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1 | package DBIx::Class::Storage::DBI::Replicated; |
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2 | |
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3 | use Moose; |
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4 | use Class::MOP; |
5 | use Moose::Util::TypeConstraints; |
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6 | use DBIx::Class::Storage::DBI; |
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7 | use DBIx::Class::Storage::DBI::Replicated::Pool; |
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8 | use DBIx::Class::Storage::DBI::Replicated::Balancer; |
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9 | |
10 | =head1 NAME |
11 | |
12 | DBIx::Class::Storage::DBI::Replicated - ALPHA Replicated database support |
13 | |
14 | =head1 SYNOPSIS |
15 | |
16 | The Following example shows how to change an existing $schema to a replicated |
17 | storage type, add some replicated (readonly) databases, and perform reporting |
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18 | tasks. |
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19 | |
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20 | ## Change storage_type in your schema class |
21 | $schema->storage_type( ['::DBI::Replicated', {balancer=>'::Random'}] ); |
22 | |
23 | ## Add some slaves. Basically this is an array of arrayrefs, where each |
24 | ## arrayref is database connect information |
25 | |
26 | $schema->storage->connect_replicants( |
27 | [$dsn1, $user, $pass, \%opts], |
28 | [$dsn2, $user, $pass, \%opts], |
29 | [$dsn3, $user, $pass, \%opts], |
30 | ); |
31 | |
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32 | ## Now, just use the $schema as normal |
33 | $schema->resultset('Source')->search({name=>'etc'}); |
34 | |
35 | ## You can force a given query to use a particular storage using the search |
36 | ### attribute 'force_pool'. For example: |
37 | |
38 | my $RS = $schema->resultset('Source')->search(undef, {force_pool=>'master'}); |
39 | |
40 | ## Now $RS will force everything (both reads and writes) to use whatever was |
41 | ## setup as the master storage. 'master' is hardcoded to always point to the |
42 | ## Master, but you can also use any Replicant name. Please see: |
43 | ## L<DBIx::Class::Storage::Replicated::Pool> and the replicants attribute for |
44 | ## More. Also see transactions and L</execute_reliably> for alternative ways |
45 | ## to force read traffic to the master. |
46 | |
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47 | =head1 DESCRIPTION |
48 | |
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49 | Warning: This class is marked BETA. This has been running a production |
50 | website using MySQL native replication as it's backend and we have some decent |
51 | test coverage but the code hasn't yet been stressed by a variety of databases. |
52 | Individual DB's may have quirks we are not aware of. Please use this in first |
53 | development and pass along your experiences/bug fixes. |
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54 | |
55 | This class implements replicated data store for DBI. Currently you can define |
56 | one master and numerous slave database connections. All write-type queries |
57 | (INSERT, UPDATE, DELETE and even LAST_INSERT_ID) are routed to master |
58 | database, all read-type queries (SELECTs) go to the slave database. |
59 | |
60 | Basically, any method request that L<DBIx::Class::Storage::DBI> would normally |
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61 | handle gets delegated to one of the two attributes: L</read_handler> or to |
62 | L</write_handler>. Additionally, some methods need to be distributed |
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63 | to all existing storages. This way our storage class is a drop in replacement |
64 | for L<DBIx::Class::Storage::DBI>. |
65 | |
66 | Read traffic is spread across the replicants (slaves) occuring to a user |
67 | selected algorithm. The default algorithm is random weighted. |
68 | |
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69 | =head1 NOTES |
70 | |
71 | The consistancy betweeen master and replicants is database specific. The Pool |
72 | gives you a method to validate it's replicants, removing and replacing them |
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73 | when they fail/pass predefined criteria. Please make careful use of the ways |
74 | to force a query to run against Master when needed. |
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75 | |
76 | =head1 ATTRIBUTES |
77 | |
78 | This class defines the following attributes. |
79 | |
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80 | =head2 schema |
81 | |
82 | The underlying L<DBIx::Class::Schema> object this storage is attaching |
