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/;
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
315 relname_to_table_alias
316 _straight_join_to_node
319 _default_dbi_connect_attributes
324 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
344 _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
372 has _master_connect_info_opts =>
373 (is => 'rw', isa => HashRef, default => sub { {} });
375 =head2 around: connect_info
377 Preserves master's C<connect_info> options (for merging with replicants.)
378 Also sets any Replicated-related options from connect_info, such as
379 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
383 around connect_info => sub {
384 my ($next, $self, $info, @extra) = @_;
386 my $wantarray = wantarray;
388 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
391 for my $arg (@$info) {
392 next unless (reftype($arg)||'') eq 'HASH';
393 %opts = %{ $merge->merge($arg, \%opts) };
397 if (@opts{qw/pool_type pool_args/}) {
398 $self->pool_type(delete $opts{pool_type})
402 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
405 $self->pool($self->_build_pool)
409 if (@opts{qw/balancer_type balancer_args/}) {
410 $self->balancer_type(delete $opts{balancer_type})
411 if $opts{balancer_type};
413 $self->balancer_args(
414 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
417 $self->balancer($self->_build_balancer)
421 $self->_master_connect_info_opts(\%opts);
425 @res = $self->$next($info, @extra);
427 $res = $self->$next($info, @extra);
430 # Make sure master is blessed into the correct class and apply role to it.
431 my $master = $self->master;
432 $master->_determine_driver;
433 Moose::Meta::Class->initialize(ref $master);
435 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
437 # link pool back to master
438 $self->pool->master($master);
440 $wantarray ? @res : $res;
445 This class defines the following methods.
449 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
450 first argument. So we need to massage the arguments a bit so that all the
451 bits get put into the correct places.
456 my ($class, $schema, $storage_type_args, @args) = @_;
467 Lazy builder for the L</master> attribute.
473 my $master = DBIx::Class::Storage::DBI->new($self->schema);
479 Lazy builder for the L</pool> attribute.
485 $self->create_pool(%{$self->pool_args});
488 =head2 _build_balancer
490 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
491 the balancer knows which pool it's balancing.
495 sub _build_balancer {
497 $self->create_balancer(
499 master=>$self->master,
500 %{$self->balancer_args},
504 =head2 _build_write_handler
506 Lazy builder for the L</write_handler> attribute. The default is to set this to
511 sub _build_write_handler {
512 return shift->master;
515 =head2 _build_read_handler
517 Lazy builder for the L</read_handler> attribute. The default is to set this to
522 sub _build_read_handler {
523 return shift->balancer;
526 =head2 around: connect_replicants
528 All calls to connect_replicants needs to have an existing $schema tacked onto
529 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
530 options merged with the master, with replicant opts having higher priority.
534 around connect_replicants => sub {
535 my ($next, $self, @args) = @_;
538 $r = [ $r ] unless reftype $r eq 'ARRAY';
540 $self->throw_exception('coderef replicant connect_info not supported')
541 if ref $r->[0] && reftype $r->[0] eq 'CODE';
543 # any connect_info options?
545 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
548 $r->[$i] = {} unless $r->[$i];
550 # merge if two hashes
551 my @hashes = @$r[$i .. $#{$r}];
553 $self->throw_exception('invalid connect_info options')
554 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
556 $self->throw_exception('too many hashrefs in connect_info')
559 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
560 my %opts = %{ $merge->merge(reverse @hashes) };
563 splice @$r, $i+1, ($#{$r} - $i), ();
565 # make sure master/replicants opts don't clash
566 my %master_opts = %{ $self->_master_connect_info_opts };
567 if (exists $opts{dbh_maker}) {
568 delete @master_opts{qw/dsn user password/};
570 delete $master_opts{dbh_maker};
573 %opts = %{ $merge->merge(\%opts, \%master_opts) };
579 $self->$next($self->schema, @args);
584 Returns an array of of all the connected storage backends. The first element
585 in the returned array is the master, and the remainings are each of the
592 return grep {defined $_ && blessed $_} (
594 values %{ $self->replicants },
598 =head2 execute_reliably ($coderef, ?@args)
600 Given a coderef, saves the current state of the L</read_handler>, forces it to
601 use reliable storage (e.g. sets it to the master), executes a coderef and then
602 restores the original state.
608 $schema->resultset('User')->create({name=>$name});
609 my $user_rs = $schema->resultset('User')->find({name=>$name});
613 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
615 Use this when you must be certain of your database state, such as when you just
616 inserted something and need to get a resultset including it, etc.
620 sub execute_reliably {
621 my ($self, $coderef, @args) = @_;
623 unless( ref $coderef eq 'CODE') {
624 $self->throw_exception('Second argument must be a coderef');
627 ##Get copy of master storage
628 my $master = $self->master;
630 ##Get whatever the current read hander is
631 my $current = $self->read_handler;
633 ##Set the read handler to master
634 $self->read_handler($master);
636 ## do whatever the caller needs
638 my $want_array = wantarray;
642 @result = $coderef->(@args);
643 } elsif(defined $want_array) {
644 ($result[0]) = ($coderef->(@args));
650 ##Reset to the original state
651 $self->read_handler($current);
653 ##Exception testing has to come last, otherwise you might leave the
654 ##read_handler set to master.
