1 package DBIx::Class::Storage::DBI::Replicated;
4 use DBIx::Class::Storage::DBI;
5 use DBIx::Class::Storage::DBI::Replicated::Pool;
6 use DBIx::Class::Storage::DBI::Replicated::Balancer;
7 use Scalar::Util qw(blessed);
9 extends 'DBIx::Class::Storage::DBI', 'Moose::Object';
13 DBIx::Class::Storage::DBI::Replicated - ALPHA Replicated database support
17 The Following example shows how to change an existing $schema to a replicated
18 storage type, add some replicated (readonly) databases, and perform reporting
21 ## Change storage_type in your schema class
22 $schema->storage_type( ['::DBI::Replicated', {balancer=>'::Random'}] );
24 ## Add some slaves. Basically this is an array of arrayrefs, where each
25 ## arrayref is database connect information
27 $schema->storage->connect_replicants(
28 [$dsn1, $user, $pass, \%opts],
29 [$dsn1, $user, $pass, \%opts],
30 [$dsn1, $user, $pass, \%opts],
35 Warning: This class is marked ALPHA. We are using this in development and have
36 some basic test coverage but the code hasn't yet been stressed by a variety
37 of databases. Individual DB's may have quirks we are not aware of. Please
38 use this in development and pass along your experiences/bug fixes.
40 This class implements replicated data store for DBI. Currently you can define
41 one master and numerous slave database connections. All write-type queries
42 (INSERT, UPDATE, DELETE and even LAST_INSERT_ID) are routed to master
43 database, all read-type queries (SELECTs) go to the slave database.
45 Basically, any method request that L<DBIx::Class::Storage::DBI> would normally
46 handle gets delegated to one of the two attributes: L</read_handler> or to
47 L</write_handler>. Additionally, some methods need to be distributed
48 to all existing storages. This way our storage class is a drop in replacement
49 for L<DBIx::Class::Storage::DBI>.
51 Read traffic is spread across the replicants (slaves) occuring to a user
52 selected algorithm. The default algorithm is random weighted.
56 The consistancy betweeen master and replicants is database specific. The Pool
57 gives you a method to validate it's replicants, removing and replacing them
58 when they fail/pass predefined criteria. It is recommened that your application
59 define two schemas, one using the replicated storage and another that just
60 connects to the master.
64 This class defines the following attributes.
68 Contains the classname which will instantiate the L</pool> object. Defaults
69 to: L<DBIx::Class::Storage::DBI::Replicated::Pool>.
78 'create_pool' => 'new',
84 Contains a hashref of initialized information to pass to the Balancer object.
85 See L<DBIx::Class::Storage::Replicated::Pool> for available arguments.
100 The replication pool requires a balance class to provider the methods for
101 choose how to spread the query load across each replicant in the pool.
105 has 'balancer_type' => (
110 'create_balancer' => 'new',
116 Contains a hashref of initialized information to pass to the Balancer object.
117 See L<DBIx::Class::Storage::Replicated::Balancer> for available arguments.
121 has 'balancer_args' => (
131 Is a <DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a
132 container class for one or more replicated databases.
138 isa=>'DBIx::Class::Storage::DBI::Replicated::Pool',
149 Is a <DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This
150 is a class that takes a pool (<DBIx::Class::Storage::DBI::Replicated::Pool>)
156 isa=>'DBIx::Class::Storage::DBI::Replicated::Balancer',
158 handles=>[qw/auto_validate_every/],
163 The master defines the canonical state for a pool of connected databases. All
164 the replicants are expected to match this databases state. Thus, in a classic
165 Master / Slaves distributed system, all the slaves are expected to replicate
166 the Master's state as quick as possible. This is the only database in the
167 pool of databases that is allowed to handle write traffic.
173 isa=>'DBIx::Class::Storage::DBI',
177 =head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE
179 The following methods are delegated all the methods required for the
180 L<DBIx::Class::Storage::DBI> interface.
184 Defines an object that implements the read side of L<BIx::Class::Storage::DBI>.
188 has 'read_handler' => (
201 Defines an object that implements the write side of L<BIx::Class::Storage::DBI>.
205 has 'write_handler' => (
218 deployment_statements
237 This class defines the following methods.
241 L<DBIx::Class::Schema> when instantiating it's storage passed itself as the
242 first argument. We need to invoke L</new> on the underlying parent class, make
243 sure we properly give it a L<Moose> meta class, and then correctly instantiate
244 our attributes. Basically we pass on whatever the schema has in it's class
245 data for 'storage_type_args' to our replicated storage type.
250 my $class = shift @_;
251 my $schema = shift @_;
252 my $storage_type_args = shift @_;
253 my $obj = $class->SUPER::new($schema, $storage_type_args, @_);
255 ## Hate to do it this way, but can't seem to get advice on the attribute working right
256 ## maybe we can do a type and coercion for it.
