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/;
18 use Context::Preserve 'preserve_context';
21 use namespace::clean -except => 'meta';
27 DBIx::Class::Storage::DBI::Replicated - BETA Replicated database support
31 The Following example shows how to change an existing $schema to a replicated
32 storage type, add some replicated (read-only) databases, and perform reporting
35 You should set the 'storage_type attribute to a replicated type. You should
36 also define your arguments, such as which balancer you want and any arguments
37 that the Pool object should get.
39 my $schema = Schema::Class->clone;
40 $schema->storage_type( ['::DBI::Replicated', {balancer=>'::Random'}] );
41 $schema->connection(...);
43 Next, you need to add in the Replicants. Basically this is an array of
44 arrayrefs, where each arrayref is database connect information. Think of these
45 arguments as what you'd pass to the 'normal' $schema->connect method.
47 $schema->storage->connect_replicants(
48 [$dsn1, $user, $pass, \%opts],
49 [$dsn2, $user, $pass, \%opts],
50 [$dsn3, $user, $pass, \%opts],
53 Now, just use the $schema as you normally would. Automatically all reads will
54 be delegated to the replicants, while writes to the master.
56 $schema->resultset('Source')->search({name=>'etc'});
58 You can force a given query to use a particular storage using the search
59 attribute 'force_pool'. For example:
61 my $rs = $schema->resultset('Source')->search(undef, {force_pool=>'master'});
63 Now $rs will force everything (both reads and writes) to use whatever was setup
64 as the master storage. 'master' is hardcoded to always point to the Master,
65 but you can also use any Replicant name. Please see:
66 L<DBIx::Class::Storage::DBI::Replicated::Pool> and the replicants attribute for more.
68 Also see transactions and L</execute_reliably> for alternative ways to
69 force read traffic to the master. In general, you should wrap your statements
70 in a transaction when you are reading and writing to the same tables at the
71 same time, since your replicants will often lag a bit behind the master.
73 If you have a multi-statement read only transaction you can force it to select
74 a random server in the pool by:
76 my $rs = $schema->resultset('Source')->search( undef,
77 { force_pool => $db->storage->read_handler->next_storage }
82 Warning: This class is marked BETA. This has been running a production
83 website using MySQL native replication as its backend and we have some decent
84 test coverage but the code hasn't yet been stressed by a variety of databases.
85 Individual DBs may have quirks we are not aware of. Please use this in first
86 development and pass along your experiences/bug fixes.
88 This class implements replicated data store for DBI. Currently you can define
89 one master and numerous slave database connections. All write-type queries
90 (INSERT, UPDATE, DELETE and even LAST_INSERT_ID) are routed to master
91 database, all read-type queries (SELECTs) go to the slave database.
93 Basically, any method request that L<DBIx::Class::Storage::DBI> would normally
94 handle gets delegated to one of the two attributes: L</read_handler> or to
95 L</write_handler>. Additionally, some methods need to be distributed
96 to all existing storages. This way our storage class is a drop in replacement
97 for L<DBIx::Class::Storage::DBI>.
99 Read traffic is spread across the replicants (slaves) occurring to a user
100 selected algorithm. The default algorithm is random weighted.
104 The consistency between master and replicants is database specific. The Pool
105 gives you a method to validate its replicants, removing and replacing them
106 when they fail/pass predefined criteria. Please make careful use of the ways
107 to force a query to run against Master when needed.
111 Replicated Storage has additional requirements not currently part of
112 L<DBIx::Class>. See L<DBIx::Class::Optional::Dependencies> for more details.
116 This class defines the following attributes.
120 The underlying L<DBIx::Class::Schema> object this storage is attaching
133 Contains the classname which will instantiate the L</pool> object. Defaults
134 to: L<DBIx::Class::Storage::DBI::Replicated::Pool>.
141 default=>'DBIx::Class::Storage::DBI::Replicated::Pool',
143 'create_pool' => 'new',
149 Contains a hashref of initialized information to pass to the Balancer object.
150 See L<DBIx::Class::Storage::DBI::Replicated::Pool> for available arguments.
164 The replication pool requires a balance class to provider the methods for
165 choose how to spread the query load across each replicant in the pool.
169 has 'balancer_type' => (
171 isa=>BalancerClassNamePart,
174 default=> 'DBIx::Class::Storage::DBI::Replicated::Balancer::First',
176 'create_balancer' => 'new',
182 Contains a hashref of initialized information to pass to the Balancer object.
183 See L<DBIx::Class::Storage::DBI::Replicated::Balancer> for available arguments.
187 has 'balancer_args' => (
197 Is a L<DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a
198 container class for one or more replicated databases.
