1 package DBIx::Class::Storage::DBI::Replicated;
5 die('The following modules are required for Replication ' . DBIx::Class::Optional::Dependencies->req_missing_for ('replicated') . "\n" )
6 unless DBIx::Class::Optional::Dependencies->req_ok_for ('replicated');
10 use DBIx::Class::Storage::DBI;
11 use DBIx::Class::Storage::DBI::Replicated::Pool;
12 use DBIx::Class::Storage::DBI::Replicated::Balancer;
13 use DBIx::Class::Storage::DBI::Replicated::Types qw/BalancerClassNamePart DBICSchema DBICStorageDBI/;
14 use MooseX::Types::Moose qw/ClassName HashRef Object/;
15 use Scalar::Util 'reftype';
17 use List::Util qw/min max reduce/;
21 use namespace::clean -except => 'meta';
25 DBIx::Class::Storage::DBI::Replicated - BETA Replicated database support
29 The Following example shows how to change an existing $schema to a replicated
30 storage type, add some replicated (read-only) databases, and perform reporting
33 You should set the 'storage_type attribute to a replicated type. You should
34 also define your arguments, such as which balancer you want and any arguments
35 that the Pool object should get.
37 my $schema = Schema::Class->clone;
38 $schema->storage_type( ['::DBI::Replicated', {balancer=>'::Random'}] );
39 $schema->connection(...);
41 Next, you need to add in the Replicants. Basically this is an array of
42 arrayrefs, where each arrayref is database connect information. Think of these
43 arguments as what you'd pass to the 'normal' $schema->connect method.
45 $schema->storage->connect_replicants(
46 [$dsn1, $user, $pass, \%opts],
47 [$dsn2, $user, $pass, \%opts],
48 [$dsn3, $user, $pass, \%opts],
51 Now, just use the $schema as you normally would. Automatically all reads will
52 be delegated to the replicants, while writes to the master.
54 $schema->resultset('Source')->search({name=>'etc'});
56 You can force a given query to use a particular storage using the search
57 attribute 'force_pool'. For example:
59 my $rs = $schema->resultset('Source')->search(undef, {force_pool=>'master'});
61 Now $rs will force everything (both reads and writes) to use whatever was setup
62 as the master storage. 'master' is hardcoded to always point to the Master,
63 but you can also use any Replicant name. Please see:
64 L<DBIx::Class::Storage::DBI::Replicated::Pool> and the replicants attribute for more.
66 Also see transactions and L</execute_reliably> for alternative ways to
67 force read traffic to the master. In general, you should wrap your statements
68 in a transaction when you are reading and writing to the same tables at the
69 same time, since your replicants will often lag a bit behind the master.
71 If you have a multi-statement read only transaction you can force it to select
72 a random server in the pool by:
74 my $rs = $schema->resultset('Source')->search( undef,
75 { force_pool => $db->storage->read_handler->next_storage }
80 Warning: This class is marked BETA. This has been running a production
81 website using MySQL native replication as its backend and we have some decent
82 test coverage but the code hasn't yet been stressed by a variety of databases.
83 Individual DBs may have quirks we are not aware of. Please use this in first
84 development and pass along your experiences/bug fixes.
86 This class implements replicated data store for DBI. Currently you can define
87 one master and numerous slave database connections. All write-type queries
88 (INSERT, UPDATE, DELETE and even LAST_INSERT_ID) are routed to master
89 database, all read-type queries (SELECTs) go to the slave database.
91 Basically, any method request that L<DBIx::Class::Storage::DBI> would normally
92 handle gets delegated to one of the two attributes: L</read_handler> or to
93 L</write_handler>. Additionally, some methods need to be distributed
94 to all existing storages. This way our storage class is a drop in replacement
95 for L<DBIx::Class::Storage::DBI>.
97 Read traffic is spread across the replicants (slaves) occurring to a user
98 selected algorithm. The default algorithm is random weighted.
