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          * @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 $class;
  85         }
  86
  87         /**
  88          * Shut down, close connections and destroy the cached instance.
  89          */
  90         static function destroyInstance() {
  91                 if ( self::$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         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 function __construct( $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 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 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 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 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 function forEachLB( $callback, $params = array() );
 160
 161         /**
 162          * Prepare all tracked load balancers for shutdown
 163          * STUB
 164          */
 165         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         function forEachLBCallMethod( $methodName, $args = array() ) {
 175                 $this->forEachLB( array( $this, 'callMethod' ), array( $methodName, $args ) );
 176         }
 177
 178         /**
 179          * Private helper for forEachLBCallMethod
 180          * @param LoadBalancer $loadBalancer
 181          * @param string $methodName
 182          * @param $args
 183          */
 184         function callMethod( $loadBalancer, $methodName, $args ) {
 185                 call_user_func_array( array( $loadBalancer, $methodName ), $args );
 186         }
 187
 188         /**
 189          * Commit changes on all master connections
 190          */
 191         function commitMasterChanges() {
 192                 $this->forEachLBCallMethod( 'commitMasterChanges' );
 193         }
 194 }
 195
 196 /**
 197  * A simple single-master LBFactory that gets its configuration from the b/c globals
 198  */
 199 class LBFactorySimple extends LBFactory {
 200         /** @var LoadBalancer */
 201         protected $mainLB;
 202
 203         /** @var LoadBalancer[] */
 204         protected $extLBs = array();
 205
 206         /** @var ChronologyProtector */
 207         protected $chronProt;
 208
 209         function __construct( $conf ) {
 210                 $this->chronProt = new ChronologyProtector;
 211         }
 212
 213         /**
 214          * @param bool|string $wiki
 215          * @return LoadBalancer
 216          */
 217         function newMainLB( $wiki = false ) {
 218                 global $wgDBservers, $wgMasterWaitTimeout;
 219                 if ( $wgDBservers ) {
 220                         $servers = $wgDBservers;
 221                 } else {
 222                         global $wgDBserver, $wgDBuser, $wgDBpassword, $wgDBname, $wgDBtype, $wgDebugDumpSql;
 223                         global $wgDBssl, $wgDBcompress;
 224
 225                         $flags = ( $wgDebugDumpSql ? DBO_DEBUG : 0 ) | DBO_DEFAULT;
 226                         if ( $wgDBssl ) {
 227                                 $flags |= DBO_SSL;
 228                         }
 229                         if ( $wgDBcompress ) {
 230                                 $flags |= DBO_COMPRESS;
 231                         }
 232
 233                         $servers = array( array(
 234                                 'host' => $wgDBserver,
 235                                 'user' => $wgDBuser,
 236                                 'password' => $wgDBpassword,
 237                                 'dbname' => $wgDBname,
 238                                 'type' => $wgDBtype,
 239                                 'load' => 1,
 240                                 'flags' => $flags
 241                         ) );
 242                 }
 243
 244                 return new LoadBalancer( array(
 245                         'servers' => $servers,
 246                         'masterWaitTimeout' => $wgMasterWaitTimeout
 247                 ) );
 248         }
 249
 250         /**
 251          * @param bool|string $wiki
 252          * @return LoadBalancer
 253          */
 254         function getMainLB( $wiki = false ) {
 255                 if ( !isset( $this->mainLB ) ) {
 256                         $this->mainLB = $this->newMainLB( $wiki );
 257                         $this->mainLB->parentInfo( array( 'id' => 'main' ) );
 258                         $this->chronProt->initLB( $this->mainLB );
 259                 }
 260
 261                 return $this->mainLB;
 262         }
 263
 264         /**
 265          * @throws MWException
 266          * @param string $cluster
 267          * @param bool|string $wiki
 268          * @return LoadBalancer
 269          */
 270         function newExternalLB( $cluster, $wiki = false ) {
 271                 global $wgExternalServers;
 272                 if ( !isset( $wgExternalServers[$cluster] ) ) {
 273                         throw new MWException( __METHOD__ . ": Unknown cluster \"$cluster\"" );
 274                 }
 275
 276                 return new LoadBalancer( array(
 277                         'servers' => $wgExternalServers[$cluster]
 278                 ) );
 279         }
 280
 281         /**
 282          * @param string $cluster
 283          * @param bool|string $wiki
 284          * @return array
 285          */
 286         function &getExternalLB( $cluster, $wiki = false ) {
 287                 if ( !isset( $this->extLBs[$cluster] ) ) {
 288                         $this->extLBs[$cluster] = $this->newExternalLB( $cluster, $wiki );
 289                         $this->extLBs[$cluster]->parentInfo( array( 'id' => "ext-$cluster" ) );
 290                         $this->chronProt->initLB( $this->extLBs[$cluster] );
 291                 }
 292
 293                 return $this->extLBs[$cluster];
 294         }
 295
 296         /**
 297          * Execute a function for each tracked load balancer
 298          * The callback is called with the load balancer as the first parameter,
 299          * and $params passed as the subsequent parameters.
 300          *
 301          * @param callable $callback
 302          * @param array $params
 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 }