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/;
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
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
373 my @unimplemented = qw(
374 _arm_global_destructor
375 _preserve_foreign_dbh
378 for my $method (@unimplemented) {
379 __PACKAGE__->meta->add_method($method, sub {
380 croak "$method must not be called on ".(blessed shift).' objects';
384 has _master_connect_info_opts =>
385 (is => 'rw', isa => HashRef, default => sub { {} });
387 =head2 around: connect_info
389 Preserves master's C<connect_info> options (for merging with replicants.)
390 Also sets any Replicated-related options from connect_info, such as
391 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
395 around connect_info => sub {
396 my ($next, $self, $info, @extra) = @_;
398 my $wantarray = wantarray;
400 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
403 for my $arg (@$info) {
404 next unless (reftype($arg)||'') eq 'HASH';
405 %opts = %{ $merge->merge($arg, \%opts) };
409 if (@opts{qw/pool_type pool_args/}) {
410 $self->pool_type(delete $opts{pool_type})
414 $merge->merge((delete $opts{pool_args} || {}), $self->pool_args)
417 $self->pool($self->_build_pool)
421 if (@opts{qw/balancer_type balancer_args/}) {
422 $self->balancer_type(delete $opts{balancer_type})
423 if $opts{balancer_type};
425 $self->balancer_args(
426 $merge->merge((delete $opts{balancer_args} || {}), $self->balancer_args)
429 $self->balancer($self->_build_balancer)
433 $self->_master_connect_info_opts(\%opts);
437 @res = $self->$next($info, @extra);
439 $res = $self->$next($info, @extra);
442 # Make sure master is blessed into the correct class and apply role to it.
443 my $master = $self->master;
444 $master->_determine_driver;
445 Moose::Meta::Class->initialize(ref $master);
447 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
449 # link pool back to master
450 $self->pool->master($master);
452 $wantarray ? @res : $res;
457 This class defines the following methods.
461 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
462 first argument. So we need to massage the arguments a bit so that all the
463 bits get put into the correct places.
468 my ($class, $schema, $storage_type_args, @args) = @_;
479 Lazy builder for the L</master> attribute.
485 my $master = DBIx::Class::Storage::DBI->new($self->schema);
491 Lazy builder for the L</pool> attribute.
497 $self->create_pool(%{$self->pool_args});
500 =head2 _build_balancer
502 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
503 the balancer knows which pool it's balancing.
507 sub _build_balancer {
509 $self->create_balancer(
511 master=>$self->master,
512 %{$self->balancer_args},
516 =head2 _build_write_handler
518 Lazy builder for the L</write_handler> attribute. The default is to set this to
523 sub _build_write_handler {
524 return shift->master;
527 =head2 _build_read_handler
529 Lazy builder for the L</read_handler> attribute. The default is to set this to
534 sub _build_read_handler {
535 return shift->balancer;
538 =head2 around: connect_replicants
540 All calls to connect_replicants needs to have an existing $schema tacked onto
541 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
542 options merged with the master, with replicant opts having higher priority.
546 around connect_replicants => sub {
547 my ($next, $self, @args) = @_;
550 $r = [ $r ] unless reftype $r eq 'ARRAY';
552 $self->throw_exception('coderef replicant connect_info not supported')
553 if ref $r->[0] && reftype $r->[0] eq 'CODE';
555 # any connect_info options?
557 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
560 $r->[$i] = {} unless $r->[$i];
562 # merge if two hashes
563 my @hashes = @$r[$i .. $#{$r}];
565 $self->throw_exception('invalid connect_info options')
566 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
568 $self->throw_exception('too many hashrefs in connect_info')
571 my $merge = Hash::Merge->new('LEFT_PRECEDENT');
572 my %opts = %{ $merge->merge(reverse @hashes) };
575 splice @$r, $i+1, ($#{$r} - $i), ();
577 # make sure master/replicants opts don't clash
578 my %master_opts = %{ $self->_master_connect_info_opts };
579 if (exists $opts{dbh_maker}) {
580 delete @master_opts{qw/dsn user password/};
582 delete $master_opts{dbh_maker};
585 %opts = %{ $merge->merge(\%opts, \%master_opts) };
591 $self->$next($self->schema, @args);
596 Returns an array of of all the connected storage backends. The first element
597 in the returned array is the master, and the remainings are each of the
604 return grep {defined $_ && blessed $_} (
606 values %{ $self->replicants },
610 =head2 execute_reliably ($coderef, ?@args)
612 Given a coderef, saves the current state of the L</read_handler>, forces it to
613 use reliable storage (e.g. sets it to the master), executes a coderef and then
614 restores the original state.
