardcoded to always point to the Master,
67 but you can also use any Replicant name. Please see:
68 L<DBIx::Class::Storage::DBI::Replicated::Pool> and the replicants attribute for more.
70 Also see transactions and L</execute_reliably> for alternative ways to
71 force read traffic to the master. In general, you should wrap your statements
72 in a transaction when you are reading and writing to the same tables at the
73 same time, since your replicants will often lag a bit behind the master.
75 If you have a multi-statement read only transaction you can force it to select
76 a random server in the pool by:
78 my $rs = $schema->resultset('Source')->search( undef,
79 { force_pool => $db->storage->read_handler->next_storage }
84 Warning: This class is marked BETA. This has been running a production
85 website using MySQL native replication as its backend and we have some decent
86 test coverage but the code hasn't yet been stressed by a variety of databases.
87 Individual DBs may have quirks we are not aware of. Please use this in first
88 development and pass along your experiences/bug fixes.
90 This class implements replicated data store for DBI. Currently you can define
91 one master and numerous slave database connections. All write-type queries
92 (INSERT, UPDATE, DELETE and even LAST_INSERT_ID) are routed to master
93 database, all read-type queries (SELECTs) go to the slave database.
95 Basically, any method request that L<DBIx::Class::Storage::DBI> would normally
96 handle gets delegated to one of the two attributes: L</read_handler> or to
97 L</write_handler>. Additionally, some methods need to be distributed
98 to all existing storages. This way our storage class is a drop in replacement
99 for L<DBIx::Class::Storage::DBI>.
101 Read traffic is spread across the replicants (slaves) occurring to a user
102 selected algorithm. The default algorithm is random weighted.
106 The consistency between master and replicants is database specific. The Pool
107 gives you a method to validate its replicants, removing and replacing them
108 when they fail/pass predefined criteria. Please make careful use of the ways
109 to force a query to run against Master when needed.
113 Replicated Storage has additional requirements not currently part of
114 L<DBIx::Class>. See L<DBIx::Class::Optional::Dependencies> for more details.
118 This class defines the following attributes.
122 The underlying L<DBIx::Class::Schema> object this storage is attaching
135 Contains the classname which will instantiate the L</pool> object. Defaults
136 to: L<DBIx::Class::Storage::DBI::Replicated::Pool>.
143 default=>'DBIx::Class::Storage::DBI::Replicated::Pool',
145 'create_pool' => 'new',
151 Contains a hashref of initialized information to pass to the Balancer object.
152 See L<DBIx::Class::Storage::DBI::Replicated::Pool> for available arguments.
166 The replication pool requires a balance class to provider the methods for
167 choose how to spread the query load across each replicant in the pool.
171 has 'balancer_type' => (
173 isa=>BalancerClassNamePart,
176 default=> 'DBIx::Class::Storage::DBI::Replicated::Balancer::First',
178 'create_balancer' => 'new',
184 Contains a hashref of initialized information to pass to the Balancer object.
185 See L<DBIx::Class::Storage::DBI::Replicated::Balancer> for available arguments.
189 has 'balancer_args' => (
199 Is a L<DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a
200 container class for one or more replicated databases.
206 isa=>'DBIx::Class::Storage::DBI::Replicated::Pool',
217 Is a L<DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This
218 is a class that takes a pool (L<DBIx::Class::Storage::DBI::Replicated::Pool>)
224 isa=>'DBIx::Class::Storage::DBI::Replicated::Balancer',
226 handles=>[qw/auto_validate_every/],
231 The master defines the canonical state for a pool of connected databases. All
232 the replicants are expected to match this databases state. Thus, in a classic
233 Master / Slaves distributed system, all the slaves are expected to replicate
234 the Master's state as quick as possible. This is the only database in the
235 pool of databases that is allowed to handle write traffic.
