includes/db/LBFactory.php

   1 <?php
   2 /**
   3  * Generator of database load balancing objects.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Database
  22  */
  23
  24 /**
  25  * An interface for generating database load balancers
  26  * @ingroup Database
  27  */
  28 abstract class LBFactory {
  29         /** @var LBFactory */
  30         private static $instance;
  31
  32         /**
  33          * Disables all access to the load balancer, will cause all database access
  34          * to throw a DBAccessError
  35          */
  36         public static function disableBackend() {
  37                 global $wgLBFactoryConf;
  38                 self::$instance = new LBFactoryFake( $wgLBFactoryConf );
  39         }
  40
  41         /**
  42          * Get an LBFactory instance
  43          *
  44          * @return LBFactory
  45          */
  46         public static function singleton() {
  47                 global $wgLBFactoryConf;
  48
  49                 if ( is_null( self::$instance ) ) {
  50                         $class = self::getLBFactoryClass( $wgLBFactoryConf );
  51
  52                         self::$instance = new $class( $wgLBFactoryConf );
  53                 }
  54
  55                 return self::$instance;
  56         }
  57
  58         /**
  59          * Returns the LBFactory class to use and the load balancer configuration.
  60          *
  61          * @param array $config (e.g. $wgLBFactoryConf)
  62          * @return string Class name
  63          */
  64         public static function getLBFactoryClass( array $config ) {
  65                 // For configuration backward compatibility after removing
  66                 // underscores from class names in MediaWiki 1.23.
  67                 $bcClasses = array(
  68                         'LBFactory_Simple' => 'LBFactorySimple',
  69                         'LBFactory_Single' => 'LBFactorySingle',
  70                         'LBFactory_Multi' => 'LBFactoryMulti',
  71                         'LBFactory_Fake' => 'LBFactoryFake',
  72                 );
  73
  74                 $class = $config['class'];
  75
  76                 if ( isset( $bcClasses[$class] ) ) {
  77                         $class = $bcClasses[$class];
  78                         wfDeprecated(
  79                                 '$wgLBFactoryConf must be updated. See RELEASE-NOTES for details',
  80                                 '1.23'
  81                         );
  82                 }
  83
  84                 return $class;
  85         }
  86
  87         /**
  88          * Shut down, close connections and destroy the cached instance.
  89          */
  90         public static function destroyInstance() {
  91                 if ( self::$instance ) {
  92                         self::$instance->shutdown();
  93                         self::$instance->forEachLBCallMethod( 'closeAll' );
  94                         self::$instance = null;
  95                 }
  96         }
  97
  98         /**
  99          * Set the instance to be the given object
 100          *
 101          * @param LBFactory $instance
 102          */
 103         public static function setInstance( $instance ) {
 104                 self::destroyInstance();
 105                 self::$instance = $instance;
 106         }
 107
 108         /**
 109          * Construct a factory based on a configuration array (typically from $wgLBFactoryConf)
 110          * @param array $conf
 111          */
 112         abstract public function __construct( array $conf );
 113
 114         /**
 115          * Create a new load balancer object. The resulting object will be untracked,
 116          * not chronology-protected, and the caller is responsible for cleaning it up.
 117          *
 118          * @param bool|string $wiki Wiki ID, or false for the current wiki
 119          * @return LoadBalancer
 120          */
 121         abstract public function newMainLB( $wiki = false );
 122
 123         /**
 124          * Get a cached (tracked) load balancer object.
 125          *
 126          * @param bool|string $wiki Wiki ID, or false for the current wiki
 127          * @return LoadBalancer
 128          */
 129         abstract public function getMainLB( $wiki = false );
 130
 131         /**
 132          * Create a new load balancer for external storage. The resulting object will be
 133          * untracked, not chronology-protected, and the caller is responsible for
 134          * cleaning it up.