620 $schema->resultset('User')->create({name=>$name});
621 my $user_rs = $schema->resultset('User')->find({name=>$name});
625 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
627 Use this when you must be certain of your database state, such as when you just
628 inserted something and need to get a resultset including it, etc.
632 sub execute_reliably {
633 my ($self, $coderef, @args) = @_;
635 unless( ref $coderef eq 'CODE') {
636 $self->throw_exception('Second argument must be a coderef');
639 ##Get copy of master storage
640 my $master = $self->master;
642 ##Get whatever the current read hander is
643 my $current = $self->read_handler;
645 ##Set the read handler to master
646 $self->read_handler($master);
648 ## do whatever the caller needs
650 my $want_array = wantarray;
654 @result = $coderef->(@args);
655 } elsif(defined $want_array) {
656 ($result[0]) = ($coderef->(@args));
662 ##Reset to the original state
663 $self->read_handler($current);
665 ##Exception testing has to come last, otherwise you might leave the
666 ##read_handler set to master.
669 $self->throw_exception("coderef returned an error: $@");
671 return $want_array ? @result : $result[0];
675 =head2 set_reliable_storage
677 Sets the current $schema to be 'reliable', that is all queries, both read and
678 write are sent to the master
682 sub set_reliable_storage {
684 my $schema = $self->schema;
685 my $write_handler = $self->schema->storage->write_handler;
687 $schema->storage->read_handler($write_handler);
690 =head2 set_balanced_storage
692 Sets the current $schema to be use the </balancer> for all reads, while all
693 writes are sent to the master only
697 sub set_balanced_storage {
699 my $schema = $self->schema;
700 my $balanced_handler = $self->schema->storage->balancer;
702 $schema->storage->read_handler($balanced_handler);
707 Check that the master and at least one of the replicants is connected.
714 $self->master->connected &&
715 $self->pool->connected_replicants;
718 =head2 ensure_connected
720 Make sure all the storages are connected.
724 sub ensure_connected {
726 foreach my $source ($self->all_storages) {
727 $source->ensure_connected(@_);
733 Set the limit_dialect for all existing storages
739 foreach my $source ($self->all_storages) {
740 $source->limit_dialect(@_);
742 return $self->master->quote_char;
747 Set the quote_char for all existing storages
753 foreach my $source ($self->all_storages) {
754 $source->quote_char(@_);
756 return $self->master->quote_char;
761 Set the name_sep for all existing storages
767 foreach my $source ($self->all_storages) {
768 $source->name_sep(@_);
770 return $self->master->name_sep;
775 Set the schema object for all existing storages
781 foreach my $source ($self->all_storages) {
782 $source->set_schema(@_);
788 set a debug flag across all storages
795 foreach my $source ($self->all_storages) {
799 return $self->master->debug;
810 return $self->master->debugobj(@_);
821 return $self->master->debugfh(@_);
832 return $self->master->debugcb(@_);
837 disconnect everything
843 foreach my $source ($self->all_storages) {
844 $source->disconnect(@_);
850 set cursor class on all storages, or return master's
855 my ($self, $cursor_class) = @_;
858 $_->cursor_class($cursor_class) for $self->all_storages;
860 $self->master->cursor_class;
865 set cursor class on all storages, or return master's, alias for L</cursor_class>
871 my ($self, $cursor_class) = @_;
874 $_->cursor($cursor_class) for $self->all_storages;
876 $self->master->cursor;
881 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
882 master's current setting
890 $_->unsafe(@_) for $self->all_storages;
893 return $self->master->unsafe;
896 =head2 disable_sth_caching
898 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
899 or returns master's current setting
903 sub disable_sth_caching {
907 $_->disable_sth_caching(@_) for $self->all_storages;
910 return $self->master->disable_sth_caching;
913 =head2 lag_behind_master
915 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
920 sub lag_behind_master {
