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1 | package DBIx::Class::Storage::DBI::Replicated::Pool; |
2 | |
3 | use Moose; |
4 | use MooseX::AttributeHelpers; |
5 | use DBIx::Class::Storage::DBI::Replicated::Replicant; |
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6 | use List::Util 'sum'; |
7 | use Scalar::Util 'reftype'; |
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 | |
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 |
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. |
27 | |
28 | =head1 ATTRIBUTES |
29 | |
30 | This class defines the following attributes. |
31 | |
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32 | =head2 maximum_lag ($num) |
33 | |
34 | This is a number which defines the maximum allowed lag returned by the |
35 | L<DBIx::Class::Storage::DBI/lag_behind_master> method. The default is 0. In |
36 | general, this should return a larger number when the replicant is lagging |
37 | behind it's master, however the implementation of this is database specific, so |
38 | don't count on this number having a fixed meaning. For example, MySQL will |
39 | return a number of seconds that the replicating database is lagging. |
40 | |
41 | =cut |
42 | |
43 | has 'maximum_lag' => ( |
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44 | is=>'rw', |
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45 | isa=>Num, |
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46 | required=>1, |
47 | lazy=>1, |
48 | default=>0, |
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49 | ); |
50 | |
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51 | =head2 last_validated |
52 | |
53 | This is an integer representing a time since the last time the replicants were |
54 | validated. It's nothing fancy, just an integer provided via the perl time |
55 | builtin. |
56 | |
57 | =cut |
58 | |
59 | has 'last_validated' => ( |
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60 | is=>'rw', |
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61 | isa=>Int, |
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62 | reader=>'last_validated', |
63 | writer=>'_last_validated', |
64 | lazy=>1, |
65 | default=>0, |
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66 | ); |
67 | |
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68 | =head2 replicant_type ($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', |
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 |
89 | actual replicant storage. For example if the $dsn element is something like: |
90 | |
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91 | "dbi:SQLite:dbname=dbfile" |
92 | |
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93 | You could access the specific replicant via: |
94 | |
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95 | $schema->storage->replicants->{'dbname=dbfile'} |
96 | |
97 | This attributes also supports the following helper methods: |
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98 | |
99 | =over 4 |
100 | |
101 | =item set_replicant($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 | |
119 | removes the replicant under $key from the pool |
120 | |
121 | =back |
122 | |
123 | =cut |
124 | |
125 | has 'replicants' => ( |
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126 | is=>'rw', |
127 | metaclass => 'Collection::Hash', |
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128 | isa=>HashRef['DBIx::Class::Storage::DBI'], |
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129 | default=>sub {{}}, |
130 | provides => { |
131 | 'set' => 'set_replicant', |
132 | 'get' => 'get_replicant', |
133 | 'empty' => 'has_replicants', |
134 | 'count' => 'num_replicants', |
135 | 'delete' => 'delete_replicant', |
136 | }, |
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137 | ); |
138 | |
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139 | =head1 METHODS |
140 | |
141 | This class defines the following methods. |
142 | |
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143 | =head2 connect_replicants ($schema, Array[$connect_info]) |
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144 | |
145 | Given an array of $dsn suitable for connected to a database, create an |
146 | L<DBIx::Class::Storage::DBI::Replicated::Replicant> object and store it in the |
147 | L</replicants> attribute. |
148 | |
149 | =cut |
150 | |
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151 | sub connect_replicants { |
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152 | my $self = shift @_; |
153 | my $schema = shift @_; |
154 | |
155 | my @newly_created = (); |
156 | foreach my $connect_info (@_) { |
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157 | $connect_info = [ $connect_info ] |
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158 | if reftype $connect_info ne 'ARRAY'; |
159 | |
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160 | croak "coderef replicant connect_info not supported" |
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161 | if ref $connect_info->[0] && reftype $connect_info->[0] eq 'CODE'; |
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162 | |
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163 | my $replicant = $self->connect_replicant($schema, $connect_info); |
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164 | |
165 | my $key = $connect_info->[0]; |
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166 | $key = $key->{dsn} if ref $key && reftype $key eq 'HASH'; |
2cd3ccc4 |
167 | ($key) = ($key =~ m/^dbi\:.+\:(.+)$/); |
168 | |
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169 | $self->set_replicant( $key => $replicant); |
170 | push @newly_created, $replicant; |
171 | } |
172 | |
173 | return @newly_created; |
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174 | } |
175 | |
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176 | =head2 connect_replicant ($schema, $connect_info) |
177 | |
178 | Given a schema object and a hashref of $connect_info, connect the replicant |
179 | and return it. |
180 | |
181 | =cut |
182 | |
183 | sub connect_replicant { |
184 | my ($self, $schema, $connect_info) = @_; |
185 | my $replicant = $self->create_replicant($schema); |
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186 | $replicant->connect_info($connect_info); |
187 | $self->_safely_ensure_connected($replicant); |
188 | DBIx::Class::Storage::DBI::Replicated::Replicant->meta->apply($replicant); |
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189 | return $replicant; |
190 | } |
191 | |
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192 | =head2 _safely_ensure_connected ($replicant) |
193 | |
194 | The standard ensure_connected method with throw an exception should it fail to |
195 | connect. For the master database this is desirable, but since replicants are |
