includes/JobQueue.php

   1 <?php
   2
   3 if ( !defined( 'MEDIAWIKI' ) ) {
   4         die( "This file is part of MediaWiki, it is not a valid entry point\n" );
   5 }
   6
   7 /**
   8  * Class to both describe a background job and handle jobs.
   9  */
  10 abstract class Job {
  11         var $command,
  12                 $title,
  13                 $params,
  14                 $id,
  15                 $removeDuplicates,
  16                 $error;
  17
  18         /*-------------------------------------------------------------------------
  19          * Abstract functions
  20          *------------------------------------------------------------------------*/
  21
  22         /**
  23          * Run the job
  24          * @return boolean success
  25          */
  26         abstract function run();
  27
  28         /*-------------------------------------------------------------------------
  29          * Static functions
  30          *------------------------------------------------------------------------*/
  31
  32         /**
  33          * @deprecated use LinksUpdate::queueRecursiveJobs()
  34          */
  35         /**
  36          * static function queueLinksJobs( $titles ) {}
  37          */
  38
  39         /**
  40          * Pop a job off the front of the queue
  41          * @static
  42          * @param $offset Number of jobs to skip
  43          * @return Job or false if there's no jobs
  44          */
  45         static function pop($offset=0) {
  46                 wfProfileIn( __METHOD__ );
  47
  48                 $dbr = wfGetDB( DB_SLAVE );
  49
  50                 /* Get a job from the slave, start with an offset,
  51                         scan full set afterwards, avoid hitting purged rows
  52
  53                         NB: If random fetch previously was used, offset
  54                                 will always be ahead of few entries
  55                 */
  56
  57                 $row = $dbr->selectRow( 'job', '*', "job_id >= ${offset}", __METHOD__,
  58                         array( 'ORDER BY' => 'job_id', 'LIMIT' => 1 ));
  59
  60                 // Refetching without offset is needed as some of job IDs could have had delayed commits
  61                 // and have lower IDs than jobs already executed, blame concurrency :)
  62                 //
  63                 if ( $row === false) {
  64                         if ($offset!=0)
  65                                 $row = $dbr->selectRow( 'job', '*', '', __METHOD__,
  66                                         array( 'ORDER BY' => 'job_id', 'LIMIT' => 1 ));
  67
  68                         if ($row === false ) {
  69                                 wfProfileOut( __METHOD__ );
  70                                 return false;
  71                         }
  72                 }
  73                 $offset = $row->job_id;
  74
  75                 // Try to delete it from the master
  76                 $dbw = wfGetDB( DB_MASTER );
  77                 $dbw->delete( 'job', array( 'job_id' => $row->job_id ), __METHOD__ );
  78                 $affected = $dbw->affectedRows();
  79                 $dbw->immediateCommit();
  80
  81                 if ( !$affected ) {
  82                         // Failed, someone else beat us to it
  83                         // Try getting a random row
  84                         $row = $dbw->selectRow( 'job', array( 'MIN(job_id) as minjob',
  85                                 'MAX(job_id) as maxjob' ), "job_id >= $offset", __METHOD__ );
  86                         if ( $row === false || is_null( $row->minjob ) || is_null( $row->maxjob ) ) {
  87                                 // No jobs to get
  88                                 wfProfileOut( __METHOD__ );
  89                                 return false;
  90                         }
  91                         // Get the random row
  92                         $row = $dbw->selectRow( 'job', '*',
  93                                 'job_id >= ' . mt_rand( $row->minjob, $row->maxjob ),   __METHOD__ );
  94                         if ( $row === false ) {
  95                                 // Random job gone before we got the chance to select it
  96                                 // Give up
  97                                 wfProfileOut( __METHOD__ );
  98                                 return false;
  99                         }
 100                         // Delete the random row
 101                         $dbw->delete( 'job', array( 'job_id' => $row->job_id ), __METHOD__ );
 102                         $affected = $dbw->affectedRows();
 103                         $dbw->immediateCommit();
 104
 105                         if ( !$affected ) {
 106                                 // Random job gone before we exclusively deleted it
 107                                 // Give up
 108                                 wfProfileOut( __METHOD__ );
 109                                 return false;
 110                         }
 111                 }
 112
 113                 // If execution got to here, there's a row in $row that has been deleted from the database
 114                 // by this thread. Hence the concurrent pop was successful.
 115                 $namespace = $row->job_namespace;
 116                 $dbkey = $row->job_title;
 117                 $title = Title::makeTitleSafe( $namespace, $dbkey );
 118                 $job = Job::factory( $row->job_cmd, $title, Job::extractBlob( $row->job_params ), $row->job_id );
 119
 120                 // Remove any duplicates it may have later in the queue
 121                 $dbw->delete( 'job', $job->insertFields(), __METHOD__ );
 122
 123                 wfProfileOut( __METHOD__ );
 124                 return $job;
 125         }
 126
 127         /**
 128          * Create an object of a subclass
 129          */
 130         static function factory( $command, $title, $params = false, $id = 0 ) {
 131                 switch ( $command ) {
 132                         case 'refreshLinks':
 133                                 return new RefreshLinksJob( $title, $params, $id );
 134                         case 'htmlCacheUpdate':
 135                         case 'html_cache_update': # BC
 136                                 return new HTMLCacheUpdateJob( $title, $params['table'], $params['start'], $params['end'], $id );
 137                         default:
 138                                 throw new MWException( "Invalid job command \"$command\"" );
 139                 }
 140         }
 141
 142         static function makeBlob( $params ) {
 143                 if ( $params !== false ) {
 144                         return serialize( $params );
 145                 } else {
 146                         return '';
 147                 }
 148         }
 149
 150         static function extractBlob( $blob ) {
 151                 if ( (string)$blob !== '' ) {
 152                         return unserialize( $blob );
 153                 } else {
 154                         return false;
 155                 }
 156         }
 157
 158         /**
 159          * Batch-insert a group of jobs into the queue.
