package DBIx::Class::Storage::DBI::Replicated::Pool;
use Moose;
-use MooseX::AttributeHelpers;
use DBIx::Class::Storage::DBI::Replicated::Replicant;
-use List::Util qw(sum);
+use List::Util 'sum';
+use Scalar::Util 'reftype';
+use DBI ();
+use Carp::Clan qw/^DBIx::Class/;
+use MooseX::Types::Moose qw/Num Int ClassName HashRef/;
+use DBIx::Class::Storage::DBI::Replicated::Types 'DBICStorageDBI';
+
+use namespace::clean -except => 'meta';
=head1 NAME
This class is used internally by L<DBIx::Class::Storage::DBI::Replicated>. You
shouldn't need to create instances of this class.
-
+
=head1 DESCRIPTION
In a replicated storage type, there is at least one replicant to handle the
This is a number which defines the maximum allowed lag returned by the
L<DBIx::Class::Storage::DBI/lag_behind_master> method. The default is 0. In
general, this should return a larger number when the replicant is lagging
-behind it's master, however the implementation of this is database specific, so
+behind its master, however the implementation of this is database specific, so
don't count on this number having a fixed meaning. For example, MySQL will
return a number of seconds that the replicating database is lagging.
has 'maximum_lag' => (
is=>'rw',
- isa=>'Num',
+ isa=>Num,
required=>1,
lazy=>1,
default=>0,
=head2 last_validated
This is an integer representing a time since the last time the replicants were
-validated. It's nothing fancy, just an integer provided via the perl time
+validated. It's nothing fancy, just an integer provided via the perl L<time|perlfunc/time>
builtin.
=cut
has 'last_validated' => (
is=>'rw',
- isa=>'Int',
+ isa=>Int,
reader=>'last_validated',
writer=>'_last_validated',
lazy=>1,
has 'replicant_type' => (
is=>'ro',
- isa=>'ClassName',
+ isa=>ClassName,
required=>1,
default=>'DBIx::Class::Storage::DBI',
handles=>{
actual replicant storage. For example if the $dsn element is something like:
"dbi:SQLite:dbname=dbfile"
-
+
You could access the specific replicant via:
$schema->storage->replicants->{'dbname=dbfile'}
-
+
This attributes also supports the following helper methods:
=over 4
has 'replicants' => (
is=>'rw',
- metaclass => 'Collection::Hash',
- isa=>'HashRef[DBIx::Class::Storage::DBI]',
+ traits => ['Hash'],
+ isa=>HashRef['Object'],
default=>sub {{}},
- provides => {
- 'set' => 'set_replicant',
- 'get' => 'get_replicant',
- 'empty' => 'has_replicants',
- 'count' => 'num_replicants',
- 'delete' => 'delete_replicant',
+ handles => {
+ 'set_replicant' => 'set',
+ 'get_replicant' => 'get',
+ 'has_replicants' => 'is_empty',
+ 'num_replicants' => 'count',
+ 'delete_replicant' => 'delete',
+ 'all_replicant_storages' => 'values',
},
);
+around has_replicants => sub {
+ my ($orig, $self) = @_;
+ return !$self->$orig;
+};
+
+has next_unknown_replicant_id => (
+ is => 'rw',
+ traits => ['Counter'],
+ isa => Int,
+ default => 1,
+ handles => {
+ 'inc_unknown_replicant_id' => 'inc',
+ },
+);
+
+=head2 master
+
+Reference to the master Storage.
+
+=cut
+
+has master => (is => 'rw', isa => DBICStorageDBI, weak_ref => 1);
+
=head1 METHODS
This class defines the following methods.
=head2 connect_replicants ($schema, Array[$connect_info])
-Given an array of $dsn suitable for connected to a database, create an
-L<DBIx::Class::Storage::DBI::Replicated::Replicant> object and store it in the
-L</replicants> attribute.
+Given an array of $dsn or connect_info structures suitable for connected to a
+database, create an L<DBIx::Class::Storage::DBI::Replicated::Replicant> object
+and store it in the L</replicants> attribute.
