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1 | package DBIx::Class::Storage::DBI::Replicated::Pool; |
2 | |
3 | use Moose; |
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4 | use DBIx::Class::Storage::DBI::Replicated::Replicant; |
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5 | use Scalar::Util 'reftype'; |
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6 | use DBI (); |
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7 | use MooseX::Types::Moose qw/Num Int ClassName HashRef/; |
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8 | use DBIx::Class::Storage::DBI::Replicated::Types 'DBICStorageDBI'; |
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9 | use DBIx::Class::_Util qw( dbic_internal_try dbic_internal_catch ); |
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10 | |
11 | use namespace::clean -except => 'meta'; |
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12 | |
13 | =head1 NAME |
14 | |
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15 | DBIx::Class::Storage::DBI::Replicated::Pool - Manage a pool of replicants |
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16 | |
17 | =head1 SYNOPSIS |
18 | |
19 | This class is used internally by L<DBIx::Class::Storage::DBI::Replicated>. You |
20 | shouldn't need to create instances of this class. |
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21 | |
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22 | =head1 DESCRIPTION |
23 | |
24 | In a replicated storage type, there is at least one replicant to handle the |
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25 | read-only traffic. The Pool class manages this replicant, or list of |
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26 | replicants, and gives some methods for querying information about their status. |
27 | |
28 | =head1 ATTRIBUTES |
29 | |
30 | This class defines the following attributes. |
31 | |
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32 | =head2 maximum_lag ($num) |
33 | |
34 | This is a number which defines the maximum allowed lag returned by the |
35 | L<DBIx::Class::Storage::DBI/lag_behind_master> method. The default is 0. In |
36 | general, this should return a larger number when the replicant is lagging |
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37 | behind its master, however the implementation of this is database specific, so |
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38 | don't count on this number having a fixed meaning. For example, MySQL will |
39 | return a number of seconds that the replicating database is lagging. |
40 | |
41 | =cut |
42 | |
43 | has 'maximum_lag' => ( |
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44 | is=>'rw', |
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45 | isa=>Num, |
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46 | required=>1, |
47 | lazy=>1, |
48 | default=>0, |
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49 | ); |
50 | |
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51 | =head2 last_validated |
52 | |
53 | This is an integer representing a time since the last time the replicants were |
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54 | validated. It's nothing fancy, just an integer provided via the perl L<time|perlfunc/time> |
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55 | built-in. |
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56 | |
57 | =cut |
58 | |
59 | has 'last_validated' => ( |
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60 | is=>'rw', |
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61 | isa=>Int, |
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62 | reader=>'last_validated', |
63 | writer=>'_last_validated', |
64 | lazy=>1, |
65 | default=>0, |
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66 | ); |
67 | |
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68 | =head2 replicant_type ($classname) |
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69 | |
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. |
73 | |
74 | =cut |
75 | |
76 | has 'replicant_type' => ( |
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77 | is=>'ro', |
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78 | isa=>ClassName, |
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79 | required=>1, |
80 | default=>'DBIx::Class::Storage::DBI', |
81 | handles=>{ |
82 | 'create_replicant' => 'new', |
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83 | }, |
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84 | ); |
85 | |
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86 | =head2 replicants |
87 | |
88 | A hashref of replicant, with the key being the dsn and the value returning the |
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89 | actual replicant storage. For example, if the $dsn element is something like: |
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90 | |
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91 | "dbi:SQLite:dbname=dbfile" |
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92 | |
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93 | You could access the specific replicant via: |
94 | |
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95 | $schema->storage->replicants->{'dbname=dbfile'} |
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96 | |
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97 | This attributes also supports the following helper methods: |
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98 | |
99 | =over 4 |
100 | |
101 | =item set_replicant($key=>$storage) |
102 | |
103 | Pushes a replicant onto the HashRef under $key |
104 | |
105 | =item get_replicant($key) |
106 | |
107 | Retrieves the named replicant |
108 | |
109 | =item has_replicants |
110 | |
111 | Returns true if the Pool defines replicants. |
112 | |
113 | =item num_replicants |
114 | |
115 | The number of replicants in the pool |
116 | |
117 | =item delete_replicant ($key) |
118 | |
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119 | Removes the replicant under $key from the pool |
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120 | |
121 | =back |
122 | |
123 | =cut |
124 | |
125 | has 'replicants' => ( |
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126 | is=>'rw', |
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127 | traits => ['Hash'], |
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128 | isa=>HashRef['Object'], |