83 | |
84 | =cut |
85 | |
86 | has 'schema' => ( |
87 | is=>'rw', |
88 | isa=>'DBIx::Class::Schema', |
89 | weak_ref=>1, |
90 | required=>1, |
91 | ); |
92 | |
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93 | =head2 pool_type |
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94 | |
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95 | Contains the classname which will instantiate the L</pool> object. Defaults |
96 | to: L<DBIx::Class::Storage::DBI::Replicated::Pool>. |
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97 | |
98 | =cut |
99 | |
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100 | has 'pool_type' => ( |
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101 | is=>'ro', |
102 | isa=>'ClassName', |
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103 | required=>1, |
104 | default=>'DBIx::Class::Storage::DBI::Replicated::Pool', |
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105 | handles=>{ |
106 | 'create_pool' => 'new', |
107 | }, |
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108 | ); |
109 | |
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110 | =head2 pool_args |
111 | |
112 | Contains a hashref of initialized information to pass to the Balancer object. |
113 | See L<DBIx::Class::Storage::Replicated::Pool> for available arguments. |
114 | |
115 | =cut |
116 | |
117 | has 'pool_args' => ( |
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118 | is=>'ro', |
119 | isa=>'HashRef', |
120 | lazy=>1, |
121 | required=>1, |
122 | default=>sub { {} }, |
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123 | ); |
124 | |
125 | |
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126 | =head2 balancer_type |
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127 | |
128 | The replication pool requires a balance class to provider the methods for |
129 | choose how to spread the query load across each replicant in the pool. |
130 | |
131 | =cut |
132 | |
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133 | subtype 'DBIx::Class::Storage::DBI::Replicated::BalancerClassNamePart', |
134 | as 'ClassName'; |
135 | |
136 | coerce 'DBIx::Class::Storage::DBI::Replicated::BalancerClassNamePart', |
137 | from 'Str', |
138 | via { |
139 | my $type = $_; |
140 | if($type=~m/^::/) { |
141 | $type = 'DBIx::Class::Storage::DBI::Replicated::Balancer'.$type; |
142 | } |
143 | Class::MOP::load_class($type); |
144 | $type; |
145 | }; |
146 | |
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147 | has 'balancer_type' => ( |
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148 | is=>'ro', |
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149 | isa=>'DBIx::Class::Storage::DBI::Replicated::BalancerClassNamePart', |
150 | coerce=>1, |
151 | required=>1, |
152 | default=> 'DBIx::Class::Storage::DBI::Replicated::Balancer::First', |
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153 | handles=>{ |
154 | 'create_balancer' => 'new', |
155 | }, |
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156 | ); |
157 | |
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158 | =head2 balancer_args |
159 | |
160 | Contains a hashref of initialized information to pass to the Balancer object. |
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161 | See L<DBIx::Class::Storage::Replicated::Balancer> for available arguments. |
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162 | |
163 | =cut |
164 | |
165 | has 'balancer_args' => ( |
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166 | is=>'ro', |
167 | isa=>'HashRef', |
168 | lazy=>1, |
169 | required=>1, |
170 | default=>sub { {} }, |
17b05c13 |
171 | ); |
172 | |
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173 | =head2 pool |
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174 | |
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175 | Is a <DBIx::Class::Storage::DBI::Replicated::Pool> or derived class. This is a |
176 | container class for one or more replicated databases. |
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177 | |
178 | =cut |
179 | |
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180 | has 'pool' => ( |
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181 | is=>'ro', |
182 | isa=>'DBIx::Class::Storage::DBI::Replicated::Pool', |
183 | lazy_build=>1, |
184 | handles=>[qw/ |
185 | connect_replicants |
186 | replicants |
187 | has_replicants |
188 | /], |
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189 | ); |
190 | |
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191 | =head2 balancer |
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192 | |
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193 | Is a <DBIx::Class::Storage::DBI::Replicated::Balancer> or derived class. This |
