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  * @todo Make this work on PostgreSQL and maybe other database servers
  21  * @ingroup Maintenance
  22  */
  23
  24 require_once( dirname( __FILE__ ) . '/Maintenance.php' );
  25
  26 class nextJobDB extends Maintenance {
  27         public function __construct() {
  28                 parent::__construct();
  29                 $this->mDescription = "Pick a database that has pending jobs";
  30                 $this->addOption( 'type', "The type of job to search for", false, true );
  31         }
  32
  33         public function execute() {
  34                 global $wgMemc;
  35                 $type = $this->getOption( 'type', false );
  36
  37                 $memcKey = 'jobqueue:dbs:v2';
  38                 $pendingDBs = $wgMemc->get( $memcKey );
  39
  40                 // If the cache entry wasn't present, or in 1% of cases otherwise,
  41                 // regenerate the cache.
  42                 if ( !$pendingDBs || mt_rand( 0, 100 ) == 0 ) {
  43                         $pendingDBs = $this->getPendingDbs();
  44                         $wgMemc->set( $memcKey, $pendingDBs, 300 );
  45                 }
  46
  47                 if ( !$pendingDBs ) {
  48                         return;
  49                 }
  50
  51                 do {
  52                         $again = false;
  53
  54                         if ( $type === false ) {
  55                                 $candidates = call_user_func_array( 'array_merge', $pendingDBs );
  56                         } elseif ( isset( $pendingDBs[$type] ) ) {
  57                                 $candidates = $pendingDBs[$type];
  58                         } else {
  59                                 $candidates = array();
  60                         }
  61                         if ( !$candidates ) {
  62                                 return;
  63                         }
  64
  65                         $candidates = array_values( $candidates );
  66                         $db = $candidates[ mt_rand( 0, count( $candidates ) - 1 ) ];
  67                         if ( !$this->checkJob( $type, $db ) ) {
  68                                 // This job is not available in the current database. Remove it from
  69                                 // the cache.
  70                                 if ( $type === false ) {
  71                                         foreach ( $pendingDBs as $type2 => $dbs ) {
  72                                                 $pendingDBs[$type2] = array_diff( $pendingDBs[$type2], array( $db ) );
  73                                         }
  74                                 } else {
  75                                         $pendingDBs[$type] = array_diff( $pendingDBs[$type], array( $db ) );
  76                                 }
  77
  78                                 $wgMemc->set( $memcKey, $pendingDBs, 300 );
  79                                 $again = true;
  80                         }
  81                 } while ( $again );
  82
  83                 $this->output( $db . "\n" );
  84         }
  85
  86         /**
  87          * Check if the specified database has a job of the specified type in it.
  88          * The type may be false to indicate "all".
  89          * @param $type string
  90          * @param $dbName string
  91          * @return bool
  92          */
  93         function checkJob( $type, $dbName ) {
  94                 $lb = wfGetLB( $dbName );
  95                 $db = $lb->getConnection( DB_MASTER, array(), $dbName );
  96                 if ( $type === false ) {
  97                         $conds = array();
  98                 } else {
  99                         $conds = array( 'job_cmd' => $type );
 100                 }
 101
 102                 $exists = (bool) $db->selectField( 'job', '1', $conds, __METHOD__ );
 103                 $lb->reuseConnection( $db );
 104                 return $exists;
 105         }
 106
 107         /**
 108          * Get all databases that have a pending job
 109          * @param $type String Job type
 110          * @return array
 111          */
 112         private function getPendingDbs() {
 113                 global $wgLocalDatabases;
 114                 $pendingDBs = array();
 115                 # Cross-reference DBs by master DB server
 116                 $dbsByMaster = array();
 117                 foreach ( $wgLocalDatabases as $db ) {
 118                         $lb = wfGetLB( $db );
 119                         $dbsByMaster[$lb->getServerName( 0 )][] = $db;
 120                 }
 121
 122                 foreach ( $dbsByMaster as $dbs ) {
 123                         $dbConn = wfGetDB( DB_MASTER, array(), $dbs[0] );
 124
 125                         # Padding row for MySQL bug
 126                         $pad = str_repeat( '-', 40 );
 127                         $sql = "(SELECT '$pad' as db, '$pad' as job_cmd)";
 128                         foreach ( $dbs as $wikiId ) {
 129                                 if ( $sql != '' ) {
 130                                         $sql .= ' UNION ';
 131                                 }
 132
 133                                 list( $dbName, $tablePrefix ) = wfSplitWikiID( $wikiId );
 134                                 $dbConn->tablePrefix( $tablePrefix );
 135                                 $jobTable = $dbConn->tableName( 'job' );
 136
 137                                 $sql .= "(SELECT DISTINCT '$wikiId' as db, job_cmd FROM $dbName.$jobTable GROUP BY job_cmd)";
 138                         }
 139                         $res = $dbConn->query( $sql, __METHOD__ );
 140                         $first = true;
 141                         foreach ( $res as $row ) {
 142                                 if ( $first ) {
 143                                         // discard padding row
 144                                         $first = false;
 145                                         continue;
 146                                 }
 147                                 $pendingDBs[$row->job_cmd][] = $row->db;
 148                         }
 149                 }
 150                 return $pendingDBs;
 151         }
 152 }
 153
 154 $maintClass = "nextJobDb";
 155 require_once( RUN_MAINTENANCE_IF_MAIN );