204 isa=>'DBIx::Class::Storage::DBI::Replicated::Pool',
215 Is a L<DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This
216 is a class that takes a pool (L<DBIx::Class::Storage::DBI::Replicated::Pool>)
222 isa=>'DBIx::Class::Storage::DBI::Replicated::Balancer',
224 handles=>[qw/auto_validate_every/],
229 The master defines the canonical state for a pool of connected databases. All
230 the replicants are expected to match this databases state. Thus, in a classic
231 Master / Slaves distributed system, all the slaves are expected to replicate
232 the Master's state as quick as possible. This is the only database in the
233 pool of databases that is allowed to handle write traffic.
243 =head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE
245 The following methods are delegated all the methods required for the
246 L<DBIx::Class::Storage::DBI> interface.
250 my $method_dispatch = {
262 deployment_statements
265 build_datetime_parser
281 with_deferred_fk_checks
289 relname_to_table_alias
291 _default_dbi_connect_attributes
293 _dbic_connect_attributes
299 bind_attribute_by_data_type
303 _dbh_execute_for_fetch
305 _dbh_execute_inserts_with_no_binds
306 _select_args_to_query
309 _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 get_use_dbms_capability
334 set_use_dbms_capability
340 _determine_connector_driver
341 _extract_driver_from_connect_info
343 _warn_undetermined_driver
350 _perform_autoinc_retrieval
351 _autoinc_supplied_for_op
364 # the capability framework
365 # not sure if CMOP->initialize does evil things to DBIC::S::DBI, fix if a problem
367 { $_ =~ /^ _ (?: use | supports | determine_supports ) _ /x }
368 ( Class::MOP::Class->initialize('DBIx::Class::Storage::DBI')->get_all_method_names )
372 if (DBIx::Class::_ENV_::DBICTEST) {
375 for my $type (keys %$method_dispatch) {
376 for (@{$method_dispatch->{$type}}) {
377 push @{$seen->{$_}}, $type;
381 if (my @dupes = grep { @{$seen->{$_}} > 1 } keys %$seen) {
383 'The following methods show up multiple times in ::Storage::DBI::Replicated handlers:',
384 (map { "$_: " . (join ', ', @{$seen->{$_}}) } sort @dupes),
389 if (my @cant = grep { ! DBIx::Class::Storage::DBI->can($_) } keys %$seen) {
391 '::Storage::DBI::Replicated specifies handling of the following *NON EXISTING* ::Storage::DBI methods:',
398 for my $method (@{$method_dispatch->{unimplemented}}) {
399 __PACKAGE__->meta->add_method($method, sub {
401 $self->throw_exception("$method() must not be called on ".(blessed $self).' objects');
407 Defines an object that implements the read side of L<BIx::Class::Storage::DBI>.
411 has 'read_handler' => (
415 handles=>$method_dispatch->{reader},
420 Defines an object that implements the write side of L<BIx::Class::Storage::DBI>,
421 as well as methods that don't write or read that can be called on only one
422 storage, methods that return a C<$dbh>, and any methods that don't make sense to
427 has 'write_handler' => (
431 handles=>$method_dispatch->{writer},
436 has _master_connect_info_opts =>
437 (is => 'rw', isa => HashRef, default => sub { {} });
439 =head2 around: connect_info
441 Preserves master's C<connect_info> options (for merging with replicants.)
442 Also sets any Replicated-related options from connect_info, such as
443 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
447 around connect_info => sub {
448 my ($next, $self, $info, @extra) = @_;
450 $self->throw_exception(
451 'connect_info can not be retrieved from a replicated storage - '
452 . 'accessor must be called on a specific pool instance'
453 ) unless defined $info;
455 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
458 for my $arg (@$info) {
459 next unless (reftype($arg)||'') eq 'HASH';
460 %opts = %{ $merge->merge($arg, \%opts) };
464 if (@opts{qw/pool_type pool_args/}) {
465 $self->pool_type(delete $opts{pool_type})
469 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
472 ## Since we possibly changed the pool_args, we need to clear the current
473 ## pool object so that next time it is used it will be rebuilt.
477 if (@opts{qw/balancer_type balancer_args/}) {
478 $self->balancer_type(delete $opts{balancer_type})
479 if $opts{balancer_type};
481 $self->balancer_args(
482 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
485 $self->balancer($self->_build_balancer)
489 $self->_master_connect_info_opts(\%opts);
491 return preserve_context {
492 $self->$next($info, @extra);
494 # Make sure master is blessed into the correct class and apply role to it.
495 my $master = $self->master;
496 $master->_determine_driver;
497 Moose::Meta::Class->initialize(ref $master);
499 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
501 # link pool back to master
502 $self->pool->master($master);
508 This class defines the following methods.
512 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
513 first argument. So we need to massage the arguments a bit so that all the
514 bits get put into the correct places.
