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1 | package DBIx::Class::Storage::DBI::Replicated::Pool; |
2 | |
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3 | use Moo; |
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4 | use DBIx::Class::Storage::DBI::Replicated::Replicant; |
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5 | use List::Util 'sum'; |
6 | use Scalar::Util 'reftype'; |
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7 | use DBI (); |
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8 | use Types::Standard qw/Num Int ClassName HashRef Object/; |
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9 | use DBIx::Class::Storage::DBI::Replicated::Types 'DBICStorageDBI'; |
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10 | use Try::Tiny; |
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11 | |
12 | use namespace::clean -except => 'meta'; |
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13 | |
14 | =head1 NAME |
15 | |
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16 | DBIx::Class::Storage::DBI::Replicated::Pool - Manage a pool of replicants |
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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. |
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22 | |
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23 | =head1 DESCRIPTION |
24 | |
25 | In a replicated storage type, there is at least one replicant to handle the |
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26 | read-only traffic. The Pool class manages this replicant, or list of |
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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 | |
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33 | =head2 maximum_lag ($num) |
34 | |
35 | This is a number which defines the maximum allowed lag returned by the |
36 | L<DBIx::Class::Storage::DBI/lag_behind_master> method. The default is 0. In |
37 | general, this should return a larger number when the replicant is lagging |
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38 | behind its master, however the implementation of this is database specific, so |
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39 | don't count on this number having a fixed meaning. For example, MySQL will |
40 | return a number of seconds that the replicating database is lagging. |
41 | |
42 | =cut |
43 | |
44 | has 'maximum_lag' => ( |
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45 | is=>'rw', |
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46 | isa=>Num, |
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47 | lazy=>1, |
48 | default=>0, |
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49 | ); |
50 | |
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51 | =head2 last_validated |
52 | |
53 | This is an integer representing a time since the last time the replicants were |
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54 | validated. It's nothing fancy, just an integer provided via the perl L<time|perlfunc/time> |
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55 | built-in. |
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56 | |
57 | =cut |
58 | |
59 | has 'last_validated' => ( |
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60 | is=>'rw', |
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61 | isa=>Int, |
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62 | reader=>'last_validated', |
63 | writer=>'_last_validated', |
64 | lazy=>1, |
65 | default=>0, |
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66 | ); |
67 | |
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68 | =head2 replicant_type ($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 | isa=>HashRef[Object], |
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128 | default=>sub {{}}, |
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129 | ); |
130 | |
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131 | sub set_replicant { $_[0]->replicants->{$_[1]} = $_[2] } |
132 | sub get_replicant { $_[0]->replicants->{$_[1]} } |
133 | sub has_replicants { !!keys %{$_[0]->replicants} } |
134 | sub num_replicants { 0+keys %{$_[0]->replicants} } |
135 | sub delete_replicant { delete $_[0]->replicants->{$_[1]} } |
136 | sub all_replicant_storages { values %{$_[0]->replicants} } |
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137 | |
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138 | has next_unknown_replicant_id => ( |
139 | is => 'rw', |
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140 | isa => Int, |
141 | default => 1, |
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142 | ); |
143 | |
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144 | sub inc_unknown_replicant_id { |
145 | my ($self) = @_; |
146 | $self->next_unknown_replicant_id($self->next_unknown_replicant_id + 1); |
147 | } |
148 | |
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149 | =head2 master |
150 | |
151 | Reference to the master Storage. |
152 | |
153 | =cut |
154 | |
155 | has master => (is => 'rw', isa => DBICStorageDBI, weak_ref => 1); |
156 | |
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157 | =head1 METHODS |
158 | |
159 | This class defines the following methods. |
160 | |
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161 | =head2 connect_replicants ($schema, Array[$connect_info]) |
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162 | |
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163 | Given an array of $dsn or connect_info structures suitable for connected to a |
164 | database, create an L<DBIx::Class::Storage::DBI::Replicated::Replicant> object |
165 | and store it in the L</replicants> attribute. |
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166 | |
167 | =cut |
168 | |
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169 | sub connect_replicants { |
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170 | my $self = shift @_; |
171 | my $schema = shift @_; |
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172 | |
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173 | my @newly_created = (); |
174 | foreach my $connect_info (@_) { |
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175 | $connect_info = [ $connect_info ] |
