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 reduce/;
22 use namespace::clean -except => 'meta';
26 DBIx::Class::Storage::DBI::Replicated - BETA Replicated database support
30 The Following example shows how to change an existing $schema to a replicated
31 storage type, add some replicated (read-only) databases, and perform reporting
34 You should set the 'storage_type attribute to a replicated type. You should
35 also define your arguments, such as which balancer you want and any arguments
36 that the Pool object should get.
38 my $schema = Schema::Class->clone;
39 $schema->storage_type( ['::DBI::Replicated', {balancer=>'::Random'}] );
40 $schema->connection(...);
42 Next, you need to add in the Replicants. Basically this is an array of
43 arrayrefs, where each arrayref is database connect information. Think of these
44 arguments as what you'd pass to the 'normal' $schema->connect method.
46 $schema->storage->connect_replicants(
47 [$dsn1, $user, $pass, \%opts],
48 [$dsn2, $user, $pass, \%opts],
49 [$dsn3, $user, $pass, \%opts],
52 Now, just use the $schema as you normally would. Automatically all reads will
53 be delegated to the replicants, while writes to the master.
55 $schema->resultset('Source')->search({name=>'etc'});
57 You can force a given query to use a particular storage using the search
58 attribute 'force_pool'. For example:
60 my $RS = $schema->resultset('Source')->search(undef, {force_pool=>'master'});
62 Now $RS will force everything (both reads and writes) to use whatever was setup
63 as the master storage. 'master' is hardcoded to always point to the Master,
64 but you can also use any Replicant name. Please see:
65 L<DBIx::Class::Storage::DBI::Replicated::Pool> and the replicants attribute for more.
67 Also see transactions and L</execute_reliably> for alternative ways to
68 force read traffic to the master. In general, you should wrap your statements
69 in a transaction when you are reading and writing to the same tables at the
70 same time, since your replicants will often lag a bit behind the master.
72 See L<DBIx::Class::Storage::DBI::Replicated::Instructions> for more help and
77 Warning: This class is marked BETA. This has been running a production
78 website using MySQL native replication as its backend and we have some decent
79 test coverage but the code hasn't yet been stressed by a variety of databases.
80 Individual DBs may have quirks we are not aware of. Please use this in first
81 development and pass along your experiences/bug fixes.
83 This class implements replicated data store for DBI. Currently you can define
84 one master and numerous slave database connections. All write-type queries
85 (INSERT, UPDATE, DELETE and even LAST_INSERT_ID) are routed to master
86 database, all read-type queries (SELECTs) go to the slave database.
88 Basically, any method request that L<DBIx::Class::Storage::DBI> would normally
89 handle gets delegated to one of the two attributes: L</read_handler> or to
90 L</write_handler>. Additionally, some methods need to be distributed
91 to all existing storages. This way our storage class is a drop in replacement
92 for L<DBIx::Class::Storage::DBI>.
94 Read traffic is spread across the replicants (slaves) occurring to a user
95 selected algorithm. The default algorithm is random weighted.
99 The consistency between master and replicants is database specific. The Pool
100 gives you a method to validate its replicants, removing and replacing them
101 when they fail/pass predefined criteria. Please make careful use of the ways
102 to force a query to run against Master when needed.
106 Replicated Storage has additional requirements not currently part of
107 L<DBIx::Class>. See L<DBIx::Class::Optional::Dependencies> for more details.
111 This class defines the following attributes.
115 The underlying L<DBIx::Class::Schema> object this storage is attaching
128 Contains the classname which will instantiate the L</pool> object. Defaults
129 to: L<DBIx::Class::Storage::DBI::Replicated::Pool>.
136 default=>'DBIx::Class::Storage::DBI::Replicated::Pool',
138 'create_pool' => 'new',
144 Contains a hashref of initialized information to pass to the Balancer object.
145 See L<DBIx::Class::Storage::DBI::Replicated::Pool> for available arguments.
159 The replication pool requires a balance class to provider the methods for
160 choose how to spread the query load across each replicant in the pool.
164 has 'balancer_type' => (
166 isa=>BalancerClassNamePart,
169 default=> 'DBIx::Class::Storage::DBI::Replicated::Balancer::First',
171 'create_balancer' => 'new',
177 Contains a hashref of initialized information to pass to the Balancer object.
178 See L<DBIx::Class::Storage::DBI::Replicated::Balancer> for available arguments.
182 has 'balancer_args' => (
192 Is a <DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a
193 container class for one or more replicated databases.
