includes/job/Job.php

   1 <?php
   2 /**
   3  * Job queue base code.
   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  * @file
  21  * @defgroup JobQueue JobQueue
  22  */
  23
  24 /**
  25  * Class to both describe a background job and handle jobs.
  26  *
  27  * @ingroup JobQueue
  28  */
  29 abstract class Job {
  30
  31         /**
  32          * @var Title
  33          */
  34         var $title;
  35
  36         var $command,
  37                 $params,
  38                 $id,
  39                 $removeDuplicates,
  40                 $error;
  41
  42         /*-------------------------------------------------------------------------
  43          * Abstract functions
  44          *------------------------------------------------------------------------*/
  45
  46         /**
  47          * Run the job
  48          * @return boolean success
  49          */
  50         abstract function run();
  51
  52         /*-------------------------------------------------------------------------
  53          * Static functions
  54          *------------------------------------------------------------------------*/
  55
  56         /**
  57          * Pop a job of a certain type.  This tries less hard than pop() to
  58          * actually find a job; it may be adversely affected by concurrent job
  59          * runners.
  60          *
  61          * @param $type string
  62          *
  63          * @return Job
  64          */
  65         static function pop_type( $type ) {
  66                 wfProfilein( __METHOD__ );
  67
  68                 $dbw = wfGetDB( DB_MASTER );
  69
  70                 $dbw->begin( __METHOD__ );
  71
  72                 $row = $dbw->selectRow(
  73                         'job',
  74                         '*',
  75                         array( 'job_cmd' => $type ),
  76                         __METHOD__,
  77                         array( 'LIMIT' => 1, 'FOR UPDATE' )
  78                 );
  79
  80                 if ( $row === false ) {
  81                         $dbw->commit( __METHOD__ );
  82                         wfProfileOut( __METHOD__ );
  83                         return false;
  84                 }
  85
  86                 /* Ensure we "own" this row */
  87                 $dbw->delete( 'job', array( 'job_id' => $row->job_id ), __METHOD__ );
  88                 $affected = $dbw->affectedRows();
  89                 $dbw->commit( __METHOD__ );
  90
  91                 if ( $affected == 0 ) {
  92                         wfProfileOut( __METHOD__ );
  93                         return false;
  94                 }
  95
  96                 wfIncrStats( 'job-pop' );
  97                 $namespace = $row->job_namespace;
  98                 $dbkey = $row->job_title;
  99                 $title = Title::makeTitleSafe( $namespace, $dbkey );
 100                 $job = Job::factory( $row->job_cmd, $title, Job::extractBlob( $row->job_params ),
 101                         $row->job_id );
 102
 103                 $job->removeDuplicates();
 104
 105                 wfProfileOut( __METHOD__ );
 106                 return $job;
 107         }
 108
 109         /**
 110          * Pop a job off the front of the queue
 111          *
 112          * @param $offset Integer: Number of jobs to skip
 113          * @return Job or false if there's no jobs
 114          */
 115         static function pop( $offset = 0 ) {
 116                 wfProfileIn( __METHOD__ );
 117
 118                 $dbr = wfGetDB( DB_SLAVE );
 119
 120                 /* Get a job from the slave, start with an offset,
 121                         scan full set afterwards, avoid hitting purged rows
 122
 123                         NB: If random fetch previously was used, offset
 124                                 will always be ahead of few entries
 125                 */
 126
 127                 $conditions = self::defaultQueueConditions();
 128
 129                 $offset = intval( $offset );
 130                 $options = array( 'ORDER BY' => 'job_id', 'USE INDEX' => 'PRIMARY' );
 131
 132                 $row = $dbr->selectRow( 'job', '*',
 133                         array_merge( $conditions, array( "job_id >= $offset" ) ),
 134                         __METHOD__,
 135                         $options
 136                 );
 137
 138                 // Refetching without offset is needed as some of job IDs could have had delayed commits
 139                 // and have lower IDs than jobs already executed, blame concurrency :)
 140                 //
 141                 if ( $row === false ) {
 142                         if ( $offset != 0 ) {
 143                                 $row = $dbr->selectRow( 'job', '*', $conditions, __METHOD__, $options );
 144                         }
 145
 146                         if ( $row === false ) {
 147                                 wfProfileOut( __METHOD__ );
 148                                 return false;
 149                         }
 150                 }
 151
 152                 // Try to delete it from the master
 153                 $dbw = wfGetDB( DB_MASTER );
 154                 $dbw->delete( 'job', array( 'job_id' => $row->job_id ), __METHOD__ );
 155                 $affected = $dbw->affectedRows();
 156                 $dbw->commit( __METHOD__ );
 157
 158                 if ( !$affected ) {
 159                         // Failed, someone else beat us to it
 160                         // Try getting a random row
 161                         $row = $dbw->selectRow( 'job', array( 'MIN(job_id) as minjob',
 162                                 'MAX(job_id) as maxjob' ), '1=1', __METHOD__ );
 163                         if ( $row === false || is_null( $row->minjob ) || is_null( $row->maxjob ) ) {
 164                                 // No jobs to get
 165                                 wfProfileOut( __METHOD__ );
 166                                 return false;
 167                         }
 168                         // Get the random row
 169                         $row = $dbw->selectRow( 'job', '*',
 170                                 'job_id >= ' . mt_rand( $row->minjob, $row->maxjob ), __METHOD__ );
 171                         if ( $row === false ) {
 172                                 // Random job gone before we got the chance to select it
 173                                 // Give up
 174                                 wfProfileOut( __METHOD__ );
 175                                 return false;
 176                         }
 177                         // Delete the random row
 178                         $dbw->delete( 'job', array( 'job_id' => $row->job_id ), __METHOD__ );
 179                         $affected = $dbw->affectedRows();
 180                         $dbw->commit( __METHOD__ );
 181
 182                         if ( !$affected ) {
 183                                 // Random job gone before we exclusively deleted it
 184                                 // Give up
 185                                 wfProfileOut( __METHOD__ );
 186                                 return false;
 187                         }
 188                 }
 189
 190                 // If execution got to here, there's a row in $row that has been deleted from the database
 191                 // by this thread. Hence the concurrent pop was successful.
