X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FDBIx%2FClass%2FStorage%2FDBI%2FReplicated.pm;h=8d75590f28e548f63420365bd7255cff7cbd83f2;hb=3fbe08e3152f04c6bb297c922b40a953dbdb3149;hp=7323b42c9475c2d3dae9da894121028d11055125;hpb=7edf5f1cd3b097de79d262ed02d65128336f5893;p=dbsrgits%2FDBIx-Class.git diff --git a/lib/DBIx/Class/Storage/DBI/Replicated.pm b/lib/DBIx/Class/Storage/DBI/Replicated.pm index 7323b42..8d75590 100644 --- a/lib/DBIx/Class/Storage/DBI/Replicated.pm +++ b/lib/DBIx/Class/Storage/DBI/Replicated.pm @@ -1,12 +1,11 @@ package DBIx::Class::Storage::DBI::Replicated; use Moose; +use Class::MOP; +use Moose::Util::TypeConstraints; use DBIx::Class::Storage::DBI; use DBIx::Class::Storage::DBI::Replicated::Pool; use DBIx::Class::Storage::DBI::Replicated::Balancer; -use Scalar::Util qw(blessed); - -extends 'DBIx::Class::Storage::DBI', 'Moose::Object'; =head1 NAME @@ -18,24 +17,40 @@ 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, $pass, \%opts], - [$dsn1, $user, $pass, \%opts], - [$dsn1, $user, $pass, \%opts], - ); - + ## 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 and the replicants attribute for + ## More. Also see transactions and L for alternative ways + ## to force read traffic to the master. + =head1 DESCRIPTION -Warning: This class is marked ALPHA. We are using this in development and have -some basic 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 development and pass along your experiences/bug fixes. +Warning: This class is marked BETA. This has been running a production +website using MySQL native replication as it's 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 @@ -43,20 +58,38 @@ one master and numerous slave database connections. All write-type queries database, all read-type queries (SELECTs) go to the slave database. Basically, any method request that L would normally -handle gets delegated to one of the two attributes: L or to -L. Additionally, some methods need to be distributed +handle gets delegated to one of the two attributes: L or to +L. Additionally, some methods need to be distributed to all existing storages. This way our storage class is a drop in replacement for L. Read traffic is spread across the replicants (slaves) occuring to a user selected algorithm. The default algorithm is random weighted. -TODO more details about the algorithm. +=head1 NOTES + +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. =head1 ATTRIBUTES This class defines the following attributes. +=head2 schema + +The underlying L object this storage is attaching + +=cut + +has 'schema' => ( + is=>'rw', + isa=>'DBIx::Class::Schema', + weak_ref=>1, + required=>1, +); + =head2 pool_type Contains the classname which will instantiate the L object. Defaults @@ -65,26 +98,31 @@ to: L. =cut has 'pool_type' => ( - is=>'ro', - isa=>'ClassName', - lazy_build=>1, - handles=>{ - 'create_pool' => 'new', - }, + is=>'ro', + isa=>'ClassName', + required=>1, + default=>'DBIx::Class::Storage::DBI::Replicated::Pool', + handles=>{ + 'create_pool' => 'new', + }, ); =head2 pool_args -Contains a hashref of initialized information to pass to the Pool object. See -L for available arguments. +Contains a hashref of initialized information to pass to the Balancer object. +See L for available arguments. =cut has 'pool_args' => ( - is=>'ro', - isa=>'HashRef', + is=>'ro', + isa=>'HashRef', + lazy=>1, + required=>1, + default=>sub { {} }, ); + =head2 balancer_type The replication pool requires a balance class to provider the methods for @@ -92,13 +130,44 @@ choose how to spread the query load across each replicant in the pool. =cut +subtype 'DBIx::Class::Storage::DBI::Replicated::BalancerClassNamePart', + as 'ClassName'; + +coerce 'DBIx::Class::Storage::DBI::Replicated::BalancerClassNamePart', + from 'Str', + via { + my $type = $_; + if($type=~m/^::/) { + $type = 'DBIx::Class::Storage::DBI::Replicated::Balancer'.