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