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         /**
  30          * @var LBFactory
  31          */
  32         static $instance;
  33
  34         /**
  35          * Disables all access to the load balancer, will cause all database access
  36          * to throw a DBAccessError
  37          */
  38         public static function disableBackend() {
  39                 global $wgLBFactoryConf;
  40                 self::$instance = new LBFactoryFake( $wgLBFactoryConf );
  41         }
  42
  43         /**
  44          * Get an LBFactory instance
  45          *
  46          * @return LBFactory
  47          */
  48         static function &singleton() {
  49                 global $wgLBFactoryConf;
  50
  51                 if ( is_null( self::$instance ) ) {
  52                         $class = self::getLBFactoryClass( $wgLBFactoryConf );
  53
  54                         self::$instance = new $class( $wgLBFactoryConf );
  55                 }
  56
  57                 return self::$instance;
  58         }
  59
  60         /**
  61          * Returns the LBFactory class to use and the load balancer configuration.
  62          *
  63          * @param array $config (e.g. $wgLBFactoryConf)
  64          *
  65          * @return string class name
  66          */
  67         public static function getLBFactoryClass( array $config ) {
  68                 // For configuration backward compatibility after removing
  69                 // underscores from class names in MediaWiki 1.23.
  70                 $bcClasses = array(
  71                         'LBFactory_Simple' => 'LBFactorySimple',
  72                         'LBFactory_Single' => 'LBFactorySingle',
  73                         'LBFactory_Multi' => 'LBFactoryMulti',
  74                         'LBFactory_Fake' => 'LBFactoryFake',
  75                 );
  76
  77                 $class = $config['class'];
  78
  79                 if ( isset( $bcClasses[$class] ) ) {
  80                         $class = $bcClasses[$class];
  81                         wfDeprecated(
  82                                 '$wgLBFactoryConf must be updated. See RELEASE-NOTES for details',
  83                                 '1.23'
  84                         );
  85                 }
  86
  87                 return $class;
  88         }
  89
  90         /**
  91          * Shut down, close connections and destroy the cached instance.
  92          */
  93         static function destroyInstance() {
  94                 if ( self::$instance ) {
  95                         self::$instance->shutdown();
  96                         self::$instance->forEachLBCallMethod( 'closeAll' );
  97                         self::$instance = null;
  98                 }
  99         }
 100
 101         /**
 102          * Set the instance to be the given object
 103          *
 104          * @param $instance LBFactory
 105          */
 106         static function setInstance( $instance ) {
 107                 self::destroyInstance();
 108                 self::$instance = $instance;
 109         }
 110
 111         /**
 112          * Construct a factory based on a configuration array (typically from $wgLBFactoryConf)
 113          * @param $conf
 114          */
 115         abstract function __construct( $conf );
 116
 117         /**
 118          * Create a new load balancer object. The resulting object will be untracked,
 119          * not chronology-protected, and the caller is responsible for cleaning it up.
 120          *
 121          * @param string $wiki wiki ID, or false for the current wiki
 122          * @return LoadBalancer
 123          */
 124         abstract function newMainLB( $wiki = false );
 125
 126         /**
 127          * Get a cached (tracked) load balancer object.
 128          *
 129          * @param string $wiki wiki ID, or false for the current wiki
 130          * @return LoadBalancer
 131          */
 132         abstract function getMainLB( $wiki = false );
 133
 134         /**
 135          * Create a new load balancer for external storage. The resulting object will be
 136          * untracked, not chronology-protected, and the caller is responsible for
 137          * cleaning it up.
 138          *
 139          * @param string $cluster external storage cluster, or false for core
 140          * @param string $wiki wiki ID, or false for the current wiki
 141          *
 142          * @return LoadBalancer
 143          */
 144         abstract function newExternalLB( $cluster, $wiki = false );
 145
 146         /**
 147          * Get a cached (tracked) load balancer for external storage
 148          *
 149          * @param string $cluster external storage cluster, or false for core
 150          * @param string $wiki wiki ID, or false for the current wiki
 151          *
 152          * @return LoadBalancer
 153          */
 154         abstract function &getExternalLB( $cluster, $wiki = false );
 155
 156         /**
 157          * Execute a function for each tracked load balancer
 158          * The callback is called with the load balancer as the first parameter,
 159          * and $params passed as the subsequent parameters.