519 my ($class, $schema, $storage_type_args, @args) = @_;
530 Lazy builder for the L</master> attribute.
536 my $master = DBIx::Class::Storage::DBI->new($self->schema);
542 Lazy builder for the L</pool> attribute.
548 $self->create_pool(%{$self->pool_args});
551 =head2 _build_balancer
553 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
554 the balancer knows which pool it's balancing.
558 sub _build_balancer {
560 $self->create_balancer(
562 master=>$self->master,
563 %{$self->balancer_args},
567 =head2 _build_write_handler
569 Lazy builder for the L</write_handler> attribute. The default is to set this to
574 sub _build_write_handler {
575 return shift->master;
578 =head2 _build_read_handler
580 Lazy builder for the L</read_handler> attribute. The default is to set this to
585 sub _build_read_handler {
586 return shift->balancer;
589 =head2 around: connect_replicants
591 All calls to connect_replicants needs to have an existing $schema tacked onto
592 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
593 options merged with the master, with replicant opts having higher priority.
597 around connect_replicants => sub {
598 my ($next, $self, @args) = @_;
601 $r = [ $r ] unless reftype $r eq 'ARRAY';
603 $self->throw_exception('coderef replicant connect_info not supported')
604 if ref $r->[0] && reftype $r->[0] eq 'CODE';
606 # any connect_info options?
608 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
611 $r->[$i] = {} unless $r->[$i];
613 # merge if two hashes
614 my @hashes = @$r[$i .. $#{$r}];
616 $self->throw_exception('invalid connect_info options')
617 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
619 $self->throw_exception('too many hashrefs in connect_info')
622 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
623 my %opts = %{ $merge->merge(reverse @hashes) };
626 splice @$r, $i+1, ($#{$r} - $i), ();
628 # make sure master/replicants opts don't clash
629 my %master_opts = %{ $self->_master_connect_info_opts };
630 if (exists $opts{dbh_maker}) {
631 delete @master_opts{qw/dsn user password/};
633 delete $master_opts{dbh_maker};
636 %opts = %{ $merge->merge(\%opts, \%master_opts) };
642 $self->$next($self->schema, @args);
647 Returns an array of all the connected storage backends. The first element
648 in the returned array is the master, and the rest are each of the
655 return grep {defined $_ && blessed $_} (
657 values %{ $self->replicants },
661 =head2 execute_reliably ($coderef, ?@args)
663 Given a coderef, saves the current state of the L</read_handler>, forces it to
664 use reliable storage (e.g. sets it to the master), executes a coderef and then
665 restores the original state.
671 $schema->resultset('User')->create({name=>$name});
672 my $user_rs = $schema->resultset('User')->find({name=>$name});
676 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
678 Use this when you must be certain of your database state, such as when you just
679 inserted something and need to get a resultset including it, etc.
683 sub execute_reliably {
687 unless( ref $coderef eq 'CODE') {
688 $self->throw_exception('Second argument must be a coderef');
691 ## replace the current read handler for the remainder of the scope
692 local $self->{read_handler} = $self->master;
698 $self->throw_exception("coderef returned an error: $_");
702 =head2 set_reliable_storage
704 Sets the current $schema to be 'reliable', that is all queries, both read and
705 write are sent to the master
709 sub set_reliable_storage {
711 my $schema = $self->schema;
712 my $write_handler = $self->schema->storage->write_handler;
714 $schema->storage->read_handler($write_handler);
717 =head2 set_balanced_storage
719 Sets the current $schema to be use the </balancer> for all reads, while all
720 writes are sent to the master only
724 sub set_balanced_storage {
726 my $schema = $self->schema;
727 my $balanced_handler = $self->schema->storage->balancer;
729 $schema->storage->read_handler($balanced_handler);
734 Check that the master and at least one of the replicants is connected.
741 $self->master->connected &&
742 $self->pool->connected_replicants;
