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1 | <?php |
2 | /** |
3 | * This program is free software; you can redistribute it and/or modify |
4 | * it under the terms of the GNU General Public License as published by |
5 | * the Free Software Foundation; either version 2 of the License, or |
6 | * (at your option) any later version. |
7 | * |
8 | * This program is distributed in the hope that it will be useful, |
9 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
10 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
11 | * GNU General Public License for more details. |
12 | * |
13 | * You should have received a copy of the GNU General Public License along |
14 | * with this program; if not, write to the Free Software Foundation, Inc., |
15 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
16 | * http://www.gnu.org/copyleft/gpl.html |
17 | * |
18 | * @file |
19 | */ |
20 | namespace Wikimedia\Rdbms; |
21 | |
22 | use InvalidArgumentException; |
23 | use LogicException; |
24 | use UnexpectedValueException; |
25 | |
26 | /** |
27 | * LoadBalancer manager for sites with several "main" database clusters |
28 | * |
29 | * Each database cluster consists of a "primary" server and any number of replica servers, |
30 | * all of which converge, as soon as possible, to contain the same schemas and records. If |
31 | * a replication topology has multiple primaries, then the "primary" is merely the preferred |
32 | * co-primary for the current context (e.g. datacenter). |
33 | * |
34 | * For single-primary topologies, the schemas and records of the primary define the "dataset". |
35 | * For multiple-primary topologies, the "dataset" is the convergent result of applying/merging |
36 | * all committed events (regardless of the co-primary they originated on); it possible that no |
37 | * co-primary has yet converged upon this state at any given time (especially when there are |
38 | * frequent writes and co-primaries are geographically distant). |
39 | * |
40 | * A "main" cluster contain a "main" dataset, which consists of data that is compact, highly |
41 | * relational (e.g. read by JOIN queries), and essential to one or more sites. The "external" |
42 | * clusters each store an "external" dataset, which consists of data that is non-relational |
43 | * (e.g. key/value pairs), self-contained (e.g. JOIN queries and transactions thereof never |
44 | * involve a main dataset), or too bulky to reside in a main dataset (e.g. text blobs). |
45 | * |
46 | * The class allows for large site farms to split up their data in the following ways: |
47 | * - Vertically shard compact site-specific data by site (e.g. page/comment metadata) |
48 | * - Vertically shard compact global data by module (e.g. account/notification data) |
49 | * - Horizontally shard any bulk data by blob key (e.g. page/comment content blobs) |
50 | * |
51 | * @ingroup Database |
52 | */ |
53 | class LBFactoryMulti extends LBFactory { |
54 | /** @var array<string,LoadBalancer> Map of (main section => tracked LoadBalancer) */ |
55 | private $mainLBs = []; |
56 | /** @var array<string,LoadBalancer> Map of (external cluster => tracked LoadBalancer) */ |
57 | private $externalLBs = []; |
58 | |
59 | /** @var string[] Map of (server name => IP address) */ |
60 | private $hostsByServerName; |
61 | /** @var string[] Map of (database name => main section) */ |
62 | private $sectionsByDB; |
63 | /** @var int[][][] Map of (main section => group => server name => load ratio) */ |
64 | private $groupLoadsBySection; |
65 | /** @var int[][] Map of (external cluster => server name => load ratio) */ |