194 | is a class that takes a pool (<DBIx::Class::Storage::DBI::Replicated::Pool>) |
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195 | |
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196 | =cut |
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197 | |
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198 | has 'balancer' => ( |
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199 | is=>'ro', |
200 | isa=>'DBIx::Class::Storage::DBI::Replicated::Balancer', |
201 | lazy_build=>1, |
202 | handles=>[qw/auto_validate_every/], |
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203 | ); |
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204 | |
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205 | =head2 master |
206 | |
207 | The master defines the canonical state for a pool of connected databases. All |
208 | the replicants are expected to match this databases state. Thus, in a classic |
209 | Master / Slaves distributed system, all the slaves are expected to replicate |
210 | the Master's state as quick as possible. This is the only database in the |
211 | pool of databases that is allowed to handle write traffic. |
212 | |
213 | =cut |
214 | |
215 | has 'master' => ( |
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216 | is=> 'ro', |
217 | isa=>'DBIx::Class::Storage::DBI', |
218 | lazy_build=>1, |
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219 | ); |
220 | |
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221 | =head1 ATTRIBUTES IMPLEMENTING THE DBIx::Storage::DBI INTERFACE |
222 | |
223 | The following methods are delegated all the methods required for the |
224 | L<DBIx::Class::Storage::DBI> interface. |
225 | |
226 | =head2 read_handler |
227 | |
228 | Defines an object that implements the read side of L<BIx::Class::Storage::DBI>. |
229 | |
230 | =cut |
231 | |
232 | has 'read_handler' => ( |
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233 | is=>'rw', |
234 | isa=>'Object', |
235 | lazy_build=>1, |
236 | handles=>[qw/ |
237 | select |
238 | select_single |
239 | columns_info_for |
240 | /], |
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241 | ); |
242 | |
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243 | =head2 write_handler |
244 | |
245 | Defines an object that implements the write side of L<BIx::Class::Storage::DBI>. |
246 | |
247 | =cut |
248 | |
249 | has 'write_handler' => ( |
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250 | is=>'ro', |
251 | isa=>'Object', |
252 | lazy_build=>1, |
253 | lazy_build=>1, |
254 | handles=>[qw/ |
255 | on_connect_do |
256 | on_disconnect_do |
257 | connect_info |
258 | throw_exception |
259 | sql_maker |
260 | sqlt_type |
261 | create_ddl_dir |
262 | deployment_statements |
263 | datetime_parser |
264 | datetime_parser_type |
265 | last_insert_id |
266 | insert |
267 | insert_bulk |
268 | update |
269 | delete |
270 | dbh |
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271 | txn_begin |
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272 | txn_do |
273 | txn_commit |
274 | txn_rollback |
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275 | txn_scope_guard |
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276 | sth |
277 | deploy |
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278 | |
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279 | reload_row |
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280 | _prep_for_execute |
281 | configure_sqlt |
282 | |
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283 | /], |
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284 | ); |
285 | |
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286 | =head1 METHODS |
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287 | |
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288 | This class defines the following methods. |
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289 | |
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290 | =head2 new |
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291 | |
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292 | L<DBIx::Class::Schema> when instantiating it's storage passed itself as the |
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293 | first argument. So we need to massage the arguments a bit so that all the |
294 | bits get put into the correct places. |
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295 | |
296 | =cut |
297 | |
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298 | around 'new' => sub { |
299 | my ($new, $self, $schema, $storage_type_args, @args) = @_; |
300 | return $self->$new(schema=>$schema, %$storage_type_args, @args); |
301 | }; |
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302 | |
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303 | =head2 _build_master |
