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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 List::Util 'sum'; |
6 | use Scalar::Util 'reftype'; |
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7 | use DBI (); |
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8 | use Carp::Clan qw/^DBIx::Class/; |
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9 | use MooseX::Types::Moose qw/Num Int ClassName HashRef/; |
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10 | use DBIx::Class::Storage::DBI::Replicated::Types 'DBICStorageDBI'; |
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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 ($num) |
34 | |
35 | This is a number which defines the maximum allowed lag returned by the |
36 | L<DBIx::Class::Storage::DBI/lag_behind_master> method. The default is 0. In |
37 | general, this should return a larger number when the replicant is lagging |
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38 | behind its master, however the implementation of this is database specific, so |
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39 | don't count on this number having a fixed meaning. For example, MySQL will |
40 | return a number of seconds that the replicating database is lagging. |
41 | |
42 | =cut |
43 | |
44 | has 'maximum_lag' => ( |
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45 | is=>'rw', |
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46 | isa=>Num, |
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47 | required=>1, |
48 | lazy=>1, |
49 | default=>0, |
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50 | ); |
51 | |
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52 | =head2 last_validated |
53 | |
54 | This is an integer representing a time since the last time the replicants were |
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55 | validated. It's nothing fancy, just an integer provided via the perl L<time|perlfunc/time> |
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56 | built-in. |
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57 | |
58 | =cut |
59 | |
60 | has 'last_validated' => ( |
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61 | is=>'rw', |
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62 | isa=>Int, |
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63 | reader=>'last_validated', |
64 | writer=>'_last_validated', |
65 | lazy=>1, |
66 | default=>0, |
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67 | ); |
68 | |
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69 | =head2 replicant_type ($classname) |
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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' => ( |
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78 | is=>'ro', |
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79 | isa=>ClassName, |
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80 | required=>1, |
81 | default=>'DBIx::Class::Storage::DBI', |
82 | handles=>{ |
83 | 'create_replicant' => 'new', |
84 | }, |
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85 | ); |
86 | |
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87 | =head2 replicants |
88 | |
89 | A hashref of replicant, with the key being the dsn and the value returning the |
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90 | actual replicant storage. For example, if the $dsn element is something like: |
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91 | |
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92 | "dbi:SQLite:dbname=dbfile" |
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93 | |
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94 | You could access the specific replicant via: |
95 | |
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96 | $schema->storage->replicants->{'dbname=dbfile'} |
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97 | |
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98 | This attributes also supports the following helper methods: |
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99 | |
100 | =over 4 |
101 | |
102 | =item set_replicant($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 | |
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120 | Removes the replicant under $key from the pool |
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121 | |
122 | =back |
123 | |
124 | =cut |
125 | |
126 | has 'replicants' => ( |
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127 | is=>'rw', |
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128 | traits => ['Hash'], |
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129 | isa=>HashRef['Object'], |
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130 | default=>sub {{}}, |
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131 | handles => { |
132 | 'set_replicant' => 'set', |
133 | 'get_replicant' => 'get', |
134 | 'has_replicants' => 'is_empty', |
135 | 'num_replicants' => 'count', |
136 | 'delete_replicant' => 'delete', |
137 | 'all_replicant_storages' => 'values', |
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138 | }, |
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139 | ); |
140 | |
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141 | around has_replicants => sub { |
142 | my ($orig, $self) = @_; |
143 | return !$self->$orig; |
144 | }; |
145 | |
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146 | has next_unknown_replicant_id => ( |
147 | is => 'rw', |
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148 | traits => ['Counter'], |
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149 | isa => Int, |
150 | default => 1, |
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151 | handles => { |
152 | 'inc_unknown_replicant_id' => 'inc', |
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153 | }, |
154 | ); |
155 | |
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156 | =head2 master |
157 | |
158 | Reference to the master Storage. |
159 | |
160 | =cut |
161 | |
162 | has master => (is => 'rw', isa => DBICStorageDBI, weak_ref => 1); |
163 | |
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164 | =head1 METHODS |
165 | |
166 | This class defines the following methods. |
167 | |
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168 | =head2 connect_replicants ($schema, Array[$connect_info]) |
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169 | |
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170 | Given an array of $dsn or connect_info structures suitable for connected to a |
171 | database, create an L<DBIx::Class::Storage::DBI::Replicated::Replicant> object |
172 | and store it in the L</replicants> attribute. |
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173 | |
174 | =cut |
175 | |
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176 | sub connect_replicants { |
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177 | my $self = shift @_; |
178 | my $schema = shift @_; |
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179 | |
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180 | my @newly_created = (); |
181 | foreach my $connect_info (@_) { |
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182 | $connect_info = [ $connect_info ] |
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183 | if reftype $connect_info ne 'ARRAY'; |
184 | |
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185 | my $connect_coderef = |
186 | (reftype($connect_info->[0])||'') eq 'CODE' ? $connect_info->[0] |
