includes/DataUpdate.php

   1 <?php
   2 /**
   3  * See docs/deferred.txt
   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  * Abstract base class for update jobs that do something with some secondary
  21  * data extracted from article.
  22  */
  23 abstract class DataUpdate implements DeferrableUpdate {
  24
  25         /**
  26          * Constructor
  27          */
  28         public function __construct( ) {
  29                 # noop
  30         }
  31
  32         /**
  33          * Begin an appropriate transaction, if any.
  34          * This default implementation does nothing.
  35          */
  36         public function beginTransaction() {
  37                 //noop
  38         }
  39
  40         /**
  41          * Commit the transaction started via beginTransaction, if any.
  42          * This default implementation does nothing.
  43          */
  44         public function commitTransaction() {
  45                 //noop
  46         }
  47
  48         /**
  49          * Abort / roll back the transaction started via beginTransaction, if any.
  50          * This default implementation does nothing.
  51          */
  52         public function rollbackTransaction() {
  53                 //noop
  54         }
  55
  56         /**
  57          * Convenience method, calls doUpdate() on every DataUpdate in the array.
  58          *
  59          * This methods supports transactions logic by first calling beginTransaction()
  60          * on all updates in the array, then calling doUpdate() on each, and, if all goes well,
  61          * then calling commitTransaction() on each update. If an error occurrs,
  62          * rollbackTransaction() will be called on any update object that had beginTranscation()
  63          * called but not yet commitTransaction().
  64          *
  65          * This allows for limited transactional logic across multiple backends for storing
  66          * secondary data.
  67          *
  68          * @static
  69          * @param $updates array a list of DataUpdate instances
  70          */
  71         public static function runUpdates( $updates ) {
  72                 if ( empty( $updates ) ) return; # nothing to do
  73
  74                 $open_transactions = array();
  75                 $exception = null;
  76
  77                 /**
  78                  * @var $update StorageUpdate
  79                  * @var $trans StorageUpdate
  80                  */
  81
  82                 try {
  83                         // begin transactions
  84                         foreach ( $updates as $update ) {
  85                                 $update->beginTransaction();
  86                                 $open_transactions[] = $update;
  87                         }
  88
  89                         // do work
  90                         foreach ( $updates as $update ) {
  91                                 $update->doUpdate();
  92                         }
  93
  94                         // commit transactions
  95                         while ( count( $open_transactions ) > 0 ) {
  96                                 $trans = array_pop( $open_transactions );
  97                                 $trans->commitTransaction();
  98                         }
  99                 } catch ( Exception $ex ) {
 100                         $exception = $ex;
 101                         wfDebug( "Caught exception, will rethrow after rollback: " . $ex->getMessage() );
 102                 }
 103
 104                 // rollback remaining transactions
 105                 while ( count( $open_transactions ) > 0 ) {
 106                         $trans = array_pop( $open_transactions );
 107                         $trans->rollbackTransaction();
 108                 }
 109
 110                 if ( $exception ) {
 111                         throw $exception; // rethrow after cleanup
 112                 }
 113         }
 114
 115 }