 192                 wfIncrStats( 'job-pop' );
 193                 $namespace = $row->job_namespace;
 194                 $dbkey = $row->job_title;
 195                 $title = Title::makeTitleSafe( $namespace, $dbkey );
 196
 197                 if ( is_null( $title ) ) {
 198                         wfProfileOut( __METHOD__ );
 199                         return false;
 200                 }
 201
 202                 $job = Job::factory( $row->job_cmd, $title, Job::extractBlob( $row->job_params ), $row->job_id );
 203
 204                 // Remove any duplicates it may have later in the queue
 205                 $job->removeDuplicates();
 206
 207                 wfProfileOut( __METHOD__ );
 208                 return $job;
 209         }
 210
 211         /**
 212          * Create the appropriate object to handle a specific job
 213          *
 214          * @param $command String: Job command
 215          * @param $title Title: Associated title
 216          * @param $params Array: Job parameters
 217          * @param $id Int: Job identifier
 218          * @return Job
 219          */
 220         static function factory( $command, Title $title, $params = false, $id = 0 ) {
 221                 global $wgJobClasses;
 222                 if( isset( $wgJobClasses[$command] ) ) {
 223                         $class = $wgJobClasses[$command];
 224                         return new $class( $title, $params, $id );
 225                 }
 226                 throw new MWException( "Invalid job command `{$command}`" );
 227         }
 228
 229         /**
 230          * @param $params
 231          * @return string
 232          */
 233         static function makeBlob( $params ) {
 234                 if ( $params !== false ) {
 235                         return serialize( $params );
 236                 } else {
 237                         return '';
 238                 }
 239         }
 240
 241         /**
 242          * @param $blob
 243          * @return bool|mixed
 244          */
 245         static function extractBlob( $blob ) {
 246                 if ( (string)$blob !== '' ) {
 247                         return unserialize( $blob );
 248                 } else {
 249                         return false;
 250                 }
 251         }
 252
 253         /**
 254          * Batch-insert a group of jobs into the queue.
 255          * This will be wrapped in a transaction with a forced commit.
 256          *
 257          * This may add duplicate at insert time, but they will be
 258          * removed later on, when the first one is popped.
 259          *
 260          * @param $jobs array of Job objects
 261          */
 262         static function batchInsert( $jobs ) {
 263                 if ( !count( $jobs ) ) {
 264                         return;
 265                 }
 266                 $dbw = wfGetDB( DB_MASTER );
 267                 $rows = array();
 268
 269                 /**
 270                  * @var $job Job
 271                  */
 272                 foreach ( $jobs as $job ) {
 273                         $rows[] = $job->insertFields();
 274                         if ( count( $rows ) >= 50 ) {
 275                                 # Do a small transaction to avoid slave lag
 276                                 $dbw->begin( __METHOD__ );
 277                                 $dbw->insert( 'job', $rows, __METHOD__, 'IGNORE' );
 278                                 $dbw->commit( __METHOD__ );
 279                                 $rows = array();
 280                         }
 281                 }
 282                 if ( $rows ) { // last chunk
 283                         $dbw->begin( __METHOD__ );
 284                         $dbw->insert( 'job', $rows, __METHOD__, 'IGNORE' );
 285                         $dbw->commit( __METHOD__ );
 286                 }
 287                 wfIncrStats( 'job-insert', count( $jobs ) );
 288         }
 289
 290         /**
 291          * Insert a group of jobs into the queue.
 292          *
 293          * Same as batchInsert() but does not commit and can thus
 294          * be rolled-back as part of a larger transaction. However,
 295          * large batches of jobs can cause slave lag.