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129 | default=>sub {{}}, |
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130 | handles => { |
131 | 'set_replicant' => 'set', |
132 | 'get_replicant' => 'get', |
133 | 'has_replicants' => 'is_empty', |
134 | 'num_replicants' => 'count', |
135 | 'delete_replicant' => 'delete', |
136 | 'all_replicant_storages' => 'values', |
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137 | }, |
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138 | ); |
139 | |
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140 | around has_replicants => sub { |
141 | my ($orig, $self) = @_; |
142 | return !$self->$orig; |
143 | }; |
144 | |
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145 | has next_unknown_replicant_id => ( |
146 | is => 'rw', |
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147 | traits => ['Counter'], |
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148 | isa => Int, |
149 | default => 1, |
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150 | handles => { |
151 | 'inc_unknown_replicant_id' => 'inc', |
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152 | }, |
153 | ); |
154 | |
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155 | =head2 master |
156 | |
157 | Reference to the master Storage. |
158 | |
159 | =cut |
160 | |
161 | has master => (is => 'rw', isa => DBICStorageDBI, weak_ref => 1); |
162 | |
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163 | =head1 METHODS |
164 | |
165 | This class defines the following methods. |
166 | |
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167 | =head2 connect_replicants ($schema, Array[$connect_info]) |
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168 | |
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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. |
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172 | |
173 | =cut |
174 | |
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175 | sub connect_replicants { |
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176 | my $self = shift @_; |
177 | my $schema = shift @_; |
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178 | |
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179 | my @newly_created = (); |
180 | foreach my $connect_info (@_) { |
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181 | $connect_info = [ $connect_info ] |
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182 | if reftype $connect_info ne 'ARRAY'; |
183 | |
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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}; |
188 | |
189 | my $dsn; |
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190 | my $replicant = do { |
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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 |
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193 | no warnings 'redefine'; |
194 | my $connect = \&DBI::connect; |
195 | local *DBI::connect = sub { |
196 | $dsn = $_[1]; |
197 | goto $connect; |
198 | }; |
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199 | $self->connect_replicant($schema, $connect_info); |
200 | }; |
201 | |
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202 | my $key; |
203 | |
204 | if (!$dsn) { |
205 | if (!$connect_coderef) { |
206 | $dsn = $connect_info->[0]; |
207 | $dsn = $dsn->{dsn} if (reftype($dsn)||'') eq 'HASH'; |
208 | } |
209 | else { |
210 | # all attempts to get the DSN failed |
211 | $key = "UNKNOWN_" . $self->next_unknown_replicant_id; |
212 | $self->inc_unknown_replicant_id; |
213 | } |
214 | } |
215 | if ($dsn) { |
216 | $replicant->dsn($dsn); |
217 | ($key) = ($dsn =~ m/^dbi\:.+\:(.+)$/i); |
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218 | } |
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219 | |
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220 | $replicant->id($key); |
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221 | $self->set_replicant($key => $replicant); |
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222 | |
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223 | push @newly_created, $replicant; |
224 | } |
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225 | |
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226 | return @newly_created; |
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227 | } |
228 | |
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229 | =head2 connect_replicant ($schema, $connect_info) |
230 | |
231 | Given a schema object and a hashref of $connect_info, connect the replicant |
232 | and return it. |
233 | |
234 | =cut |
235 | |
236 | sub connect_replicant { |
237 | my ($self, $schema, $connect_info) = @_; |
238 | my $replicant = $self->create_replicant($schema); |
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239 | $replicant->connect_info($connect_info); |
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240 | |
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 |
245 | ## may fail. |
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246 | ## |
247 | ## Why this is necessary at all, is that we need to have the final storage |
248 | ## class to apply the Replicant role. |
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249 | |
250 | $self->_safely($replicant, '->_determine_driver', sub { |
251 | $replicant->_determine_driver |
252 | }); |
253 | |
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254 | Moose::Meta::Class->initialize(ref $replicant); |
255 | |
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256 | DBIx::Class::Storage::DBI::Replicated::Replicant->meta->apply($replicant); |
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257 | |
258 | # link back to master |
259 | $replicant->master($self->master); |
260 | |
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261 | return $replicant; |
262 | } |
263 | |
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264 | =head2 _safely_ensure_connected ($replicant) |
265 | |
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 |
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270 | way a slave can go completely offline (e.g. the box itself can die) without |
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271 | bringing down your entire pool of databases. |
272 | |
273 | =cut |
274 | |
275 | sub _safely_ensure_connected { |
276 | my ($self, $replicant, @args) = @_; |