745 =head2 ensure_connected
747 Make sure all the storages are connected.
751 sub ensure_connected {
753 foreach my $source ($self->all_storages) {
754 $source->ensure_connected(@_);
760 Set the limit_dialect for all existing storages
766 foreach my $source ($self->all_storages) {
767 $source->limit_dialect(@_);
769 return $self->master->limit_dialect;
774 Set the quote_char for all existing storages
780 foreach my $source ($self->all_storages) {
781 $source->quote_char(@_);
783 return $self->master->quote_char;
788 Set the name_sep for all existing storages
794 foreach my $source ($self->all_storages) {
795 $source->name_sep(@_);
797 return $self->master->name_sep;
802 Set the schema object for all existing storages
808 foreach my $source ($self->all_storages) {
809 $source->set_schema(@_);
815 set a debug flag across all storages
822 foreach my $source ($self->all_storages) {
826 return $self->master->debug;
837 return $self->master->debugobj(@_);
848 return $self->master->debugfh(@_);
859 return $self->master->debugcb(@_);
864 disconnect everything
870 foreach my $source ($self->all_storages) {
871 $source->disconnect(@_);
877 set cursor class on all storages, or return master's
882 my ($self, $cursor_class) = @_;
885 $_->cursor_class($cursor_class) for $self->all_storages;
887 $self->master->cursor_class;
892 set cursor class on all storages, or return master's, alias for L</cursor_class>
898 my ($self, $cursor_class) = @_;
901 $_->cursor($cursor_class) for $self->all_storages;
903 $self->master->cursor;
908 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
909 master's current setting
917 $_->unsafe(@_) for $self->all_storages;
920 return $self->master->unsafe;
923 =head2 disable_sth_caching
925 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
926 or returns master's current setting
930 sub disable_sth_caching {
934 $_->disable_sth_caching(@_) for $self->all_storages;
937 return $self->master->disable_sth_caching;
940 =head2 lag_behind_master
942 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
947 sub lag_behind_master {
950 return max map $_->lag_behind_master, $self->replicants;
953 =head2 is_replicating
955 returns true if all replicants return true for
956 L<DBIx::Class::Storage::DBI/is_replicating>
963 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
966 =head2 connect_call_datetime_setup
968 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
972 sub connect_call_datetime_setup {
974 $_->connect_call_datetime_setup for $self->all_storages;
979 $_->_populate_dbh for $self->all_storages;
984 $_->_connect for $self->all_storages;
989 $_->_rebless for $self->all_storages;
992 sub _determine_driver {
994 $_->_determine_driver for $self->all_storages;
997 sub _driver_determined {
1001 $_->_driver_determined(@_) for $self->all_storages;
1004 return $self->master->_driver_determined;
1010 $_->_init for $self->all_storages;
1013 sub _run_connection_actions {
1016 $_->_run_connection_actions for $self->all_storages;
1019 sub _do_connection_actions {
1023 $_->_do_connection_actions(@_) for $self->all_storages;
1027 sub connect_call_do_sql {
1029 $_->connect_call_do_sql(@_) for $self->all_storages;
1032 sub disconnect_call_do_sql {
1034 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1037 sub _seems_connected {
1040 return min map $_->_seems_connected, $self->all_storages;
1046 return min map $_->_ping, $self->all_storages;
1049 # not using the normalized_version, because we want to preserve
1050 # version numbers much longer than the conventional xxx.yyyzzz
1051 my $numify_ver = sub {
1053 my @numparts = split /\D+/, $ver;
1054 my $format = '%d.' . (join '', ('%06d') x (@numparts - 1));
1056 return sprintf $format, @numparts;
1061 if (not $self->_dbh_details->{info}) {
1062 $self->_dbh_details->{info} = (
1063 reduce { $a->[0] < $b->[0] ? $a : $b }
1064 map [ $numify_ver->($_->{dbms_version}), $_ ],
1065 map $_->_server_info, $self->all_storages
1069 return $self->next::method;
1072 sub _get_server_version {
1075 return $self->_server_info->{dbms_version};
1080 Due to the fact that replicants can lag behind a master, you must take care to
1081 make sure you use one of the methods to force read queries to a master should
1082 you need realtime data integrity. For example, if you insert a row, and then
1083 immediately re-read it from the database (say, by doing $result->discard_changes)
1084 or you insert a row and then immediately build a query that expects that row
1085 to be an item, you should force the master to handle reads. Otherwise, due to
1086 the lag, there is no certainty your data will be in the expected state.
1088 For data integrity, all transactions automatically use the master storage for
1089 all read and write queries. Using a transaction is the preferred and recommended
1090 method to force the master to handle all read queries.
1092 Otherwise, you can force a single query to use the master with the 'force_pool'
1095 my $result = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1097 This attribute will safely be ignore by non replicated storages, so you can use
1098 the same code for both types of systems.
1100 Lastly, you can use the L</execute_reliably> method, which works very much like
1103 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1104 and L</set_balanced_storage>, however this operates at a global level and is not
1105 suitable if you have a shared Schema object being used by multiple processes,
1106 such as on a web application server. You can get around this limitation by
1107 using the Schema clone method.
1109 my $new_schema = $schema->clone;
1110 $new_schema->set_reliable_storage;
1112 ## $new_schema will use only the Master storage for all reads/writes while
1113 ## the $schema object will use replicated storage.
1117 John Napiorkowski <john.napiorkowski@takkle.com>
1119 Based on code originated by:
1121 Norbert Csongrádi <bert@cpan.org>
1122 Peter Siklósi <einon@einon.hu>
1126 You may distribute this code under the same terms as Perl itself.
1130 __PACKAGE__->meta->make_immutable;