102 The consistency between master and replicants is database specific. The Pool
103 gives you a method to validate its replicants, removing and replacing them
104 when they fail/pass predefined criteria. Please make careful use of the ways
105 to force a query to run against Master when needed.
109 Replicated Storage has additional requirements not currently part of
110 L<DBIx::Class>. See L<DBIx::Class::Optional::Dependencies> for more details.
114 This class defines the following attributes.
118 The underlying L<DBIx::Class::Schema> object this storage is attaching
131 Contains the classname which will instantiate the L</pool> object. Defaults
132 to: L<DBIx::Class::Storage::DBI::Replicated::Pool>.
139 default=>'DBIx::Class::Storage::DBI::Replicated::Pool',
141 'create_pool' => 'new',
147 Contains a hashref of initialized information to pass to the Balancer object.
148 See L<DBIx::Class::Storage::DBI::Replicated::Pool> for available arguments.
162 The replication pool requires a balance class to provider the methods for
163 choose how to spread the query load across each replicant in the pool.
167 has 'balancer_type' => (
169 isa=>BalancerClassNamePart,
172 default=> 'DBIx::Class::Storage::DBI::Replicated::Balancer::First',
174 'create_balancer' => 'new',
180 Contains a hashref of initialized information to pass to the Balancer object.
181 See L<DBIx::Class::Storage::DBI::Replicated::Balancer> for available arguments.
185 has 'balancer_args' => (
195 Is a L<DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a
196 container class for one or more replicated databases.
202 isa=>'DBIx::Class::Storage::DBI::Replicated::Pool',
213 Is a L<DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This
214 is a class that takes a pool (L<DBIx::Class::Storage::DBI::Replicated::Pool>)
220 isa=>'DBIx::Class::Storage::DBI::Replicated::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.
241 =head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE
243 The following methods are delegated all the methods required for the
244 L<DBIx::Class::Storage::DBI> interface.
248 my $method_dispatch = {
260 deployment_statements
263 build_datetime_parser
279 with_deferred_fk_checks
287 relname_to_table_alias
289 _default_dbi_connect_attributes
291 _dbic_connect_attributes
297 bind_attribute_by_data_type
301 _dbh_execute_for_fetch
303 _dbh_execute_inserts_with_no_binds
304 _select_args_to_query
307 _normalize_connect_info
321 /, Class::MOP::Class->initialize('DBIx::Class::Storage::DBIHacks')->get_method_list ],
326 _dbh_columns_info_for
329 unimplemented => [qw/
330 _arm_global_destructor
333 source_bind_attributes
335 get_use_dbms_capability
336 set_use_dbms_capability
347 _perform_autoinc_retrieval
348 _autoinc_supplied_for_op
359 # the capability framework
360 # not sure if CMOP->initialize does evil things to DBIC::S::DBI, fix if a problem
362 { $_ =~ /^ _ (?: use | supports | determine_supports ) _ /x }
363 ( Class::MOP::Class->initialize('DBIx::Class::Storage::DBI')->get_all_method_names )
367 if (DBIx::Class::_ENV_::DBICTEST) {
370 for my $type (keys %$method_dispatch) {
371 for (@{$method_dispatch->{$type}}) {
372 push @{$seen->{$_}}, $type;
376 if (my @dupes = grep { @{$seen->{$_}} > 1 } keys %$seen) {
378 'The following methods show up multiple times in ::Storage::DBI::Replicated handlers:',
379 (map { "$_: " . (join ', ', @{$seen->{$_}}) } sort @dupes),
384 if (my @cant = grep { ! DBIx::Class::Storage::DBI->can($_) } keys %$seen) {
386 '::Storage::DBI::Replicated specifies handling of the following *NON EXISTING* ::Storage::DBI methods:',
393 for my $method (@{$method_dispatch->{unimplemented}}) {
394 __PACKAGE__->meta->add_method($method, sub {
396 $self->throw_exception("$method must not be called on ".(blessed $self).' objects');