 135          *
 136          * @param string $cluster External storage cluster, or false for core
 137          * @param bool|string $wiki Wiki ID, or false for the current wiki
 138          * @return LoadBalancer
 139          */
 140         abstract protected function newExternalLB( $cluster, $wiki = false );
 141
 142         /**
 143          * Get a cached (tracked) load balancer for external storage
 144          *
 145          * @param string $cluster External storage cluster, or false for core
 146          * @param bool|string $wiki Wiki ID, or false for the current wiki
 147          * @return LoadBalancer
 148          */
 149         abstract public function &getExternalLB( $cluster, $wiki = false );
 150
 151         /**
 152          * Execute a function for each tracked load balancer
 153          * The callback is called with the load balancer as the first parameter,
 154          * and $params passed as the subsequent parameters.
 155          *
 156          * @param callable $callback
 157          * @param array $params
 158          */
 159         abstract public function forEachLB( $callback, array $params = array() );
 160
 161         /**
 162          * Prepare all tracked load balancers for shutdown
 163          * STUB
 164          */
 165         public function shutdown() {
 166         }
 167
 168         /**
 169          * Call a method of each tracked load balancer
 170          *
 171          * @param string $methodName
 172          * @param array $args
 173          */
 174         private function forEachLBCallMethod( $methodName, array $args = array() ) {
 175                 $this->forEachLB( function ( LoadBalancer $loadBalancer, $methodName, array $args ) {
 176                         call_user_func_array( array( $loadBalancer, $methodName ), $args );
 177                 }, array( $methodName, $args ) );
 178         }
 179
 180         /**
 181          * Commit changes on all master connections
 182          */
 183         public function commitMasterChanges() {
 184                 $this->forEachLBCallMethod( 'commitMasterChanges' );
 185         }
 186
 187         /**
 188          * Rollback changes on all master connections
 189          * @since 1.23
 190          */
 191         public function rollbackMasterChanges() {
 192                 $this->forEachLBCallMethod( 'rollbackMasterChanges' );
 193         }
 194
 195         /**
 196          * Detemine if any master connection has pending changes.
 197          * @since 1.23
 198          * @return bool
 199          */
 200         public function hasMasterChanges() {
 201                 $ret = false;
 202                 $this->forEachLB( function ( $lb ) use ( &$ret ) {
 203                         $ret = $ret || $lb->hasMasterChanges();
 204                 } );
 205                 return $ret;
 206         }
 207 }
 208
 209 /**
 210  * A simple single-master LBFactory that gets its configuration from the b/c globals
 211  */
 212 class LBFactorySimple extends LBFactory {
 213         /** @var LoadBalancer */
 214         private $mainLB;
 215
 216         /** @var LoadBalancer[] */
 217         private $extLBs = array();
 218
 219         /** @var ChronologyProtector */
 220         private $chronProt;
 221
 222         public function __construct( array $conf ) {
 223                 $this->chronProt = new ChronologyProtector;
 224         }
 225
 226         /**
 227          * @param bool|string $wiki
 228          * @return LoadBalancer
 229          */
 230         public function newMainLB( $wiki = false ) {
 231                 global $wgDBservers;
 232                 if ( $wgDBservers ) {
 233                         $servers = $wgDBservers;
 234                 } else {
 235                         global $wgDBserver, $wgDBuser, $wgDBpassword, $wgDBname, $wgDBtype, $wgDebugDumpSql;
 236                         global $wgDBssl, $wgDBcompress;
 237
 238                         $flags = DBO_DEFAULT;
 239                         if ( $wgDebugDumpSql ) {
 240                                 $flags |= DBO_DEBUG;
 241                         }
 242                         if ( $wgDBssl ) {
 243                                 $flags |= DBO_SSL;
 244                         }
 245                         if ( $wgDBcompress ) {
 246                                 $flags |= DBO_COMPRESS;
 247                         }
 248
 249                         $servers = array( array(
 250                                 'host' => $wgDBserver,
 251                                 'user' => $wgDBuser,
 252                                 'password' => $wgDBpassword,
 253                                 'dbname' => $wgDBname,
 254                                 'type' => $wgDBtype,
 255                                 'load' => 1,
