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';
17 use Hash::Merge 'merge';
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 (readonly) 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 DB's 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) occuring to a user
93 selected algorithm. The default algorithm is random weighted.
97 The consistancy betweeen 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> The missing requirements will be announced via an exception
106 when you try to load this module. You will need to install these modules
107 manually via CPAN or make them part of the Makefile for your distribution.
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
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
349 _sqlt_minimum_version
352 _typeless_placeholders_supported
359 _adjust_select_args_for_complex_prefetch
360 _resolve_ident_sources
363 _strip_cond_qualifiers
365 _resolve_aliastypes_from_select_args
373 has _master_connect_info_opts =>
374 (is => 'rw', isa => HashRef, default => sub { {} });
376 =head2 around: connect_info
378 Preserve master's C<connect_info> options (for merging with replicants.)
379 Also set any Replicated related options from connect_info, such as
380 C<pool_type>, C<pool_args>, C<balancer_type> and C<balancer_args>.
384 around connect_info => sub {
385 my ($next, $self, $info, @extra) = @_;
387 my $wantarray = wantarray;
390 for my $arg (@$info) {
391 next unless (reftype($arg)||'') eq 'HASH';
392 %opts = %{ merge($arg, \%opts) };
396 if (@opts{qw/pool_type pool_args/}) {
397 $self->pool_type(delete $opts{pool_type})
401 merge((delete $opts{pool_args} || {}), $self->pool_args)
404 $self->pool($self->_build_pool)
408 if (@opts{qw/balancer_type balancer_args/}) {
409 $self->balancer_type(delete $opts{balancer_type})
410 if $opts{balancer_type};
412 $self->balancer_args(
413 merge((delete $opts{balancer_args} || {}), $self->balancer_args)
416 $self->balancer($self->_build_balancer)
420 $self->_master_connect_info_opts(\%opts);
424 @res = $self->$next($info, @extra);
426 $res = $self->$next($info, @extra);
429 # Make sure master is blessed into the correct class and apply role to it.
430 my $master = $self->master;
431 $master->_determine_driver;
432 Moose::Meta::Class->initialize(ref $master);
434 DBIx::Class::Storage::DBI::Replicated::WithDSN->meta->apply($master);
436 # link pool back to master
437 $self->pool->master($master);
439 $wantarray ? @res : $res;
444 This class defines the following methods.
448 L<DBIx::Class::Schema> when instantiating its storage passed itself as the
449 first argument. So we need to massage the arguments a bit so that all the
450 bits get put into the correct places.
455 my ($class, $schema, $storage_type_args, @args) = @_;
466 Lazy builder for the L</master> attribute.
472 my $master = DBIx::Class::Storage::DBI->new($self->schema);
478 Lazy builder for the L</pool> attribute.
484 $self->create_pool(%{$self->pool_args});
487 =head2 _build_balancer
489 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
490 the balancer knows which pool it's balancing.
494 sub _build_balancer {
496 $self->create_balancer(
498 master=>$self->master,
499 %{$self->balancer_args},
503 =head2 _build_write_handler
505 Lazy builder for the L</write_handler> attribute. The default is to set this to
510 sub _build_write_handler {
511 return shift->master;
514 =head2 _build_read_handler
516 Lazy builder for the L</read_handler> attribute. The default is to set this to
521 sub _build_read_handler {
522 return shift->balancer;
525 =head2 around: connect_replicants
527 All calls to connect_replicants needs to have an existing $schema tacked onto
528 top of the args, since L<DBIx::Storage::DBI> needs it, and any C<connect_info>
529 options merged with the master, with replicant opts having higher priority.
533 around connect_replicants => sub {
534 my ($next, $self, @args) = @_;
537 $r = [ $r ] unless reftype $r eq 'ARRAY';
539 $self->throw_exception('coderef replicant connect_info not supported')
540 if ref $r->[0] && reftype $r->[0] eq 'CODE';
542 # any connect_info options?
