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         protected 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         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          *
  63          * @return string class name
  64          */
  65         public static function getLBFactoryClass( array $config ) {
  66                 // For configuration backward compatibility after removing
  67                 // underscores from class names in MediaWiki 1.23.
  68                 $bcClasses = array(
  69                         'LBFactory_Simple' => 'LBFactorySimple',
  70                         'LBFactory_Single' => 'LBFactorySingle',
  71                         'LBFactory_Multi' => 'LBFactoryMulti',
  72                         'LBFactory_Fake' => 'LBFactoryFake',
  73                 );
  74
  75                 $class = $config['class'];
  76
  77                 if ( isset( $bcClasses[$class] ) ) {
  78                         $class = $bcClasses[$class];
  79                         wfDeprecated(
  80                                 '$wgLBFactoryConf must be updated. See RELEASE-NOTES for details',
  81                                 '1.23'
  82                         );
  83                 }
  84
  85                 return $class;
  86         }
  87
  88         /**
  89          * Shut down, close connections and destroy the cached instance.
  90          */
  91         static function destroyInstance() {
  92                 if ( self::$instance ) {
  93                         self::$instance->shutdown();
  94                         self::$instance->forEachLBCallMethod( 'closeAll' );
  95                         self::$instance = null;
  96                 }
  97         }
  98
  99         /**
 100          * Set the instance to be the given object
 101          *
 102          * @param $instance LBFactory
 103          */
 104         static function setInstance( $instance ) {
 105                 self::destroyInstance();
 106                 self::$instance = $instance;
 107         }
 108
 109         /**
 110          * Construct a factory based on a configuration array (typically from $wgLBFactoryConf)
 111          * @param $conf
 112          */
 113         abstract function __construct( $conf );
 114
 115         /**
 116          * Create a new load balancer object. The resulting object will be untracked,
 117          * not chronology-protected, and the caller is responsible for cleaning it up.
 118          *
 119          * @param string $wiki wiki ID, or false for the current wiki
 120          * @return LoadBalancer
 121          */
 122         abstract function newMainLB( $wiki = false );
 123
 124         /**
 125          * Get a cached (tracked) load balancer object.
 126          *
 127          * @param string $wiki wiki ID, or false for the current wiki
 128          * @return LoadBalancer
 129          */
 130         abstract function getMainLB( $wiki = false );
 131
 132         /**
 133          * Create a new load balancer for external storage. The resulting object will be
 134          * untracked, not chronology-protected, and the caller is responsible for
 135          * cleaning it up.
 136          *
 137          * @param string $cluster external storage cluster, or false for core
 138          * @param string $wiki wiki ID, or false for the current wiki
 139          *
 140          * @return LoadBalancer
 141          */
 142         abstract function newExternalLB( $cluster, $wiki = false );
 143
 144         /**
 145          * Get a cached (tracked) load balancer for external storage
 146          *
 147          * @param string $cluster external storage cluster, or false for core
 148          * @param string $wiki wiki ID, or false for the current wiki
 149          *
 150          * @return LoadBalancer
 151          */
 152         abstract function &getExternalLB( $cluster, $wiki = false );
 153
 154         /**
 155          * Execute a function for each tracked load balancer
 156          * The callback is called with the load balancer as the first parameter,
 157          * and $params passed as the subsequent parameters.
 158          * @param $callback string|array
 159          * @param array $params
 160          */
 161         abstract function forEachLB( $callback, $params = array() );
 162
 163         /**
 164          * Prepare all tracked load balancers for shutdown
 165          * STUB
 166          */
 167         function shutdown() {
 168         }
 169
 170         /**
 171          * Call a method of each tracked load balancer
 172          * @param $methodName string
 173          * @param $args array
 174          */
 175         function forEachLBCallMethod( $methodName, $args = array() ) {
 176                 $this->forEachLB( array( $this, 'callMethod' ), array( $methodName, $args ) );
 177         }
 178
 179         /**
 180          * Private helper for forEachLBCallMethod
 181          * @param $loadBalancer
 182          * @param $methodName string
 183          * @param $args
 184          */
 185         function callMethod( $loadBalancer, $methodName, $args ) {
 186                 call_user_func_array( array( $loadBalancer, $methodName ), $args );
 187         }
 188
 189         /**
 190          * Commit changes on all master connections
 191          */
 192         function commitMasterChanges() {
 193                 $this->forEachLBCallMethod( 'commitMasterChanges' );
 194         }
 195 }
 196
 197 /**
 198  * A simple single-master LBFactory that gets its configuration from the b/c globals
 199  */
 200 class LBFactorySimple extends LBFactory {
 201         /** @var LoadBalancer */
 202         protected $mainLB;
 203
 204         /** @var LoadBalancer[] */
 205         protected $extLBs = array();
 206
 207         /** @var ChronologyProtector */
 208         protected $chronProt;
 209
 210         function __construct( $conf ) {
 211                 $this->chronProt = new ChronologyProtector;
