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