187 | : (reftype($connect_info->[0])||'') eq 'HASH' && |
188 | $connect_info->[0]->{dbh_maker}; |
189 | |
190 | my $dsn; |
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191 | my $replicant = do { |
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192 | # yes this is evil, but it only usually happens once (for coderefs) |
193 | # this will fail if the coderef does not actually DBI::connect |
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194 | no warnings 'redefine'; |
195 | my $connect = \&DBI::connect; |
196 | local *DBI::connect = sub { |
197 | $dsn = $_[1]; |
198 | goto $connect; |
199 | }; |
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200 | $self->connect_replicant($schema, $connect_info); |
201 | }; |
202 | |
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203 | my $key; |
204 | |
205 | if (!$dsn) { |
206 | if (!$connect_coderef) { |
207 | $dsn = $connect_info->[0]; |
208 | $dsn = $dsn->{dsn} if (reftype($dsn)||'') eq 'HASH'; |
209 | } |
210 | else { |
211 | # all attempts to get the DSN failed |
212 | $key = "UNKNOWN_" . $self->next_unknown_replicant_id; |
213 | $self->inc_unknown_replicant_id; |
214 | } |
215 | } |
216 | if ($dsn) { |
217 | $replicant->dsn($dsn); |
218 | ($key) = ($dsn =~ m/^dbi\:.+\:(.+)$/i); |
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219 | } |
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220 | |
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221 | $replicant->id($key); |
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222 | $self->set_replicant($key => $replicant); |
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223 | |
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224 | push @newly_created, $replicant; |
225 | } |
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226 | |
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227 | return @newly_created; |
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228 | } |
229 | |
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230 | =head2 connect_replicant ($schema, $connect_info) |
231 | |
232 | Given a schema object and a hashref of $connect_info, connect the replicant |
233 | and return it. |
234 | |
235 | =cut |
236 | |
237 | sub connect_replicant { |
238 | my ($self, $schema, $connect_info) = @_; |
239 | my $replicant = $self->create_replicant($schema); |
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240 | $replicant->connect_info($connect_info); |
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241 | |
242 | ## It is undesirable for catalyst to connect at ->conect_replicants time, as |
243 | ## connections should only happen on the first request that uses the database. |
244 | ## So we try to set the driver without connecting, however this doesn't always |
245 | ## work, as a driver may need to connect to determine the DB version, and this |
246 | ## may fail. |
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247 | ## |
248 | ## Why this is necessary at all, is that we need to have the final storage |
249 | ## class to apply the Replicant role. |
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250 | |
251 | $self->_safely($replicant, '->_determine_driver', sub { |
252 | $replicant->_determine_driver |
253 | }); |
254 | |
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255 | Moose::Meta::Class->initialize(ref $replicant); |
256 | |
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257 | DBIx::Class::Storage::DBI::Replicated::Replicant->meta->apply($replicant); |
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258 | |
259 | # link back to master |
260 | $replicant->master($self->master); |
261 | |
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262 | return $replicant; |
263 | } |
264 | |
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265 | =head2 _safely_ensure_connected ($replicant) |
266 | |
267 | The standard ensure_connected method with throw an exception should it fail to |
268 | connect. For the master database this is desirable, but since replicants are |
269 | allowed to fail, this behavior is not desirable. This method wraps the call |
270 | to ensure_connected in an eval in order to catch any generated errors. That |
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271 | way a slave can go completely offline (e.g. the box itself can die) without |
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272 | bringing down your entire pool of databases. |
273 | |
274 | =cut |
275 | |
276 | sub _safely_ensure_connected { |
277 | my ($self, $replicant, @args) = @_; |
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278 | |
279 | return $self->_safely($replicant, '->ensure_connected', sub { |
280 | $replicant->ensure_connected(@args) |
281 | }); |
282 | } |
283 | |
284 | =head2 _safely ($replicant, $name, $code) |
285 | |
286 | Execute C<$code> for operation C<$name> catching any exceptions and printing an |
287 | error message to the C<<$replicant->debugobj>>. |
288 | |
289 | Returns 1 on success and undef on failure. |
290 | |
291 | =cut |
292 | |
293 | sub _safely { |
294 | my ($self, $replicant, $name, $code) = @_; |
295 | |
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296 | eval { |
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297 | $code->() |
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298 | }; |
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299 | if ($@) { |
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300 | $replicant->debugobj->print(sprintf( |
301 | "Exception trying to $name for replicant %s, error is %s", |
302 | $replicant->_dbi_connect_info->[0], $@) |
303 | ); |
304 | return undef; |
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305 | } |
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306 | |
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307 | return 1; |
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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 { |
64cdad22 |
327 | my $self = shift @_; |
328 | return sum( map { |
329 | $_->connected ? 1:0 |
330 | } $self->all_replicants ); |
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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 | |
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"); |
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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"); |
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395 | next; |
396 | } else { |
397 | if($lag_behind_master <= $self->maximum_lag) { |
398 | $replicant->active(1); |
399 | } else { |
400 | $replicant->active(0); |
401 | } |
402 | } |
403 | } else { |
404 | $replicant->active(0); |
405 | } |
406 | } |
64cdad22 |
407 | } else { |
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408 | $replicant->active(0); |
7edf5f1c |
409 | } |
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410 | } |
411 | ## Mark that we completed this validation. |
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412 | $self->_last_validated(time); |
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413 | } |
414 | |
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415 | =head1 AUTHOR |
416 | |
417 | John Napiorkowski <john.napiorkowski@takkle.com> |
418 | |
419 | =head1 LICENSE |
420 | |
421 | You may distribute this code under the same terms as Perl itself. |
422 | |
423 | =cut |
424 | |
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425 | __PACKAGE__->meta->make_immutable; |
426 | |
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427 | 1; |