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<?php
/**
* 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
* @ingroup Database
*/
namespace Wikimedia\Rdbms;
use BagOStuff;
use WANObjectCache;
/**
* Basic MySQL load monitor with no external dependencies
* Uses memcached to cache the replication lag for a short time
*
* @ingroup Database
*/
class LoadMonitorMySQL extends LoadMonitor {
/** @var float What buffer pool use ratio counts as "warm" (e.g. 0.5 for 50% usage) */
private $warmCacheRatio;
public function __construct(
ILoadBalancer $lb, BagOStuff $srvCache, WANObjectCache $wCache, array $options = []
) {
parent::__construct( $lb, $srvCache, $wCache, $options );
$this->warmCacheRatio = isset( $options['warmCacheRatio'] )
? $options['warmCacheRatio']
: 0.0;
}
protected function getWeightScale( $index, IDatabase $conn = null ) {
if ( !$conn ) {
return parent::getWeightScale( $index, $conn );
}
$weight = 1.0;
if ( $this->warmCacheRatio > 0 ) {
$res = $conn->query( 'SHOW STATUS', __METHOD__ );
$s = $res ? $conn->fetchObject( $res ) : false;
if ( $s === false ) {
$host = $this->parent->getServerName( $index );
$this->replLogger->error( __METHOD__ . ": could not get status for $host" );
} else {
// https://dev.mysql.com/doc/refman/5.7/en/server-status-variables.html
if ( $s->Innodb_buffer_pool_pages_total > 0 ) {
$ratio = $s->Innodb_buffer_pool_pages_data / $s->Innodb_buffer_pool_pages_total;
} else {
$ratio = 1.0;
}
// Stop caring once $ratio >= $this->warmCacheRatio
$weight *= min( $ratio / $this->warmCacheRatio, 1.0 );
}
}
return $weight;
}
}
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