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176 | if reftype $connect_info ne 'ARRAY'; |
177 | |
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178 | my $connect_coderef = |
179 | (reftype($connect_info->[0])||'') eq 'CODE' ? $connect_info->[0] |
180 | : (reftype($connect_info->[0])||'') eq 'HASH' && |
181 | $connect_info->[0]->{dbh_maker}; |
182 | |
183 | my $dsn; |
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184 | my $replicant = do { |
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185 | # yes this is evil, but it only usually happens once (for coderefs) |
186 | # this will fail if the coderef does not actually DBI::connect |
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187 | no warnings 'redefine'; |
188 | my $connect = \&DBI::connect; |
189 | local *DBI::connect = sub { |
190 | $dsn = $_[1]; |
191 | goto $connect; |
192 | }; |
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193 | $self->connect_replicant($schema, $connect_info); |
194 | }; |
195 | |
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196 | my $key; |
197 | |
198 | if (!$dsn) { |
199 | if (!$connect_coderef) { |
200 | $dsn = $connect_info->[0]; |
201 | $dsn = $dsn->{dsn} if (reftype($dsn)||'') eq 'HASH'; |
202 | } |
203 | else { |
204 | # all attempts to get the DSN failed |
205 | $key = "UNKNOWN_" . $self->next_unknown_replicant_id; |
206 | $self->inc_unknown_replicant_id; |
207 | } |
208 | } |
209 | if ($dsn) { |
210 | $replicant->dsn($dsn); |
211 | ($key) = ($dsn =~ m/^dbi\:.+\:(.+)$/i); |
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212 | } |
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213 | |
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214 | $replicant->id($key); |
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215 | $self->set_replicant($key => $replicant); |
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216 | |
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217 | push @newly_created, $replicant; |
218 | } |
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219 | |
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220 | return @newly_created; |
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221 | } |
222 | |
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223 | =head2 connect_replicant ($schema, $connect_info) |
224 | |
225 | Given a schema object and a hashref of $connect_info, connect the replicant |
226 | and return it. |
227 | |
228 | =cut |
229 | |
230 | sub connect_replicant { |
231 | my ($self, $schema, $connect_info) = @_; |
232 | my $replicant = $self->create_replicant($schema); |
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233 | $replicant->connect_info($connect_info); |
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234 | |
235 | ## It is undesirable for catalyst to connect at ->conect_replicants time, as |
236 | ## connections should only happen on the first request that uses the database. |
237 | ## So we try to set the driver without connecting, however this doesn't always |
238 | ## work, as a driver may need to connect to determine the DB version, and this |
239 | ## may fail. |
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240 | ## |
241 | ## Why this is necessary at all, is that we need to have the final storage |
242 | ## class to apply the Replicant role. |
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243 | |
244 | $self->_safely($replicant, '->_determine_driver', sub { |
245 | $replicant->_determine_driver |
246 | }); |
247 | |
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248 | Moo::Role->apply_roles_to_object( |
249 | $replicant, |
250 | 'DBIx::Class::Storage::DBI::Replicated::Replicant', |
251 | ); |
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252 | |
253 | # link back to master |
254 | $replicant->master($self->master); |
255 | |
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256 | return $replicant; |
257 | } |
258 | |
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259 | =head2 _safely_ensure_connected ($replicant) |
260 | |
261 | The standard ensure_connected method with throw an exception should it fail to |
262 | connect. For the master database this is desirable, but since replicants are |
263 | allowed to fail, this behavior is not desirable. This method wraps the call |
264 | to ensure_connected in an eval in order to catch any generated errors. That |
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265 | way a slave can go completely offline (e.g. the box itself can die) without |
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266 | bringing down your entire pool of databases. |
267 | |
268 | =cut |
269 | |
270 | sub _safely_ensure_connected { |
271 | my ($self, $replicant, @args) = @_; |
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272 | |
273 | return $self->_safely($replicant, '->ensure_connected', sub { |
274 | $replicant->ensure_connected(@args) |
275 | }); |
276 | } |
277 | |
278 | =head2 _safely ($replicant, $name, $code) |
279 | |
280 | Execute C<$code> for operation C<$name> catching any exceptions and printing an |
281 | error message to the C<<$replicant->debugobj>>. |
282 | |
283 | Returns 1 on success and undef on failure. |
284 | |
285 | =cut |
286 | |
287 | sub _safely { |
288 | my ($self, $replicant, $name, $code) = @_; |
289 | |
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290 | return try { |
291 | $code->(); |
292 | 1; |
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293 | } catch { |
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294 | $replicant->debugobj->print(sprintf( |
295 | "Exception trying to $name for replicant %s, error is %s", |
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296 | $replicant->_dbi_connect_info->[0], $_) |
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297 | ); |
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298 | undef; |
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299 | }; |
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300 | } |
301 | |
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302 | =head2 connected_replicants |
303 | |
304 | Returns true if there are connected replicants. Actually is overloaded to |