199 isa=>'DBIx::Class::Storage::DBI::Replicated::Pool',
210 Is a <DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This
211 is a class that takes a pool (<DBIx::Class::Storage::DBI::Replicated::Pool>)
217 isa=>'DBIx::Class::Storage::DBI::Replicated::Balancer',
219 handles=>[qw/auto_validate_every/],
224 The master defines the canonical state for a pool of connected databases. All
225 the replicants are expected to match this databases state. Thus, in a classic
226 Master / Slaves distributed system, all the slaves are expected to replicate
227 the Master's state as quick as possible. This is the only database in the
228 pool of databases that is allowed to handle write traffic.
238 =head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE
240 The following methods are delegated all the methods required for the
241 L<DBIx::Class::Storage::DBI> interface.
245 Defines an object that implements the read side of L<BIx::Class::Storage::DBI>.
249 has 'read_handler' => (
257 _dbh_columns_info_for
264 Defines an object that implements the write side of L<BIx::Class::Storage::DBI>,
265 as well as methods that don't write or read that can be called on only one
266 storage, methods that return a C<$dbh>, and any methods that don't make sense to
271 has 'write_handler' => (
286 deployment_statements
289 build_datetime_parser
303 with_deferred_fk_checks
306 with_deferred_fk_checks
311 _supports_insert_returning
317 relname_to_table_alias
318 _straight_join_to_node
321 _default_dbi_connect_attributes
326 bind_attribute_by_data_type
335 _per_row_update_delete
337 _dbh_execute_inserts_with_no_binds
338 _select_args_to_query
340 _multipk_update_delete
341 source_bind_attributes
342 _normalize_connect_info
346 _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
374 my @unimplemented = qw(
375 _arm_global_destructor
376 _preserve_foreign_dbh
381 for my $method (@unimplemented) {
382 __PACKAGE__->meta->add_method($method, sub {
383 croak "$method must not be called on ".(blessed shift).' objects';
387 has _master_connect_info_opts =>
388 (is => 'rw', isa => HashRef, default => sub { {} });
390 =head2 around: connect_info
392 Preserves master's C<connect_info> options (for merging with replicants.)
393 Also sets any Replicated-related options from connect_info, such as
394 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
398 around connect_info => sub {
399 my ($next, $self, $info, @extra) = @_;
401 my $wantarray = wantarray;
403 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
406 for my $arg (@$info) {
407 next unless (reftype($arg)||'') eq 'HASH';
408 %opts = %{ $merge->merge($arg, \%opts) };
412 if (@opts{qw/pool_type pool_args/}) {
413 $self->pool_type(delete $opts{pool_type})
417 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
420 $self->pool($self->_build_pool)
424 if (@opts{qw/balancer_type balancer_args/}) {
425 $self->balancer_type(delete $opts{balancer_type})
426 if $opts{balancer_type};
428 $self->balancer_args(
429 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
432 $self->balancer($self->_build_balancer)
436 $self->_master_connect_info_opts(\%opts);
440 @res = $self->$next($info, @extra);
442 $res = $self->$next($info, @extra);
445 # Make sure master is blessed into the correct class and apply role to it.
446 my $master = $self->master;
447 $master->_determine_driver;
448 Moose::Meta::Class->initialize(ref $master);
450 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
452 # link pool back to master
453 $self->pool->master($master);
455 $wantarray ? @res : $res;
460 This class defines the following methods.
464 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
465 first argument. So we need to massage the arguments a bit so that all the
466 bits get put into the correct places.
471 my ($class, $schema, $storage_type_args, @args) = @_;
482 Lazy builder for the L</master> attribute.
488 my $master = DBIx::Class::Storage::DBI->new($self->schema);
494 Lazy builder for the L</pool> attribute.
500 $self->create_pool(%{$self->pool_args});
503 =head2 _build_balancer
505 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
506 the balancer knows which pool it's balancing.
510 sub _build_balancer {
512 $self->create_balancer(
514 master=>$self->master,
515 %{$self->balancer_args},
519 =head2 _build_write_handler
521 Lazy builder for the L</write_handler> attribute. The default is to set this to
526 sub _build_write_handler {
527 return shift->master;
530 =head2 _build_read_handler
532 Lazy builder for the L</read_handler> attribute. The default is to set this to
537 sub _build_read_handler {
538 return shift->balancer;
541 =head2 around: connect_replicants
543 All calls to connect_replicants needs to have an existing $schema tacked onto
544 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
545 options merged with the master, with replicant opts having higher priority.
