| DBIx::Class::Storage::DBI::Replicated - BETA Replicated database support |
DBIx::Class::Storage::DBI::Replicated - BETA Replicated database support
The Following example shows how to change an existing $schema to a replicated storage type, add some replicated (readonly) databases, and perform reporting tasks.
## Change storage_type in your schema class $schema->storage_type( ['::DBI::Replicated', {balancer=>'::Random'}] ); ## Add some slaves. Basically this is an array of arrayrefs, where each ## arrayref is database connect information $schema->storage->connect_replicants( [$dsn1, $user, $pass, \%opts], [$dsn2, $user, $pass, \%opts], [$dsn3, $user, $pass, \%opts], ); ## Now, just use the $schema as normal $schema->resultset('Source')->search({name=>'etc'}); ## You can force a given query to use a particular storage using the search ### attribute 'force_pool'. For example: my $RS = $schema->resultset('Source')->search(undef, {force_pool=>'master'}); ## Now $RS will force everything (both reads and writes) to use whatever was ## setup as the master storage. 'master' is hardcoded to always point to the ## Master, but you can also use any Replicant name. Please see: ## L<DBIx::Class::Storage::Replicated::Pool> and the replicants attribute for ## More. Also see transactions and L</execute_reliably> for alternative ways ## to force read traffic to the master. =head1 DESCRIPTION
Warning: This class is marked BETA. This has been running a production website using MySQL native replication as its backend and we have some decent test coverage but the code hasn't yet been stressed by a variety of databases. Individual DB's may have quirks we are not aware of. Please use this in first development and pass along your experiences/bug fixes.
This class implements replicated data store for DBI. Currently you can define one master and numerous slave database connections. All write-type queries (INSERT, UPDATE, DELETE and even LAST_INSERT_ID) are routed to master database, all read-type queries (SELECTs) go to the slave database.
Basically, any method request that the DBIx::Class::Storage::DBI manpage would normally handle gets delegated to one of the two attributes: read_handler or to write_handler. Additionally, some methods need to be distributed to all existing storages. This way our storage class is a drop in replacement for the DBIx::Class::Storage::DBI manpage.
Read traffic is spread across the replicants (slaves) occuring to a user selected algorithm. The default algorithm is random weighted.
The consistancy betweeen master and replicants is database specific. The Pool gives you a method to validate it's replicants, removing and replacing them when they fail/pass predefined criteria. Please make careful use of the ways to force a query to run against Master when needed.
Replicated Storage has additional requirements not currently part of the DBIx::Class manpage
Moose => 0.77 MooseX::AttributeHelpers => 0.12 MooseX::Types => 0.10 namespace::clean => 0.11 Hash::Merge => 0.11 You will need to install these modules manually via CPAN or make them part of the Makefile for your distribution.
This class defines the following attributes.
The underlying the DBIx::Class::Schema manpage object this storage is attaching
Contains the classname which will instantiate the pool object. Defaults to: the DBIx::Class::Storage::DBI::Replicated::Pool manpage.
Contains a hashref of initialized information to pass to the Balancer object. See the DBIx::Class::Storage::Replicated::Pool manpage for available arguments.
The replication pool requires a balance class to provider the methods for choose how to spread the query load across each replicant in the pool.
Contains a hashref of initialized information to pass to the Balancer object. See the DBIx::Class::Storage::Replicated::Balancer manpage for available arguments.
Is a <DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a container class for one or more replicated databases.
Is a <DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This is a class that takes a pool (<DBIx::Class::Storage::DBI::Replicated::Pool>)
The master defines the canonical state for a pool of connected databases. All the replicants are expected to match this databases state. Thus, in a classic Master / Slaves distributed system, all the slaves are expected to replicate the Master's state as quick as possible. This is the only database in the pool of databases that is allowed to handle write traffic.
The following methods are delegated all the methods required for the the DBIx::Class::Storage::DBI manpage interface.
Defines an object that implements the read side of the BIx::Class::Storage::DBI manpage.
Defines an object that implements the write side of the BIx::Class::Storage::DBI manpage.
Preserve master's connect_info options (for merging with replicants.)
Also set any Replicated related options from connect_info, such as
pool_type, pool_args, balancer_type and balancer_args.
This class defines the following methods.
the DBIx::Class::Schema manpage when instantiating it's storage passed itself as the first argument. So we need to massage the arguments a bit so that all the bits get put into the correct places.
Lazy builder for the master attribute.
Lazy builder for the pool attribute.
Lazy builder for the balancer attribute. This takes a Pool object so that the balancer knows which pool it's balancing.
Lazy builder for the write_handler attribute. The default is to set this to the master.
Lazy builder for the read_handler attribute. The default is to set this to the balancer.
All calls to connect_replicants needs to have an existing $schema tacked onto
top of the args, since the DBIx::Storage::DBI manpage needs it, and any connect_info
options merged with the master, with replicant opts having higher priority.
Returns an array of of all the connected storage backends. The first element in the returned array is the master, and the remainings are each of the replicants.
Given a coderef, saves the current state of the read_handler, forces it to use reliable storage (ie sets it to the master), executes a coderef and then restores the original state.
Example:
my $reliably = sub { my $name = shift @_; $schema->resultset('User')->create({name=>$name}); my $user_rs = $schema->resultset('User')->find({name=>$name}); return $user_rs; };
my $user_rs = $schema->storage->execute_reliably($reliably, 'John');
Use this when you must be certain of your database state, such as when you just inserted something and need to get a resultset including it, etc.
Sets the current $schema to be 'reliable', that is all queries, both read and write are sent to the master
=cut
sub set_reliable_storage { my $self = shift @_; my $schema = $self->schema; my $write_handler = $self->schema->storage->write_handler;
$schema->storage->read_handler($write_handler); }
Sets the current $schema to be use the </balancer> for all reads, while all writea are sent to the master only
=cut
sub set_balanced_storage { my $self = shift @_; my $schema = $self->schema; my $write_handler = $self->schema->storage->balancer;
$schema->storage->read_handler($write_handler); }
Overload to the txn_do method, which is delegated to whatever the the write_handler manpage is set to. We overload this in order to wrap in inside a execute_reliably method.
Check that the master and at least one of the replicants is connected.
Make sure all the storages are connected.
Set the limit_dialect for all existing storages
Set the quote_char for all existing storages
Set the name_sep for all existing storages
Set the schema object for all existing storages
set a debug flag across all storages
set a debug object across all storages
set a debugfh object across all storages
set a debug callback across all storages
disconnect everything
set cursor class on all storages, or return master's
John Napiorkowski <john.napiorkowski@takkle.com>
Based on code originated by:
Norbert Csongrádi <bert@cpan.org> Peter Siklósi <einon@einon.hu>
You may distribute this code under the same terms as Perl itself.
| DBIx::Class::Storage::DBI::Replicated - BETA Replicated database support |