245 =head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE
247 The following methods are delegated all the methods required for the
248 L<DBIx::Class::Storage::DBI> interface.
252 my $method_dispatch = {
264 deployment_statements
267 build_datetime_parser
282 with_deferred_fk_checks
290 relname_to_table_alias
292 _default_dbi_connect_attributes
294 _dbic_connect_attributes
300 bind_attribute_by_data_type
304 _dbh_execute_for_fetch
306 _dbh_execute_inserts_with_no_binds
307 _select_args_to_query
310 _normalize_connect_info
325 /, Class::MOP::Class->initialize('DBIx::Class::Storage::DBIHacks')->get_method_list ],
330 _dbh_columns_info_for
333 unimplemented => [qw/
334 _arm_global_destructor
337 get_use_dbms_capability
338 set_use_dbms_capability
344 _determine_connector_driver
345 _extract_driver_from_connect_info
347 _warn_undetermined_driver
354 _perform_autoinc_retrieval
355 _autoinc_supplied_for_op
368 # the capability framework
369 # not sure if CMOP->initialize does evil things to DBIC::S::DBI, fix if a problem
371 { $_ =~ /^ _ (?: use | supports | determine_supports ) _ /x and $_ ne '_use_multicolumn_in' }
372 ( Class::MOP::Class->initialize('DBIx::Class::Storage::DBI')->get_all_method_names )
376 if (DBIx::Class::_ENV_::DBICTEST) {
379 for my $type (keys %$method_dispatch) {
380 for (@{$method_dispatch->{$type}}) {
381 push @{$seen->{$_}}, $type;
385 if (my @dupes = grep { @{$seen->{$_}} > 1 } keys %$seen) {
387 'The following methods show up multiple times in ::Storage::DBI::Replicated handlers:',
388 (map { "$_: " . (join ', ', @{$seen->{$_}}) } sort @dupes),
393 if (my @cant = grep { ! DBIx::Class::Storage::DBI->can($_) } keys %$seen) {
395 '::Storage::DBI::Replicated specifies handling of the following *NON EXISTING* ::Storage::DBI methods:',
402 for my $method (@{$method_dispatch->{unimplemented}}) {
403 __PACKAGE__->meta->add_method($method, sub {
405 $self->throw_exception("$method() must not be called on ".(blessed $self).' objects');
411 Defines an object that implements the read side of L<DBIx::Class::Storage::DBI>.
415 has 'read_handler' => (
419 handles=>$method_dispatch->{reader},
424 Defines an object that implements the write side of L<DBIx::Class::Storage::DBI>,
425 as well as methods that don't write or read that can be called on only one
426 storage, methods that return a C<$dbh>, and any methods that don't make sense to
431 has 'write_handler' => (
435 handles=>$method_dispatch->{writer},
440 has _master_connect_info_opts =>
441 (is => 'rw', isa => HashRef, default => sub { {} });
443 =head2 around: connect_info
445 Preserves master's C<connect_info> options (for merging with replicants.)
446 Also sets any Replicated-related options from connect_info, such as
447 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
451 around connect_info => sub {
452 my ($next, $self, $info, @extra) = @_;
454 $self->throw_exception(
455 'connect_info can not be retrieved from a replicated storage - '
456 . 'accessor must be called on a specific pool instance'
457 ) unless defined $info;
459 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
462 for my $arg (@$info) {
463 next unless (reftype($arg)||'') eq 'HASH';
464 %opts = %{ $merge->merge($arg, \%opts) };
468 if (@opts{qw/pool_type pool_args/}) {
469 $self->pool_type(delete $opts{pool_type})
473 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
476 ## Since we possibly changed the pool_args, we need to clear the current
477 ## pool object so that next time it is used it will be rebuilt.
481 if (@opts{qw/balancer_type balancer_args/}) {
482 $self->balancer_type(delete $opts{balancer_type})
483 if $opts{balancer_type};
485 $self->balancer_args(
486 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
489 $self->balancer($self->_build_balancer)
493 $self->_master_connect_info_opts(\%opts);
495 return preserve_context {
496 $self->$next($info, @extra);
498 # Make sure master is blessed into the correct class and apply role to it.
499 my $master = $self->master;
500 $master->_determine_driver;
501 Moose::Meta::Class->initialize(ref $master);
503 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
505 # link pool back to master
506 $self->pool->master($master);
512 This class defines the following methods.
516 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
517 first argument. So we need to massage the arguments a bit so that all the
518 bits get put into the correct places.
523 my ($class, $schema, $storage_type_args, @args) = @_;
534 Lazy builder for the L</master> attribute.
540 my $master = DBIx::Class::Storage::DBI->new($self->schema);
546 Lazy builder for the L</pool> attribute.
552 $self->create_pool(%{$self->pool_args});
555 =head2 _build_balancer
557 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
558 the balancer knows which pool it's balancing.
562 sub _build_balancer {
564 $self->create_balancer(
566 master=>$self->master,
567 %{$self->balancer_args},
571 =head2 _build_write_handler
573 Lazy builder for the L</write_handler> attribute. The default is to set this to
578 sub _build_write_handler {
579 return shift->master;
582 =head2 _build_read_handler
584 Lazy builder for the L</read_handler> attribute. The default is to set this to
589 sub _build_read_handler {
590 return shift->balancer;
593 =head2 around: connect_replicants
595 All calls to connect_replicants needs to have an existing $schema tacked onto
596 top of the args, since L<DBIx::Class::Storage::DBI> needs it, and any
597 L<connect_info|DBIx::Class::Storage::DBI/connect_info>
598 options merged with the master, with replicant opts having higher priority.