257 if( $storage_type_args->{balancer_type} && $storage_type_args->{balancer_type}=~m/^::/) {
258 $storage_type_args->{balancer_type} = 'DBIx::Class::Storage::DBI::Replicated::Balancer'.$storage_type_args->{balancer_type};
259 eval "require $storage_type_args->{balancer_type}";
262 return $class->meta->new_object(
263 __INSTANCE__ => $obj,
271 Lazy builder for the L</master> attribute.
276 DBIx::Class::Storage::DBI->new;
279 =head2 _build_pool_type
281 Lazy builder for the L</pool_type> attribute.
285 sub _build_pool_type {
286 return 'DBIx::Class::Storage::DBI::Replicated::Pool';
291 Lazy builder for the L</pool> attribute.
297 $self->create_pool(%{$self->pool_args});
300 =head2 _build_balancer_type
302 Lazy builder for the L</balancer_type> attribute.
306 sub _build_balancer_type {
307 return 'DBIx::Class::Storage::DBI::Replicated::Balancer::First';
310 =head2 _build_balancer
312 Lazy builder for the L</balancer> attribute. This takes a Pool object so that
313 the balancer knows which pool it's balancing.
317 sub _build_balancer {
319 $self->create_balancer(
321 master=>$self->master,
322 %{$self->balancer_args},);
325 =head2 _build_write_handler
327 Lazy builder for the L</write_handler> attribute. The default is to set this to
332 sub _build_write_handler {
333 return shift->master;
336 =head2 _build_read_handler
338 Lazy builder for the L</read_handler> attribute. The default is to set this to
343 sub _build_read_handler {
344 return shift->balancer;
347 =head2 around: connect_replicants
349 All calls to connect_replicants needs to have an existing $schema tacked onto
350 top of the args, since L<DBIx::Storage::DBI> needs it.
354 around 'connect_replicants' => sub {
355 my ($method, $self, @args) = @_;
356 $self->$method($self->schema, @args);
361 Returns an array of of all the connected storage backends. The first element
362 in the returned array is the master, and the remainings are each of the
370 return grep {defined $_ && blessed $_} (
376 =head2 execute_reliably ($coderef, ?@args)
378 Given a coderef, saves the current state of the L</read_handler>, forces it to
379 use reliable storage (ie sets it to the master), executes a coderef and then
380 restores the original state.
386 $schema->resultset('User')->create({name=>$name});
387 my $user_rs = $schema->resultset('User')->find({name=>$name});
390 $schema->storage->execute_reliably($reliably, 'John');
392 Use this when you must be certain of your database state, such as when you just
393 inserted something and need to get a resultset including it, etc.
397 sub execute_reliably {
398 my ($self, $coderef, @args) = @_;
400 unless( ref $coderef eq 'CODE') {
401 $self->throw_exception('Second argument must be a coderef');
404 ##Get copy of master storage
405 my $master = $self->master;
407 ##Get whatever the current read hander is
408 my $current = $self->read_handler;
410 ##Set the read handler to master
411 $self->read_handler($master);
413 ## do whatever the caller needs
419 $self->throw_exception("coderef returned an error: $@");
422 ##Reset to the original state
423 $self->schema->storage->read_handler($current);
426 =head2 set_reliable_storage
428 Sets the current $schema to be 'reliable', that is all queries, both read and
429 write are sent to the master
433 sub set_reliable_storage {
435 my $schema = $self->schema;
436 my $write_handler = $self->schema->storage->write_handler;
438 $schema->storage->read_handler($write_handler);
441 =head2 set_balanced_storage
443 Sets the current $schema to be use the </balancer> for all reads, while all
444 writea are sent to the master only
448 sub set_balanced_storage {
450 my $schema = $self->schema;
451 my $write_handler = $self->schema->storage->balancer;
453 $schema->storage->read_handler($write_handler);
456 =head2 txn_do ($coderef)
458 Overload to the txn_do method, which is delegated to whatever the
459 L<write_handler> is set to. We overload this in order to wrap in inside a
460 L</execute_reliably> method.
465 my($self, $coderef, @args) = @_;
466 $self->execute_reliably($coderef, @args);
471 Check that the master and at least one of the replicants is connected.
479 $self->master->connected &&
480 $self->pool->connected_replicants;
483 =head2 ensure_connected
485 Make sure all the storages are connected.
489 sub ensure_connected {
491 foreach my $source ($self->all_storages) {
492 $source->ensure_connected(@_);
498 Set the limit_dialect for all existing storages
504 foreach my $source ($self->all_storages) {
505 $source->limit_dialect(@_);
511 Set the quote_char for all existing storages
517 foreach my $source ($self->all_storages) {
518 $source->quote_char(@_);
524 Set the name_sep for all existing storages
530 foreach my $source ($self->all_storages) {
531 $source->name_sep(@_);
537 Set the schema object for all existing storages
543 foreach my $source ($self->all_storages) {
544 $source->set_schema(@_);
550 set a debug flag across all storages
556 foreach my $source ($self->all_storages) {
563 set a debug object across all storages
569 foreach my $source ($self->all_storages) {
570 $source->debugobj(@_);
576 set a debugfh object across all storages
582 foreach my $source ($self->all_storages) {
583 $source->debugfh(@_);
589 set a debug callback across all storages
595 foreach my $source ($self->all_storages) {
596 $source->debugcb(@_);
602 disconnect everything
608 foreach my $source ($self->all_storages) {
609 $source->disconnect(@_);
615 John Napiorkowski <john.napiorkowski@takkle.com>
617 Based on code originated by:
619 Norbert Csongrádi <bert@cpan.org>
620 Peter Siklósi <einon@einon.hu>
624 You may distribute this code under the same terms as Perl itself.