Commit | Line | Data |
26ab719a |
1 | package DBIx::Class::Storage::DBI::Replicated::Pool; |
2 | |
3 | use Moose; |
4 | use MooseX::AttributeHelpers; |
5 | use DBIx::Class::Storage::DBI::Replicated::Replicant; |
9901aad7 |
6 | use List::Util 'sum'; |
7 | use Scalar::Util 'reftype'; |
0bd8e058 |
8 | use DBI (); |
9901aad7 |
9 | use Carp::Clan qw/^DBIx::Class/; |
41916570 |
10 | use MooseX::Types::Moose qw/Num Int ClassName HashRef/; |
9901aad7 |
11 | |
12 | use namespace::clean -except => 'meta'; |
26ab719a |
13 | |
14 | =head1 NAME |
15 | |
21fc4719 |
16 | DBIx::Class::Storage::DBI::Replicated::Pool - Manage a pool of replicants |
26ab719a |
17 | |
18 | =head1 SYNOPSIS |
19 | |
20 | This class is used internally by L<DBIx::Class::Storage::DBI::Replicated>. You |
21 | shouldn't need to create instances of this class. |
d4daee7b |
22 | |
26ab719a |
23 | =head1 DESCRIPTION |
24 | |
25 | In a replicated storage type, there is at least one replicant to handle the |
26 | read only traffic. The Pool class manages this replicant, or list of |
27 | replicants, and gives some methods for querying information about their status. |
28 | |
29 | =head1 ATTRIBUTES |
30 | |
31 | This class defines the following attributes. |
32 | |
4a607d7a |
33 | =head2 maximum_lag ($num) |
34 | |
35 | This is a number which defines the maximum allowed lag returned by the |
36 | L<DBIx::Class::Storage::DBI/lag_behind_master> method. The default is 0. In |
37 | general, this should return a larger number when the replicant is lagging |
faaba25f |
38 | behind its master, however the implementation of this is database specific, so |
4a607d7a |
39 | don't count on this number having a fixed meaning. For example, MySQL will |
40 | return a number of seconds that the replicating database is lagging. |
41 | |
42 | =cut |
43 | |
44 | has 'maximum_lag' => ( |
64cdad22 |
45 | is=>'rw', |
41916570 |
46 | isa=>Num, |
64cdad22 |
47 | required=>1, |
48 | lazy=>1, |
49 | default=>0, |
4a607d7a |
50 | ); |
51 | |
17b05c13 |
52 | =head2 last_validated |
53 | |
54 | This is an integer representing a time since the last time the replicants were |
faaba25f |
55 | validated. It's nothing fancy, just an integer provided via the perl L<time|perlfunc/time> |
17b05c13 |
56 | builtin. |
57 | |
58 | =cut |
59 | |
60 | has 'last_validated' => ( |
64cdad22 |
61 | is=>'rw', |
41916570 |
62 | isa=>Int, |
64cdad22 |
63 | reader=>'last_validated', |
64 | writer=>'_last_validated', |
65 | lazy=>1, |
66 | default=>0, |
17b05c13 |
67 | ); |
68 | |
4a607d7a |
69 | =head2 replicant_type ($classname) |
26ab719a |
70 | |
71 | Base class used to instantiate replicants that are in the pool. Unless you |
72 | need to subclass L<DBIx::Class::Storage::DBI::Replicated::Replicant> you should |
73 | just leave this alone. |
74 | |
75 | =cut |
76 | |
77 | has 'replicant_type' => ( |
64cdad22 |
78 | is=>'ro', |
41916570 |
79 | isa=>ClassName, |
64cdad22 |
80 | required=>1, |
81 | default=>'DBIx::Class::Storage::DBI', |
82 | handles=>{ |
83 | 'create_replicant' => 'new', |
84 | }, |
26ab719a |
85 | ); |
86 | |
26ab719a |
87 | =head2 replicants |
88 | |
89 | A hashref of replicant, with the key being the dsn and the value returning the |
90 | actual replicant storage. For example if the $dsn element is something like: |
91 | |
64cdad22 |
92 | "dbi:SQLite:dbname=dbfile" |
d4daee7b |
93 | |
26ab719a |
94 | You could access the specific replicant via: |
95 | |
64cdad22 |
96 | $schema->storage->replicants->{'dbname=dbfile'} |
d4daee7b |
97 | |
64cdad22 |
98 | This attributes also supports the following helper methods: |
26ab719a |
99 | |
100 | =over 4 |
101 | |