402 Defines an object that implements the read side of L<BIx::Class::Storage::DBI>.
406 has 'read_handler' => (
410 handles=>$method_dispatch->{reader},
415 Defines an object that implements the write side of L<BIx::Class::Storage::DBI>,
416 as well as methods that don't write or read that can be called on only one
417 storage, methods that return a C<$dbh>, and any methods that don't make sense to
422 has 'write_handler' => (
426 handles=>$method_dispatch->{writer},
431 has _master_connect_info_opts =>
432 (is => 'rw', isa => HashRef, default => sub { {} });
434 =head2 around: connect_info
436 Preserves master's C<connect_info> options (for merging with replicants.)
437 Also sets any Replicated-related options from connect_info, such as
438 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
442 around connect_info => sub {
443 my ($next, $self, $info, @extra) = @_;
445 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
448 for my $arg (@$info) {
449 next unless (reftype($arg)||'') eq 'HASH';
450 %opts = %{ $merge->merge($arg, \%opts) };
454 if (@opts{qw/pool_type pool_args/}) {
455 $self->pool_type(delete $opts{pool_type})
459 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
462 ## Since we possibly changed the pool_args, we need to clear the current
463 ## pool object so that next time it is used it will be rebuilt.
467 if (@opts{qw/balancer_type balancer_args/}) {
468 $self->balancer_type(delete $opts{balancer_type})
469 if $opts{balancer_type};
471 $self->balancer_args(
472 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
475 $self->balancer($self->_build_balancer)
479 $self->_master_connect_info_opts(\%opts);
483 @res = $self->$next($info, @extra);
485 $res[0] = $self->$next($info, @extra);
488 # Make sure master is blessed into the correct class and apply role to it.
489 my $master = $self->master;
490 $master->_determine_driver;
491 Moose::Meta::Class->initialize(ref $master);
493 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
495 # link pool back to master
496 $self->pool->master($master);
498 wantarray ? @res : $res[0];
503 This class defines the following methods.
507 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
508 first argument. So we need to massage the arguments a bit so that all the
509 bits get put into the correct places.
514 my ($class, $schema, $storage_type_args, @args) = @_;
525 Lazy builder for the L</master> attribute.
531 my $master = DBIx::Class::Storage::DBI->new($self->schema);
537 Lazy builder for the L</pool> attribute.
543 $self->create_pool(%{$self->pool_args});
546 =head2 _build_balancer
548 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
549 the balancer knows which pool it's balancing.
553 sub _build_balancer {
555 $self->create_balancer(
557 master=>$self->master,
558 %{$self->balancer_args},
562 =head2 _build_write_handler
564 Lazy builder for the L</write_handler> attribute. The default is to set this to
569 sub _build_write_handler {
570 return shift->master;
573 =head2 _build_read_handler
575 Lazy builder for the L</read_handler> attribute. The default is to set this to
580 sub _build_read_handler {
581 return shift->balancer;
584 =head2 around: connect_replicants
586 All calls to connect_replicants needs to have an existing $schema tacked onto
587 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
588 options merged with the master, with replicant opts having higher priority.
592 around connect_replicants => sub {
593 my ($next, $self, @args) = @_;
596 $r = [ $r ] unless reftype $r eq 'ARRAY';
598 $self->throw_exception('coderef replicant connect_info not supported')
599 if ref $r->[0] && reftype $r->[0] eq 'CODE';
601 # any connect_info options?
603 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
606 $r->[$i] = {} unless $r->[$i];
608 # merge if two hashes
609 my @hashes = @$r[$i .. $#{$r}];
611 $self->throw_exception('invalid connect_info options')
612 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
614 $self->throw_exception('too many hashrefs in connect_info')
617 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
618 my %opts = %{ $merge->merge(reverse @hashes) };
621 splice @$r, $i+1, ($#{$r} - $i), ();
623 # make sure master/replicants opts don't clash
624 my %master_opts = %{ $self->_master_connect_info_opts };
625 if (exists $opts{dbh_maker}) {
626 delete @master_opts{qw/dsn user password/};
628 delete $master_opts{dbh_maker};
631 %opts = %{ $merge->merge(\%opts, \%master_opts) };
637 $self->$next($self->schema, @args);
642 Returns an array of of all the connected storage backends. The first element
643 in the returned array is the master, and the remainings are each of the
650 return grep {defined $_ && blessed $_} (
652 values %{ $self->replicants },
656 =head2 execute_reliably ($coderef, ?@args)
658 Given a coderef, saves the current state of the L</read_handler>, forces it to
659 use reliable storage (e.g. sets it to the master), executes a coderef and then
660 restores the original state.