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304 | |
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305 | Lazy builder for the L</master> attribute. |
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306 | |
307 | =cut |
308 | |
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309 | sub _build_master { |
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310 | my $self = shift @_; |
311 | DBIx::Class::Storage::DBI->new($self->schema); |
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312 | } |
313 | |
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314 | =head2 _build_pool |
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315 | |
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316 | Lazy builder for the L</pool> attribute. |
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317 | |
318 | =cut |
319 | |
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320 | sub _build_pool { |
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321 | my $self = shift @_; |
322 | $self->create_pool(%{$self->pool_args}); |
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323 | } |
324 | |
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325 | =head2 _build_balancer |
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326 | |
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327 | Lazy builder for the L</balancer> attribute. This takes a Pool object so that |
328 | the balancer knows which pool it's balancing. |
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329 | |
330 | =cut |
331 | |
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332 | sub _build_balancer { |
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333 | my $self = shift @_; |
334 | $self->create_balancer( |
335 | pool=>$self->pool, |
336 | master=>$self->master, |
337 | %{$self->balancer_args}, |
338 | ); |
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339 | } |
340 | |
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341 | =head2 _build_write_handler |
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342 | |
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343 | Lazy builder for the L</write_handler> attribute. The default is to set this to |
344 | the L</master>. |
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345 | |
346 | =cut |
347 | |
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348 | sub _build_write_handler { |
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349 | return shift->master; |
cb6ec758 |
350 | } |
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351 | |
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352 | =head2 _build_read_handler |
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353 | |
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354 | Lazy builder for the L</read_handler> attribute. The default is to set this to |
355 | the L</balancer>. |
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356 | |
357 | =cut |
358 | |
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359 | sub _build_read_handler { |
64cdad22 |
360 | return shift->balancer; |
cb6ec758 |
361 | } |
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362 | |
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363 | =head2 around: connect_replicants |
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364 | |
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365 | All calls to connect_replicants needs to have an existing $schema tacked onto |
366 | top of the args, since L<DBIx::Storage::DBI> needs it. |
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367 | |
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368 | =cut |
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369 | |
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370 | around 'connect_replicants' => sub { |
64cdad22 |
371 | my ($method, $self, @args) = @_; |
372 | $self->$method($self->schema, @args); |
955a6df6 |
373 | }; |
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374 | |
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375 | =head2 all_storages |
376 | |
377 | Returns an array of of all the connected storage backends. The first element |
378 | in the returned array is the master, and the remainings are each of the |
379 | replicants. |
380 | |
381 | =cut |
382 | |
383 | sub all_storages { |
64cdad22 |
384 | my $self = shift @_; |
385 | return grep {defined $_ && blessed $_} ( |
386 | $self->master, |
387 | $self->replicants, |
388 | ); |
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389 | } |
390 | |
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391 | =head2 execute_reliably ($coderef, ?@args) |
392 | |
393 | Given a coderef, saves the current state of the L</read_handler>, forces it to |