102 | =item set_replicant($key=>$storage) |
103 | |
104 | Pushes a replicant onto the HashRef under $key |
105 | |
106 | =item get_replicant($key) |
107 | |
108 | Retrieves the named replicant |
109 | |
110 | =item has_replicants |
111 | |
112 | Returns true if the Pool defines replicants. |
113 | |
114 | =item num_replicants |
115 | |
116 | The number of replicants in the pool |
117 | |
118 | =item delete_replicant ($key) |
119 | |
120 | removes the replicant under $key from the pool |
121 | |
122 | =back |
123 | |
124 | =cut |
125 | |
126 | has 'replicants' => ( |
64cdad22 |
127 | is=>'rw', |
128 | metaclass => 'Collection::Hash', |
071bbccb |
129 | isa=>HashRef['Object'], |
64cdad22 |
130 | default=>sub {{}}, |
131 | provides => { |
132 | 'set' => 'set_replicant', |
d4daee7b |
133 | 'get' => 'get_replicant', |
64cdad22 |
134 | 'empty' => 'has_replicants', |
135 | 'count' => 'num_replicants', |
136 | 'delete' => 'delete_replicant', |
d4daee7b |
137 | 'values' => 'all_replicant_storages', |
64cdad22 |
138 | }, |
26ab719a |
139 | ); |
140 | |
ede99b9f |
141 | has next_unknown_replicant_id => ( |
142 | is => 'rw', |
143 | metaclass => 'Counter', |
144 | isa => Int, |
145 | default => 1, |
146 | provides => { |
147 | inc => 'inc_unknown_replicant_id' |
148 | }, |
149 | ); |
150 | |
26ab719a |
151 | =head1 METHODS |
152 | |
153 | This class defines the following methods. |
154 | |
955a6df6 |
155 | =head2 connect_replicants ($schema, Array[$connect_info]) |
26ab719a |
156 | |
d40080c3 |
157 | Given an array of $dsn or connect_info structures suitable for connected to a |
158 | database, create an L<DBIx::Class::Storage::DBI::Replicated::Replicant> object |
159 | and store it in the L</replicants> attribute. |
26ab719a |
160 | |
161 | =cut |
162 | |
955a6df6 |
163 | sub connect_replicants { |
64cdad22 |
164 | my $self = shift @_; |
165 | my $schema = shift @_; |
d4daee7b |
166 | |
64cdad22 |
167 | my @newly_created = (); |
168 | foreach my $connect_info (@_) { |
2cd3ccc4 |
169 | $connect_info = [ $connect_info ] |
9901aad7 |
170 | if reftype $connect_info ne 'ARRAY'; |
171 | |
0bd8e058 |
172 | my $connect_coderef = |
173 | (reftype($connect_info->[0])||'') eq 'CODE' ? $connect_info->[0] |
174 | : (reftype($connect_info->[0])||'') eq 'HASH' && |
175 | $connect_info->[0]->{dbh_maker}; |
176 | |
177 | my $dsn; |
4c91f824 |
178 | my $replicant = do { |
ede99b9f |
179 | # yes this is evil, but it only usually happens once (for coderefs) |
180 | # this will fail if the coderef does not actually DBI::connect |
0bd8e058 |
181 | no warnings 'redefine'; |
182 | my $connect = \&DBI::connect; |
183 | local *DBI::connect = sub { |
184 | $dsn = $_[1]; |
185 | goto $connect; |
186 | }; |
4c91f824 |
187 | $self->connect_replicant($schema, $connect_info); |
188 | }; |
189 | |
ede99b9f |
190 | my $key; |
191 | |
192 | if (!$dsn) { |
193 | if (!$connect_coderef) { |
194 | $dsn = $connect_info->[0]; |
195 | $dsn = $dsn->{dsn} if (reftype($dsn)||'') eq 'HASH'; |
196 | } |
197 | else { |
198 | # all attempts to get the DSN failed |
199 | $key = "UNKNOWN_" . $self->next_unknown_replicant_id; |
200 | $self->inc_unknown_replicant_id; |
201 | } |
202 | } |
203 | if ($dsn) { |
204 | $replicant->dsn($dsn); |
205 | ($key) = ($dsn =~ m/^dbi\:.+\:(.+)$/i); |
0bd8e058 |
206 | } |
0bd8e058 |
207 | |
ede99b9f |
208 | $replicant->id($key); |
0bd8e058 |
209 | $self->set_replicant($key => $replicant); |
ede99b9f |
210 | |
64cdad22 |
211 | push @newly_created, $replicant; |
212 | } |
d4daee7b |
213 | |
64cdad22 |
214 | return @newly_created; |
26ab719a |
215 | } |
216 | |
bbafcf26 |
217 | =head2 connect_replicant ($schema, $connect_info) |
218 | |