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277 | |
278 | return $self->_safely($replicant, '->ensure_connected', sub { |
279 | $replicant->ensure_connected(@args) |
280 | }); |
281 | } |
282 | |
283 | =head2 _safely ($replicant, $name, $code) |
284 | |
285 | Execute C<$code> for operation C<$name> catching any exceptions and printing an |
286 | error message to the C<<$replicant->debugobj>>. |
287 | |
288 | Returns 1 on success and undef on failure. |
289 | |
290 | =cut |
291 | |
292 | sub _safely { |
293 | my ($self, $replicant, $name, $code) = @_; |
294 | |
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295 | dbic_internal_try { |
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296 | $code->(); |
297 | 1; |
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298 | } |
299 | dbic_internal_catch { |
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300 | $replicant->debugobj->print(sprintf( |
301 | "Exception trying to $name for replicant %s, error is %s", |
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302 | $replicant->_dbi_connect_info->[0], $_) |
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303 | ); |
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304 | |
305 | # rv |
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306 | undef; |
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307 | }; |
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308 | } |
309 | |
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310 | =head2 connected_replicants |
311 | |
312 | Returns true if there are connected replicants. Actually is overloaded to |
313 | return the number of replicants. So you can do stuff like: |
314 | |
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315 | if( my $num_connected = $storage->has_connected_replicants ) { |
316 | print "I have $num_connected connected replicants"; |
317 | } else { |
318 | print "Sorry, no replicants."; |
319 | } |
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320 | |
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. |
323 | |
324 | =cut |
325 | |
326 | sub connected_replicants { |
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327 | return scalar grep |
328 | { $_->connected } |
329 | shift->all_replicants |
330 | ; |
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331 | } |
332 | |
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333 | =head2 active_replicants |
334 | |
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. |
338 | |
339 | =cut |
340 | |
341 | sub active_replicants { |
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342 | my $self = shift @_; |
343 | return ( grep {$_} map { |
344 | $_->active ? $_:0 |
345 | } $self->all_replicants ); |
50336325 |
346 | } |
347 | |
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348 | =head2 all_replicants |
349 | |
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. |
352 | |
353 | =cut |
354 | |
355 | sub all_replicants { |
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356 | my $self = shift @_; |
357 | return values %{$self->replicants}; |
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358 | } |
359 | |
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360 | =head2 validate_replicants |
361 | |
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. |
366 | |
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367 | This tests L</all_replicants>, since a replicant that has been previous marked |
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368 | as inactive can be reactivated should it start to pass the validation tests again. |
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369 | |
370 | See L<DBIx::Class::Storage::DBI> for more about checking if a replicating |
371 | connection is not following a master or is lagging. |
372 | |
373 | Calling this method will generate queries on the replicant databases so it is |
374 | not recommended that you run them very often. |
375 | |
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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. |
379 | |
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380 | =cut |
381 | |
382 | sub validate_replicants { |
64cdad22 |
383 | my $self = shift @_; |
384 | foreach my $replicant($self->all_replicants) { |
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385 | if($self->_safely_ensure_connected($replicant)) { |
386 | my $is_replicating = $replicant->is_replicating; |
387 | unless(defined $is_replicating) { |
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388 | $replicant->debugobj->print("Storage Driver ".ref($self)." Does not support the 'is_replicating' method. Assuming you are manually managing.\n"); |
13b9e828 |
389 | next; |
390 | } else { |
391 | if($is_replicating) { |
392 | my $lag_behind_master = $replicant->lag_behind_master; |
393 | unless(defined $lag_behind_master) { |
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394 | $replicant->debugobj->print("Storage Driver ".ref($self)." Does not support the 'lag_behind_master' method. Assuming you are manually managing.\n"); |
13b9e828 |
395 | next; |
396 | } else { |
397 | if($lag_behind_master <= $self->maximum_lag) { |
398 | $replicant->active(1); |
399 | } else { |
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400 | $replicant->active(0); |
13b9e828 |
401 | } |
8273e845 |
402 | } |
13b9e828 |
403 | } else { |
404 | $replicant->active(0); |
405 | } |
406 | } |
64cdad22 |
407 | } else { |
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408 | $replicant->active(0); |
7edf5f1c |
409 | } |
64cdad22 |
410 | } |
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411 | ## Mark that we completed this validation. |
412 | $self->_last_validated(time); |
4a607d7a |
413 | } |
414 | |
a2bd3796 |
415 | =head1 FURTHER QUESTIONS? |
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416 | |
a2bd3796 |
417 | Check the list of L<additional DBIC resources|DBIx::Class/GETTING HELP/SUPPORT>. |
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418 | |
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419 | =head1 COPYRIGHT AND LICENSE |
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420 | |
a2bd3796 |
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>. |
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425 | |
426 | =cut |
427 | |
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428 | __PACKAGE__->meta->make_immutable; |
429 | |
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430 | 1; |