666 $schema->resultset('User')->create({name=>$name});
667 my $user_rs = $schema->resultset('User')->find({name=>$name});
671 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
673 Use this when you must be certain of your database state, such as when you just
674 inserted something and need to get a resultset including it, etc.
678 sub execute_reliably {
679 my ($self, $coderef, @args) = @_;
681 unless( ref $coderef eq 'CODE') {
682 $self->throw_exception('Second argument must be a coderef');
685 ##Get copy of master storage
686 my $master = $self->master;
688 ##Get whatever the current read hander is
689 my $current = $self->read_handler;
691 ##Set the read handler to master
692 $self->read_handler($master);
694 ## do whatever the caller needs
696 my $want_array = wantarray;
700 @result = $coderef->(@args);
701 } elsif(defined $want_array) {
702 ($result[0]) = ($coderef->(@args));
707 $self->throw_exception("coderef returned an error: $_");
709 ##Reset to the original state
710 $self->read_handler($current);
713 return wantarray ? @result : $result[0];
716 =head2 set_reliable_storage
718 Sets the current $schema to be 'reliable', that is all queries, both read and
719 write are sent to the master
723 sub set_reliable_storage {
725 my $schema = $self->schema;
726 my $write_handler = $self->schema->storage->write_handler;
728 $schema->storage->read_handler($write_handler);
731 =head2 set_balanced_storage
733 Sets the current $schema to be use the </balancer> for all reads, while all
734 writes are sent to the master only
738 sub set_balanced_storage {
740 my $schema = $self->schema;
741 my $balanced_handler = $self->schema->storage->balancer;
743 $schema->storage->read_handler($balanced_handler);
748 Check that the master and at least one of the replicants is connected.
755 $self->master->connected &&
756 $self->pool->connected_replicants;
759 =head2 ensure_connected
761 Make sure all the storages are connected.
765 sub ensure_connected {
767 foreach my $source ($self->all_storages) {
768 $source->ensure_connected(@_);
774 Set the limit_dialect for all existing storages
780 foreach my $source ($self->all_storages) {
781 $source->limit_dialect(@_);
783 return $self->master->limit_dialect;
788 Set the quote_char for all existing storages
794 foreach my $source ($self->all_storages) {
795 $source->quote_char(@_);
797 return $self->master->quote_char;
802 Set the name_sep for all existing storages
808 foreach my $source ($self->all_storages) {
809 $source->name_sep(@_);
811 return $self->master->name_sep;
816 Set the schema object for all existing storages
822 foreach my $source ($self->all_storages) {
823 $source->set_schema(@_);
829 set a debug flag across all storages
836 foreach my $source ($self->all_storages) {
840 return $self->master->debug;
851 return $self->master->debugobj(@_);
862 return $self->master->debugfh(@_);
873 return $self->master->debugcb(@_);
878 disconnect everything
884 foreach my $source ($self->all_storages) {
885 $source->disconnect(@_);
891 set cursor class on all storages, or return master's
896 my ($self, $cursor_class) = @_;
899 $_->cursor_class($cursor_class) for $self->all_storages;
901 $self->master->cursor_class;
906 set cursor class on all storages, or return master's, alias for L</cursor_class>
912 my ($self, $cursor_class) = @_;
915 $_->cursor($cursor_class) for $self->all_storages;
917 $self->master->cursor;
922 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
923 master's current setting
931 $_->unsafe(@_) for $self->all_storages;
934 return $self->master->unsafe;
937 =head2 disable_sth_caching
939 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
940 or returns master's current setting
944 sub disable_sth_caching {
948 $_->disable_sth_caching(@_) for $self->all_storages;
951 return $self->master->disable_sth_caching;
954 =head2 lag_behind_master
956 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
961 sub lag_behind_master {
