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
309 _supports_insert_returning
316 relname_to_table_alias
317 _straight_join_to_node
320 _default_dbi_connect_attributes
325 bind_attribute_by_data_type
334 _per_row_update_delete
336 _dbh_execute_inserts_with_no_binds
337 _select_args_to_query
339 _multipk_update_delete
340 source_bind_attributes
341 _normalize_connect_info
345 _placeholders_supported
348 _sqlt_minimum_version
351 _typeless_placeholders_supported
358 _adjust_select_args_for_complex_prefetch
359 _resolve_ident_sources
362 _strip_cond_qualifiers
364 _resolve_aliastypes_from_select_args
369 _prefetch_insert_auto_nextvals
372 # TODO these need to be spread out to ALL servers not just the master
381 has _master_connect_info_opts =>
382 (is => 'rw', isa => HashRef, default => sub { {} });
384 =head2 around: connect_info
386 Preserves master's C<connect_info> options (for merging with replicants.)
387 Also sets any Replicated-related options from connect_info, such as
388 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
392 around connect_info => sub {
393 my ($next, $self, $info, @extra) = @_;
395 my $wantarray = wantarray;
397 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
400 for my $arg (@$info) {
401 next unless (reftype($arg)||'') eq 'HASH';
402 %opts = %{ $merge->merge($arg, \%opts) };
406 if (@opts{qw/pool_type pool_args/}) {
407 $self->pool_type(delete $opts{pool_type})
411 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
414 $self->pool($self->_build_pool)
418 if (@opts{qw/balancer_type balancer_args/}) {
419 $self->balancer_type(delete $opts{balancer_type})
420 if $opts{balancer_type};
422 $self->balancer_args(
423 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
426 $self->balancer($self->_build_balancer)
430 $self->_master_connect_info_opts(\%opts);
434 @res = $self->$next($info, @extra);
436 $res = $self->$next($info, @extra);
439 # Make sure master is blessed into the correct class and apply role to it.
440 my $master = $self->master;
441 $master->_determine_driver;
442 Moose::Meta::Class->initialize(ref $master);
444 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
446 # link pool back to master
447 $self->pool->master($master);
449 $wantarray ? @res : $res;
454 This class defines the following methods.
458 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
459 first argument. So we need to massage the arguments a bit so that all the
460 bits get put into the correct places.
465 my ($class, $schema, $storage_type_args, @args) = @_;
476 Lazy builder for the L</master> attribute.
482 my $master = DBIx::Class::Storage::DBI->new($self->schema);
488 Lazy builder for the L</pool> attribute.
494 $self->create_pool(%{$self->pool_args});
497 =head2 _build_balancer
499 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
500 the balancer knows which pool it's balancing.
504 sub _build_balancer {
506 $self->create_balancer(
508 master=>$self->master,
509 %{$self->balancer_args},
513 =head2 _build_write_handler
515 Lazy builder for the L</write_handler> attribute. The default is to set this to
520 sub _build_write_handler {
521 return shift->master;
524 =head2 _build_read_handler
526 Lazy builder for the L</read_handler> attribute. The default is to set this to
531 sub _build_read_handler {
532 return shift->balancer;
535 =head2 around: connect_replicants
537 All calls to connect_replicants needs to have an existing $schema tacked onto
538 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
539 options merged with the master, with replicant opts having higher priority.
543 around connect_replicants => sub {
544 my ($next, $self, @args) = @_;
547 $r = [ $r ] unless reftype $r eq 'ARRAY';
549 $self->throw_exception('coderef replicant connect_info not supported')
550 if ref $r->[0] && reftype $r->[0] eq 'CODE';
552 # any connect_info options?
