1 package DBIx::Class::Storage::DBI::Replicated::Pool;
4 use DBIx::Class::Storage::DBI::Replicated::Replicant;
5 use Scalar::Util 'reftype';
7 use MooseX::Types::Moose qw/Num Int ClassName HashRef/;
8 use DBIx::Class::Storage::DBI::Replicated::Types 'DBICStorageDBI';
9 use DBIx::Class::_Util qw( dbic_internal_try dbic_internal_catch );
11 use namespace::clean -except => 'meta';
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 ($num)
34 This is a number which defines the maximum allowed lag returned by the
35 L<DBIx::Class::Storage::DBI/lag_behind_master> method. The default is 0. In
36 general, this should return a larger number when the replicant is lagging
37 behind its master, however the implementation of this is database specific, so
38 don't count on this number having a fixed meaning. For example, MySQL will
39 return a number of seconds that the replicating database is lagging.
43 has 'maximum_lag' => (
53 This is an integer representing a time since the last time the replicants were
54 validated. It's nothing fancy, just an integer provided via the perl L<time|perlfunc/time>
59 has 'last_validated' => (
62 reader=>'last_validated',
63 writer=>'_last_validated',
68 =head2 replicant_type ($classname)
70 Base class used to instantiate replicants that are in the pool. Unless you
71 need to subclass L<DBIx::Class::Storage::DBI::Replicated::Replicant> you should
72 just leave this alone.
76 has 'replicant_type' => (
80 default=>'DBIx::Class::Storage::DBI',
82 'create_replicant' => 'new',
88 A hashref of replicant, with the key being the dsn and the value returning the
89 actual replicant storage. For example, if the $dsn element is something like:
91 "dbi:SQLite:dbname=dbfile"
93 You could access the specific replicant via:
95 $schema->storage->replicants->{'dbname=dbfile'}
97 This attributes also supports the following helper methods:
101 =item set_replicant($key=>$storage)
103 Pushes a replicant onto the HashRef under $key
105 =item get_replicant($key)
107 Retrieves the named replicant
111 Returns true if the Pool defines replicants.
115 The number of replicants in the pool
117 =item delete_replicant ($key)
119 Removes the replicant under $key from the pool
125 has 'replicants' => (
128 isa=>HashRef['Object'],
131 'set_replicant' => 'set',
132 'get_replicant' => 'get',
133 'has_replicants' => 'is_empty',
134 'num_replicants' => 'count',
135 'delete_replicant' => 'delete',
136 'all_replicant_storages' => 'values',
140 around has_replicants => sub {
141 my ($orig, $self) = @_;
142 return !$self->$orig;
145 has next_unknown_replicant_id => (
147 traits => ['Counter'],
151 'inc_unknown_replicant_id' => 'inc',
157 Reference to the master Storage.
161 has master => (is => 'rw', isa => DBICStorageDBI, weak_ref => 1);
165 This class defines the following methods.
167 =head2 connect_replicants ($schema, Array[$connect_info])
169 Given an array of $dsn or connect_info structures suitable for connected to a
170 database, create an L<DBIx::Class::Storage::DBI::Replicated::Replicant> object
171 and store it in the L</replicants> attribute.
175 sub connect_replicants {
177 my $schema = shift @_;
179 my @newly_created = ();
180 foreach my $connect_info (@_) {
181 $connect_info = [ $connect_info ]
182 if reftype $connect_info ne 'ARRAY';
184 my $connect_coderef =
185 (reftype($connect_info->[0])||'') eq 'CODE' ? $connect_info->[0]
186 : (reftype($connect_info->[0])||'') eq 'HASH' &&
187 $connect_info->[0]->{dbh_maker};
191 # yes this is evil, but it only usually happens once (for coderefs)
192 # this will fail if the coderef does not actually DBI::connect
193 no warnings 'redefine';
194 my $connect = \&DBI::connect;
195 local *DBI::connect = sub {
199 $self->connect_replicant($schema, $connect_info);
205 if (!$connect_coderef) {
206 $dsn = $connect_info->[0];
207 $dsn = $dsn->{dsn} if (reftype($dsn)||'') eq 'HASH';
210 # all attempts to get the DSN failed
211 $key = "UNKNOWN_" . $self->next_unknown_replicant_id;
212 $self->inc_unknown_replicant_id;
216 $replicant->dsn($dsn);
217 ($key) = ($dsn =~ m/^dbi\:.+\:(.+)$/i);
220 $replicant->id($key);
221 $self->set_replicant($key => $replicant);
223 push @newly_created, $replicant;
226 return @newly_created;
229 =head2 connect_replicant ($schema, $connect_info)
231 Given a schema object and a hashref of $connect_info, connect the replicant
236 sub connect_replicant {
237 my ($self, $schema, $connect_info) = @_;
238 my $replicant = $self->create_replicant($schema);
239 $replicant->connect_info($connect_info);
241 ## It is undesirable for catalyst to connect at ->conect_replicants time, as
242 ## connections should only happen on the first request that uses the database.