964 return max map $_->lag_behind_master, $self->replicants;
967 =head2 is_replicating
969 returns true if all replicants return true for
970 L<DBIx::Class::Storage::DBI/is_replicating>
977 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
980 =head2 connect_call_datetime_setup
982 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
986 sub connect_call_datetime_setup {
988 $_->connect_call_datetime_setup for $self->all_storages;
993 $_->_populate_dbh for $self->all_storages;
998 $_->_connect for $self->all_storages;
1003 $_->_rebless for $self->all_storages;
1006 sub _determine_driver {
1008 $_->_determine_driver for $self->all_storages;
1011 sub _driver_determined {
1015 $_->_driver_determined(@_) for $self->all_storages;
1018 return $self->master->_driver_determined;
1024 $_->_init for $self->all_storages;
1027 sub _run_connection_actions {
1030 $_->_run_connection_actions for $self->all_storages;
1033 sub _do_connection_actions {
1037 $_->_do_connection_actions(@_) for $self->all_storages;
1041 sub connect_call_do_sql {
1043 $_->connect_call_do_sql(@_) for $self->all_storages;
1046 sub disconnect_call_do_sql {
1048 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1051 sub _seems_connected {
1054 return min map $_->_seems_connected, $self->all_storages;
1060 return min map $_->_ping, $self->all_storages;
1063 # not using the normalized_version, because we want to preserve
1064 # version numbers much longer than the conventional xxx.yyyzzz
1065 my $numify_ver = sub {
1067 my @numparts = split /\D+/, $ver;
1068 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1070 return sprintf $format, @numparts;
1075 if (not $self->_dbh_details->{info}) {
1076 $self->_dbh_details->{info} = (
1077 reduce { $a->[0] < $b->[0] ? $a : $b }
1078 map [ $numify_ver->($_->{dbms_version}), $_ ],
1079 map $_->_server_info, $self->all_storages
1083 return $self->next::method;
1086 sub _get_server_version {
1089 return $self->_server_info->{dbms_version};
1094 Due to the fact that replicants can lag behind a master, you must take care to
1095 make sure you use one of the methods to force read queries to a master should
1096 you need realtime data integrity. For example, if you insert a row, and then
1097 immediately re-read it from the database (say, by doing $row->discard_changes)
1098 or you insert a row and then immediately build a query that expects that row
1099 to be an item, you should force the master to handle reads. Otherwise, due to
1100 the lag, there is no certainty your data will be in the expected state.
1102 For data integrity, all transactions automatically use the master storage for
1103 all read and write queries. Using a transaction is the preferred and recommended
1104 method to force the master to handle all read queries.
1106 Otherwise, you can force a single query to use the master with the 'force_pool'
1109 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1111 This attribute will safely be ignore by non replicated storages, so you can use
1112 the same code for both types of systems.
1114 Lastly, you can use the L</execute_reliably> method, which works very much like
1117 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1118 and L</set_balanced_storage>, however this operates at a global level and is not
1119 suitable if you have a shared Schema object being used by multiple processes,
1120 such as on a web application server. You can get around this limitation by
1121 using the Schema clone method.
1123 my $new_schema = $schema->clone;
1124 $new_schema->set_reliable_storage;
1126 ## $new_schema will use only the Master storage for all reads/writes while
1127 ## the $schema object will use replicated storage.
1131 John Napiorkowski <john.napiorkowski@takkle.com>
1133 Based on code originated by:
1135 Norbert Csongrádi <bert@cpan.org>
1136 Peter Siklósi <einon@einon.hu>
1140 You may distribute this code under the same terms as Perl itself.
1144 __PACKAGE__->meta->make_immutable;