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( dirname( __FILE__ ) . '/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                 $type = $this->getOption( 'type', false );
  42
  43                 $memcKey = 'jobqueue:dbs:v2';
  44                 $pendingDBs = $wgMemc->get( $memcKey );
  45
  46                 // If the cache entry wasn't present, or in 1% of cases otherwise,
  47                 // regenerate the cache.
  48                 if ( !$pendingDBs || mt_rand( 0, 100 ) == 0 ) {
  49                         $pendingDBs = $this->getPendingDbs();
  50                         $wgMemc->set( $memcKey, $pendingDBs, 300 );
  51                 }
  52
  53                 if ( !$pendingDBs ) {
  54                         return;
  55                 }
  56
  57                 do {
  58                         $again = false;
  59
  60                         if ( $type === false ) {
  61                                 $candidates = call_user_func_array( 'array_merge', $pendingDBs );
  62                         } elseif ( isset( $pendingDBs[$type] ) ) {
  63                                 $candidates = $pendingDBs[$type];
  64                         } else {
  65                                 $candidates = array();
  66                         }
  67                         if ( !$candidates ) {
  68                                 return;
  69                         }
  70
  71                         $candidates = array_values( $candidates );
  72                         $db = $candidates[ mt_rand( 0, count( $candidates ) - 1 ) ];
  73                         if ( !$this->checkJob( $type, $db ) ) {
  74                                 // This job is not available in the current database. Remove it from
  75                                 // the cache.
  76                                 if ( $type === false ) {
  77                                         foreach ( $pendingDBs as $type2 => $dbs ) {
  78                                                 $pendingDBs[$type2] = array_diff( $pendingDBs[$type2], array( $db ) );
  79                                         }
  80                                 } else {
  81                                         $pendingDBs[$type] = array_diff( $pendingDBs[$type], array( $db ) );
  82                                 }
  83
  84                                 $wgMemc->set( $memcKey, $pendingDBs, 300 );
  85                                 $again = true;
  86                         }
  87                 } while ( $again );
  88
  89                 $this->output( $db . "\n" );
  90         }
  91
  92         /**
  93          * Check if the specified database has a job of the specified type in it.
  94          * The type may be false to indicate "all".
  95          * @param $type string
  96          * @param $dbName string
  97          * @return bool
  98          */
  99         function checkJob( $type, $dbName ) {
 100                 $lb = wfGetLB( $dbName );
 101                 $db = $lb->getConnection( DB_MASTER, array(), $dbName );
 102                 if ( $type === false ) {
 103                         $conds = Job::defaultQueueConditions( );
 104                 } else {
 105                         $conds = array( 'job_cmd' => $type );
 106                 }
 107
 108
 109                 $exists = (bool) $db->selectField( 'job', '1', $conds, __METHOD__ );
 110                 $lb->reuseConnection( $db );
 111                 return $exists;
 112         }
 113
 114         /**
 115          * Get all databases that have a pending job
 116          * @return array
 117          */
 118         private function getPendingDbs() {
 119                 global $wgLocalDatabases;
 120                 $pendingDBs = array();
 121                 # Cross-reference DBs by master DB server
 122                 $dbsByMaster = array();
 123                 foreach ( $wgLocalDatabases as $db ) {
 124                         $lb = wfGetLB( $db );
 125                         $dbsByMaster[$lb->getServerName( 0 )][] = $db;
 126                 }
 127
 128                 foreach ( $dbsByMaster as $dbs ) {
 129                         $dbConn = wfGetDB( DB_MASTER, array(), $dbs[0] );
 130
 131                         # Padding row for MySQL bug
 132                         $pad = str_repeat( '-', 40 );
 133                         $sql = "(SELECT '$pad' as db, '$pad' as job_cmd)";
 134                         foreach ( $dbs as $wikiId ) {
 135                                 if ( $sql != '' ) {
 136                                         $sql .= ' UNION ';
 137                                 }
 138
 139                                 list( $dbName, $tablePrefix ) = wfSplitWikiID( $wikiId );
 140                                 $dbConn->tablePrefix( $tablePrefix );
 141                                 $jobTable = $dbConn->tableName( 'job' );
 142
 143                                 $sql .= "(SELECT DISTINCT '$wikiId' as db, job_cmd FROM $dbName.$jobTable GROUP BY job_cmd)";
 144                         }
 145                         $res = $dbConn->query( $sql, __METHOD__ );
 146                         $first = true;
 147                         foreach ( $res as $row ) {
 148                                 if ( $first ) {
 149                                         // discard padding row
 150                                         $first = false;
 151                                         continue;
 152                                 }
 153                                 $pendingDBs[$row->job_cmd][] = $row->db;
 154                         }
 155                 }
 156                 return $pendingDBs;
 157         }
 158 }
 159
 160 $maintClass = "nextJobDb";
 161 require_once( RUN_MAINTENANCE_IF_MAIN );