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<?php
/**
* Pick a database that has pending jobs
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
* @todo Make this work on PostgreSQL and maybe other database servers
* @ingroup Maintenance
*/
require_once( __DIR__ . '/Maintenance.php' );
/**
* Maintenance script that picks a database that has pending jobs.
*
* @ingroup Maintenance
*/
class nextJobDB extends Maintenance {
public function __construct() {
parent::__construct();
$this->mDescription = "Pick a database that has pending jobs";
$this->addOption( 'type', "The type of job to search for", false, true );
}
public function execute() {
global $wgMemc;
$type = $this->getOption( 'type', false );
$memcKey = 'jobqueue:dbs:v2';
$pendingDBs = $wgMemc->get( $memcKey );
// If the cache entry wasn't present, or in 1% of cases otherwise,
// regenerate the cache.
if ( !$pendingDBs || mt_rand( 0, 100 ) == 0 ) {
$pendingDBs = $this->getPendingDbs();
$wgMemc->set( $memcKey, $pendingDBs, 300 );
}
if ( !$pendingDBs ) {
return;
}
do {
$again = false;
if ( $type === false ) {
$candidates = call_user_func_array( 'array_merge', $pendingDBs );
} elseif ( isset( $pendingDBs[$type] ) ) {
$candidates = $pendingDBs[$type];
} else {
$candidates = array();
}
if ( !$candidates ) {
return;
}
$candidates = array_values( $candidates );
$db = $candidates[ mt_rand( 0, count( $candidates ) - 1 ) ];
if ( !$this->checkJob( $type, $db ) ) {
// This job is not available in the current database. Remove it from
// the cache.
if ( $type === false ) {
foreach ( $pendingDBs as $type2 => $dbs ) {
$pendingDBs[$type2] = array_diff( $pendingDBs[$type2], array( $db ) );
}
} else {
$pendingDBs[$type] = array_diff( $pendingDBs[$type], array( $db ) );
}
$wgMemc->set( $memcKey, $pendingDBs, 300 );
$again = true;
}
} while ( $again );
$this->output( $db . "\n" );
}
/**
* Check if the specified database has a job of the specified type in it.
* The type may be false to indicate "all".
* @param $type string
* @param $dbName string
* @return bool
*/
function checkJob( $type, $dbName ) {
$lb = wfGetLB( $dbName );
$db = $lb->getConnection( DB_MASTER, array(), $dbName );
if ( $type === false ) {
$conds = Job::defaultQueueConditions( );
} else {
$conds = array( 'job_cmd' => $type );
}
$exists = (bool) $db->selectField( 'job', '1', $conds, __METHOD__ );
$lb->reuseConnection( $db );
return $exists;
}
/**
* Get all databases that have a pending job
* @return array
*/
private function getPendingDbs() {
global $wgLocalDatabases;
$pendingDBs = array();
# Cross-reference DBs by master DB server
$dbsByMaster = array();
foreach ( $wgLocalDatabases as $db ) {
$lb = wfGetLB( $db );
$dbsByMaster[$lb->getServerName( 0 )][] = $db;
}
foreach ( $dbsByMaster as $dbs ) {
$dbConn = wfGetDB( DB_MASTER, array(), $dbs[0] );
# Padding row for MySQL bug
$pad = str_repeat( '-', 40 );
$sql = "(SELECT '$pad' as db, '$pad' as job_cmd)";
foreach ( $dbs as $wikiId ) {
if ( $sql != '' ) {
$sql .= ' UNION ';
}
list( $dbName, $tablePrefix ) = wfSplitWikiID( $wikiId );
$dbConn->tablePrefix( $tablePrefix );
$jobTable = $dbConn->tableName( 'job' );
$sql .= "(SELECT DISTINCT '$wikiId' as db, job_cmd FROM $dbName.$jobTable GROUP BY job_cmd)";
}
$res = $dbConn->query( $sql, __METHOD__ );
$first = true;
foreach ( $res as $row ) {
if ( $first ) {
// discard padding row
$first = false;
continue;
}
$pendingDBs[$row->job_cmd][] = $row->db;
}
}
return $pendingDBs;
}
}
$maintClass = "nextJobDb";
require_once( RUN_MAINTENANCE_IF_MAIN );
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