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  * @ingroup Maintenance
  22  */
  23
  24 require_once( __DIR__ . '/Maintenance.php' );
  25
  26 /**
  27  * Maintenance script that picks a database that has pending jobs.
  28  *
  29  * @ingroup Maintenance
  30  */
  31 class nextJobDB extends Maintenance {
  32         public function __construct() {
  33                 parent::__construct();
  34                 $this->mDescription = "Pick a database that has pending jobs";
  35                 $this->addOption( 'type', "The type of job to search for", false, true );
  36         }
  37
  38         public function execute() {
  39                 global $wgMemc;
  40
  41                 $type = $this->getOption( 'type', false );
  42
  43                 $memcKey = 'jobqueue:dbs:v3';
  44                 $pendingDbInfo = $wgMemc->get( $memcKey );
  45
  46                 // If the cache entry wasn't present, is stale, or in .1% of cases otherwise,
  47                 // regenerate the cache. Use any available stale cache if another process is
  48                 // currently regenerating the pending DB information.
  49                 if ( !is_array( $pendingDbInfo )
  50                         || ( time() - $pendingDbInfo['timestamp'] ) > 300 // 5 minutes
  51                         || mt_rand( 0, 999 ) == 0
  52                 ) {
  53                         if ( $wgMemc->add( "$memcKey:rebuild", 1, 1800 ) ) { // lock
  54                                 $pendingDbInfo = array(
  55                                         'pendingDBs' => $this->getPendingDbs(),
  56                                         'timestamp'  => time()
  57                                 );
  58                                 for ( $attempts=1; $attempts <= 25; ++$attempts ) {
  59                                         if ( $wgMemc->add( "$memcKey:lock", 1, 60 ) ) { // lock
  60                                                 $wgMemc->set( $memcKey, $pendingDbInfo );
  61                                                 $wgMemc->delete( "$memcKey:lock" ); // unlock
  62                                                 break;
  63                                         }
  64                                 }
  65                                 $wgMemc->delete( "$memcKey:rebuild" ); // unlock
  66                         }
  67                 }
  68
  69                 if ( !is_array( $pendingDbInfo ) || !$pendingDbInfo['pendingDBs'] ) {
  70                         return; // no DBs with jobs or cache is both empty and locked
  71                 }
  72
  73                 $pendingDBs = $pendingDbInfo['pendingDBs']; // convenience
  74                 do {
  75                         $again = false;
  76
  77                         if ( $type === false ) {
  78                                 $candidates = call_user_func_array( 'array_merge', $pendingDBs );
  79                         } elseif ( isset( $pendingDBs[$type] ) ) {
  80                                 $candidates = $pendingDBs[$type];
  81                         } else {
  82                                 $candidates = array();
  83                         }
  84                         if ( !$candidates ) {
  85                                 return;
  86                         }
  87
  88                         $candidates = array_values( $candidates );
  89                         $db = $candidates[ mt_rand( 0, count( $candidates ) - 1 ) ];
  90                         if ( !$this->checkJob( $type, $db ) ) {
  91                                 $pendingDBs = $this->delistDB( $pendingDBs, $db, $type );
  92                                 // Update the cache to remove the outdated information.
  93                                 // Make sure that this does not race (especially with full rebuilds).
  94                                 if ( $wgMemc->add( "$memcKey:lock", 1, 60 ) ) { // lock
  95                                         $curInfo = $wgMemc->get( $memcKey );
  96                                         if ( is_array( $curInfo ) ) {
  97                                                 $curInfo['pendingDBs'] =
  98                                                         $this->delistDB( $curInfo['pendingDBs'], $db, $type );
  99                                                 $wgMemc->set( $memcKey, $curInfo );
 100                                                 // May as well make use of this newer information
 101                                                 $pendingDBs = $curInfo['pendingDBs'];
 102                                         }
 103                                         $wgMemc->delete( "$memcKey:lock" ); // unlock
 104                                 }
 105                                 $again = true;
 106                         }
 107                 } while ( $again );
 108
 109                 $this->output( $db . "\n" );
 110         }
 111
 112         private function delistDB( array $pendingDBs, $db, $type ) {
 113                 if ( $type === false ) {
 114                         // There are no jobs available in the current database
 115                         foreach ( $pendingDBs as $type2 => $dbs ) {
 116                                 $pendingDBs[$type2] = array_diff( $pendingDBs[$type2], array( $db ) );
 117                         }
 118                 } else {
 119                         // There are no jobs of this type available in the current database
 120                         $pendingDBs[$type] = array_diff( $pendingDBs[$type], array( $db ) );
 121                 }
 122                 return $pendingDBs;
 123         }
 124
 125         /**
 126          * Check if the specified database has a job of the specified type in it.
 127          * The type may be false to indicate "all".
 128          * @param $type string
 129          * @param $dbName string
 130          * @return bool
 131          */
 132         private function checkJob( $type, $dbName ) {
 133                 $group = JobQueueGroup::singleton( $dbName );
 134                 if ( $type === false ) {
 135                         foreach ( $group->getDefaultQueueTypes() as $type ) {
 136                                 if ( !$group->get( $type )->isEmpty() ) {
 137                                         return true;
 138                                 }
 139                         }
 140                         return false;
 141                 } else {
 142                         return !$group->get( $type )->isEmpty();
 143                 }
 144         }
 145
 146         /**
 147          * Get all databases that have a pending job
 148          * @return array
 149          */
 150         private function getPendingDbs() {
 151                 global $wgLocalDatabases;
 152
 153                 $pendingDBs = array(); // (job type => (db list))
 154                 foreach ( $wgLocalDatabases as $db ) {
 155                         $types = JobQueueGroup::singleton( $db )->getQueuesWithJobs();
 156                         foreach ( $types as $type ) {
 157                                 $pendingDBs[$type][] = $db;
 158                         }
 159                 }
 160
 161                 return $pendingDBs;
 162         }
 163 }
 164
 165 $maintClass = "nextJobDb";
 166 require_once( RUN_MAINTENANCE_IF_MAIN );