196 | allowed to fail, this behavior is not desirable. This method wraps the call |
197 | to ensure_connected in an eval in order to catch any generated errors. That |
198 | way a slave to go completely offline (ie, the box itself can die) without |
199 | bringing down your entire pool of databases. |
200 | |
201 | =cut |
202 | |
203 | sub _safely_ensure_connected { |
204 | my ($self, $replicant, @args) = @_; |
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205 | eval { |
206 | $replicant->ensure_connected(@args); |
207 | }; |
208 | if ($@) { |
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209 | $replicant |
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210 | ->debugobj |
211 | ->print( |
212 | sprintf( "Exception trying to ->ensure_connected for replicant %s, error is %s", |
213 | $replicant->_dbi_connect_info->[0], $@) |
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214 | ); |
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215 | return; |
13b9e828 |
216 | } |
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217 | return 1; |
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218 | } |
219 | |
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220 | =head2 connected_replicants |
221 | |
222 | Returns true if there are connected replicants. Actually is overloaded to |
223 | return the number of replicants. So you can do stuff like: |
224 | |
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225 | if( my $num_connected = $storage->has_connected_replicants ) { |
226 | print "I have $num_connected connected replicants"; |
227 | } else { |
228 | print "Sorry, no replicants."; |
229 | } |
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230 | |
231 | This method will actually test that each replicant in the L</replicants> hashref |
232 | is actually connected, try not to hit this 10 times a second. |
233 | |
234 | =cut |
235 | |
236 | sub connected_replicants { |
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237 | my $self = shift @_; |
238 | return sum( map { |
239 | $_->connected ? 1:0 |
240 | } $self->all_replicants ); |
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241 | } |
242 | |
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243 | =head2 active_replicants |
244 | |
245 | This is an array of replicants that are considered to be active in the pool. |
246 | This does not check to see if they are connected, but if they are not, DBIC |
247 | should automatically reconnect them for us when we hit them with a query. |
248 | |
249 | =cut |
250 | |
251 | sub active_replicants { |
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252 | my $self = shift @_; |
253 | return ( grep {$_} map { |
254 | $_->active ? $_:0 |
255 | } $self->all_replicants ); |
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256 | } |
257 | |
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258 | =head2 all_replicants |
259 | |
260 | Just a simple array of all the replicant storages. No particular order to the |
261 | array is given, nor should any meaning be derived. |
262 | |
263 | =cut |
264 | |
265 | sub all_replicants { |
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266 | my $self = shift @_; |
267 | return values %{$self->replicants}; |
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268 | } |
269 | |
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270 | =head2 validate_replicants |
271 | |
272 | This does a check to see if 1) each replicate is connected (or reconnectable), |
273 | 2) that is ->is_replicating, and 3) that it is not exceeding the lag amount |
274 | defined by L</maximum_lag>. Replicants that fail any of these tests are set to |
275 | inactive, and thus removed from the replication pool. |
276 | |
277 | This tests L<all_replicants>, since a replicant that has been previous marked |
278 | as inactive can be reactived should it start to pass the validation tests again. |
279 | |
280 | See L<DBIx::Class::Storage::DBI> for more about checking if a replicating |
281 | connection is not following a master or is lagging. |
282 | |
283 | Calling this method will generate queries on the replicant databases so it is |
284 | not recommended that you run them very often. |
285 | |
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286 | This method requires that your underlying storage engine supports some sort of |
287 | native replication mechanism. Currently only MySQL native replication is |
288 | supported. Your patches to make other replication types work are welcomed. |
289 | |
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290 | =cut |
291 | |
292 | sub validate_replicants { |
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293 | my $self = shift @_; |
294 | foreach my $replicant($self->all_replicants) { |
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295 | if($self->_safely_ensure_connected($replicant)) { |
296 | my $is_replicating = $replicant->is_replicating; |
297 | unless(defined $is_replicating) { |
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298 | $replicant->debugobj->print("Storage Driver ".ref($self)." Does not support the 'is_replicating' method. Assuming you are manually managing.\n"); |
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299 | next; |
300 | } else { |
301 | if($is_replicating) { |
302 | my $lag_behind_master = $replicant->lag_behind_master; |
303 | unless(defined $lag_behind_master) { |
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304 | $replicant->debugobj->print("Storage Driver ".ref($self)." Does not support the 'lag_behind_master' method. Assuming you are manually managing.\n"); |
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305 | next; |
306 | } else { |
307 | if($lag_behind_master <= $self->maximum_lag) { |
308 | $replicant->active(1); |
309 | } else { |
310 | $replicant->active(0); |
311 | } |
312 | } |
313 | } else { |
314 | $replicant->active(0); |
315 | } |
316 | } |
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317 | } else { |
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318 | $replicant->active(0); |
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319 | } |
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320 | } |
321 | ## Mark that we completed this validation. |
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322 | $self->_last_validated(time); |
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323 | } |
324 | |
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325 | =head1 AUTHOR |
326 | |
327 | John Napiorkowski <john.napiorkowski@takkle.com> |
328 | |
329 | =head1 LICENSE |
330 | |
331 | You may distribute this code under the same terms as Perl itself. |
332 | |
333 | =cut |
334 | |
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335 | __PACKAGE__->meta->make_immutable; |
336 | |
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337 | 1; |