 212         }
 213
 214         /**
 215          * @param $wiki
 216          * @return LoadBalancer
 217          */
 218         function newMainLB( $wiki = false ) {
 219                 global $wgDBservers, $wgMasterWaitTimeout;
 220                 if ( $wgDBservers ) {
 221                         $servers = $wgDBservers;
 222                 } else {
 223                         global $wgDBserver, $wgDBuser, $wgDBpassword, $wgDBname, $wgDBtype, $wgDebugDumpSql;
 224                         global $wgDBssl, $wgDBcompress;
 225
 226                         $flags = ( $wgDebugDumpSql ? DBO_DEBUG : 0 ) | DBO_DEFAULT;
 227                         if ( $wgDBssl ) {
 228                                 $flags |= DBO_SSL;
 229                         }
 230                         if ( $wgDBcompress ) {
 231                                 $flags |= DBO_COMPRESS;
 232                         }
 233
 234                         $servers = array( array(
 235                                 'host' => $wgDBserver,
 236                                 'user' => $wgDBuser,
 237                                 'password' => $wgDBpassword,
 238                                 'dbname' => $wgDBname,
 239                                 'type' => $wgDBtype,
 240                                 'load' => 1,
 241                                 'flags' => $flags
 242                         ) );
 243                 }
 244
 245                 return new LoadBalancer( array(
 246                         'servers' => $servers,
 247                         'masterWaitTimeout' => $wgMasterWaitTimeout
 248                 ) );
 249         }
 250
 251         /**
 252          * @param $wiki
 253          * @return LoadBalancer
 254          */
 255         function getMainLB( $wiki = false ) {
 256                 if ( !isset( $this->mainLB ) ) {
 257                         $this->mainLB = $this->newMainLB( $wiki );
 258                         $this->mainLB->parentInfo( array( 'id' => 'main' ) );
 259                         $this->chronProt->initLB( $this->mainLB );
 260                 }
 261
 262                 return $this->mainLB;
 263         }
 264
 265         /**
 266          * @throws MWException
 267          * @param $cluster
 268          * @param $wiki
 269          * @return LoadBalancer
 270          */
 271         function newExternalLB( $cluster, $wiki = false ) {
 272                 global $wgExternalServers;
 273                 if ( !isset( $wgExternalServers[$cluster] ) ) {
 274                         throw new MWException( __METHOD__ . ": Unknown cluster \"$cluster\"" );
 275                 }
 276
 277                 return new LoadBalancer( array(
 278                         'servers' => $wgExternalServers[$cluster]
 279                 ) );
 280         }
 281
 282         /**
 283          * @param $cluster
 284          * @param $wiki
 285          * @return array
 286          */
 287         function &getExternalLB( $cluster, $wiki = false ) {
 288                 if ( !isset( $this->extLBs[$cluster] ) ) {
 289                         $this->extLBs[$cluster] = $this->newExternalLB( $cluster, $wiki );
 290                         $this->extLBs[$cluster]->parentInfo( array( 'id' => "ext-$cluster" ) );
 291                         $this->chronProt->initLB( $this->extLBs[$cluster] );
 292                 }
 293
 294                 return $this->extLBs[$cluster];
 295         }
 296
 297         /**
 298          * Execute a function for each tracked load balancer
 299          * The callback is called with the load balancer as the first parameter,
 300          * and $params passed as the subsequent parameters.
 301          * @param $callback
 302          * @param $params array
 303          */
 304         function forEachLB( $callback, $params = array() ) {
 305                 if ( isset( $this->mainLB ) ) {
 306                         call_user_func_array( $callback, array_merge( array( $this->mainLB ), $params ) );
 307                 }
 308                 foreach ( $this->extLBs as $lb ) {
 309                         call_user_func_array( $callback, array_merge( array( $lb ), $params ) );
 310                 }
 311         }
 312
 313         function shutdown() {
 314                 if ( $this->mainLB ) {
 315                         $this->chronProt->shutdownLB( $this->mainLB );
 316                 }
 317                 foreach ( $this->extLBs as $extLB ) {
 318                         $this->chronProt->shutdownLB( $extLB );
 319                 }
 320                 $this->chronProt->shutdown();
 321                 $this->commitMasterChanges();
 322         }
 323 }
 324
 325 /**
 326  * LBFactory class that throws an error on any attempt to use it.
 327  * This will typically be done via wfGetDB().
 328  * Call LBFactory::disableBackend() to start using this, and
 329  * LBFactory::enableBackend() to return to normal behavior
 330  */
 331 class LBFactoryFake extends LBFactory {
 332         function __construct( $conf ) {
 333         }
 334
 335         function newMainLB( $wiki = false ) {
 336                 throw new DBAccessError;
 337         }
 338
 339         function getMainLB( $wiki = false ) {
 340                 throw new DBAccessError;
 341         }
 342
 343         function newExternalLB( $cluster, $wiki = false ) {
 344                 throw new DBAccessError;
 345         }
 346
 347         function &getExternalLB( $cluster, $wiki = false ) {
 348                 throw new DBAccessError;
 349         }
 350
 351         function forEachLB( $callback, $params = array() ) {
 352         }
 353 }
 354
 355 /**
 356  * Exception class for attempted DB access
 357  */
 358 class DBAccessError extends MWException {
 359         function __construct() {
 360                 parent::__construct( "Mediawiki tried to access the database via wfGetDB(). " .
 361                         "This is not allowed." );
 362         }
 363 }