1 package DBIx::Class::Storage::DBI::Replicated::Pool;
4 use DBIx::Class::Storage::DBI::Replicated::Replicant;
6 use Scalar::Util 'reftype';
8 use DBIx::Class::_Types qw(HashRef Number Integer LoadableClass DBICStorageDBI);
15 DBIx::Class::Storage::DBI::Replicated::Pool - Manage a pool of replicants
19 This class is used internally by L<DBIx::Class::Storage::DBI::Replicated>. You
20 shouldn't need to create instances of this class.
24 In a replicated storage type, there is at least one replicant to handle the
25 read-only traffic. The Pool class manages this replicant, or list of
26 replicants, and gives some methods for querying information about their status.
30 This class defines the following attributes.
32 =head2 maximum_lag ($num)
34 This is a number which defines the maximum allowed lag returned by the
35 L<DBIx::Class::Storage::DBI/lag_behind_master> method. The default is 0. In
36 general, this should return a larger number when the replicant is lagging
37 behind its master, however the implementation of this is database specific, so
38 don't count on this number having a fixed meaning. For example, MySQL will
39 return a number of seconds that the replicating database is lagging.
43 has 'maximum_lag' => (
52 This is an integer representing a time since the last time the replicants were
53 validated. It's nothing fancy, just an integer provided via the perl L<time|perlfunc/time>
58 has 'last_validated' => (
61 reader=>'last_validated',
62 writer=>'_last_validated',
67 =head2 replicant_type ($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' => (
130 sub set_replicant { $_[0]->replicants->{$_[1]} = $_[2] }
131 sub get_replicant { $_[0]->replicants->{$_[1]} }
132 sub has_replicants { !!keys %{$_[0]->replicants} }
133 sub num_replicants { 0+keys %{$_[0]->replicants} }
134 sub delete_replicant { delete $_[0]->replicants->{$_[1]} }
135 sub all_replicant_storages { values %{$_[0]->replicants} }
137 has next_unknown_replicant_id => (
143 sub inc_unknown_replicant_id {
145 $self->next_unknown_replicant_id($self->next_unknown_replicant_id + 1);
150 Reference to the master Storage.
154 has master => (is => 'rw', isa => DBICStorageDBI, weak_ref => 1);
158 This class defines the following methods.
160 =head2 connect_replicants ($schema, Array[$connect_info])
162 Given an array of $dsn or connect_info structures suitable for connected to a
163 database, create an L<DBIx::Class::Storage::DBI::Replicated::Replicant> object
164 and store it in the L</replicants> attribute.
168 sub connect_replicants {
170 my $schema = shift @_;
172 my @newly_created = ();
173 foreach my $connect_info (@_) {
174 $connect_info = [ $connect_info ]
175 if reftype $connect_info ne 'ARRAY';
177 my $connect_coderef =
178 (reftype($connect_info->[0])||'') eq 'CODE' ? $connect_info->[0]
179 : (reftype($connect_info->[0])||'') eq 'HASH' &&
180 $connect_info->[0]->{dbh_maker};
184 # yes this is evil, but it only usually happens once (for coderefs)
185 # this will fail if the coderef does not actually DBI::connect
186 no warnings 'redefine';
187 my $connect = \&DBI::connect;
188 local *DBI::connect = sub {
192 $self->connect_replicant($schema, $connect_info);
198 if (!$connect_coderef) {
199 $dsn = $connect_info->[0];
200 $dsn = $dsn->{dsn} if (reftype($dsn)||'') eq 'HASH';
203 # all attempts to get the DSN failed
204 $key = "UNKNOWN_" . $self->next_unknown_replicant_id;
205 $self->inc_unknown_replicant_id;
209 $replicant->dsn($dsn);
210 ($key) = ($dsn =~ m/^dbi\:.+\:(.+)$/i);
213 $replicant->id($key);
214 $self->set_replicant($key => $replicant);
216 push @newly_created, $replicant;
219 return @newly_created;
222 =head2 connect_replicant ($schema, $connect_info)
224 Given a schema object and a hashref of $connect_info, connect the replicant
229 sub connect_replicant {
230 my ($self, $schema, $connect_info) = @_;
231 my $replicant = $self->create_replicant($schema);
232 $replicant->connect_info($connect_info);
234 ## It is undesirable for catalyst to connect at ->conect_replicants time, as
235 ## connections should only happen on the first request that uses the database.
236 ## So we try to set the driver without connecting, however this doesn't always
237 ## work, as a driver may need to connect to determine the DB version, and this
240 ## Why this is necessary at all, is that we need to have the final storage
241 ## class to apply the Replicant role.