602 around connect_replicants => sub {
603 my ($next, $self, @args) = @_;
606 $r = [ $r ] unless reftype $r eq 'ARRAY';
608 $self->throw_exception('coderef replicant connect_info not supported')
609 if ref $r->[0] && reftype $r->[0] eq 'CODE';
611 # any connect_info options?
613 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
616 $r->[$i] = {} unless $r->[$i];
618 # merge if two hashes
619 my @hashes = @$r[$i .. $#{$r}];
621 $self->throw_exception('invalid connect_info options')
622 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
624 $self->throw_exception('too many hashrefs in connect_info')
627 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
628 my %opts = %{ $merge->merge(reverse @hashes) };
631 splice @$r, $i+1, ($#{$r} - $i), ();
633 # make sure master/replicants opts don't clash
634 my %master_opts = %{ $self->_master_connect_info_opts };
635 if (exists $opts{dbh_maker}) {
636 delete @master_opts{qw/dsn user password/};
638 delete $master_opts{dbh_maker};
641 %opts = %{ $merge->merge(\%opts, \%master_opts) };
647 $self->$next($self->schema, @args);
652 Returns an array of all the connected storage backends. The first element
653 in the returned array is the master, and the rest are each of the
660 return grep {defined $_ && blessed $_} (
662 values %{ $self->replicants },
666 =head2 execute_reliably ($coderef, ?@args)
668 Given a coderef, saves the current state of the L</read_handler>, forces it to
669 use reliable storage (e.g. sets it to the master), executes a coderef and then
670 restores the original state.
676 $schema->resultset('User')->create({name=>$name});
677 my $user_rs = $schema->resultset('User')->find({name=>$name});
681 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
683 Use this when you must be certain of your database state, such as when you just
684 inserted something and need to get a resultset including it, etc.
688 sub execute_reliably {
692 unless( ref $coderef eq 'CODE') {
693 $self->throw_exception('Second argument must be a coderef');
696 ## replace the current read handler for the remainder of the scope
697 local $self->{read_handler} = $self->master;
703 $self->throw_exception("coderef returned an error: $_");
707 =head2 set_reliable_storage
709 Sets the current $schema to be 'reliable', that is all queries, both read and
710 write are sent to the master
714 sub set_reliable_storage {
716 my $schema = $self->schema;
717 my $write_handler = $self->schema->storage->write_handler;
719 $schema->storage->read_handler($write_handler);
722 =head2 set_balanced_storage
724 Sets the current $schema to be use the </balancer> for all reads, while all
725 writes are sent to the master only
729 sub set_balanced_storage {
731 my $schema = $self->schema;
732 my $balanced_handler = $self->schema->storage->balancer;
734 $schema->storage->read_handler($balanced_handler);
739 Check that the master and at least one of the replicants is connected.
746 $self->master->connected &&
747 $self->pool->connected_replicants;
