maintenance/nextJobDB.php

   1 <?php
   2 /**
   3  * Pick a database that has pending jobs
   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  * @todo Make this work on PostgreSQL and maybe other database servers
  22  * @ingroup Maintenance
  23  */
  24
  25 require_once( __DIR__ . '/Maintenance.php' );
  26
  27 /**
  28  * Maintenance script that picks a database that has pending jobs.
  29  *
  30  * @ingroup Maintenance
  31  */
  32 class nextJobDB extends Maintenance {
  33         public function __construct() {
  34                 parent::__construct();
  35                 $this->mDescription = "Pick a database that has pending jobs";
  36                 $this->addOption( 'type', "The type of job to search for", false, true );
  37         }
  38
  39         public function execute() {
  40                 global $wgMemc;
  41
  42                 $type = $this->getOption( 'type', false );
  43
  44                 $memcKey = 'jobqueue:dbs:v3';
  45                 $pendingDbInfo = $wgMemc->get( $memcKey );
  46
  47                 // If the cache entry wasn't present, or in 1% of cases otherwise,
  48                 // regenerate the cache. Use any available stale cache if another
  49                 // process is currently regenerating the pending DB information.
  50                 if ( !$pendingDbInfo || mt_rand( 0, 100 ) == 0 ) {
  51                         $lock = $wgMemc->add( 'jobqueue:dbs:v3:lock', 1, 1800 ); // lock
  52                         if ( $lock ) {
  53                                 $pendingDbInfo = array(
  54                                         'pendingDBs' => $this->getPendingDbs(),
  55                                         'timestamp'  => time()
  56                                 );
  57                                 $wgMemc->set( $memcKey, $pendingDbInfo );
  58                                 $wgMemc->delete( 'jobqueue:dbs:v3:lock' ); // unlock
  59                         }
  60                 }
  61
  62                 if ( !$pendingDbInfo || !$pendingDbInfo['pendingDBs'] ) {
  63                         return; // no DBs with jobs or cache is both empty and locked
  64                 }
  65                 $pendingDBs = $pendingDbInfo['pendingDBs'];
  66
  67                 do {
  68                         $again = false;
  69
  70                         if ( $type === false ) {
  71                                 $candidates = call_user_func_array( 'array_merge', $pendingDBs );
  72                         } elseif ( isset( $pendingDBs[$type] ) ) {
  73                                 $candidates = $pendingDBs[$type];
  74                         } else {
  75                                 $candidates = array();
  76                         }
  77                         if ( !$candidates ) {
  78                                 return;
  79                         }
  80
  81                         $candidates = array_values( $candidates );
  82                         $db = $candidates[ mt_rand( 0, count( $candidates ) - 1 ) ];
  83                         if ( !$this->checkJob( $type, $db ) ) {
  84                                 if ( $type === false ) {
  85                                         // There are no jobs available in the current database
  86                                         foreach ( $pendingDBs as $type2 => $dbs ) {
  87                                                 $pendingDBs[$type2] = array_diff( $pendingDBs[$type2], array( $db ) );
  88                                         }
  89                                 } else {
  90                                         // There are no jobs of this type available in the current database
  91                                         $pendingDBs[$type] = array_diff( $pendingDBs[$type], array( $db ) );
  92                                 }
  93                                 // Update the cache to remove the outdated information
  94                                 $pendingDbInfo['pendingDBs'] = $pendingDBs;
  95                                 // @TODO: fix race condition with these updates
  96                                 $wgMemc->set( $memcKey, $pendingDbInfo );
  97                                 $again = true;
  98                         }
  99                 } while ( $again );
 100
 101                 $this->output( $db . "\n" );
 102         }
 103
 104         /**
 105          * Check if the specified database has a job of the specified type in it.
 106          * The type may be false to indicate "all".
 107          * @param $type string
 108          * @param $dbName string
 109          * @return bool
 110          */
 111         function checkJob( $type, $dbName ) {
 112                 $group = JobQueueGroup::singleton( $dbName );
 113                 if ( $type === false ) {
 114                         foreach ( $group->getDefaultQueueTypes() as $type ) {
 115                                 if ( !$group->get( $type )->isEmpty() ) {
 116                                         return true;
 117                                 }
 118                         }
 119                         return false;
 120                 } else {
 121                         return !$group->get( $type )->isEmpty();
 122                 }
 123         }
 124
 125         /**
 126          * Get all databases that have a pending job
 127          * @return array
 128          */
 129         private function getPendingDbs() {
 130                 global $wgLocalDatabases;
 131
 132                 $pendingDBs = array(); // (job type => (db list))
 133                 foreach ( $wgLocalDatabases as $db ) {
 134                         $types = JobQueueGroup::singleton( $db )->getQueuesWithJobs();
 135                         foreach ( $types as $type ) {
 136                                 $pendingDBs[$type][] = $db;
 137                         }
 138                 }
 139
 140                 return $pendingDBs;
 141         }
 142 }
 143
 144 $maintClass = "nextJobDb";
 145 require_once( RUN_MAINTENANCE_IF_MAIN );