 296          *
 297          * @param $jobs array of Job objects
 298          */
 299         static function safeBatchInsert( $jobs ) {
 300                 if ( !count( $jobs ) ) {
 301                         return;
 302                 }
 303                 $dbw = wfGetDB( DB_MASTER );
 304                 $rows = array();
 305                 foreach ( $jobs as $job ) {
 306                         $rows[] = $job->insertFields();
 307                         if ( count( $rows ) >= 500 ) {
 308                                 $dbw->insert( 'job', $rows, __METHOD__, 'IGNORE' );
 309                                 $rows = array();
 310                         }
 311                 }
 312                 if ( $rows ) { // last chunk
 313                         $dbw->insert( 'job', $rows, __METHOD__, 'IGNORE' );
 314                 }
 315                 wfIncrStats( 'job-insert', count( $jobs ) );
 316         }
 317
 318
 319         /**
 320          * SQL conditions to apply on most JobQueue queries
 321          *
 322          * Whenever we exclude jobs types from the default queue, we want to make
 323          * sure that queries to the job queue actually ignore them.
 324          *
 325          * @return array SQL conditions suitable for Database:: methods
 326          */
 327         static function defaultQueueConditions( ) {
 328                 global $wgJobTypesExcludedFromDefaultQueue;
 329                 $conditions = array();
 330                 if ( count( $wgJobTypesExcludedFromDefaultQueue ) > 0 ) {
 331                         $dbr = wfGetDB( DB_SLAVE );
 332                         foreach ( $wgJobTypesExcludedFromDefaultQueue as $cmdType ) {
 333                                 $conditions[] = "job_cmd != " . $dbr->addQuotes( $cmdType );
 334                         }
 335                 }
 336                 return $conditions;
 337         }
 338
 339         /*-------------------------------------------------------------------------
 340          * Non-static functions
 341          *------------------------------------------------------------------------*/
 342
 343         /**
 344          * @param $command
 345          * @param $title
 346          * @param $params array
 347          * @param int $id
 348          */
 349         function __construct( $command, $title, $params = false, $id = 0 ) {
 350                 $this->command = $command;
 351                 $this->title = $title;
 352                 $this->params = $params;
 353                 $this->id = $id;
 354
 355                 // A bit of premature generalisation
 356                 // Oh well, the whole class is premature generalisation really
 357                 $this->removeDuplicates = true;
 358         }
 359
 360         /**
 361          * Insert a single job into the queue.
 362          * @return bool true on success
 363          */
 364         function insert() {
 365                 $fields = $this->insertFields();
 366
 367                 $dbw = wfGetDB( DB_MASTER );
 368
 369                 if ( $this->removeDuplicates ) {
 370                         $res = $dbw->select( 'job', array( '1' ), $fields, __METHOD__ );
 371                         if ( $dbw->numRows( $res ) ) {
 372                                 return true;
 373                         }
 374                 }
 375                 wfIncrStats( 'job-insert' );
 376                 return $dbw->insert( 'job', $fields, __METHOD__ );
 377         }
 378
 379         /**
 380          * @return array
 381          */
 382         protected function insertFields() {
 383                 $dbw = wfGetDB( DB_MASTER );
 384                 return array(
 385                         'job_id' => $dbw->nextSequenceValue( 'job_job_id_seq' ),
 386                         'job_cmd' => $this->command,
 387                         'job_namespace' => $this->title->getNamespace(),
 388                         'job_title' => $this->title->getDBkey(),
 389                         'job_timestamp' => $dbw->timestamp(),
 390                         'job_params' => Job::makeBlob( $this->params )
 391                 );
 392         }
 393
 394         /**
 395          * Remove jobs in the job queue which are duplicates of this job.
 396          * This is deadlock-prone and so starts its own transaction.
 397          */
 398         function removeDuplicates() {
 399                 if ( !$this->removeDuplicates ) {
 400                         return;
 401                 }
 402
 403                 $fields = $this->insertFields();
 404                 unset( $fields['job_id'] );
 405                 $dbw = wfGetDB( DB_MASTER );
 406                 $dbw->begin( __METHOD__ );
 407                 $dbw->delete( 'job', $fields, __METHOD__ );
 408                 $affected = $dbw->affectedRows();
 409                 $dbw->commit( __METHOD__ );
 410                 if ( $affected ) {
 411                         wfIncrStats( 'job-dup-delete', $affected );
 412                 }
 413         }
 414
 415         /**
 416          * @return string
 417          */
 418         function toString() {
 419                 $paramString = '';
 420                 if ( $this->params ) {
 421                         foreach ( $this->params as $key => $value ) {
 422                                 if ( $paramString != '' ) {
 423                                         $paramString .= ' ';
 424                                 }
 425                                 $paramString .= "$key=$value";
 426                         }
 427                 }
 428
 429                 if ( is_object( $this->title ) ) {
 430                         $s = "{$this->command} " . $this->title->getPrefixedDBkey();
 431                         if ( $paramString !== '' ) {
 432                                 $s .= ' ' . $paramString;
 433                         }
 434                         return $s;
 435                 } else {
 436                         return "{$this->command} $paramString";
 437                 }
 438         }
 439
 440         protected function setLastError( $error ) {
 441                 $this->error = $error;
 442         }
 443
 444         function getLastError() {
 445                 return $this->error;
 446         }
 447 }