includes/deferred/DeferredUpdates.php

   1 <?php
   2 /**
   3  * Interface and manager for deferred updates.
   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  */
  22
  23 /**
  24  * Interface that deferrable updates should implement. Basically required so we
  25  * can validate input on DeferredUpdates::addUpdate()
  26  *
  27  * @since 1.19
  28  */
  29 interface DeferrableUpdate {
  30         /**
  31          * Perform the actual work
  32          */
  33         function doUpdate();
  34 }
  35
  36 /**
  37  * Class for managing the deferred updates
  38  *
  39  * Deferred updates can be run at the end of the request,
  40  * after the HTTP response has been sent. In CLI mode, updates
  41  * are only deferred until there is no local master DB transaction.
  42  * When updates are deferred, they go into a simple FIFO queue.
  43  *
  44  * @since 1.19
  45  */
  46 class DeferredUpdates {
  47         /**
  48          * @var array Updates to be deferred until the end of the request.
  49          */
  50         private static $updates = array();
  51
  52         /**
  53          * Add an update to the deferred list
  54          * @param DeferrableUpdate $update Some object that implements doUpdate()
  55          */
  56         public static function addUpdate( DeferrableUpdate $update ) {
  57                 global $wgCommandLineMode;
  58
  59                 array_push( self::$updates, $update );
  60
  61                 // CLI scripts may forget to periodically flush these updates,
  62                 // so try to handle that rather than OOMing and losing them.
  63                 // Try to run the updates as soon as there is no local transaction.
  64                 static $waitingOnTrx = false; // de-duplicate callback
  65                 if ( $wgCommandLineMode && !$waitingOnTrx ) {
  66                         $lb = wfGetLB();
  67                         $dbw = $lb->getAnyOpenConnection( $lb->getWriterIndex() );
  68                         // Do the update as soon as there is no transaction
  69                         if ( $dbw && $dbw->trxLevel() ) {
  70                                 $waitingOnTrx = true;
  71                                 $dbw->onTransactionIdle( function() use ( &$waitingOnTrx ) {
  72                                         DeferredUpdates::doUpdates();
  73                                         $waitingOnTrx = false;
  74                                 } );
  75                         } else {
  76                                 self::doUpdates();
  77                         }
  78                 }
  79         }
  80
  81         /**
  82          * Add a callable update.  In a lot of cases, we just need a callback/closure,
  83          * defining a new DeferrableUpdate object is not necessary
  84          * @see MWCallableUpdate::__construct()
  85          * @param callable $callable
  86          */
  87         public static function addCallableUpdate( $callable ) {
  88                 self::addUpdate( new MWCallableUpdate( $callable ) );
  89         }
  90
  91         /**
  92          * Do any deferred updates and clear the list
  93          *
  94          * @param string $commit Set to 'commit' to commit after every update to
  95          *   prevent lock contention
  96          */
  97         public static function doUpdates( $commit = '' ) {
  98                 $updates = self::$updates;
  99
 100                 while ( count( $updates ) ) {
 101                         self::clearPendingUpdates();
 102
 103                         /** @var DeferrableUpdate $update */
 104                         foreach ( $updates as $update ) {
 105                                 try {
 106                                         $update->doUpdate();
 107
 108                                         if ( $commit === 'commit' ) {
 109                                                 wfGetLBFactory()->commitMasterChanges();
 110                                         }
 111                                 } catch ( Exception $e ) {
 112                                         // We don't want exceptions thrown during deferred updates to
 113                                         // be reported to the user since the output is already sent.
 114                                         // Instead we just log them.
 115                                         if ( !$e instanceof ErrorPageError ) {
 116                                                 MWExceptionHandler::logException( $e );
 117                                         }
 118                                 }
 119                         }
 120
 121                         $updates = self::$updates;
 122                 }
 123         }
 124
 125         /**
 126          * Clear all pending updates without performing them. Generally, you don't
 127          * want or need to call this. Unit tests need it though.
 128          */
 129         public static function clearPendingUpdates() {
 130                 self::$updates = array();
 131         }
 132 }