549 around connect_replicants => sub {
550 my ($next, $self, @args) = @_;
553 $r = [ $r ] unless reftype $r eq 'ARRAY';
555 $self->throw_exception('coderef replicant connect_info not supported')
556 if ref $r->[0] && reftype $r->[0] eq 'CODE';
558 # any connect_info options?
560 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
563 $r->[$i] = {} unless $r->[$i];
565 # merge if two hashes
566 my @hashes = @$r[$i .. $#{$r}];
568 $self->throw_exception('invalid connect_info options')
569 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
571 $self->throw_exception('too many hashrefs in connect_info')
574 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
575 my %opts = %{ $merge->merge(reverse @hashes) };
578 splice @$r, $i+1, ($#{$r} - $i), ();
580 # make sure master/replicants opts don't clash
581 my %master_opts = %{ $self->_master_connect_info_opts };
582 if (exists $opts{dbh_maker}) {
583 delete @master_opts{qw/dsn user password/};
585 delete $master_opts{dbh_maker};
588 %opts = %{ $merge->merge(\%opts, \%master_opts) };
594 $self->$next($self->schema, @args);
599 Returns an array of of all the connected storage backends. The first element
600 in the returned array is the master, and the remainings are each of the
607 return grep {defined $_ && blessed $_} (
609 values %{ $self->replicants },
613 =head2 execute_reliably ($coderef, ?@args)
615 Given a coderef, saves the current state of the L</read_handler>, forces it to
616 use reliable storage (e.g. sets it to the master), executes a coderef and then
617 restores the original state.
623 $schema->resultset('User')->create({name=>$name});
624 my $user_rs = $schema->resultset('User')->find({name=>$name});
628 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
630 Use this when you must be certain of your database state, such as when you just
631 inserted something and need to get a resultset including it, etc.
635 sub execute_reliably {
636 my ($self, $coderef, @args) = @_;
638 unless( ref $coderef eq 'CODE') {
639 $self->throw_exception('Second argument must be a coderef');
642 ##Get copy of master storage
643 my $master = $self->master;
645 ##Get whatever the current read hander is
646 my $current = $self->read_handler;
648 ##Set the read handler to master
649 $self->read_handler($master);
651 ## do whatever the caller needs
653 my $want_array = wantarray;
657 @result = $coderef->(@args);
658 } elsif(defined $want_array) {
659 ($result[0]) = ($coderef->(@args));
664 $self->throw_exception("coderef returned an error: $_");
666 ##Reset to the original state
667 $self->read_handler($current);
670 return $want_array ? @result : $result[0];
673 =head2 set_reliable_storage
675 Sets the current $schema to be 'reliable', that is all queries, both read and
676 write are sent to the master
680 sub set_reliable_storage {
682 my $schema = $self->schema;
683 my $write_handler = $self->schema->storage->write_handler;
685 $schema->storage->read_handler($write_handler);
688 =head2 set_balanced_storage
690 Sets the current $schema to be use the </balancer> for all reads, while all
691 writes are sent to the master only
695 sub set_balanced_storage {
697 my $schema = $self->schema;
698 my $balanced_handler = $self->schema->storage->balancer;
700 $schema->storage->read_handler($balanced_handler);
705 Check that the master and at least one of the replicants is connected.
712 $self->master->connected &&
713 $self->pool->connected_replicants;
