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