243 ## So we try to set the driver without connecting, however this doesn't always
244 ## work, as a driver may need to connect to determine the DB version, and this
247 ## Why this is necessary at all, is that we need to have the final storage
248 ## class to apply the Replicant role.
250 $self->_safely($replicant, '->_determine_driver', sub {
251 $replicant->_determine_driver
254 Moose::Meta::Class->initialize(ref $replicant);
256 DBIx::Class::Storage::DBI::Replicated::Replicant->meta->apply($replicant);
258 # link back to master
259 $replicant->master($self->master);
264 =head2 _safely_ensure_connected ($replicant)
266 The standard ensure_connected method with throw an exception should it fail to
267 connect. For the master database this is desirable, but since replicants are
268 allowed to fail, this behavior is not desirable. This method wraps the call
269 to ensure_connected in an eval in order to catch any generated errors. That
270 way a slave can go completely offline (e.g. the box itself can die) without
271 bringing down your entire pool of databases.
275 sub _safely_ensure_connected {
276 my ($self, $replicant, @args) = @_;
278 return $self->_safely($replicant, '->ensure_connected', sub {
279 $replicant->ensure_connected(@args)
283 =head2 _safely ($replicant, $name, $code)
285 Execute C<$code> for operation C<$name> catching any exceptions and printing an
286 error message to the C<<$replicant->debugobj>>.
288 Returns 1 on success and undef on failure.
293 my ($self, $replicant, $name, $code) = @_;
299 dbic_internal_catch {
300 $replicant->debugobj->print(sprintf(
301 "Exception trying to $name for replicant %s, error is %s",
302 $replicant->_dbi_connect_info->[0], $_)
310 =head2 connected_replicants
312 Returns true if there are connected replicants. Actually is overloaded to
313 return the number of replicants. So you can do stuff like:
315 if( my $num_connected = $storage->has_connected_replicants ) {
316 print "I have $num_connected connected replicants";
318 print "Sorry, no replicants.";
321 This method will actually test that each replicant in the L</replicants> hashref
322 is actually connected, try not to hit this 10 times a second.
326 sub connected_replicants {
329 shift->all_replicants
333 =head2 active_replicants
335 This is an array of replicants that are considered to be active in the pool.
336 This does not check to see if they are connected, but if they are not, DBIC
337 should automatically reconnect them for us when we hit them with a query.
341 sub active_replicants {
343 return ( grep {$_} map {
345 } $self->all_replicants );
348 =head2 all_replicants
350 Just a simple array of all the replicant storages. No particular order to the
351 array is given, nor should any meaning be derived.
357 return values %{$self->replicants};
360 =head2 validate_replicants
362 This does a check to see if 1) each replicate is connected (or reconnectable),
363 2) that is ->is_replicating, and 3) that it is not exceeding the lag amount
364 defined by L</maximum_lag>. Replicants that fail any of these tests are set to
365 inactive, and thus removed from the replication pool.
367 This tests L</all_replicants>, since a replicant that has been previous marked
368 as inactive can be reactivated should it start to pass the validation tests again.
370 See L<DBIx::Class::Storage::DBI> for more about checking if a replicating
371 connection is not following a master or is lagging.
373 Calling this method will generate queries on the replicant databases so it is
374 not recommended that you run them very often.
376 This method requires that your underlying storage engine supports some sort of
377 native replication mechanism. Currently only MySQL native replication is
378 supported. Your patches to make other replication types work are welcomed.
382 sub validate_replicants {
384 foreach my $replicant($self->all_replicants) {
385 if($self->_safely_ensure_connected($replicant)) {
386 my $is_replicating = $replicant->is_replicating;
387 unless(defined $is_replicating) {
388 $replicant->debugobj->print("Storage Driver ".ref($self)." Does not support the 'is_replicating' method. Assuming you are manually managing.\n");
391 if($is_replicating) {
392 my $lag_behind_master = $replicant->lag_behind_master;
393 unless(defined $lag_behind_master) {
394 $replicant->debugobj->print("Storage Driver ".ref($self)." Does not support the 'lag_behind_master' method. Assuming you are manually managing.\n");
397 if($lag_behind_master <= $self->maximum_lag) {
398 $replicant->active(1);
400 $replicant->active(0);
404 $replicant->active(0);
408 $replicant->active(0);
411 ## Mark that we completed this validation.
412 $self->_last_validated(time);
415 =head1 FURTHER QUESTIONS?
417 Check the list of L<additional DBIC resources|DBIx::Class/GETTING HELP/SUPPORT>.
419 =head1 COPYRIGHT AND LICENSE
421 This module is free software L<copyright|DBIx::Class/COPYRIGHT AND LICENSE>
422 by the L<DBIx::Class (DBIC) authors|DBIx::Class/AUTHORS>. You can
423 redistribute it and/or modify it under the same terms as the
424 L<DBIx::Class library|DBIx::Class/COPYRIGHT AND LICENSE>.
428 __PACKAGE__->meta->make_immutable;