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         public function __construct() {
  34                 // noop
  35         }
  36
  37         /**
  38          * Begin an appropriate transaction, if any.
  39          * This default implementation does nothing.
  40          */
  41         public function beginTransaction() {
  42                 // noop
  43         }
  44
  45         /**
  46          * Commit the transaction started via beginTransaction, if any.
  47          * This default implementation does nothing.
  48          */
  49         public function commitTransaction() {
  50                 // noop
  51         }
  52
  53         /**
  54          * Abort / roll back the transaction started via beginTransaction, if any.
  55          * This default implementation does nothing.
  56          */
  57         public function rollbackTransaction() {
  58                 // noop
  59         }
  60
  61         /**
  62          * Convenience method, calls doUpdate() on every DataUpdate in the array.
  63          *
  64          * This methods supports transactions logic by first calling beginTransaction()
  65          * on all updates in the array, then calling doUpdate() on each, and, if all goes well,
  66          * then calling commitTransaction() on each update. If an error occurs,
  67          * rollbackTransaction() will be called on any update object that had beginTransaction()
  68          * called but not yet commitTransaction().
  69          *
  70          * This allows for limited transactional logic across multiple backends for storing
  71          * secondary data.
  72          *
  73          * @param DataUpdate[] $updates A list of DataUpdate instances
  74          * @param string $mode Use "enqueue" to use the job queue when possible [Default: run]
  75          * @throws Exception|null
  76          */
  77         public static function runUpdates( array $updates, $mode = 'run' ) {
  78                 if ( $mode === 'enqueue' ) {
  79                         // When possible, push updates as jobs instead of calling doUpdate()
  80                         $updates = self::enqueueUpdates( $updates );
  81                 }
  82
  83                 if ( !count( $updates ) ) {
  84                         return; // nothing to do
  85                 }
  86
  87                 $open_transactions = array();
  88                 $exception = null;
  89
  90                 try {
  91                         // begin transactions
  92                         foreach ( $updates as $update ) {
  93                                 $update->beginTransaction();
  94                                 $open_transactions[] = $update;
  95                         }
  96
  97                         // do work
  98                         foreach ( $updates as $update ) {
  99                                 $update->doUpdate();
 100                         }
 101
 102                         // commit transactions
 103                         while ( count( $open_transactions ) > 0 ) {
 104                                 $trans = array_pop( $open_transactions );
 105                                 $trans->commitTransaction();
 106                         }
 107                 } catch ( Exception $ex ) {
 108                         $exception = $ex;
 109                         wfDebug( "Caught exception, will rethrow after rollback: " .
 110                                 $ex->getMessage() . "\n" );
 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         /**
 125          * Enqueue jobs for every DataUpdate that support enqueueUpdate()
 126          * and return the remaining DataUpdate objects (those that do not)
 127          *
 128          * @param DataUpdate[] $updates A list of DataUpdate instances
 129          * @return DataUpdate[]
 130          * @since 1.27
 131          */
 132         protected static function enqueueUpdates( array $updates ) {
 133                 $remaining = array();
 134
 135                 foreach ( $updates as $update ) {
 136                         if ( $update instanceof EnqueueableDataUpdate ) {
 137                                 $spec = $update->getAsJobSpecification();
 138                                 JobQueueGroup::singleton( $spec['wiki'] )->push( $spec['job'] );
 139                         } else {
 140                                 $remaining[] = $update;
 141                         }
 142                 }
 143
 144                 return $remaining;
 145         }
 146 }
 147
 148 /**
 149  * Interface that marks a DataUpdate as enqueuable via the JobQueue
 150  *
 151  * Such updates must be representable using IJobSpecification, so that
 152  * they can be serialized into jobs and enqueued for later execution
 153  *
 154  * @since 1.27
 155  */
 156 interface EnqueueableDataUpdate {
 157         /**
 158          * @return array (wiki => wiki ID, job => IJobSpecification)
 159          */
 160         public function getAsJobSpecification();
 161 }