750 =head2 ensure_connected
752 Make sure all the storages are connected.
756 sub ensure_connected {
758 foreach my $source ($self->all_storages) {
759 $source->ensure_connected(@_);
765 Set the limit_dialect for all existing storages
771 foreach my $source ($self->all_storages) {
772 $source->limit_dialect(@_);
774 return $self->master->limit_dialect;
779 Set the quote_char for all existing storages
785 foreach my $source ($self->all_storages) {
786 $source->quote_char(@_);
788 return $self->master->quote_char;
793 Set the name_sep for all existing storages
799 foreach my $source ($self->all_storages) {
800 $source->name_sep(@_);
802 return $self->master->name_sep;
807 Set the schema object for all existing storages
813 foreach my $source ($self->all_storages) {
814 $source->set_schema(@_);
820 set a debug flag across all storages
827 foreach my $source ($self->all_storages) {
831 return $self->master->debug;
842 return $self->master->debugobj(@_);
853 return $self->master->debugfh(@_);
864 return $self->master->debugcb(@_);
869 disconnect everything
875 foreach my $source ($self->all_storages) {
876 $source->disconnect(@_);
882 set cursor class on all storages, or return master's
887 my ($self, $cursor_class) = @_;
890 $_->cursor_class($cursor_class) for $self->all_storages;
892 $self->master->cursor_class;
897 set cursor class on all storages, or return master's, alias for L</cursor_class>
903 my ($self, $cursor_class) = @_;
906 $_->cursor($cursor_class) for $self->all_storages;
908 $self->master->cursor;
913 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
914 master's current setting
922 $_->unsafe(@_) for $self->all_storages;
925 return $self->master->unsafe;
928 =head2 disable_sth_caching
930 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
931 or returns master's current setting
935 sub disable_sth_caching {
939 $_->disable_sth_caching(@_) for $self->all_storages;
942 return $self->master->disable_sth_caching;
945 =head2 lag_behind_master
947 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
952 sub lag_behind_master {
955 return max map $_->lag_behind_master, $self->replicants;
958 =head2 is_replicating
960 returns true if all replicants return true for
961 L<DBIx::Class::Storage::DBI/is_replicating>
968 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
971 =head2 connect_call_datetime_setup
973 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
977 sub connect_call_datetime_setup {
979 $_->connect_call_datetime_setup for $self->all_storages;
984 $_->_populate_dbh for $self->all_storages;
989 $_->_connect for $self->all_storages;
994 $_->_rebless for $self->all_storages;
997 sub _determine_driver {
999 $_->_determine_driver for $self->all_storages;
1002 sub _driver_determined {
1006 $_->_driver_determined(@_) for $self->all_storages;
1009 return $self->master->_driver_determined;
1015 $_->_init for $self->all_storages;
1018 sub _run_connection_actions {
1021 $_->_run_connection_actions for $self->all_storages;
1024 sub _do_connection_actions {
1028 $_->_do_connection_actions(@_) for $self->all_storages;
1032 sub connect_call_do_sql {
1034 $_->connect_call_do_sql(@_) for $self->all_storages;
1037 sub disconnect_call_do_sql {
1039 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1042 sub _seems_connected {
1045 return min map $_->_seems_connected, $self->all_storages;
1051 return min map $_->_ping, $self->all_storages;
1054 # not using the normalized_version, because we want to preserve
1055 # version numbers much longer than the conventional xxx.yyyzzz
1056 my $numify_ver = sub {
1058 my @numparts = split /\D+/, $ver;
1059 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1061 return sprintf $format, @numparts;
1066 if (not $self->_dbh_details->{info}) {
1067 $self->_dbh_details->{info} = (
1068 reduce { $a->[0] < $b->[0] ? $a : $b }
1069 map [ $numify_ver->($_->{dbms_version}), $_ ],
1070 map $_->_server_info, $self->all_storages
1074 return $self->next::method;
1077 sub _get_server_version {
1080 return $self->_server_info->{dbms_version};
1085 Due to the fact that replicants can lag behind a master, you must take care to
1086 make sure you use one of the methods to force read queries to a master should
1087 you need realtime data integrity. For example, if you insert a row, and then
1088 immediately re-read it from the database (say, by doing
1089 L<< $result->discard_changes|DBIx::Class::Row/discard_changes >>)
1090 or you insert a row and then immediately build a query that expects that row
1091 to be an item, you should force the master to handle reads. Otherwise, due to
1092 the lag, there is no certainty your data will be in the expected state.
1094 For data integrity, all transactions automatically use the master storage for
1095 all read and write queries. Using a transaction is the preferred and recommended
1096 method to force the master to handle all read queries.
1098 Otherwise, you can force a single query to use the master with the 'force_pool'
1101 my $result = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1103 This attribute will safely be ignored by non replicated storages, so you can use
1104 the same code for both types of systems.
1106 Lastly, you can use the L</execute_reliably> method, which works very much like
1109 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1110 and L</set_balanced_storage>, however this operates at a global level and is not
1111 suitable if you have a shared Schema object being used by multiple processes,
1112 such as on a web application server. You can get around this limitation by
1113 using the Schema clone method.
1115 my $new_schema = $schema->clone;
1116 $new_schema->set_reliable_storage;
1118 ## $new_schema will use only the Master storage for all reads/writes while
1119 ## the $schema object will use replicated storage.
1121 =head1 FURTHER QUESTIONS?
1123 Check the list of L<additional DBIC resources|DBIx::Class/GETTING HELP/SUPPORT>.
1125 =head1 COPYRIGHT AND LICENSE
1127 This module is free software L<copyright|DBIx::Class/COPYRIGHT AND LICENSE>
1128 by the L<DBIx::Class (DBIC) authors|DBIx::Class/AUTHORS>. You can
1129 redistribute it and/or modify it under the same terms as the
1130 L<DBIx::Class library|DBIx::Class/COPYRIGHT AND LICENSE>.
1134 __PACKAGE__->meta->make_immutable;