$type; + } + Class::MOP::load_class($type); + $type; + }; + has 'balancer_type' => ( - is=>'ro', - isa=>'ClassName', - lazy_build=>1, - handles=>{ - 'create_balancer' => 'new', - }, + is=>'ro', + isa=>'DBIx::Class::Storage::DBI::Replicated::BalancerClassNamePart', + coerce=>1, + required=>1, + default=> 'DBIx::Class::Storage::DBI::Replicated::Balancer::First', + handles=>{ + 'create_balancer' => 'new', + }, +); + +=head2 balancer_args + +Contains a hashref of initialized information to pass to the Balancer object. +See L for available arguments. + +=cut + +has 'balancer_args' => ( + is=>'ro', + isa=>'HashRef', + lazy=>1, + required=>1, + default=>sub { {} }, ); =head2 pool @@ -109,17 +178,14 @@ container class for one or more replicated databases. =cut has 'pool' => ( - is=>'ro', - isa=>'DBIx::Class::Storage::DBI::Replicated::Pool', - lazy_build=>1, - handles=>[qw/ - connect_replicants - replicants - has_replicants - num_replicants - delete_replicant - validate_replicants - /], + is=>'ro', + isa=>'DBIx::Class::Storage::DBI::Replicated::Pool', + lazy_build=>1, + handles=>[qw/ + connect_replicants + replicants + has_replicants + /], ); =head2 balancer @@ -130,9 +196,10 @@ is a class that takes a pool () =cut has 'balancer' => ( - is=>'ro', - isa=>'DBIx::Class::Storage::DBI::Replicated::Balancer', - lazy_build=>1, + is=>'ro', + isa=>'DBIx::Class::Storage::DBI::Replicated::Balancer', + lazy_build=>1, + handles=>[qw/auto_validate_every/], ); =head2 master @@ -146,9 +213,9 @@ pool of databases that is allowed to handle write traffic. =cut has 'master' => ( - is=> 'ro', - isa=>'DBIx::Class::Storage::DBI', - lazy_build=>1, + is=> 'ro', + isa=>'DBIx::Class::Storage::DBI', + lazy_build=>1, ); =head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE @@ -163,14 +230,14 @@ Defines an object that implements the read side of L. =cut has 'read_handler' => ( - is=>'rw', - isa=>'Object', - lazy_build=>1, - handles=>[qw/ - select - select_single - columns_info_for - /], + is=>'rw', + isa=>'Object', + lazy_build=>1, + handles=>[qw/ + select + select_single + columns_info_for + /], ); =head2 write_handler @@ -180,68 +247,62 @@ Defines an object that implements the write side of L. =cut has 'write_handler' => ( - is=>'ro', - isa=>'Object', - lazy_build=>1, - lazy_build=>1, - handles=>[qw/ - on_connect_do - on_disconnect_do - connect_info - throw_exception - sql_maker - sqlt_type - create_ddl_dir - deployment_statements - datetime_parser - datetime_parser_type - last_insert_id - insert - insert_bulk - update - delete - dbh - txn_do - txn_commit - txn_rollback - sth - deploy - schema - /], + is=>'ro', + isa=>'Object', + lazy_build=>1, + lazy_build=>1, + handles=>[qw/ + on_connect_do + on_disconnect_do + connect_info + throw_exception + sql_maker + sqlt_type + create_ddl_dir + deployment_statements + datetime_parser + datetime_parser_type + last_insert_id + insert + insert_bulk + update + delete + dbh + txn_begin + txn_do + txn_commit + txn_rollback + txn_scope_guard + sth + deploy + + reload_row + _prep_for_execute + configure_sqlt + + /], ); =head1 METHODS This class defines the following methods. -=head2 new +=head2 BUILDARGS L when instantiating it's storage passed itself as the -first argument. We need to invoke L on the underlying parent class, make -sure we properly give it a L meta class, and then correctly instantiate -our attributes. Basically we pass on whatever the schema has in it's class -data for 'storage_type_args' to our replicated storage type. +first argument. So we need to massage the arguments a bit so that all the +bits get put into the correct places. =cut -sub new { - my $class = shift @_; - my $schema = shift @_; - my $storage_type_args = shift @_; - my $obj = $class->SUPER::new($schema, $storage_type_args, @_); - - ## Hate to do it this way, but can't seem to get advice on the attribute working right - ## maybe we can do a type and coercion for it. - if( $storage_type_args->{balancer_type} && $storage_type_args->{balancer_type}=~m/^::/) { - $storage_type_args->{balancer_type} = 'DBIx::Class::Storage::DBI::Replicated::Balancer'.$storage_type_args->{balancer_type}; - eval "require $storage_type_args->{balancer_type}"; - } - - return $class->meta->new_object( - __INSTANCE__ => $obj, - %$storage_type_args, - @_, - ); +sub BUILDARGS { + my ($class, $schema, $storage_type_args, @args) = @_; + + return { + schema=>$schema, + %$storage_type_args, + @args + } } =head2 _build_master @@ -251,17 +312,8 @@ Lazy builder for the L attribute. =cut sub _build_master { - DBIx::Class::Storage::DBI->new; -} - -=head2 _build_pool_type - -Lazy builder for the L attribute. - -=cut - -sub _build_pool_type { - return 'DBIx::Class::Storage::DBI::Replicated::Pool'; + my $self = shift @_; + DBIx::Class::Storage::DBI->new($self->schema); } =head2 _build_pool @@ -271,18 +323,8 @@ Lazy builder for the L attribute. =cut sub _build_pool { - my $self = shift @_; - $self->create_pool($self->pool_args); -} - -=head2 _build_balancer_type - -Lazy builder for the L attribute. - -=cut - -sub _build_balancer_type { - return 'DBIx::Class::Storage::DBI::Replicated::Balancer'; + my $self = shift @_; + $self->create_pool(%{$self->pool_args}); } =head2 _build_balancer @@ -293,10 +335,12 @@ the balancer knows which pool it's balancing. =cut sub _build_balancer { - my $self = shift @_; - $self->create_balancer( - pool=>$self->pool, - master=>$self->master); + my $self = shift @_; + $self->create_balancer( + pool=>$self->pool, + master=>$self->master, + %{$self->balancer_args}, + ); } =head2 _build_write_handler @@ -307,7 +351,7 @@ the L. =cut sub _build_write_handler { - return shift->master; + return shift->master; } =head2 _build_read_handler @@ -318,7 +362,7 @@ the L. =cut sub _build_read_handler { - return shift->balancer; + return shift->balancer; } =head2 around: connect_replicants @@ -329,8 +373,8 @@ top of the args, since L needs it. =cut around 'connect_replicants' => sub { - my ($method, $self, @args) = @_; - $self->$method($self->schema, @args); + my ($method, $self, @args) = @_; + $self->$method($self->schema, @args); }; =head2 all_storages @@ -342,44 +386,123 @@ replicants. =cut sub all_storages { - my $self = shift @_; - - return grep {defined $_ && blessed $_} ( - $self->master, - $self->replicants, - ); + my $self = shift @_; + return grep {defined $_ && blessed $_} ( + $self->master, + $self->replicants, + ); +} + +=head2 execute_reliably ($coderef, ?@args) + +Given a coderef, saves the current state of the L, 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. + +=cut + +use Benchmark; + +sub execute_reliably { + my ($self, $coderef, @args) = @_; + + unless( ref $coderef eq 'CODE') { + $self->throw_exception('Second argument must be a coderef'); + } + + ##Get copy of master storage + my $master = $self->master; + + ##Get whatever the current read hander is + my $current = $self->read_handler; + + ##Set the read handler to master + $self->read_handler($master); + + ## do whatever the caller needs + my @result; + my $want_array = wantarray; + + eval { + if($want_array) { + @result = $coderef->(@args); + } elsif(defined $want_array) { + ($result[0]) = ($coderef->(@args)); + } else { + $coderef->(@args); + } + }; + + ##Reset to the original state + $self->read_handler($current); + + ##Exception testing has to come last, otherwise you might leave the + ##read_handler set to master. + + if($@) { + $self->throw_exception("coderef returned an error: $@"); + } else { + return $want_array ? @result : $result[0]; + } } =head2 set_reliable_storage 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); + my $self = shift @_; + my $schema = $self->schema; + my $write_handler = $self->schema->storage->write_handler; + + $schema->storage->read_handler($write_handler); } =head2 set_balanced_storage Sets the current $schema to be use the 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); + my $self = shift @_; + my $schema = $self->schema; + my $write_handler = $self->schema->storage->balancer; + + $schema->storage->read_handler($write_handler); } +=head2 around: txn_do ($coderef) + +Overload to the txn_do method, which is delegated to whatever the +L is set to. We overload this in order to wrap in inside a +L method. + +=cut + +around 'txn_do' => sub { + my($txn_do, $self, $coderef, @args) = @_; + $self->execute_reliably(sub {$self->$txn_do($coderef, @args)}); +}; + =head2 connected Check that the master and at least one of the replicants is connected. @@ -387,11 +510,10 @@ Check that the master and at least one of the replicants is connected. =cut sub connected { - my $self = shift @_; - - return - $self->master->connected && - $self->pool->connected_replicants; + my $self = shift @_; + return + $self->master->connected && + $self->pool->connected_replicants; } =head2 ensure_connected @@ -401,10 +523,10 @@ Make sure all the storages are connected. =cut sub ensure_connected { - my $self = shift @_; - foreach my $source ($self->all_storages) { - $source->ensure_connected(@_); - } + my $self = shift @_; + foreach my $source ($self->all_storages) { + $source->ensure_connected(@_); + } } =head2 limit_dialect @@ -414,10 +536,11 @@ Set the limit_dialect for all existing storages =cut sub limit_dialect { - my $self = shift @_; - foreach my $source ($self->all_storages) { - $source->limit_dialect(@_); - } + my $self = shift @_; + foreach my $source ($self->all_storages) { + $source->limit_dialect(@_); + } + return $self->master->quote_char; } =head2 quote_char @@ -427,10 +550,11 @@ Set the quote_char for all existing storages =cut sub quote_char { - my $self = shift @_; - foreach my $source ($self->all_storages) { - $source->quote_char(@_); - } + my $self = shift @_; + foreach my $source ($self->all_storages) { + $source->quote_char(@_); + } + return $self->master->quote_char; } =head2 name_sep @@ -440,10 +564,11 @@ Set the name_sep for all existing storages =cut sub name_sep { - my $self = shift @_; - foreach my $source ($self->all_storages) { - $source->name_sep(@_); - } + my $self = shift @_; + foreach my $source ($self->all_storages) { + $source->name_sep(@_); + } + return $self->master->name_sep; } =head2 set_schema @@ -453,10 +578,10 @@ Set the schema object for all existing storages =cut sub set_schema { - my $self = shift @_; - foreach my $source ($self->all_storages) { - $source->set_schema(@_); - } + my $self = shift @_; + foreach my $source ($self->all_storages) { + $source->set_schema(@_); + } } =head2 debug @@ -466,10 +591,13 @@ set a debug flag across all storages =cut sub debug { - my $self = shift @_; + my $self = shift @_; + if(@_) { foreach my $source ($self->all_storages) { - $source->debug(@_); - } + $source->debug(@_); + } + } + return $self->master->debug; } =head2 debugobj @@ -479,10 +607,13 @@ set a debug object across all storages =cut sub debugobj { - my $self = shift @_; + my $self = shift @_; + if(@_) { foreach my $source ($self->all_storages) { - $source->debugobj(@_); - } + $source->debugobj(@_); + } + } + return $self->master->debugobj; } =head2 debugfh @@ -492,10 +623,13 @@ set a debugfh object across all storages =cut sub debugfh { - my $self = shift @_; + my $self = shift @_; + if(@_) { foreach my $source ($self->all_storages) { - $source->debugfh(@_); - } + $source->debugfh(@_); + } + } + return $self->master->debugfh; } =head2 debugcb @@ -505,10 +639,13 @@ set a debug callback across all storages =cut sub debugcb { - my $self = shift @_; + my $self = shift @_; + if(@_) { foreach my $source ($self->all_storages) { - $source->debugcb(@_); - } + $source->debugcb(@_); + } + } + return $self->master->debugcb; } =head2 disconnect @@ -518,19 +655,57 @@ disconnect everything =cut sub disconnect { - my $self = shift @_; - foreach my $source ($self->all_storages) { - $source->disconnect(@_); - } + my $self = shift @_; + foreach my $source ($self->all_storages) { + $source->disconnect(@_); + } } +=head1 GOTCHAS + +Due to the fact that replicants can lag behind a master, you must take care to +make sure you use one of the methods to force read queries to a master should +you need realtime data integrity. For example, if you insert a row, and then +immediately re-read it from the database (say, by doing $row->discard_changes) +or you insert a row and then immediately build a query that expects that row +to be an item, you should force the master to handle reads. Otherwise, due to +the lag, there is no certainty your data will be in the expected state. + +For data integrity, all transactions automatically use the master storage for +all read and write queries. Using a transaction is the preferred and recommended +method to force the master to handle all read queries. + +Otherwise, you can force a single query to use the master with the 'force_pool' +attribute: + + my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk); + +This attribute will safely be ignore by non replicated storages, so you can use +the same code for both types of systems. + +Lastly, you can use the L method, which works very much like +a transaction. + +For debugging, you can turn replication on/off with the methods L +and L, however this operates at a global level and is not +suitable if you have a shared Schema object being used by multiple processes, +such as on a web application server. You can get around this limitation by +using the Schema clone method. + + my $new_schema = $schema->clone; + $new_schema->set_reliable_storage; + + ## $new_schema will use only the Master storage for all reads/writes while + ## the $schema object will use replicated storage. + =head1 AUTHOR -Norbert Csongrádi + John Napiorkowski -Peter Siklósi +Based on code originated by: -John Napiorkowski + Norbert Csongrádi + Peter Siklósi =head1 LICENSE @@ -538,4 +713,6 @@ You may distribute this code under the same terms as Perl itself. =cut +__PACKAGE__->meta->make_immutable; + 1;