923 return max map $_->lag_behind_master, $self->replicants;
926 =head2 is_replicating
928 returns true if all replicants return true for
929 L<DBIx::Class::Storage::DBI/is_replicating>
936 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
939 =head2 connect_call_datetime_setup
941 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
945 sub connect_call_datetime_setup {
947 $_->connect_call_datetime_setup for $self->all_storages;
952 $_->_populate_dbh for $self->all_storages;
957 $_->_connect for $self->all_storages;
962 $_->_rebless for $self->all_storages;
965 sub _determine_driver {
967 $_->_determine_driver for $self->all_storages;
970 sub _driver_determined {
974 $_->_driver_determined(@_) for $self->all_storages;
977 return $self->master->_driver_determined;
983 $_->_init for $self->all_storages;
986 sub _run_connection_actions {
989 $_->_run_connection_actions for $self->all_storages;
992 sub _do_connection_actions {
996 $_->_do_connection_actions(@_) for $self->all_storages;
1000 sub connect_call_do_sql {
1002 $_->connect_call_do_sql(@_) for $self->all_storages;
1005 sub disconnect_call_do_sql {
1007 $_->disconnect_call_do_sql(@_) for $self->all_storages;
1010 sub _seems_connected {
1013 return min map $_->_seems_connected, $self->all_storages;
1019 return min map $_->_ping, $self->all_storages;
1022 my $numify_ver = sub {
1024 my @numparts = split /\D+/, $ver;
1025 my $format = '%d.' . (join '', ('%05d') x (@numparts - 1));
1027 return sprintf $format, @numparts;
1033 if (not $self->_server_info_hash) {
1034 my $min_version_info = (
1035 reduce { $a->[0] < $b->[0] ? $a : $b }
1036 map [ $numify_ver->($_->{dbms_version}), $_ ],
1037 map $_->_server_info, $self->all_storages
1040 $self->_server_info_hash($min_version_info); # on master
1043 return $self->_server_info_hash;
1046 sub _get_server_version {
1049 return $self->_server_info->{dbms_version};
1055 for my $storage ($self->all_storages) {
1056 $storage->_verify_pid;
1063 for my $storage ($self->all_storages) {
1064 $storage->_verify_tid;
1070 Due to the fact that replicants can lag behind a master, you must take care to
1071 make sure you use one of the methods to force read queries to a master should
1072 you need realtime data integrity. For example, if you insert a row, and then
1073 immediately re-read it from the database (say, by doing $row->discard_changes)
1074 or you insert a row and then immediately build a query that expects that row
1075 to be an item, you should force the master to handle reads. Otherwise, due to
1076 the lag, there is no certainty your data will be in the expected state.
1078 For data integrity, all transactions automatically use the master storage for
1079 all read and write queries. Using a transaction is the preferred and recommended
1080 method to force the master to handle all read queries.
1082 Otherwise, you can force a single query to use the master with the 'force_pool'
1085 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1087 This attribute will safely be ignore by non replicated storages, so you can use
1088 the same code for both types of systems.
1090 Lastly, you can use the L</execute_reliably> method, which works very much like
1093 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1094 and L</set_balanced_storage>, however this operates at a global level and is not
1095 suitable if you have a shared Schema object being used by multiple processes,
1096 such as on a web application server. You can get around this limitation by
1097 using the Schema clone method.
1099 my $new_schema = $schema->clone;
1100 $new_schema->set_reliable_storage;
1102 ## $new_schema will use only the Master storage for all reads/writes while
1103 ## the $schema object will use replicated storage.
1107 John Napiorkowski <john.napiorkowski@takkle.com>
1109 Based on code originated by:
1111 Norbert Csongrádi <bert@cpan.org>
1112 Peter Siklósi <einon@einon.hu>
1116 You may distribute this code under the same terms as Perl itself.
1120 __PACKAGE__->meta->make_immutable;