 160          * @param $callback string|array
 161          * @param array $params
 162          */
 163         abstract function forEachLB( $callback, $params = array() );
 164
 165         /**
 166          * Prepare all tracked load balancers for shutdown
 167          * STUB
 168          */
 169         function shutdown() {
 170         }
 171
 172         /**
 173          * Call a method of each tracked load balancer
 174          * @param $methodName string
 175          * @param $args array
 176          */
 177         function forEachLBCallMethod( $methodName, $args = array() ) {
 178                 $this->forEachLB( array( $this, 'callMethod' ), array( $methodName, $args ) );
 179         }
 180
 181         /**
 182          * Private helper for forEachLBCallMethod
 183          * @param $loadBalancer
 184          * @param $methodName string
 185          * @param $args
 186          */
 187         function callMethod( $loadBalancer, $methodName, $args ) {
 188                 call_user_func_array( array( $loadBalancer, $methodName ), $args );
 189         }
 190
 191         /**
 192          * Commit changes on all master connections
 193          */
 194         function commitMasterChanges() {
 195                 $this->forEachLBCallMethod( 'commitMasterChanges' );
 196         }
 197 }
 198
 199 /**
 200  * A simple single-master LBFactory that gets its configuration from the b/c globals
 201  */
 202 class LBFactorySimple extends LBFactory {
 203
 204         /**
 205          * @var LoadBalancer
 206          */
 207         var $mainLB;
 208         var $extLBs = array();
 209
 210         # Chronology protector
 211         var $chronProt;
 212
 213         function __construct( $conf ) {
 214                 $this->chronProt = new ChronologyProtector;
 215         }
 216
 217         /**
 218          * @param $wiki
 219          * @return LoadBalancer
 220          */
 221         function newMainLB( $wiki = false ) {
 222                 global $wgDBservers, $wgMasterWaitTimeout;
 223                 if ( $wgDBservers ) {
 224                         $servers = $wgDBservers;
 225                 } else {
 226                         global $wgDBserver, $wgDBuser, $wgDBpassword, $wgDBname, $wgDBtype, $wgDebugDumpSql;
 227                         global $wgDBssl, $wgDBcompress;
 228
 229                         $flags = ( $wgDebugDumpSql ? DBO_DEBUG : 0 ) | DBO_DEFAULT;
 230                         if ( $wgDBssl ) {
 231                                 $flags |= DBO_SSL;
 232                         }
 233                         if ( $wgDBcompress ) {
 234                                 $flags |= DBO_COMPRESS;
 235                         }
 236
 237                         $servers = array( array(
 238                                 'host' => $wgDBserver,
 239                                 'user' => $wgDBuser,
 240                                 'password' => $wgDBpassword,
 241                                 'dbname' => $wgDBname,
 242                                 'type' => $wgDBtype,
 243                                 'load' => 1,
 244                                 'flags' => $flags
 245                         ) );
 246                 }
 247
 248                 return new LoadBalancer( array(
 249                         'servers' => $servers,
 250                         'masterWaitTimeout' => $wgMasterWaitTimeout
 251                 ) );
 252         }
 253
 254         /**
 255          * @param $wiki
 256          * @return LoadBalancer
 257          */
 258         function getMainLB( $wiki = false ) {
 259                 if ( !isset( $this->mainLB ) ) {
 260                         $this->mainLB = $this->newMainLB( $wiki );
 261                         $this->mainLB->parentInfo( array( 'id' => 'main' ) );
 262                         $this->chronProt->initLB( $this->mainLB );
 263                 }
 264
 265                 return $this->mainLB;
 266         }
 267
 268         /**
 269          * @throws MWException
 270          * @param $cluster
 271          * @param $wiki
 272          * @return LoadBalancer
 273          */
 274         function newExternalLB( $cluster, $wiki = false ) {
 275                 global $wgExternalServers;
 276                 if ( !isset( $wgExternalServers[$cluster] ) ) {
 277                         throw new MWException( __METHOD__ . ": Unknown cluster \"$cluster\"" );
 278                 }
 279
 280                 return new LoadBalancer( array(
 281                         'servers' => $wgExternalServers[$cluster]
 282                 ) );
 283         }
 284
 285         /**
 286          * @param $cluster
 287          * @param $wiki
 288          * @return array
 289          */
 290         function &getExternalLB( $cluster, $wiki = false ) {
 291                 if ( !isset( $this->extLBs[$cluster] ) ) {
 292                         $this->extLBs[$cluster] = $this->newExternalLB( $cluster, $wiki );
 293                         $this->extLBs[$cluster]->parentInfo( array( 'id' => "ext-$cluster" ) );
 294                         $this->chronProt->initLB( $this->extLBs[$cluster] );
 295                 }
 296
 297                 return $this->extLBs[$cluster];
 298         }
 299
 300         /**
 301          * Execute a function for each tracked load balancer
 302          * The callback is called with the load balancer as the first parameter,
 303          * and $params passed as the subsequent parameters.
 304          * @param $callback
 305          * @param $params array
 306          */
 307         function forEachLB( $callback, $params = array() ) {
 308                 if ( isset( $this->mainLB ) ) {
 309                         call_user_func_array( $callback, array_merge( array( $this->mainLB ), $params ) );
 310                 }
 311                 foreach ( $this->extLBs as $lb ) {
 312                         call_user_func_array( $callback, array_merge( array( $lb ), $params ) );
 313                 }
 314         }
 315
 316         function shutdown() {
 317                 if ( $this->mainLB ) {
 318                         $this->chronProt->shutdownLB( $this->mainLB );
 319                 }
 320                 foreach ( $this->extLBs as $extLB ) {
 321                         $this->chronProt->shutdownLB( $extLB );
 322                 }
 323                 $this->chronProt->shutdown();
 324                 $this->commitMasterChanges();
 325         }
 326 }
 327
 328 /**
 329  * LBFactory class that throws an error on any attempt to use it.
 330  * This will typically be done via wfGetDB().
 331  * Call LBFactory::disableBackend() to start using this, and
 332  * LBFactory::enableBackend() to return to normal behavior
 333  */
 334 class LBFactoryFake extends LBFactory {
 335         function __construct( $conf ) {
 336         }
 337
 338         function newMainLB( $wiki = false ) {
 339                 throw new DBAccessError;
 340         }
 341
 342         function getMainLB( $wiki = false ) {
 343                 throw new DBAccessError;
 344         }
 345
 346         function newExternalLB( $cluster, $wiki = false ) {
 347                 throw new DBAccessError;
 348         }
 349
 350         function &getExternalLB( $cluster, $wiki = false ) {
 351                 throw new DBAccessError;
 352         }
 353
 354         function forEachLB( $callback, $params = array() ) {
 355         }
 356 }
 357
 358 /**
 359  * Exception class for attempted DB access
 360  */
 361 class DBAccessError extends MWException {
 362         function __construct() {
 363                 parent::__construct( "Mediawiki tried to access the database via wfGetDB(). " .
 364                         "This is not allowed." );
 365         }
 366 }