394 | use reliable storage (ie sets it to the master), executes a coderef and then |
395 | restores the original state. |
396 | |
397 | Example: |
398 | |
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399 | my $reliably = sub { |
400 | my $name = shift @_; |
401 | $schema->resultset('User')->create({name=>$name}); |
402 | my $user_rs = $schema->resultset('User')->find({name=>$name}); |
403 | return $user_rs; |
404 | }; |
c4d3fae2 |
405 | |
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406 | my $user_rs = $schema->storage->execute_reliably($reliably, 'John'); |
c4d3fae2 |
407 | |
408 | Use this when you must be certain of your database state, such as when you just |
409 | inserted something and need to get a resultset including it, etc. |
410 | |
411 | =cut |
412 | |
413 | sub execute_reliably { |
64cdad22 |
414 | my ($self, $coderef, @args) = @_; |
415 | |
416 | unless( ref $coderef eq 'CODE') { |
417 | $self->throw_exception('Second argument must be a coderef'); |
418 | } |
419 | |
420 | ##Get copy of master storage |
421 | my $master = $self->master; |
422 | |
423 | ##Get whatever the current read hander is |
424 | my $current = $self->read_handler; |
425 | |
426 | ##Set the read handler to master |
427 | $self->read_handler($master); |
428 | |
429 | ## do whatever the caller needs |
430 | my @result; |
431 | my $want_array = wantarray; |
432 | |
433 | eval { |
434 | if($want_array) { |
435 | @result = $coderef->(@args); |
436 | } elsif(defined $want_array) { |
437 | ($result[0]) = ($coderef->(@args)); |
ed213e85 |
438 | } else { |
64cdad22 |
439 | $coderef->(@args); |
440 | } |
441 | }; |
442 | |
443 | ##Reset to the original state |
444 | $self->read_handler($current); |
445 | |
446 | ##Exception testing has to come last, otherwise you might leave the |
447 | ##read_handler set to master. |
448 | |
449 | if($@) { |
450 | $self->throw_exception("coderef returned an error: $@"); |
451 | } else { |
452 | return $want_array ? @result : $result[0]; |
453 | } |
c4d3fae2 |
454 | } |
455 | |
cb6ec758 |
456 | =head2 set_reliable_storage |
457 | |
458 | Sets the current $schema to be 'reliable', that is all queries, both read and |
459 | write are sent to the master |
64cdad22 |
460 | |
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461 | =cut |
462 | |
463 | sub set_reliable_storage { |
64cdad22 |
464 | my $self = shift @_; |
465 | my $schema = $self->schema; |
466 | my $write_handler = $self->schema->storage->write_handler; |
467 | |
468 | $schema->storage->read_handler($write_handler); |
cb6ec758 |
469 | } |
470 | |
471 | =head2 set_balanced_storage |
472 | |
473 | Sets the current $schema to be use the </balancer> for all reads, while all |
474 | writea are sent to the master only |
64cdad22 |
475 | |
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476 | =cut |
477 | |
478 | sub set_balanced_storage { |
64cdad22 |
479 | my $self = shift @_; |
480 | my $schema = $self->schema; |
481 | my $write_handler = $self->schema->storage->balancer; |
482 | |
483 | $schema->storage->read_handler($write_handler); |
cb6ec758 |
484 | } |
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485 | |
6834cc1d |
486 | =head2 around: txn_do ($coderef) |
c4d3fae2 |
487 | |
488 | Overload to the txn_do method, which is delegated to whatever the |
489 | L<write_handler> is set to. We overload this in order to wrap in inside a |
490 | L</execute_reliably> method. |
491 | |
492 | =cut |
493 | |
6834cc1d |
494 | around 'txn_do' => sub { |
64cdad22 |
495 | my($txn_do, $self, $coderef, @args) = @_; |
496 | $self->execute_reliably(sub {$self->$txn_do($coderef, @args)}); |
6834cc1d |
497 | }; |
c4d3fae2 |
498 | |
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499 | =head2 connected |
500 | |
501 | Check that the master and at least one of the replicants is connected. |
502 | |
503 | =cut |
504 | |
505 | sub connected { |
64cdad22 |
506 | my $self = shift @_; |
507 | return |
508 | $self->master->connected && |
509 | $self->pool->connected_replicants; |
2bf79155 |
510 | } |
511 | |
2bf79155 |
512 | =head2 ensure_connected |
513 | |
514 | Make sure all the storages are connected. |
515 | |
516 | =cut |
517 | |
518 | sub ensure_connected { |
64cdad22 |
519 | my $self = shift @_; |
520 | foreach my $source ($self->all_storages) { |
521 | $source->ensure_connected(@_); |
522 | } |
2bf79155 |
523 | } |
524 | |
2bf79155 |
525 | =head2 limit_dialect |
526 | |
527 | Set the limit_dialect for all existing storages |
528 | |
529 | =cut |
530 | |
531 | sub limit_dialect { |
64cdad22 |
532 | my $self = shift @_; |
533 | foreach my $source ($self->all_storages) { |
534 | $source->limit_dialect(@_); |
535 | } |
2bf79155 |
536 | } |
537 | |
2bf79155 |
538 | =head2 quote_char |
539 | |
540 | Set the quote_char for all existing storages |