66 | private $externalLoadsByCluster; |
67 | /** @var array Server config map ("host", "serverName", "load", and "groupLoads" ignored) */ |
68 | private $serverTemplate; |
69 | /** @var array Server config map overriding "serverTemplate" for all external servers */ |
70 | private $externalTemplateOverrides; |
71 | /** @var array[] Map of (main section => server config map overrides) */ |
72 | private $templateOverridesBySection; |
73 | /** @var array[] Map of (external cluster => server config map overrides) */ |
74 | private $templateOverridesByCluster; |
75 | /** @var array Server config override map for all main/external primary DB servers */ |
76 | private $masterTemplateOverrides; |
77 | /** @var array[] Map of (server name => server config map overrides) for all servers */ |
78 | private $templateOverridesByServer; |
79 | /** @var string[]|bool[] A map of (main section => read-only message) */ |
80 | private $readOnlyBySection; |
81 | /** @var array Configuration for the LoadMonitor to use within LoadBalancer instances */ |
82 | private $loadMonitorConfig; |
83 | /** @var DatabaseDomain[] Map of (domain ID => domain instance) */ |
84 | private $nonLocalDomainCache = []; |
85 | |
86 | /** |
87 | * Template override precedence (highest => lowest): |
88 | * - templateOverridesByServer |
89 | * - masterTemplateOverrides |
90 | * - templateOverridesBySection/templateOverridesByCluster |
91 | * - externalTemplateOverrides |
92 | * - serverTemplate |
93 | * Overrides only work on top level keys (so nested values will not be merged). |
94 | * |
95 | * Server config maps should be of the format Database::factory() requires. |
96 | * Additionally, a 'max lag' key should also be set on server maps, indicating how stale the |
97 | * data can be before the load balancer tries to avoid using it. The map can have 'is static' |
98 | * set to disable blocking replication sync checks (intended for archive servers with |
99 | * unchanging data). |
100 | * |
101 | * @see LBFactory::__construct() |
102 | * @param array $conf Additional parameters include: |
103 | * - hostsByName: map of (server name => IP address). [optional] |
104 | * - sectionsByDB: map of (database => main section). The database name "DEFAULT" is |
105 | * interpreted as a catch-all for all databases not otherwise mentioned. If no section |
106 | * name is specified for "DEFAULT", then the catch-all section is assumed to be named |
107 | * "DEFAULT". [optional] |
108 | * - sectionLoads: map of (main section => server name => load ratio); the first host |
109 | * listed in each section is the primary DB server for that section. [optional] |
110 | * - groupLoadsBySection: map of (main section => group => server name => group load ratio). |
111 | * Any ILoadBalancer::GROUP_GENERIC group will be ignored. [optional] |
112 | * - externalLoads: map of (cluster => server name => load ratio) map. [optional] |
113 | * - serverTemplate: server config map for Database::factory(). |
114 | * Note that "host", "serverName" and "load" entries will be overridden by |
115 | * "groupLoadsBySection" and "hostsByName". [optional] |
116 | * - externalTemplateOverrides: server config map overrides for external stores; |
117 | * respects the override precedence described above. [optional] |
118 | * - templateOverridesBySection: map of (main section => server config map overrides); |
119 | * respects the override precedence described above. [optional] |
120 | * - templateOverridesByCluster: map of (external cluster => server config map overrides); |
121 | * respects the override precedence described above. [optional] |