716 =head2 ensure_connected
718 Make sure all the storages are connected.
722 sub ensure_connected {
724 foreach my $source ($self->all_storages) {
725 $source->ensure_connected(@_);
731 Set the limit_dialect for all existing storages
737 foreach my $source ($self->all_storages) {
738 $source->limit_dialect(@_);
740 return $self->master->quote_char;
745 Set the quote_char for all existing storages
751 foreach my $source ($self->all_storages) {
752 $source->quote_char(@_);
754 return $self->master->quote_char;
759 Set the name_sep for all existing storages
765 foreach my $source ($self->all_storages) {
766 $source->name_sep(@_);
768 return $self->master->name_sep;
773 Set the schema object for all existing storages
779 foreach my $source ($self->all_storages) {
780 $source->set_schema(@_);
786 set a debug flag across all storages
793 foreach my $source ($self->all_storages) {
797 return $self->master->debug;
808 return $self->master->debugobj(@_);
819 return $self->master->debugfh(@_);
830 return $self->master->debugcb(@_);
835 disconnect everything
841 foreach my $source ($self->all_storages) {
842 $source->disconnect(@_);
848 set cursor class on all storages, or return master's
853 my ($self, $cursor_class) = @_;
856 $_->cursor_class($cursor_class) for $self->all_storages;
858 $self->master->cursor_class;
863 set cursor class on all storages, or return master's, alias for L</cursor_class>
869 my ($self, $cursor_class) = @_;
872 $_->cursor($cursor_class) for $self->all_storages;
874 $self->master->cursor;
879 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
880 master's current setting
888 $_->unsafe(@_) for $self->all_storages;
891 return $self->master->unsafe;
894 =head2 disable_sth_caching
896 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
897 or returns master's current setting
901 sub disable_sth_caching {
905 $_->disable_sth_caching(@_) for $self->all_storages;
908 return $self->master->disable_sth_caching;
911 =head2 lag_behind_master
913 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
918 sub lag_behind_master {
921 return max map $_->lag_behind_master, $self->replicants;
924 =head2 is_replicating
926 returns true if all replicants return true for
927 L<DBIx::Class::Storage::DBI/is_replicating>
934 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
937 =head2 connect_call_datetime_setup
939 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
943 sub connect_call_datetime_setup {
945 $_->connect_call_datetime_setup for $self->all_storages;
950 $_->_populate_dbh for $self->all_storages;
955 $_->_connect for $self->all_storages;
960 $_->_rebless for $self->all_storages;
963 sub _determine_driver {
965 $_->_determine_driver for $self->all_storages;
968 sub _driver_determined {
972 $_->_driver_determined(@_) for $self->all_storages;
975 return $self->master->_driver_determined;
981 $_->_init for $self->all_storages;
984 sub _run_connection_actions {
987 $_->_run_connection_actions for $self->all_storages;
990 sub _do_connection_actions {
994 $_->_do_connection_actions(@_) for $self->all_storages;
998 sub connect_call_do_sql {
1000 $_->connect_call_do_sql(@_) for $self->all_storages;
1003 sub disconnect_call_do_sql {
1005 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1008 sub _seems_connected {
1011 return min map $_->_seems_connected, $self->all_storages;
1017 return min map $_->_ping, $self->all_storages;
1020 my $numify_ver = sub {
1022 my @numparts = split /\D+/, $ver;
1023 my $format = '%d.' . (join '', ('%05d') x (@numparts - 1));
1025 return sprintf $format, @numparts;
1031 if (not $self->_server_info_hash) {
1032 my $min_version_info = (
1033 reduce { $a->[0] < $b->[0] ? $a : $b }
1034 map [ $numify_ver->($_->{dbms_version}), $_ ],
1035 map $_->_server_info, $self->all_storages
1038 $self->_server_info_hash($min_version_info); # on master
1041 return $self->_server_info_hash;
1044 sub _get_server_version {
1047 return $self->_server_info->{dbms_version};
1052 Due to the fact that replicants can lag behind a master, you must take care to
1053 make sure you use one of the methods to force read queries to a master should
1054 you need realtime data integrity. For example, if you insert a row, and then
1055 immediately re-read it from the database (say, by doing $row->discard_changes)
1056 or you insert a row and then immediately build a query that expects that row
1057 to be an item, you should force the master to handle reads. Otherwise, due to
1058 the lag, there is no certainty your data will be in the expected state.
1060 For data integrity, all transactions automatically use the master storage for
1061 all read and write queries. Using a transaction is the preferred and recommended
1062 method to force the master to handle all read queries.
1064 Otherwise, you can force a single query to use the master with the 'force_pool'
1067 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1069 This attribute will safely be ignore by non replicated storages, so you can use
1070 the same code for both types of systems.
1072 Lastly, you can use the L</execute_reliably> method, which works very much like
1075 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1076 and L</set_balanced_storage>, however this operates at a global level and is not
1077 suitable if you have a shared Schema object being used by multiple processes,
1078 such as on a web application server. You can get around this limitation by
1079 using the Schema clone method.
1081 my $new_schema = $schema->clone;
1082 $new_schema->set_reliable_storage;
1084 ## $new_schema will use only the Master storage for all reads/writes while
1085 ## the $schema object will use replicated storage.
1089 John Napiorkowski <john.napiorkowski@takkle.com>
1091 Based on code originated by:
1093 Norbert Csongrádi <bert@cpan.org>
1094 Peter Siklósi <einon@einon.hu>
1098 You may distribute this code under the same terms as Perl itself.
1102 __PACKAGE__->meta->make_immutable;