 256                                 'flags' => $flags
 257                         ) );
 258                 }
 259
 260                 return new LoadBalancer( array(
 261                         'servers' => $servers,
 262                 ) );
 263         }
 264
 265         /**
 266          * @param bool|string $wiki
 267          * @return LoadBalancer
 268          */
 269         public function getMainLB( $wiki = false ) {
 270                 if ( !isset( $this->mainLB ) ) {
 271                         $this->mainLB = $this->newMainLB( $wiki );
 272                         $this->mainLB->parentInfo( array( 'id' => 'main' ) );
 273                         $this->chronProt->initLB( $this->mainLB );
 274                 }
 275
 276                 return $this->mainLB;
 277         }
 278
 279         /**
 280          * @throws MWException
 281          * @param string $cluster
 282          * @param bool|string $wiki
 283          * @return LoadBalancer
 284          */
 285         protected function newExternalLB( $cluster, $wiki = false ) {
 286                 global $wgExternalServers;
 287                 if ( !isset( $wgExternalServers[$cluster] ) ) {
 288                         throw new MWException( __METHOD__ . ": Unknown cluster \"$cluster\"" );
 289                 }
 290
 291                 return new LoadBalancer( array(
 292                         'servers' => $wgExternalServers[$cluster]
 293                 ) );
 294         }
 295
 296         /**
 297          * @param string $cluster
 298          * @param bool|string $wiki
 299          * @return array
 300          */
 301         public function &getExternalLB( $cluster, $wiki = false ) {
 302                 if ( !isset( $this->extLBs[$cluster] ) ) {
 303                         $this->extLBs[$cluster] = $this->newExternalLB( $cluster, $wiki );
 304                         $this->extLBs[$cluster]->parentInfo( array( 'id' => "ext-$cluster" ) );
 305                         $this->chronProt->initLB( $this->extLBs[$cluster] );
 306                 }
 307
 308                 return $this->extLBs[$cluster];
 309         }
 310
 311         /**
 312          * Execute a function for each tracked load balancer
 313          * The callback is called with the load balancer as the first parameter,
 314          * and $params passed as the subsequent parameters.
 315          *
 316          * @param callable $callback
 317          * @param array $params
 318          */
 319         public function forEachLB( $callback, array $params = array() ) {
 320                 if ( isset( $this->mainLB ) ) {
 321                         call_user_func_array( $callback, array_merge( array( $this->mainLB ), $params ) );
 322                 }
 323                 foreach ( $this->extLBs as $lb ) {
 324                         call_user_func_array( $callback, array_merge( array( $lb ), $params ) );
 325                 }
 326         }
 327
 328         public function shutdown() {
 329                 if ( $this->mainLB ) {
 330                         $this->chronProt->shutdownLB( $this->mainLB );
 331                 }
 332                 foreach ( $this->extLBs as $extLB ) {
 333                         $this->chronProt->shutdownLB( $extLB );
 334                 }
 335                 $this->chronProt->shutdown();
 336                 $this->commitMasterChanges();
 337         }
 338 }
 339
 340 /**
 341  * LBFactory class that throws an error on any attempt to use it.
 342  * This will typically be done via wfGetDB().
 343  * Call LBFactory::disableBackend() to start using this, and
 344  * LBFactory::enableBackend() to return to normal behavior
 345  */
 346 class LBFactoryFake extends LBFactory {
 347         public function __construct( array $conf ) {
 348         }
 349
 350         public function newMainLB( $wiki = false ) {
 351                 throw new DBAccessError;
 352         }
 353
 354         public function getMainLB( $wiki = false ) {
 355                 throw new DBAccessError;
 356         }
 357
 358         protected function newExternalLB( $cluster, $wiki = false ) {
 359                 throw new DBAccessError;
 360         }
 361
 362         public function &getExternalLB( $cluster, $wiki = false ) {
 363                 throw new DBAccessError;
 364         }
 365
 366         public function forEachLB( $callback, array $params = array() ) {
 367         }
 368 }
 369
 370 /**
 371  * Exception class for attempted DB access
 372  */
 373 class DBAccessError extends MWException {
 374         public function __construct() {
 375                 parent::__construct( "Mediawiki tried to access the database via wfGetDB(). " .
 376                         "This is not allowed." );
 377         }
 378 }