122 | * - masterTemplateOverrides: server config map overrides for masters; |
123 | * respects the override precedence described above. [optional] |
124 | * - templateOverridesByServer: map of (server name => server config map overrides); |
125 | * respects the override precedence described above and applies to both core |
126 | * and external storage. [optional] |
127 | * - loadMonitor: LoadMonitor::__construct() parameters with "class" field. [optional] |
128 | * - readOnlyBySection: map of (main section => message text or false). |
129 | * String values make sections read only, whereas anything else does not |
130 | * restrict read/write mode. [optional] |
131 | * - configCallback: A callback that returns a conf array that can be passed to |
132 | * the reconfigure() method. This will be used to autoReconfigure() to load |
133 | * any updated configuration. |
134 | */ |
135 | public function __construct( array $conf ) { |
136 | parent::__construct( $conf ); |
137 | |
138 | $this->hostsByServerName = $conf['hostsByName'] ?? []; |
139 | $this->sectionsByDB = $conf['sectionsByDB']; |
140 | $this->sectionsByDB += [ self::CLUSTER_MAIN_DEFAULT => self::CLUSTER_MAIN_DEFAULT ]; |
141 | $this->groupLoadsBySection = $conf['groupLoadsBySection'] ?? []; |
142 | foreach ( ( $conf['sectionLoads'] ?? [] ) as $section => $loadsByServerName ) { |
143 | $this->groupLoadsBySection[$section][ILoadBalancer::GROUP_GENERIC] = $loadsByServerName; |
144 | } |
145 | $this->externalLoadsByCluster = $conf['externalLoads'] ?? []; |
146 | $this->serverTemplate = $conf['serverTemplate'] ?? []; |
147 | $this->externalTemplateOverrides = $conf['externalTemplateOverrides'] ?? []; |
148 | $this->templateOverridesBySection = $conf['templateOverridesBySection'] ?? []; |
149 | $this->templateOverridesByCluster = $conf['templateOverridesByCluster'] ?? []; |
150 | $this->masterTemplateOverrides = $conf['masterTemplateOverrides'] ?? []; |
151 | $this->templateOverridesByServer = $conf['templateOverridesByServer'] ?? []; |
152 | $this->readOnlyBySection = $conf['readOnlyBySection'] ?? []; |
153 | |
154 | if ( isset( $conf['loadMonitor'] ) ) { |
155 | $this->loadMonitorConfig = $conf['loadMonitor']; |
156 | } elseif ( isset( $conf['loadMonitorClass'] ) ) { // b/c |
157 | $this->loadMonitorConfig = [ 'class' => $conf['loadMonitorClass'] ]; |
158 | } else { |
159 | $this->loadMonitorConfig = [ 'class' => LoadMonitor::class ]; |
160 | } |
161 | |
162 | foreach ( $this->externalLoadsByCluster as $cluster => $_ ) { |
163 | if ( isset( $this->groupLoadsBySection[$cluster] ) ) { |
164 | throw new LogicException( |
165 | "External cluster '$cluster' has the same name as a main section/cluster" |
166 | ); |
167 | } |
168 | } |
169 | } |
170 | |
171 | public function newMainLB( $domain = false ): ILoadBalancerForOwner { |
172 | $domainInstance = $this->resolveDomainInstance( $domain ); |
173 | $database = $domainInstance->getDatabase(); |
174 | $section = $this->getSectionFromDatabase( $database ); |
175 | |
176 | if ( !isset( $this->groupLoadsBySection[$section][ILoadBalancer::GROUP_GENERIC] ) ) { |
177 | throw new UnexpectedValueException( "Section '$section' has no hosts defined." ); |
178 | } |
179 | |
180 | return $this->newLoadBalancer( |
181 | $section, |
182 | array_merge( |
183 | $this->serverTemplate, |
184 | $this->templateOverridesBySection[$section] ?? [] |
185 | ), |
186 | $this->groupLoadsBySection[$section], |
187 | // Use the LB-specific read-only reason if everything isn't already read-only |
188 | is_string( $this->readOnlyReason ) |