544 $i++ while $i < @$r && (reftype($r->[$i])||'') ne 'HASH';
547 $r->[$i] = {} unless $r->[$i];
549 # merge if two hashes
550 my @hashes = @$r[$i .. $#{$r}];
552 $self->throw_exception('invalid connect_info options')
553 if (grep { reftype($_) eq 'HASH' } @hashes) != @hashes;
555 $self->throw_exception('too many hashrefs in connect_info')
558 my %opts = %{ merge(reverse @hashes) };
561 splice @$r, $i+1, ($#{$r} - $i), ();
563 # make sure master/replicants opts don't clash
564 my %master_opts = %{ $self->_master_connect_info_opts };
565 if (exists $opts{dbh_maker}) {
566 delete @master_opts{qw/dsn user password/};
568 delete $master_opts{dbh_maker};
571 %opts = %{ merge(\%opts, \%master_opts) };
577 $self->$next($self->schema, @args);
582 Returns an array of of all the connected storage backends. The first element
583 in the returned array is the master, and the remainings are each of the
590 return grep {defined $_ && blessed $_} (
592 values %{ $self->replicants },
596 =head2 execute_reliably ($coderef, ?@args)
598 Given a coderef, saves the current state of the L</read_handler>, forces it to
599 use reliable storage (ie sets it to the master), executes a coderef and then
600 restores the original state.
606 $schema->resultset('User')->create({name=>$name});
607 my $user_rs = $schema->resultset('User')->find({name=>$name});
611 my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
613 Use this when you must be certain of your database state, such as when you just
614 inserted something and need to get a resultset including it, etc.
618 sub execute_reliably {
619 my ($self, $coderef, @args) = @_;
621 unless( ref $coderef eq 'CODE') {
622 $self->throw_exception('Second argument must be a coderef');
625 ##Get copy of master storage
626 my $master = $self->master;
628 ##Get whatever the current read hander is
629 my $current = $self->read_handler;
631 ##Set the read handler to master
632 $self->read_handler($master);
634 ## do whatever the caller needs
636 my $want_array = wantarray;
640 @result = $coderef->(@args);
641 } elsif(defined $want_array) {
642 ($result[0]) = ($coderef->(@args));
648 ##Reset to the original state
649 $self->read_handler($current);
651 ##Exception testing has to come last, otherwise you might leave the
652 ##read_handler set to master.
655 $self->throw_exception("coderef returned an error: $@");
657 return $want_array ? @result : $result[0];
661 =head2 set_reliable_storage
663 Sets the current $schema to be 'reliable', that is all queries, both read and
664 write are sent to the master
668 sub set_reliable_storage {
670 my $schema = $self->schema;
671 my $write_handler = $self->schema->storage->write_handler;
673 $schema->storage->read_handler($write_handler);
676 =head2 set_balanced_storage
678 Sets the current $schema to be use the </balancer> for all reads, while all
679 writea are sent to the master only
683 sub set_balanced_storage {
685 my $schema = $self->schema;
686 my $balanced_handler = $self->schema->storage->balancer;
688 $schema->storage->read_handler($balanced_handler);
693 Check that the master and at least one of the replicants is connected.
700 $self->master->connected &&
701 $self->pool->connected_replicants;