=cut
sub connect_replicants {
my $self = shift @_;
my $schema = shift @_;
-
+
my @newly_created = ();
foreach my $connect_info (@_) {
- my $replicant = $self->connect_replicant($schema, $connect_info);
- my ($key) = ($connect_info->[0]=~m/^dbi\:.+\:(.+)$/);
- $self->set_replicant( $key => $replicant);
+ $connect_info = [ $connect_info ]
+ if reftype $connect_info ne 'ARRAY';
+
+ my $connect_coderef =
+ (reftype($connect_info->[0])||'') eq 'CODE' ? $connect_info->[0]
+ : (reftype($connect_info->[0])||'') eq 'HASH' &&
+ $connect_info->[0]->{dbh_maker};
+
+ my $dsn;
+ my $replicant = do {
+# yes this is evil, but it only usually happens once (for coderefs)
+# this will fail if the coderef does not actually DBI::connect
+ no warnings 'redefine';
+ my $connect = \&DBI::connect;
+ local *DBI::connect = sub {
+ $dsn = $_[1];
+ goto $connect;
+ };
+ $self->connect_replicant($schema, $connect_info);
+ };
+
+ my $key;
+
+ if (!$dsn) {
+ if (!$connect_coderef) {
+ $dsn = $connect_info->[0];
+ $dsn = $dsn->{dsn} if (reftype($dsn)||'') eq 'HASH';
+ }
+ else {
+ # all attempts to get the DSN failed
+ $key = "UNKNOWN_" . $self->next_unknown_replicant_id;
+ $self->inc_unknown_replicant_id;
+ }
+ }
+ if ($dsn) {
+ $replicant->dsn($dsn);
+ ($key) = ($dsn =~ m/^dbi\:.+\:(.+)$/i);
+ }
+
+ $replicant->id($key);
+ $self->set_replicant($key => $replicant);
+
push @newly_created, $replicant;
}
-
+
return @newly_created;
}
sub connect_replicant {
my ($self, $schema, $connect_info) = @_;
my $replicant = $self->create_replicant($schema);
-
- $replicant->connect_info($connect_info);
- $replicant->ensure_connected;
+ $replicant->connect_info($connect_info);
+
+## It is undesirable for catalyst to connect at ->conect_replicants time, as
+## connections should only happen on the first request that uses the database.
+## So we try to set the driver without connecting, however this doesn't always
+## work, as a driver may need to connect to determine the DB version, and this
+## may fail.
+##
+## Why this is necessary at all, is that we need to have the final storage
+## class to apply the Replicant role.
+
+ $self->_safely($replicant, '->_determine_driver', sub {
+ $replicant->_determine_driver
+ });
+
+ Moose::Meta::Class->initialize(ref $replicant);
+
DBIx::Class::Storage::DBI::Replicated::Replicant->meta->apply($replicant);
-
+
+ # link back to master
+ $replicant->master($self->master);
+
return $replicant;
}
+=head2 _safely_ensure_connected ($replicant)
+
+The standard ensure_connected method with throw an exception should it fail to
+connect. For the master database this is desirable, but since replicants are
+allowed to fail, this behavior is not desirable. This method wraps the call
+to ensure_connected in an eval in order to catch any generated errors. That
+way a slave can go completely offline (ie, the box itself can die) without
+bringing down your entire pool of databases.
+
+=cut
+
+sub _safely_ensure_connected {
+ my ($self, $replicant, @args) = @_;
+
+ return $self->_safely($replicant, '->ensure_connected', sub {
+ $replicant->ensure_connected(@args)
+ });
+}
+
+=head2 _safely ($replicant, $name, $code)
+
+Execute C<$code> for operation C<$name> catching any exceptions and printing an
+error message to the C<<$replicant->debugobj>>.
+
+Returns 1 on success and undef on failure.
+
+=cut
+
+sub _safely {
+ my ($self, $replicant, $name, $code) = @_;
+
+ eval {
+ $code->()
+ };
+ if ($@) {
+ $replicant->debugobj->print(sprintf(
+ "Exception trying to $name for replicant %s, error is %s",
+ $replicant->_dbi_connect_info->[0], $@)
+ );
+ return undef;
+ }
+
+ return 1;
+}
+
=head2 connected_replicants
Returns true if there are connected replicants. Actually is overloaded to
Calling this method will generate queries on the replicant databases so it is
not recommended that you run them very often.
+This method requires that your underlying storage engine supports some sort of
+native replication mechanism. Currently only MySQL native replication is
+supported. Your patches to make other replication types work are welcomed.
+
=cut
sub validate_replicants {
my $self = shift @_;
foreach my $replicant($self->all_replicants) {
- if(
- $replicant->is_replicating &&
- $replicant->lag_behind_master <= $self->maximum_lag &&
- $replicant->ensure_connected
- ) {
- $replicant->active(1)
+ if($self->_safely_ensure_connected($replicant)) {
+ my $is_replicating = $replicant->is_replicating;
+ unless(defined $is_replicating) {
+ $replicant->debugobj->print("Storage Driver ".ref($self)." Does not support the 'is_replicating' method. Assuming you are manually managing.\n");
+ next;
+ } else {
+ if($is_replicating) {
+ my $lag_behind_master = $replicant->lag_behind_master;
+ unless(defined $lag_behind_master) {
+ $replicant->debugobj->print("Storage Driver ".ref($self)." Does not support the 'lag_behind_master' method. Assuming you are manually managing.\n");
+ next;
+ } else {
+ if($lag_behind_master <= $self->maximum_lag) {
+ $replicant->active(1);
+ } else {
+ $replicant->active(0);
+ }
+ }
+ } else {
+ $replicant->active(0);
+ }
+ }
} else {
$replicant->active(0);
}
}
## Mark that we completed this validation.
- $self->_last_validated(time);
+ $self->_last_validated(time);
}
=head1 AUTHOR