305 | return the number of replicants. So you can do stuff like: |
306 | |
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307 | if( my $num_connected = $storage->has_connected_replicants ) { |
308 | print "I have $num_connected connected replicants"; |
309 | } else { |
310 | print "Sorry, no replicants."; |
311 | } |
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312 | |
313 | This method will actually test that each replicant in the L</replicants> hashref |
314 | is actually connected, try not to hit this 10 times a second. |
315 | |
316 | =cut |
317 | |
318 | sub connected_replicants { |
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319 | my $self = shift @_; |
320 | return sum( map { |
321 | $_->connected ? 1:0 |
322 | } $self->all_replicants ); |
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323 | } |
324 | |
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325 | =head2 active_replicants |
326 | |
327 | This is an array of replicants that are considered to be active in the pool. |
328 | This does not check to see if they are connected, but if they are not, DBIC |
329 | should automatically reconnect them for us when we hit them with a query. |
330 | |
331 | =cut |
332 | |
333 | sub active_replicants { |
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334 | my $self = shift @_; |
335 | return ( grep {$_} map { |
336 | $_->active ? $_:0 |
337 | } $self->all_replicants ); |
50336325 |
338 | } |
339 | |
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340 | =head2 all_replicants |
341 | |
342 | Just a simple array of all the replicant storages. No particular order to the |
343 | array is given, nor should any meaning be derived. |
344 | |
345 | =cut |
346 | |
347 | sub all_replicants { |
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348 | my $self = shift @_; |
349 | return values %{$self->replicants}; |
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350 | } |
351 | |
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352 | =head2 validate_replicants |
353 | |
354 | This does a check to see if 1) each replicate is connected (or reconnectable), |
355 | 2) that is ->is_replicating, and 3) that it is not exceeding the lag amount |
356 | defined by L</maximum_lag>. Replicants that fail any of these tests are set to |
357 | inactive, and thus removed from the replication pool. |
358 | |
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359 | This tests L</all_replicants>, since a replicant that has been previous marked |
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360 | as inactive can be reactivated should it start to pass the validation tests again. |
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361 | |
362 | See L<DBIx::Class::Storage::DBI> for more about checking if a replicating |
363 | connection is not following a master or is lagging. |
364 | |
365 | Calling this method will generate queries on the replicant databases so it is |
366 | not recommended that you run them very often. |
367 | |
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368 | This method requires that your underlying storage engine supports some sort of |
369 | native replication mechanism. Currently only MySQL native replication is |
370 | supported. Your patches to make other replication types work are welcomed. |
371 | |
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372 | =cut |
373 | |
374 | sub validate_replicants { |
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375 | my $self = shift @_; |
376 | foreach my $replicant($self->all_replicants) { |
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377 | if($self->_safely_ensure_connected($replicant)) { |
378 | my $is_replicating = $replicant->is_replicating; |
379 | unless(defined $is_replicating) { |
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380 | $replicant->debugobj->print("Storage Driver ".ref($self)." Does not support the 'is_replicating' method. Assuming you are manually managing.\n"); |
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381 | next; |
382 | } else { |
383 | if($is_replicating) { |
384 | my $lag_behind_master = $replicant->lag_behind_master; |
385 | unless(defined $lag_behind_master) { |
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386 | $replicant->debugobj->print("Storage Driver ".ref($self)." Does not support the 'lag_behind_master' method. Assuming you are manually managing.\n"); |
13b9e828 |
387 | next; |
388 | } else { |
389 | if($lag_behind_master <= $self->maximum_lag) { |
390 | $replicant->active(1); |
391 | } else { |
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392 | $replicant->active(0); |
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393 | } |
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394 | } |
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395 | } else { |
396 | $replicant->active(0); |
397 | } |
398 | } |
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399 | } else { |
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400 | $replicant->active(0); |
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401 | } |
64cdad22 |
402 | } |
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403 | ## Mark that we completed this validation. |
404 | $self->_last_validated(time); |
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405 | } |
406 | |
a2bd3796 |
407 | =head1 FURTHER QUESTIONS? |
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408 | |
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409 | Check the list of L<additional DBIC resources|DBIx::Class/GETTING HELP/SUPPORT>. |
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410 | |
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411 | =head1 COPYRIGHT AND LICENSE |
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412 | |
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413 | This module is free software L<copyright|DBIx::Class/COPYRIGHT AND LICENSE> |
414 | by the L<DBIx::Class (DBIC) authors|DBIx::Class/AUTHORS>. You can |
415 | redistribute it and/or modify it under the same terms as the |
416 | L<DBIx::Class library|DBIx::Class/COPYRIGHT AND LICENSE>. |
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417 | |
418 | =cut |
419 | |
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420 | 1; |