657 $self->throw_exception("coderef returned an error: $@");
659 return $want_array ? @result : $result[0];
663 =head2 set_reliable_storage
665 Sets the current $schema to be 'reliable', that is all queries, both read and
666 write are sent to the master
670 sub set_reliable_storage {
672 my $schema = $self->schema;
673 my $write_handler = $self->schema->storage->write_handler;
675 $schema->storage->read_handler($write_handler);
678 =head2 set_balanced_storage
680 Sets the current $schema to be use the </balancer> for all reads, while all
681 writes are sent to the master only
685 sub set_balanced_storage {
687 my $schema = $self->schema;
688 my $balanced_handler = $self->schema->storage->balancer;
690 $schema->storage->read_handler($balanced_handler);
695 Check that the master and at least one of the replicants is connected.
702 $self->master->connected &&
703 $self->pool->connected_replicants;
706 =head2 ensure_connected
708 Make sure all the storages are connected.
712 sub ensure_connected {
714 foreach my $source ($self->all_storages) {
715 $source->ensure_connected(@_);
721 Set the limit_dialect for all existing storages
727 foreach my $source ($self->all_storages) {
728 $source->limit_dialect(@_);
730 return $self->master->quote_char;
735 Set the quote_char for all existing storages
741 foreach my $source ($self->all_storages) {
742 $source->quote_char(@_);
744 return $self->master->quote_char;
749 Set the name_sep for all existing storages
755 foreach my $source ($self->all_storages) {
756 $source->name_sep(@_);
758 return $self->master->name_sep;
763 Set the schema object for all existing storages
769 foreach my $source ($self->all_storages) {
770 $source->set_schema(@_);
776 set a debug flag across all storages
783 foreach my $source ($self->all_storages) {
787 return $self->master->debug;
798 return $self->master->debugobj(@_);
809 return $self->master->debugfh(@_);
820 return $self->master->debugcb(@_);
825 disconnect everything
831 foreach my $source ($self->all_storages) {
832 $source->disconnect(@_);
838 set cursor class on all storages, or return master's
843 my ($self, $cursor_class) = @_;
846 $_->cursor_class($cursor_class) for $self->all_storages;
848 $self->master->cursor_class;
853 set cursor class on all storages, or return master's, alias for L</cursor_class>
859 my ($self, $cursor_class) = @_;
862 $_->cursor($cursor_class) for $self->all_storages;
864 $self->master->cursor;
869 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
870 master's current setting
878 $_->unsafe(@_) for $self->all_storages;
881 return $self->master->unsafe;
884 =head2 disable_sth_caching
886 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
887 or returns master's current setting
891 sub disable_sth_caching {
895 $_->disable_sth_caching(@_) for $self->all_storages;
898 return $self->master->disable_sth_caching;
901 =head2 lag_behind_master
903 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
908 sub lag_behind_master {
911 return max map $_->lag_behind_master, $self->replicants;
914 =head2 is_replicating
916 returns true if all replicants return true for
917 L<DBIx::Class::Storage::DBI/is_replicating>
924 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
927 =head2 connect_call_datetime_setup
929 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
933 sub connect_call_datetime_setup {
935 $_->connect_call_datetime_setup for $self->all_storages;
940 $_->_populate_dbh for $self->all_storages;
945 $_->_connect for $self->all_storages;
950 $_->_rebless for $self->all_storages;
953 sub _determine_driver {
955 $_->_determine_driver for $self->all_storages;
958 sub _driver_determined {
962 $_->_driver_determined(@_) for $self->all_storages;
965 return $self->master->_driver_determined;
971 $_->_init for $self->all_storages;
974 sub _run_connection_actions {
977 $_->_run_connection_actions for $self->all_storages;
980 sub _do_connection_actions {
984 $_->_do_connection_actions(@_) for $self->all_storages;
988 sub connect_call_do_sql {
990 $_->connect_call_do_sql(@_) for $self->all_storages;
993 sub disconnect_call_do_sql {
995 $_->disconnect_call_do_sql(@_) for $self->all_storages;
998 sub _seems_connected {
1001 return min map $_->_seems_connected, $self->all_storages;
1007 return min map $_->_ping, $self->all_storages;
1012 Due to the fact that replicants can lag behind a master, you must take care to
1013 make sure you use one of the methods to force read queries to a master should
1014 you need realtime data integrity. For example, if you insert a row, and then
1015 immediately re-read it from the database (say, by doing $row->discard_changes)
1016 or you insert a row and then immediately build a query that expects that row
1017 to be an item, you should force the master to handle reads. Otherwise, due to
1018 the lag, there is no certainty your data will be in the expected state.
1020 For data integrity, all transactions automatically use the master storage for
1021 all read and write queries. Using a transaction is the preferred and recommended
1022 method to force the master to handle all read queries.
1024 Otherwise, you can force a single query to use the master with the 'force_pool'
1027 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1029 This attribute will safely be ignore by non replicated storages, so you can use
1030 the same code for both types of systems.
1032 Lastly, you can use the L</execute_reliably> method, which works very much like
1035 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1036 and L</set_balanced_storage>, however this operates at a global level and is not
1037 suitable if you have a shared Schema object being used by multiple processes,
1038 such as on a web application server. You can get around this limitation by
1039 using the Schema clone method.
1041 my $new_schema = $schema->clone;
1042 $new_schema->set_reliable_storage;
1044 ## $new_schema will use only the Master storage for all reads/writes while
1045 ## the $schema object will use replicated storage.
1049 John Napiorkowski <john.napiorkowski@takkle.com>
1051 Based on code originated by:
1053 Norbert Csongrádi <bert@cpan.org>
1054 Peter Siklósi <einon@einon.hu>
1058 You may distribute this code under the same terms as Perl itself.
1062 __PACKAGE__->meta->make_immutable;