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', "Search by job type", false, true );
  37                 $this->addOption( 'types', "Space separated list of job types to search for", false, true );
  38         }
  39
  40         public function execute() {
  41                 global $wgMemc;
  42
  43                 $type = false; // job type required/picked
  44                 if ( $this->hasOption( 'types' ) ) {
  45                         $types = explode( ' ', $this->getOption( 'types' ) );
  46                 } elseif ( $this->hasOption( 'type' ) ) {
  47                         $types = array( $this->getOption( 'type' ) );
  48                 } else {
  49                         $types = false;
  50                 }
  51
  52                 $memcKey = 'jobqueue:dbs:v3';
  53                 $pendingDbInfo = $wgMemc->get( $memcKey );
  54
  55                 // If the cache entry wasn't present, is stale, or in .1% of cases otherwise,
  56                 // regenerate the cache. Use any available stale cache if another process is
  57                 // currently regenerating the pending DB information.
  58                 if ( !is_array( $pendingDbInfo )
  59                         || ( time() - $pendingDbInfo['timestamp'] ) > 300 // 5 minutes
  60                         || mt_rand( 0, 999 ) == 0
  61                 ) {
  62                         if ( $wgMemc->add( "$memcKey:rebuild", 1, 1800 ) ) { // lock
  63                                 $pendingDbInfo = array(
  64                                         'pendingDBs' => $this->getPendingDbs(),
  65                                         'timestamp'  => time()
  66                                 );
  67                                 for ( $attempts=1; $attempts <= 25; ++$attempts ) {
  68                                         if ( $wgMemc->add( "$memcKey:lock", 1, 60 ) ) { // lock
  69                                                 $wgMemc->set( $memcKey, $pendingDbInfo );
  70                                                 $wgMemc->delete( "$memcKey:lock" ); // unlock
  71                                                 break;
  72                                         }
  73                                 }
  74                                 $wgMemc->delete( "$memcKey:rebuild" ); // unlock
  75                         }
  76                 }
  77
  78                 if ( !is_array( $pendingDbInfo ) || !$pendingDbInfo['pendingDBs'] ) {
  79                         return; // no DBs with jobs or cache is both empty and locked
  80                 }
  81
  82                 $pendingDBs = $pendingDbInfo['pendingDBs']; // convenience
  83                 do {
  84                         $again = false;
  85
  86                         if ( $types === false ) {
  87                                 $candidates = call_user_func_array( 'array_merge', $pendingDBs );
  88                         } else {
  89                                 $candidates = array();
  90                                 $possTypes = array_intersect( $types, array_keys( $pendingDBs ) );
  91                                 if ( $possTypes ) {
  92                                         $possTypes = array_values( $possTypes );
  93                                         $type = $possTypes[ mt_rand( 0, count( $possTypes ) - 1 ) ];
  94                                         $candidates = $pendingDBs[$type];
  95                                 }
  96                         }
  97                         if ( !$candidates ) {
  98                                 return; // no jobs for this type
  99                         }
 100
 101                         $candidates = array_values( $candidates );
 102                         $db = $candidates[ mt_rand( 0, count( $candidates ) - 1 ) ];
 103                         if ( !$this->checkJob( $type, $db ) ) {
 104                                 if ( $type === false ) {
 105                                         // There are no jobs available in the current database
 106                                         foreach ( $pendingDBs as $type2 => $dbs ) {
 107                                                 $pendingDBs[$type2] = array_diff( $pendingDBs[$type2], array( $db ) );
 108                                         }
 109                                 } else {
 110                                         // There are no jobs of this type available in the current database
 111                                         $pendingDBs[$type] = array_diff( $pendingDBs[$type], array( $db ) );
 112                                 }
 113                                 // Update the cache to remove the outdated information.
 114                                 // Make sure that this does not race (especially with full rebuilds).
 115                                 $pendingDbInfo['pendingDBs'] = $pendingDBs;
 116                                 if ( $wgMemc->add( "$memcKey:lock", 1, 60 ) ) { // lock
 117                                         $curInfo = $wgMemc->get( $memcKey );
 118                                         if ( $curInfo && $curInfo['timestamp'] === $pendingDbInfo['timestamp'] ) {
 119                                                 $wgMemc->set( $memcKey, $pendingDbInfo );
 120                                         }
 121                                         $wgMemc->delete( "$memcKey:lock" ); // unlock
 122                                 }
 123                                 $again = true;
 124                         }
 125                 } while ( $again );
 126
 127                 if ( $this->hasOption( 'types' ) ) {
 128                         $this->output( $db . " " . $type . "\n" );
 129                 } else {
 130                         $this->output( $db . "\n" );
 131                 }
 132         }
 133
 134         /**
 135          * Check if the specified database has a job of the specified type in it.
 136          * The type may be false to indicate "all".
 137          * @param $type string
 138          * @param $dbName string
 139          * @return bool
 140          */
 141         function checkJob( $type, $dbName ) {
 142                 $group = JobQueueGroup::singleton( $dbName );
 143                 if ( $type === false ) {
 144                         foreach ( $group->getDefaultQueueTypes() as $type ) {
 145                                 if ( !$group->get( $type )->isEmpty() ) {
 146                                         return true;
 147                                 }
 148                         }
 149                         return false;
 150                 } else {
 151                         return !$group->get( $type )->isEmpty();
 152                 }
 153         }
 154
 155         /**
 156          * Get all databases that have a pending job
 157          * @return array
 158          */
 159         private function getPendingDbs() {
 160                 global $wgLocalDatabases;
 161
 162                 $pendingDBs = array(); // (job type => (db list))
 163                 foreach ( $wgLocalDatabases as $db ) {
 164                         $types = JobQueueGroup::singleton( $db )->getQueuesWithJobs();
 165                         foreach ( $types as $type ) {
 166                                 $pendingDBs[$type][] = $db;
 167                         }
 168                 }
 169
 170                 return $pendingDBs;
 171         }
 172 }
 173
 174 $maintClass = "nextJobDb";
 175 require_once( RUN_MAINTENANCE_IF_MAIN );