1 package DBIx::Class::Storage::DBI::Replicated::Pool;
4 use MooseX::AttributeHelpers;
5 use DBIx::Class::Storage::DBI::Replicated::Replicant;
7 use Scalar::Util 'reftype';
8 use Carp::Clan qw/^DBIx::Class/;
10 use namespace::clean -except => 'meta';
14 DBIx::Class::Storage::DBI::Replicated::Pool - Manage a pool of replicants
18 This class is used internally by L<DBIx::Class::Storage::DBI::Replicated>. You
19 shouldn't need to create instances of this class.
23 In a replicated storage type, there is at least one replicant to handle the
24 read only traffic. The Pool class manages this replicant, or list of
25 replicants, and gives some methods for querying information about their status.
29 This class defines the following attributes.
31 =head2 maximum_lag ($num)
33 This is a number which defines the maximum allowed lag returned by the
34 L<DBIx::Class::Storage::DBI/lag_behind_master> method. The default is 0. In
35 general, this should return a larger number when the replicant is lagging
36 behind it's master, however the implementation of this is database specific, so
37 don't count on this number having a fixed meaning. For example, MySQL will
38 return a number of seconds that the replicating database is lagging.
42 has 'maximum_lag' => (
52 This is an integer representing a time since the last time the replicants were
53 validated. It's nothing fancy, just an integer provided via the perl time
58 has 'last_validated' => (
61 reader=>'last_validated',
62 writer=>'_last_validated',
67 =head2 replicant_type ($classname)
69 Base class used to instantiate replicants that are in the pool. Unless you
70 need to subclass L<DBIx::Class::Storage::DBI::Replicated::Replicant> you should
71 just leave this alone.
75 has 'replicant_type' => (
79 default=>'DBIx::Class::Storage::DBI',
81 'create_replicant' => 'new',
87 A hashref of replicant, with the key being the dsn and the value returning the
88 actual replicant storage. For example if the $dsn element is something like:
90 "dbi:SQLite:dbname=dbfile"
92 You could access the specific replicant via:
94 $schema->storage->replicants->{'dbname=dbfile'}
96 This attributes also supports the following helper methods:
100 =item set_replicant($key=>$storage)
102 Pushes a replicant onto the HashRef under $key
104 =item get_replicant($key)
106 Retrieves the named replicant
110 Returns true if the Pool defines replicants.
114 The number of replicants in the pool
116 =item delete_replicant ($key)
118 removes the replicant under $key from the pool
124 has 'replicants' => (
126 metaclass => 'Collection::Hash',
127 isa=>'HashRef[DBIx::Class::Storage::DBI]',
130 'set' => 'set_replicant',
131 'get' => 'get_replicant',
132 'empty' => 'has_replicants',
133 'count' => 'num_replicants',
134 'delete' => 'delete_replicant',
140 This class defines the following methods.
142 =head2 connect_replicants ($schema, Array[$connect_info])
144 Given an array of $dsn suitable for connected to a database, create an
145 L<DBIx::Class::Storage::DBI::Replicated::Replicant> object and store it in the
146 L</replicants> attribute.
150 sub connect_replicants {
152 my $schema = shift @_;
154 my @newly_created = ();
155 foreach my $connect_info (@_) {
156 $connect_info = [ $connect_info ]
157 if reftype $connect_info ne 'ARRAY';
159 croak "coderef connect_info not supported"
160 if ref $connect_info->[0] && reftype $connect_info->[0] eq 'CODE';
162 my $replicant = $self->connect_replicant($schema, $connect_info);
164 my $key = $connect_info->[0];
165 $key = $key->{dsn} if ref $key && reftype $key eq 'HASH';
166 ($key) = ($key =~ m/^dbi\:.+\:(.+)$/);
168 $self->set_replicant( $key => $replicant);
169 push @newly_created, $replicant;
172 return @newly_created;
175 =head2 connect_replicant ($schema, $connect_info)
177 Given a schema object and a hashref of $connect_info, connect the replicant
182 sub connect_replicant {
183 my ($self, $schema, $connect_info) = @_;
184 my $replicant = $self->create_replicant($schema);
185 $replicant->connect_info($connect_info);
186 $self->_safely_ensure_connected($replicant);
187 DBIx::Class::Storage::DBI::Replicated::Replicant->meta->apply($replicant);
191 =head2 _safely_ensure_connected ($replicant)
193 The standard ensure_connected method with throw an exception should it fail to
194 connect. For the master database this is desirable, but since replicants are
195 allowed to fail, this behavior is not desirable. This method wraps the call
196 to ensure_connected in an eval in order to catch any generated errors. That
197 way a slave to go completely offline (ie, the box itself can die) without
198 bringing down your entire pool of databases.
