includes/deferred/DataUpdate.php

   1 <?php
   2 /**
   3  * Base code for update jobs that do something with some secondary
   4  * data extracted from article.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with this program; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  19  * http://www.gnu.org/copyleft/gpl.html
  20  *
  21  * @file
  22  */
  23
  24 /**
  25  * Abstract base class for update jobs that do something with some secondary
  26  * data extracted from article.
  27  *
  28  * @note subclasses should NOT start or commit transactions in their doUpdate() method,
  29  *       a transaction will automatically be wrapped around the update. If need be,
  30  *       subclasses can override the beginTransaction() and commitTransaction() methods.
  31  */
  32 abstract class DataUpdate implements DeferrableUpdate {
  33         /**
  34          * Constructor
  35          */
  36         public function __construct() {
  37                 # noop
  38         }
  39
  40         /**
  41          * Begin an appropriate transaction, if any.
  42          * This default implementation does nothing.
  43          */
  44         public function beginTransaction() {
  45                 //noop
  46         }
  47
  48         /**
  49          * Commit the transaction started via beginTransaction, if any.
  50          * This default implementation does nothing.
  51          */
  52         public function commitTransaction() {
  53                 //noop
  54         }
  55
  56         /**
  57          * Abort / roll back the transaction started via beginTransaction, if any.
  58          * This default implementation does nothing.
  59          */
  60         public function rollbackTransaction() {
  61                 //noop
  62         }
  63
  64         /**
  65          * Convenience method, calls doUpdate() on every DataUpdate in the array.
  66          *
  67          * This methods supports transactions logic by first calling beginTransaction()
  68          * on all updates in the array, then calling doUpdate() on each, and, if all goes well,
  69          * then calling commitTransaction() on each update. If an error occurs,
  70          * rollbackTransaction() will be called on any update object that had beginTransaction()
  71          * called but not yet commitTransaction().
  72          *
  73          * This allows for limited transactional logic across multiple backends for storing
  74          * secondary data.
  75          *
  76          * @param array $updates a list of DataUpdate instances
  77          * @throws Exception|null
  78          */
  79         public static function runUpdates( $updates ) {
  80                 if ( empty( $updates ) ) {
  81                         return; # nothing to do
  82                 }
  83
  84                 $open_transactions = array();
  85                 $exception = null;
  86
  87                 /**
  88                  * @var $update DataUpdate
  89                  * @var $trans DataUpdate
  90                  */
  91
  92                 try {
  93                         // begin transactions
  94                         foreach ( $updates as $update ) {
  95                                 $update->beginTransaction();
  96                                 $open_transactions[] = $update;
  97                         }
  98
  99                         // do work
 100                         foreach ( $updates as $update ) {
 101                                 $update->doUpdate();
 102                         }
 103
 104                         // commit transactions
 105                         while ( count( $open_transactions ) > 0 ) {
 106                                 $trans = array_pop( $open_transactions );
 107                                 $trans->commitTransaction();
 108                         }
 109                 } catch ( Exception $ex ) {
 110                         $exception = $ex;
 111                         wfDebug( "Caught exception, will rethrow after rollback: " .
 112                                 $ex->getMessage() . "\n" );
 113                 }
 114
 115                 // rollback remaining transactions
 116                 while ( count( $open_transactions ) > 0 ) {
 117                         $trans = array_pop( $open_transactions );
 118                         $trans->rollbackTransaction();
 119                 }
 120
 121                 if ( $exception ) {
 122                         throw $exception; // rethrow after cleanup
 123                 }
 124         }
 125 }