219 | Given a schema object and a hashref of $connect_info, connect the replicant |
220 | and return it. |
221 | |
222 | =cut |
223 | |
224 | sub connect_replicant { |
225 | my ($self, $schema, $connect_info) = @_; |
226 | my $replicant = $self->create_replicant($schema); |
f15afa13 |
227 | $replicant->connect_info($connect_info); |
d40080c3 |
228 | |
229 | ## It is undesirable for catalyst to connect at ->conect_replicants time, as |
230 | ## connections should only happen on the first request that uses the database. |
231 | ## So we try to set the driver without connecting, however this doesn't always |
232 | ## work, as a driver may need to connect to determine the DB version, and this |
233 | ## may fail. |
d6e80959 |
234 | ## |
235 | ## Why this is necessary at all, is that we need to have the final storage |
236 | ## class to apply the Replicant role. |
d40080c3 |
237 | |
238 | $self->_safely($replicant, '->_determine_driver', sub { |
239 | $replicant->_determine_driver |
240 | }); |
241 | |
f15afa13 |
242 | DBIx::Class::Storage::DBI::Replicated::Replicant->meta->apply($replicant); |
bbafcf26 |
243 | return $replicant; |
244 | } |
245 | |
f15afa13 |
246 | =head2 _safely_ensure_connected ($replicant) |
247 | |
248 | The standard ensure_connected method with throw an exception should it fail to |
249 | connect. For the master database this is desirable, but since replicants are |
250 | allowed to fail, this behavior is not desirable. This method wraps the call |
251 | to ensure_connected in an eval in order to catch any generated errors. That |
d40080c3 |
252 | way a slave can go completely offline (ie, the box itself can die) without |
f15afa13 |
253 | bringing down your entire pool of databases. |
254 | |
255 | =cut |
256 | |
257 | sub _safely_ensure_connected { |
258 | my ($self, $replicant, @args) = @_; |
d40080c3 |
259 | |
260 | return $self->_safely($replicant, '->ensure_connected', sub { |
261 | $replicant->ensure_connected(@args) |
262 | }); |
263 | } |
264 | |
265 | =head2 _safely ($replicant, $name, $code) |
266 | |
267 | Execute C<$code> for operation C<$name> catching any exceptions and printing an |
268 | error message to the C<<$replicant->debugobj>>. |
269 | |
270 | Returns 1 on success and undef on failure. |
271 | |
272 | =cut |
273 | |
274 | sub _safely { |
275 | my ($self, $replicant, $name, $code) = @_; |
276 | |
6ffb5be5 |
277 | eval { |
d40080c3 |
278 | $code->() |
6ffb5be5 |
279 | }; |
280 | if ($@) { |
13b9e828 |
281 | $replicant |
6ffb5be5 |
282 | ->debugobj |
283 | ->print( |
d40080c3 |
284 | sprintf( "Exception trying to $name for replicant %s, error is %s", |
6ffb5be5 |
285 | $replicant->_dbi_connect_info->[0], $@) |
13b9e828 |
286 | ); |
6ffb5be5 |
287 | return; |
13b9e828 |
288 | } |
6ffb5be5 |
289 | return 1; |
f15afa13 |
290 | } |
291 | |
26ab719a |
292 | =head2 connected_replicants |
293 | |
294 | Returns true if there are connected replicants. Actually is overloaded to |
295 | return the number of replicants. So you can do stuff like: |
296 | |
64cdad22 |
297 | if( my $num_connected = $storage->has_connected_replicants ) { |
298 | print "I have $num_connected connected replicants"; |
299 | } else { |
300 | print "Sorry, no replicants."; |
301 | } |
26ab719a |
302 | |
303 | This method will actually test that each replicant in the L</replicants> hashref |
304 | is actually connected, try not to hit this 10 times a second. |
305 | |
306 | =cut |
307 | |
308 | sub connected_replicants { |
64cdad22 |
309 | my $self = shift @_; |
310 | return sum( map { |
311 | $_->connected ? 1:0 |
312 | } $self->all_replicants ); |
26ab719a |
313 | } |
314 | |
50336325 |
315 | =head2 active_replicants |
