includes/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         /**
  35          * Constructor
  36          */
  37         public function __construct() {
  38                 # noop
  39         }
  40
  41         /**
  42          * Begin an appropriate transaction, if any.
  43          * This default implementation does nothing.
  44          */
  45         public function beginTransaction() {
  46                 //noop
  47         }
  48
  49         /**
  50          * Commit the transaction started via beginTransaction, if any.
  51          * This default implementation does nothing.
  52          */
  53         public function commitTransaction() {
  54                 //noop
  55         }
  56
  57         /**
  58          * Abort / roll back the transaction started via beginTransaction, if any.
  59          * This default implementation does nothing.
  60          */
  61         public function rollbackTransaction() {
  62                 //noop
  63         }
  64
  65         /**
  66          * Convenience method, calls doUpdate() on every DataUpdate in the array.
  67          *
  68          * This methods supports transactions logic by first calling beginTransaction()
  69          * on all updates in the array, then calling doUpdate() on each, and, if all goes well,
  70          * then calling commitTransaction() on each update. If an error occurs,
  71          * rollbackTransaction() will be called on any update object that had beginTransaction()
  72          * called but not yet commitTransaction().
  73          *
  74          * This allows for limited transactional logic across multiple backends for storing
  75          * secondary data.
  76          *
  77          * @param array $updates a list of DataUpdate instances
  78          * @throws Exception|null
  79          */
  80         public static function runUpdates( $updates ) {
  81                 if ( empty( $updates ) ) return; # nothing to do
  82
  83                 $open_transactions = array();
  84                 $exception = null;
  85
  86                 /**
  87                  * @var $update DataUpdate
  88                  * @var $trans DataUpdate
  89                  */
  90
  91                 try {
  92                         // begin transactions
  93                         foreach ( $updates as $update ) {
  94                                 $update->beginTransaction();
  95                                 $open_transactions[] = $update;
  96                         }
  97
  98                         // do work
  99                         foreach ( $updates as $update ) {
 100                                 $update->doUpdate();
 101                         }
 102
 103                         // commit transactions
 104                         while ( count( $open_transactions ) > 0 ) {
 105                                 $trans = array_pop( $open_transactions );
 106                                 $trans->commitTransaction();
 107                         }
 108                 } catch ( Exception $ex ) {
 109                         $exception = $ex;
 110                         wfDebug( "Caught exception, will rethrow after rollback: " . $ex->getMessage() );
 111                 }
 112
 113                 // rollback remaining transactions
 114                 while ( count( $open_transactions ) > 0 ) {
 115                         $trans = array_pop( $open_transactions );
 116                         $trans->rollbackTransaction();
 117                 }
 118
 119                 if ( $exception ) {
 120                         throw $exception; // rethrow after cleanup
 121                 }
 122         }
 123
 124 }