189 | ? $this->readOnlyReason |
190 | : ( $this->readOnlyBySection[$section] ?? false ) |
191 | ); |
192 | } |
193 | |
194 | /** |
195 | * @param DatabaseDomain|string|false $domain |
196 | * @return DatabaseDomain |
197 | */ |
198 | private function resolveDomainInstance( $domain ) { |
199 | if ( $domain instanceof DatabaseDomain ) { |
200 | return $domain; // already a domain instance |
201 | } elseif ( $domain === false || $domain === $this->localDomain->getId() ) { |
202 | return $this->localDomain; |
203 | } elseif ( isset( $this->domainAliases[$domain] ) ) { |
204 | // This array acts as both the original map and as instance cache. |
205 | // Instances pass-through DatabaseDomain::newFromId as-is. |
206 | $this->domainAliases[$domain] = |
207 | DatabaseDomain::newFromId( $this->domainAliases[$domain] ); |
208 | |
209 | return $this->domainAliases[$domain]; |
210 | } |
211 | |
212 | $cachedDomain = $this->nonLocalDomainCache[$domain] ?? null; |
213 | if ( $cachedDomain === null ) { |
214 | $cachedDomain = DatabaseDomain::newFromId( $domain ); |
215 | $this->nonLocalDomainCache = [ $domain => $cachedDomain ]; |
216 | } |
217 | |
218 | return $cachedDomain; |
219 | } |
220 | |
221 | public function getMainLB( $domain = false ): ILoadBalancer { |
222 | $domainInstance = $this->resolveDomainInstance( $domain ); |
223 | $section = $this->getSectionFromDatabase( $domainInstance->getDatabase() ); |
224 | |
225 | if ( !isset( $this->mainLBs[$section] ) ) { |
226 | $this->mainLBs[$section] = $this->newMainLB( $domain ); |
227 | } |
228 | |
229 | return $this->mainLBs[$section]; |
230 | } |
231 | |
232 | public function newExternalLB( $cluster ): ILoadBalancerForOwner { |
233 | if ( !isset( $this->externalLoadsByCluster[$cluster] ) ) { |
234 | throw new InvalidArgumentException( "Unknown cluster '$cluster'" ); |
235 | } |
236 | return $this->newLoadBalancer( |
237 | $cluster, |
238 | array_merge( |
239 | $this->serverTemplate, |
240 | $this->externalTemplateOverrides, |
241 | $this->templateOverridesByCluster[$cluster] ?? [] |
242 | ), |
243 | [ ILoadBalancer::GROUP_GENERIC => $this->externalLoadsByCluster[$cluster] ], |
244 | $this->readOnlyReason |
245 | ); |
246 | } |
247 | |
248 | public function getExternalLB( $cluster ): ILoadBalancer { |
249 | if ( !isset( $this->externalLBs[$cluster] ) ) { |
250 | $this->externalLBs[$cluster] = $this->newExternalLB( |
251 | $cluster |
252 | ); |
253 | } |
254 | |
255 | return $this->externalLBs[$cluster]; |
256 | } |
257 | |
258 | public function getAllMainLBs(): array { |
259 | $lbs = []; |
260 | foreach ( $this->sectionsByDB as $db => $section ) { |
261 | if ( !isset( $lbs[$section] ) ) { |
262 | $lbs[$section] = $this->getMainLB( $db ); |
263 | } |
264 | } |
265 | |
266 | return $lbs; |
267 | } |
268 | |
269 | public function getAllExternalLBs(): array { |
270 | $lbs = []; |
271 | foreach ( $this->externalLoadsByCluster as $cluster => $unused ) { |
272 | $lbs[$cluster] = $this->getExternalLB( $cluster ); |
273 | } |
274 | |
275 | return $lbs; |
276 | } |
277 | |
278 | protected function getLBsForOwner() { |
279 | foreach ( $this->mainLBs as $lb ) { |
280 | yield $lb; |
281 | } |
282 | foreach ( $this->externalLBs as $lb ) { |
283 | yield $lb; |
284 | } |
285 | } |
286 | |
287 | /** |
288 | * Make a new load balancer object based on template and load array |
289 | * |
290 | * @param string $clusterName |
291 | * @param array $serverTemplate |
292 | * @param array $groupLoads |
293 | * @param string|false $readOnlyReason |
294 | * @return LoadBalancer |
295 | */ |
296 | private function newLoadBalancer( |