316 | |
317 | This is an array of replicants that are considered to be active in the pool. |
318 | This does not check to see if they are connected, but if they are not, DBIC |
319 | should automatically reconnect them for us when we hit them with a query. |
320 | |
321 | =cut |
322 | |
323 | sub active_replicants { |
64cdad22 |
324 | my $self = shift @_; |
325 | return ( grep {$_} map { |
326 | $_->active ? $_:0 |
327 | } $self->all_replicants ); |
50336325 |
328 | } |
329 | |
26ab719a |
330 | =head2 all_replicants |
331 | |
332 | Just a simple array of all the replicant storages. No particular order to the |
333 | array is given, nor should any meaning be derived. |
334 | |
335 | =cut |
336 | |
337 | sub all_replicants { |
64cdad22 |
338 | my $self = shift @_; |
339 | return values %{$self->replicants}; |
26ab719a |
340 | } |
341 | |
4a607d7a |
342 | =head2 validate_replicants |
343 | |
344 | This does a check to see if 1) each replicate is connected (or reconnectable), |
345 | 2) that is ->is_replicating, and 3) that it is not exceeding the lag amount |
346 | defined by L</maximum_lag>. Replicants that fail any of these tests are set to |
347 | inactive, and thus removed from the replication pool. |
348 | |
349 | This tests L<all_replicants>, since a replicant that has been previous marked |
350 | as inactive can be reactived should it start to pass the validation tests again. |
351 | |
352 | See L<DBIx::Class::Storage::DBI> for more about checking if a replicating |
353 | connection is not following a master or is lagging. |
354 | |
355 | Calling this method will generate queries on the replicant databases so it is |
356 | not recommended that you run them very often. |
357 | |
13b9e828 |
358 | This method requires that your underlying storage engine supports some sort of |
359 | native replication mechanism. Currently only MySQL native replication is |
360 | supported. Your patches to make other replication types work are welcomed. |
361 | |
4a607d7a |
362 | =cut |
363 | |
364 | sub validate_replicants { |
64cdad22 |
365 | my $self = shift @_; |
366 | foreach my $replicant($self->all_replicants) { |
13b9e828 |
367 | if($self->_safely_ensure_connected($replicant)) { |
368 | my $is_replicating = $replicant->is_replicating; |
369 | unless(defined $is_replicating) { |
9901aad7 |
370 | $replicant->debugobj->print("Storage Driver ".ref($self)." Does not support the 'is_replicating' method. Assuming you are manually managing.\n"); |
13b9e828 |
371 | next; |
372 | } else { |
373 | if($is_replicating) { |
374 | my $lag_behind_master = $replicant->lag_behind_master; |
375 | unless(defined $lag_behind_master) { |
9901aad7 |
376 | $replicant->debugobj->print("Storage Driver ".ref($self)." Does not support the 'lag_behind_master' method. Assuming you are manually managing.\n"); |
13b9e828 |
377 | next; |
378 | } else { |
379 | if($lag_behind_master <= $self->maximum_lag) { |
380 | $replicant->active(1); |
381 | } else { |
382 | $replicant->active(0); |
383 | } |
384 | } |
385 | } else { |
386 | $replicant->active(0); |
387 | } |
388 | } |
64cdad22 |
389 | } else { |
64cdad22 |
390 | $replicant->active(0); |
7edf5f1c |
391 | } |
64cdad22 |
392 | } |
393 | ## Mark that we completed this validation. |
13b9e828 |
394 | $self->_last_validated(time); |
4a607d7a |
395 | } |
396 | |
26ab719a |
397 | =head1 AUTHOR |
398 | |
399 | John Napiorkowski <john.napiorkowski@takkle.com> |
400 | |
401 | =head1 LICENSE |
402 | |
403 | You may distribute this code under the same terms as Perl itself. |
404 | |
405 | =cut |
406 | |
c354902c |
407 | __PACKAGE__->meta->make_immutable; |
408 | |
cb6ec758 |
409 | 1; |