243 $self->_safely($replicant, '->_determine_driver', sub {
244 $replicant->_determine_driver
247 Moo::Role->apply_roles_to_object($replicant, 'DBIx::Class::Storage::DBI::Replicated::Replicant');
249 # link back to master
250 $replicant->master($self->master);
255 =head2 _safely_ensure_connected ($replicant)
257 The standard ensure_connected method with throw an exception should it fail to
258 connect. For the master database this is desirable, but since replicants are
259 allowed to fail, this behavior is not desirable. This method wraps the call
260 to ensure_connected in an eval in order to catch any generated errors. That
261 way a slave can go completely offline (e.g. the box itself can die) without
262 bringing down your entire pool of databases.
266 sub _safely_ensure_connected {
267 my ($self, $replicant, @args) = @_;
269 return $self->_safely($replicant, '->ensure_connected', sub {
270 $replicant->ensure_connected(@args)
274 =head2 _safely ($replicant, $name, $code)
276 Execute C<$code> for operation C<$name> catching any exceptions and printing an
277 error message to the C<<$replicant->debugobj>>.
279 Returns 1 on success and undef on failure.
284 my ($self, $replicant, $name, $code) = @_;
290 $replicant->debugobj->print(sprintf(
291 "Exception trying to $name for replicant %s, error is %s",
292 $replicant->_dbi_connect_info->[0], $_)
298 =head2 connected_replicants
300 Returns true if there are connected replicants. Actually is overloaded to
301 return the number of replicants. So you can do stuff like:
303 if( my $num_connected = $storage->has_connected_replicants ) {
304 print "I have $num_connected connected replicants";
306 print "Sorry, no replicants.";
309 This method will actually test that each replicant in the L</replicants> hashref
310 is actually connected, try not to hit this 10 times a second.
314 sub connected_replicants {
318 } $self->all_replicants );
321 =head2 active_replicants
323 This is an array of replicants that are considered to be active in the pool.
324 This does not check to see if they are connected, but if they are not, DBIC
325 should automatically reconnect them for us when we hit them with a query.
329 sub active_replicants {
331 return ( grep {$_} map {
333 } $self->all_replicants );
336 =head2 all_replicants
338 Just a simple array of all the replicant storages. No particular order to the
339 array is given, nor should any meaning be derived.
345 return values %{$self->replicants};
348 =head2 validate_replicants
350 This does a check to see if 1) each replicate is connected (or reconnectable),
351 2) that is ->is_replicating, and 3) that it is not exceeding the lag amount
352 defined by L</maximum_lag>. Replicants that fail any of these tests are set to
353 inactive, and thus removed from the replication pool.
355 This tests L</all_replicants>, since a replicant that has been previous marked
356 as inactive can be reactivated should it start to pass the validation tests again.
358 See L<DBIx::Class::Storage::DBI> for more about checking if a replicating
359 connection is not following a master or is lagging.
361 Calling this method will generate queries on the replicant databases so it is
362 not recommended that you run them very often.
364 This method requires that your underlying storage engine supports some sort of
365 native replication mechanism. Currently only MySQL native replication is
366 supported. Your patches to make other replication types work are welcomed.
370 sub validate_replicants {
372 foreach my $replicant($self->all_replicants) {
373 if($self->_safely_ensure_connected($replicant)) {
374 my $is_replicating = $replicant->is_replicating;
375 unless(defined $is_replicating) {
376 $replicant->debugobj->print("Storage Driver ".ref($self)." Does not support the 'is_replicating' method. Assuming you are manually managing.\n");
379 if($is_replicating) {
380 my $lag_behind_master = $replicant->lag_behind_master;
381 unless(defined $lag_behind_master) {
382 $replicant->debugobj->print("Storage Driver ".ref($self)." Does not support the 'lag_behind_master' method. Assuming you are manually managing.\n");
385 if($lag_behind_master <= $self->maximum_lag) {
386 $replicant->active(1);
388 $replicant->active(0);
392 $replicant->active(0);
396 $replicant->active(0);
399 ## Mark that we completed this validation.
400 $self->_last_validated(time);
403 =head1 FURTHER QUESTIONS?
405 Check the list of L<additional DBIC resources|DBIx::Class/GETTING HELP/SUPPORT>.
407 =head1 COPYRIGHT AND LICENSE
409 This module is free software L<copyright|DBIx::Class/COPYRIGHT AND LICENSE>
410 by the L<DBIx::Class (DBIC) authors|DBIx::Class/AUTHORS>. You can
411 redistribute it and/or modify it under the same terms as the
412 L<DBIx::Class library|DBIx::Class/COPYRIGHT AND LICENSE>.