202 sub _safely_ensure_connected {
203 my ($self, $replicant, @args) = @_;
205 $replicant->ensure_connected(@args);
211 sprintf( "Exception trying to ->ensure_connected for replicant %s, error is %s",
212 $replicant->_dbi_connect_info->[0], $@)
219 =head2 connected_replicants
221 Returns true if there are connected replicants. Actually is overloaded to
222 return the number of replicants. So you can do stuff like:
224 if( my $num_connected = $storage->has_connected_replicants ) {
225 print "I have $num_connected connected replicants";
227 print "Sorry, no replicants.";
230 This method will actually test that each replicant in the L</replicants> hashref
231 is actually connected, try not to hit this 10 times a second.
235 sub connected_replicants {
239 } $self->all_replicants );
242 =head2 active_replicants
244 This is an array of replicants that are considered to be active in the pool.
245 This does not check to see if they are connected, but if they are not, DBIC
246 should automatically reconnect them for us when we hit them with a query.
250 sub active_replicants {
252 return ( grep {$_} map {
254 } $self->all_replicants );
257 =head2 all_replicants
259 Just a simple array of all the replicant storages. No particular order to the
260 array is given, nor should any meaning be derived.
266 return values %{$self->replicants};
269 =head2 validate_replicants
271 This does a check to see if 1) each replicate is connected (or reconnectable),
272 2) that is ->is_replicating, and 3) that it is not exceeding the lag amount
273 defined by L</maximum_lag>. Replicants that fail any of these tests are set to
274 inactive, and thus removed from the replication pool.
276 This tests L<all_replicants>, since a replicant that has been previous marked
277 as inactive can be reactived should it start to pass the validation tests again.
279 See L<DBIx::Class::Storage::DBI> for more about checking if a replicating
280 connection is not following a master or is lagging.
282 Calling this method will generate queries on the replicant databases so it is
283 not recommended that you run them very often.
285 This method requires that your underlying storage engine supports some sort of
286 native replication mechanism. Currently only MySQL native replication is
287 supported. Your patches to make other replication types work are welcomed.
291 sub validate_replicants {
293 foreach my $replicant($self->all_replicants) {
294 if($self->_safely_ensure_connected($replicant)) {
295 my $is_replicating = $replicant->is_replicating;
296 unless(defined $is_replicating) {
297 $replicant->debugobj->print("Storage Driver ".ref($self)." Does not support the 'is_replicating' method. Assuming you are manually managing.\n");
300 if($is_replicating) {
301 my $lag_behind_master = $replicant->lag_behind_master;
302 unless(defined $lag_behind_master) {
303 $replicant->debugobj->print("Storage Driver ".ref($self)." Does not support the 'lag_behind_master' method. Assuming you are manually managing.\n");
306 if($lag_behind_master <= $self->maximum_lag) {
307 $replicant->active(1);
309 $replicant->active(0);
313 $replicant->active(0);
317 $replicant->active(0);
320 ## Mark that we completed this validation.
321 $self->_last_validated(time);
326 John Napiorkowski <john.napiorkowski@takkle.com>
330 You may distribute this code under the same terms as Perl itself.
334 __PACKAGE__->meta->make_immutable;