704 =head2 ensure_connected
706 Make sure all the storages are connected.
710 sub ensure_connected {
712 foreach my $source ($self->all_storages) {
713 $source->ensure_connected(@_);
719 Set the limit_dialect for all existing storages
725 foreach my $source ($self->all_storages) {
726 $source->limit_dialect(@_);
728 return $self->master->quote_char;
733 Set the quote_char for all existing storages
739 foreach my $source ($self->all_storages) {
740 $source->quote_char(@_);
742 return $self->master->quote_char;
747 Set the name_sep for all existing storages
753 foreach my $source ($self->all_storages) {
754 $source->name_sep(@_);
756 return $self->master->name_sep;
761 Set the schema object for all existing storages
767 foreach my $source ($self->all_storages) {
768 $source->set_schema(@_);
774 set a debug flag across all storages
781 foreach my $source ($self->all_storages) {
785 return $self->master->debug;
796 return $self->master->debugobj(@_);
807 return $self->master->debugfh(@_);
818 return $self->master->debugcb(@_);
823 disconnect everything
829 foreach my $source ($self->all_storages) {
830 $source->disconnect(@_);
836 set cursor class on all storages, or return master's
841 my ($self, $cursor_class) = @_;
844 $_->cursor_class($cursor_class) for $self->all_storages;
846 $self->master->cursor_class;
851 set cursor class on all storages, or return master's, alias for L</cursor_class>
857 my ($self, $cursor_class) = @_;
860 $_->cursor($cursor_class) for $self->all_storages;
862 $self->master->cursor;
867 sets the L<DBIx::Class::Storage::DBI/unsafe> option on all storages or returns
868 master's current setting
876 $_->unsafe(@_) for $self->all_storages;
879 return $self->master->unsafe;
882 =head2 disable_sth_caching
884 sets the L<DBIx::Class::Storage::DBI/disable_sth_caching> option on all storages
885 or returns master's current setting
889 sub disable_sth_caching {
893 $_->disable_sth_caching(@_) for $self->all_storages;
896 return $self->master->disable_sth_caching;
899 =head2 lag_behind_master
901 returns the highest Replicant L<DBIx::Class::Storage::DBI/lag_behind_master>
906 sub lag_behind_master {
909 return max map $_->lag_behind_master, $self->replicants;
912 =head2 is_replicating
914 returns true if all replicants return true for
915 L<DBIx::Class::Storage::DBI/is_replicating>
922 return (grep $_->is_replicating, $self->replicants) == ($self->replicants);
925 =head2 connect_call_datetime_setup
927 calls L<DBIx::Class::Storage::DBI/connect_call_datetime_setup> for all storages
931 sub connect_call_datetime_setup {
933 $_->connect_call_datetime_setup for $self->all_storages;
938 $_->_populate_dbh for $self->all_storages;
943 $_->_connect for $self->all_storages;
948 $_->_rebless for $self->all_storages;
951 sub _determine_driver {
953 $_->_determine_driver for $self->all_storages;
956 sub _driver_determined {
960 $_->_driver_determined(@_) for $self->all_storages;
963 return $self->master->_driver_determined;
969 $_->_init for $self->all_storages;
972 sub _run_connection_actions {
975 $_->_run_connection_actions for $self->all_storages;
978 sub _do_connection_actions {
982 $_->_do_connection_actions(@_) for $self->all_storages;
986 sub connect_call_do_sql {
988 $_->connect_call_do_sql(@_) for $self->all_storages;
991 sub disconnect_call_do_sql {
993 $_->disconnect_call_do_sql(@_) for $self->all_storages;
996 sub _seems_connected {
999 return min map $_->_seems_connected, $self->all_storages;
1005 return min map $_->_ping, $self->all_storages;
1010 Due to the fact that replicants can lag behind a master, you must take care to
1011 make sure you use one of the methods to force read queries to a master should
1012 you need realtime data integrity. For example, if you insert a row, and then
1013 immediately re-read it from the database (say, by doing $row->discard_changes)
1014 or you insert a row and then immediately build a query that expects that row
1015 to be an item, you should force the master to handle reads. Otherwise, due to
1016 the lag, there is no certainty your data will be in the expected state.
1018 For data integrity, all transactions automatically use the master storage for
1019 all read and write queries. Using a transaction is the preferred and recommended
1020 method to force the master to handle all read queries.
1022 Otherwise, you can force a single query to use the master with the 'force_pool'
1025 my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk);
1027 This attribute will safely be ignore by non replicated storages, so you can use
1028 the same code for both types of systems.
1030 Lastly, you can use the L</execute_reliably> method, which works very much like
1033 For debugging, you can turn replication on/off with the methods L</set_reliable_storage>
1034 and L</set_balanced_storage>, however this operates at a global level and is not
1035 suitable if you have a shared Schema object being used by multiple processes,
1036 such as on a web application server. You can get around this limitation by
1037 using the Schema clone method.
1039 my $new_schema = $schema->clone;
1040 $new_schema->set_reliable_storage;
1042 ## $new_schema will use only the Master storage for all reads/writes while
1043 ## the $schema object will use replicated storage.
1047 John Napiorkowski <john.napiorkowski@takkle.com>
1049 Based on code originated by:
1051 Norbert Csongrádi <bert@cpan.org>
1052 Peter Siklósi <einon@einon.hu>
1056 You may distribute this code under the same terms as Perl itself.
1060 __PACKAGE__->meta->make_immutable;