541 | |
542 | =cut |
543 | |
544 | sub quote_char { |
64cdad22 |
545 | my $self = shift @_; |
546 | foreach my $source ($self->all_storages) { |
547 | $source->quote_char(@_); |
548 | } |
2bf79155 |
549 | } |
550 | |
2bf79155 |
551 | =head2 name_sep |
552 | |
553 | Set the name_sep for all existing storages |
554 | |
555 | =cut |
556 | |
557 | sub name_sep { |
64cdad22 |
558 | my $self = shift @_; |
559 | foreach my $source ($self->all_storages) { |
560 | $source->name_sep(@_); |
561 | } |
2bf79155 |
562 | } |
563 | |
2bf79155 |
564 | =head2 set_schema |
565 | |
566 | Set the schema object for all existing storages |
567 | |
568 | =cut |
569 | |
570 | sub set_schema { |
64cdad22 |
571 | my $self = shift @_; |
572 | foreach my $source ($self->all_storages) { |
573 | $source->set_schema(@_); |
574 | } |
2bf79155 |
575 | } |
576 | |
2bf79155 |
577 | =head2 debug |
578 | |
579 | set a debug flag across all storages |
580 | |
581 | =cut |
582 | |
583 | sub debug { |
64cdad22 |
584 | my $self = shift @_; |
585 | foreach my $source ($self->all_storages) { |
586 | $source->debug(@_); |
587 | } |
2bf79155 |
588 | } |
589 | |
2bf79155 |
590 | =head2 debugobj |
591 | |
592 | set a debug object across all storages |
593 | |
594 | =cut |
595 | |
596 | sub debugobj { |
64cdad22 |
597 | my $self = shift @_; |
598 | foreach my $source ($self->all_storages) { |
599 | $source->debugobj(@_); |
600 | } |
2bf79155 |
601 | } |
602 | |
2bf79155 |
603 | =head2 debugfh |
604 | |
605 | set a debugfh object across all storages |
606 | |
607 | =cut |
608 | |
609 | sub debugfh { |
64cdad22 |
610 | my $self = shift @_; |
611 | foreach my $source ($self->all_storages) { |
612 | $source->debugfh(@_); |
613 | } |
2bf79155 |
614 | } |
615 | |
2bf79155 |
616 | =head2 debugcb |
617 | |
618 | set a debug callback across all storages |
619 | |
620 | =cut |
621 | |
622 | sub debugcb { |
64cdad22 |
623 | my $self = shift @_; |
624 | foreach my $source ($self->all_storages) { |
625 | $source->debugcb(@_); |
626 | } |
2bf79155 |
627 | } |
628 | |
2bf79155 |
629 | =head2 disconnect |
630 | |
631 | disconnect everything |
632 | |
633 | =cut |
634 | |
635 | sub disconnect { |
64cdad22 |
636 | my $self = shift @_; |
637 | foreach my $source ($self->all_storages) { |
638 | $source->disconnect(@_); |
639 | } |
2bf79155 |
640 | } |
641 | |
7e38d850 |
642 | =head1 GOTCHAS |
643 | |
644 | Due to the fact that replicants can lag behind a master, you must take care to |
645 | make sure you use one of the methods to force read queries to a master should |
646 | you need realtime data integrity. For example, if you insert a row, and then |
647 | immediately re-read it from the database (say, by doing $row->discard_changes) |
648 | or you insert a row and then immediately build a query that expects that row |
649 | to be an item, you should force the master to handle reads. Otherwise, due to |
650 | the lag, there is no certainty your data will be in the expected state. |
651 | |
652 | For data integrity, all transactions automatically use the master storage for |
653 | all read and write queries. Using a transaction is the preferred and recommended |
654 | method to force the master to handle all read queries. |
655 | |
656 | Otherwise, you can force a single query to use the master with the 'force_pool' |
657 | attribute: |
658 | |
659 | my $row = $resultset->search(undef, {force_pool=>'master'})->find($pk); |
660 | |
661 | This attribute will safely be ignore by non replicated storages, so you can use |
662 | the same code for both types of systems. |
663 | |
664 | Lastly, you can use the L</execute_reliably> method, which works very much like |
665 | a transaction. |
666 | |
667 | For debugging, you can turn replication on/off with the methods L</set_reliable_storage> |
668 | and L</set_balanced_storage>, however this operates at a global level and is not |
669 | suitable if you have a shared Schema object being used by multiple processes, |
670 | such as on a web application server. You can get around this limitation by |
671 | using the Schema clone method. |
672 | |
673 | my $new_schema = $schema->clone; |
674 | $new_schema->set_reliable_storage; |
675 | |
676 | ## $new_schema will use only the Master storage for all reads/writes while |
677 | ## the $schema object will use replicated storage. |
678 | |
f5d3a5de |
679 | =head1 AUTHOR |
680 | |
64cdad22 |
681 | John Napiorkowski <john.napiorkowski@takkle.com> |
f5d3a5de |
682 | |
c4d3fae2 |
683 | Based on code originated by: |
f5d3a5de |
684 | |
64cdad22 |
685 | Norbert Csongrádi <bert@cpan.org> |
686 | Peter Siklósi <einon@einon.hu> |
2156bbdd |
687 | |
f5d3a5de |
688 | =head1 LICENSE |
689 | |
690 | You may distribute this code under the same terms as Perl itself. |
691 | |
692 | =cut |
693 | |
694 | 1; |