554 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
557 $r->[$i] = {} unless $r->[$i];
559 # merge if two hashes
560 my @hashes = @$r[$i .. $#{$r}];
562 $self->throw_exception('invalid connect_info options')
563 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
565 $self->throw_exception('too many hashrefs in connect_info')
568 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
569 my %opts = %{ $merge->merge(reverse @hashes) };
572 splice @$r, $i+1, ($#{$r} - $i), ();
574 # make sure master/replicants opts don't clash
575 my %master_opts = %{ $self->_master_connect_info_opts };
576 if (exists $opts{dbh_maker}) {
577 delete @master_opts{qw/dsn user password/};
579 delete $master_opts{dbh_maker};
582 %opts = %{ $merge->merge(\%opts, \%master_opts) };
588 $self->$next($self->schema, @args);
593 Returns an array of of all the connected storage backends. The first element
594 in the returned array is the master, and the remainings are each of the
601 return grep {defined $_ && blessed $_} (
603 values %{ $self->replicants },
607 =head2 execute_reliably ($coderef, ?@args)
609 Given a coderef, saves the current state of the L</read_handler>, forces it to
610 use reliable storage (e.g. sets it to the master), executes a coderef and then
611 restores the original state.
617 $schema->resultset('User')->create({name=>$name});
618 my $user_rs = $schema->resultset('User')->find({name=>$name});
622 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
624 Use this when you must be certain of your database state, such as when you just
625 inserted something and need to get a resultset including it, etc.
629 sub execute_reliably {
630 my ($self, $coderef, @args) = @_;
632 unless( ref $coderef eq 'CODE') {
633 $self->throw_exception('Second argument must be a coderef');
636 ##Get copy of master storage
637 my $master = $self->master;
639 ##Get whatever the current read hander is
640 my $current = $self->read_handler;
642 ##Set the read handler to master
643 $self->read_handler($master);
645 ## do whatever the caller needs
647 my $want_array = wantarray;
651 @result = $coderef->(@args);
652 } elsif(defined $want_array) {
653 ($result[0]) = ($coderef->(@args));
659 ##Reset to the original state
660 $self->read_handler($current);
662 ##Exception testing has to come last, otherwise you might leave the
663 ##read_handler set to master.
666 $self->throw_exception("coderef returned an error: $@");
668 return $want_array ? @result : $result[0];
672 =head2 set_reliable_storage
674 Sets the current $schema to be 'reliable', that is all queries, both read and
675 write are sent to the master
679 sub set_reliable_storage {
681 my $schema = $self->schema;
682 my $write_handler = $self->schema->storage->write_handler;
684 $schema->storage->read_handler($write_handler);
687 =head2 set_balanced_storage
689 Sets the current $schema to be use the </balancer> for all reads, while all
690 writes are sent to the master only
694 sub set_balanced_storage {
696 my $schema = $self->schema;
697 my $balanced_handler = $self->schema->storage->balancer;
699 $schema->storage->read_handler($balanced_handler);
704 Check that the master and at least one of the replicants is connected.
711 $self->master->connected &&
712 $self->pool->connected_replicants;
