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