 160          * This will be wrapped in a transaction with a forced commit.
 161          *
 162          * This may add duplicate at insert time, but they will be
 163          * removed later on, when the first one is popped.
 164          *
 165          * @param $jobs array of Job objects
 166          */
 167         static function batchInsert( $jobs ) {
 168                 if( count( $jobs ) ) {
 169                         $dbw = wfGetDB( DB_MASTER );
 170                         $dbw->begin();
 171                         foreach( $jobs as $job ) {
 172                                 $rows[] = $job->insertFields();
 173                         }
 174                         $dbw->insert( 'job', $rows, __METHOD__, 'IGNORE' );
 175                         $dbw->commit();
 176                 }
 177         }
 178
 179         /*-------------------------------------------------------------------------
 180          * Non-static functions
 181          *------------------------------------------------------------------------*/
 182
 183         function __construct( $command, $title, $params = false, $id = 0 ) {
 184                 $this->command = $command;
 185                 $this->title = $title;
 186                 $this->params = $params;
 187                 $this->id = $id;
 188
 189                 // A bit of premature generalisation
 190                 // Oh well, the whole class is premature generalisation really
 191                 $this->removeDuplicates = true;
 192         }
 193
 194         /**
 195          * Insert a single job into the queue.
 196          */
 197         function insert() {
 198                 $fields = $this->insertFields();
 199
 200                 $dbw = wfGetDB( DB_MASTER );
 201
 202                 if ( $this->removeDuplicates ) {
 203                         $res = $dbw->select( 'job', array( '1' ), $fields, __METHOD__ );
 204                         if ( $dbw->numRows( $res ) ) {
 205                                 return;
 206                         }
 207                 }
 208                 $fields['job_id'] = $dbw->nextSequenceValue( 'job_job_id_seq' );
 209                 $dbw->insert( 'job', $fields, __METHOD__ );
 210         }
 211
 212         protected function insertFields() {
 213                 return array(
 214                         'job_cmd' => $this->command,
 215                         'job_namespace' => $this->title->getNamespace(),
 216                         'job_title' => $this->title->getDBkey(),
 217                         'job_params' => Job::makeBlob( $this->params )
 218                 );
 219         }
 220
 221         function toString() {
 222                 $paramString = '';
 223                 if ( $this->params ) {
 224                         foreach ( $this->params as $key => $value ) {
 225                                 if ( $paramString != '' ) {
 226                                         $paramString .= ' ';
 227                                 }
 228                                 $paramString .= "$key=$value";
 229                         }
 230                 }
 231
 232                 if ( is_object( $this->title ) ) {
 233                         $s = "{$this->command} " . $this->title->getPrefixedDBkey();
 234                         if ( $paramString !== '' ) {
 235                                 $s .= ' ' . $paramString;
 236                         }
 237                         return $s;
 238                 } else {
 239                         return "{$this->command} $paramString";
 240                 }
 241         }
 242
 243         function getLastError() {
 244                 return $this->error;
 245         }
 246 }
 247
 248
 249 /**
 250  * Background job to update links for a given title.
 251  */
 252 class RefreshLinksJob extends Job {
 253         function __construct( $title, $params = '', $id = 0 ) {
 254                 parent::__construct( 'refreshLinks', $title, $params, $id );
 255         }
 256
 257         /**
 258          * Run a refreshLinks job
 259          * @return boolean success
 260          */
 261         function run() {
 262                 global $wgParser;
 263                 wfProfileIn( __METHOD__ );
 264
 265                 $linkCache =& LinkCache::singleton();
 266                 $linkCache->clear();
 267
 268                 if ( is_null( $this->title ) ) {
 269                         $this->error = "refreshLinks: Invalid title";
 270                         wfProfileOut( __METHOD__ );
 271                         return false;
 272                 }
 273
 274                 $revision = Revision::newFromTitle( $this->title );
 275                 if ( !$revision ) {
 276                         $this->error = 'refreshLinks: Article not found "' . $this->title->getPrefixedDBkey() . '"';
 277                         wfProfileOut( __METHOD__ );
 278                         return false;
 279                 }
 280
 281                 wfProfileIn( __METHOD__.'-parse' );
 282                 $options = new ParserOptions;
 283                 $parserOutput = $wgParser->parse( $revision->getText(), $this->title, $options, true, true, $revision->getId() );
 284                 wfProfileOut( __METHOD__.'-parse' );
 285                 wfProfileIn( __METHOD__.'-update' );
 286                 $update = new LinksUpdate( $this->title, $parserOutput, false );
 287                 $update->doUpdate();
 288                 wfProfileOut( __METHOD__.'-update' );
 289                 wfProfileOut( __METHOD__ );
 290                 return true;
 291         }
 292 }
 293
 294 ?>