297 | string $clusterName, |
298 | array $serverTemplate, |
299 | array $groupLoads, |
300 | $readOnlyReason |
301 | ) { |
302 | $lb = new LoadBalancer( array_merge( |
303 | $this->baseLoadBalancerParams(), |
304 | [ |
305 | 'servers' => $this->makeServerConfigArrays( $serverTemplate, $groupLoads ), |
306 | 'loadMonitor' => $this->loadMonitorConfig, |
307 | 'readOnlyReason' => $readOnlyReason, |
308 | 'clusterName' => $clusterName |
309 | ] |
310 | ) ); |
311 | $this->initLoadBalancer( $lb ); |
312 | |
313 | return $lb; |
314 | } |
315 | |
316 | /** |
317 | * Make a server array as expected by LoadBalancer::__construct() |
318 | * |
319 | * @param array $serverTemplate Server config map |
320 | * @param int[][] $groupLoads Map of (group => server name => load) |
321 | * @return array[] List of server config maps |
322 | */ |
323 | private function makeServerConfigArrays( array $serverTemplate, array $groupLoads ) { |
324 | // The primary DB server is the first host explicitly listed in the generic load group |
325 | if ( !$groupLoads[ILoadBalancer::GROUP_GENERIC] ) { |
326 | throw new UnexpectedValueException( "Empty generic load array; no primary DB defined." ); |
327 | } |
328 | $groupLoadsByServerName = []; |
329 | foreach ( $groupLoads as $group => $loadByServerName ) { |
330 | foreach ( $loadByServerName as $serverName => $load ) { |
331 | $groupLoadsByServerName[$serverName][$group] = $load; |
332 | } |
333 | } |
334 | |
335 | // Get the ordered map of (server name => load); the primary DB server is first |
336 | $genericLoads = $groupLoads[ILoadBalancer::GROUP_GENERIC]; |
337 | // Implicitly append any hosts that only appear in custom load groups |
338 | $genericLoads += array_fill_keys( array_keys( $groupLoadsByServerName ), 0 ); |
339 | $servers = []; |
340 | foreach ( $genericLoads as $serverName => $load ) { |
341 | $servers[] = array_merge( |
342 | $serverTemplate, |
343 | $servers ? [] : $this->masterTemplateOverrides, |
344 | $this->templateOverridesByServer[$serverName] ?? [], |
345 | [ |
346 | 'host' => $this->hostsByServerName[$serverName] ?? $serverName, |
347 | 'serverName' => $serverName, |
348 | 'load' => $load, |
349 | 'groupLoads' => $groupLoadsByServerName[$serverName] ?? [] |
350 | ] |
351 | ); |
352 | } |
353 | |
354 | return $servers; |
355 | } |
356 | |
357 | /** |
358 | * @param string $database |
359 | * @return string Main section name |
360 | */ |
361 | private function getSectionFromDatabase( $database ) { |
362 | return $this->sectionsByDB[$database] |
363 | ?? $this->sectionsByDB[self::CLUSTER_MAIN_DEFAULT] |
364 | ?? self::CLUSTER_MAIN_DEFAULT; |
365 | } |
366 | |
367 | public function reconfigure( array $conf ): void { |
368 | if ( !$conf ) { |
369 | return; |
370 | } |
371 | |
372 | foreach ( $this->mainLBs as $lb ) { |
373 | // Approximate what LBFactoryMulti::__construct does (T346365) |
374 | $groupLoads = $conf['groupLoadsBySection'][$lb->getClusterName()] ?? []; |
375 | $groupLoads[ILoadBalancer::GROUP_GENERIC] = $conf['sectionLoads'][$lb->getClusterName()]; |
376 | $config = [ |
377 | 'servers' => $this->makeServerConfigArrays( $conf['serverTemplate'] ?? [], $groupLoads ) |
378 | ]; |
379 | $lb->reconfigure( $config ); |
380 | |
381 | } |
382 | foreach ( $this->externalLBs as $lb ) { |
383 | $groupLoads = [ |
384 | ILoadBalancer::GROUP_GENERIC => $conf['externalLoads'][$lb->getClusterName()] |
385 | ]; |
386 | $config = [ |
387 | 'servers' => $this->makeServerConfigArrays( $conf['serverTemplate'] ?? [], $groupLoads ) |
388 | ]; |
389 | $lb->reconfigure( $config ); |
390 | } |
391 | } |
392 | } |