715 =head2 ensure_connected
717 Make sure all the storages are connected.
721 sub ensure_connected {
723 foreach my $source ($self->all_storages) {
724 $source->ensure_connected(@_);
730 Set the limit_dialect for all existing storages
736 foreach my $source ($self->all_storages) {
737 $source->limit_dialect(@_);
739 return $self->master->quote_char;
744 Set the quote_char for all existing storages
750 foreach my $source ($self->all_storages) {
751 $source->quote_char(@_);
753 return $self->master->quote_char;
758 Set the name_sep for all existing storages
764 foreach my $source ($self->all_storages) {
765 $source->name_sep(@_);
767 return $self->master->name_sep;
772 Set the schema object for all existing storages
778 foreach my $source ($self->all_storages) {
779 $source->set_schema(@_);
785 set a debug flag across all storages
792 foreach my $source ($self->all_storages) {
796 return $self->master->debug;
807 return $self->master->debugobj(@_);
818 return $self->master->debugfh(@_);
829 return $self->master->debugcb(@_);
834 disconnect everything
840 foreach my $source ($self->all_storages) {
841 $source->disconnect(@_);
847 set cursor class on all storages, or return master's
852 my ($self, $cursor_class) = @_;
855 $_->cursor_class($cursor_class) for $self->all_storages;
857 $self->master->cursor_class;
862 set cursor class on all storages, or return master's, alias for L</cursor_class>
868 my ($self, $cursor_class) = @_;
871 $_->cursor($cursor_class) for $self->all_storages;
873 $self->master->cursor;
878 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
879 master's current setting
887 $_->unsafe(@_) for $self->all_storages;
890 return $self->master->unsafe;
893 =head2 disable_sth_caching
895 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
896 or returns master's current setting
900 sub disable_sth_caching {
904 $_->disable_sth_caching(@_) for $self->all_storages;
907 return $self->master->disable_sth_caching;
910 =head2 lag_behind_master
912 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
917 sub lag_behind_master {
920 return max map $_->lag_behind_master, $self->replicants;
923 =head2 is_replicating
925 returns true if all replicants return true for
926 L<DBIx::Class::Storage::DBI/is_replicating>
933 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
936 =head2 connect_call_datetime_setup
938 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
942 sub connect_call_datetime_setup {
944 $_->connect_call_datetime_setup for $self->all_storages;
949 $_->_populate_dbh for $self->all_storages;
954 $_->_connect for $self->all_storages;
959 $_->_rebless for $self->all_storages;
962 sub _determine_driver {
964 $_->_determine_driver for $self->all_storages;
967 sub _driver_determined {
971 $_->_driver_determined(@_) for $self->all_storages;
974 return $self->master->_driver_determined;
980 $_->_init for $self->all_storages;
983 sub _run_connection_actions {
986 $_->_run_connection_actions for $self->all_storages;
989 sub _do_connection_actions {
993 $_->_do_connection_actions(@_) for $self->all_storages;
997 sub connect_call_do_sql {
999 $_->connect_call_do_sql(@_) for $self->all_storages;
1002 sub disconnect_call_do_sql {
1004 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1007 sub _seems_connected {
1010 return min map $_->_seems_connected, $self->all_storages;
1016 return min map $_->_ping, $self->all_storages;
1021 Due to the fact that replicants can lag behind a master, you must take care to
1022 make sure you use one of the methods to force read queries to a master should
1023 you need realtime data integrity. For example, if you insert a row, and then
1024 immediately re-read it from the database (say, by doing $row->discard_changes)
1025 or you insert a row and then immediately build a query that expects that row
1026 to be an item, you should force the master to handle reads. Otherwise, due to
1027 the lag, there is no certainty your data will be in the expected state.
1029 For data integrity, all transactions automatically use the master storage for
1030 all read and write queries. Using a transaction is the preferred and recommended
1031 method to force the master to handle all read queries.
1033 Otherwise, you can force a single query to use the master with the 'force_pool'
1036 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1038 This attribute will safely be ignore by non replicated storages, so you can use
1039 the same code for both types of systems.
1041 Lastly, you can use the L</execute_reliably> method, which works very much like
1044 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1045 and L</set_balanced_storage>, however this operates at a global level and is not
1046 suitable if you have a shared Schema object being used by multiple processes,
1047 such as on a web application server. You can get around this limitation by
1048 using the Schema clone method.
1050 my $new_schema = $schema->clone;
1051 $new_schema->set_reliable_storage;
1053 ## $new_schema will use only the Master storage for all reads/writes while
1054 ## the $schema object will use replicated storage.
1058 John Napiorkowski <john.napiorkowski@takkle.com>
1060 Based on code originated by:
1062 Norbert Csongrádi <bert@cpan.org>
1063 Peter Siklósi <einon@einon.hu>
1067 You may distribute this code under the same terms as Perl itself.
1071 __PACKAGE__->meta->make_immutable;