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