includes/libs/rdbms/loadmonitor/LoadMonitorMySQL.php

   1 <?php
   2 /**
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2 of the License, or
   6  * (at your option) any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  16  * http://www.gnu.org/copyleft/gpl.html
  17  *
  18  * @file
  19  * @ingroup Database
  20  */
  21
  22 namespace Wikimedia\Rdbms;
  23
  24 use IDatabase;
  25 use BagOStuff;
  26
  27 /**
  28  * Basic MySQL load monitor with no external dependencies
  29  * Uses memcached to cache the replication lag for a short time
  30  *
  31  * @ingroup Database
  32  */
  33 class LoadMonitorMySQL extends LoadMonitor {
  34         /** @var float What buffer pool use ratio counts as "warm" (e.g. 0.5 for 50% usage) */
  35         private $warmCacheRatio;
  36
  37         public function __construct(
  38                 ILoadBalancer $lb, BagOStuff $srvCache, BagOStuff $cache, array $options = []
  39         ) {
  40                 parent::__construct( $lb, $srvCache, $cache, $options );
  41
  42                 $this->warmCacheRatio = isset( $options['warmCacheRatio'] )
  43                         ? $options['warmCacheRatio']
  44                         : 0.0;
  45         }
  46
  47         protected function getWeightScale( $index, IDatabase $conn = null ) {
  48                 if ( !$conn ) {
  49                         return 0.0;
  50                 }
  51
  52                 $weight = 1.0;
  53                 if ( $this->warmCacheRatio > 0 ) {
  54                         $res = $conn->query( 'SHOW STATUS', false );
  55                         $s = $res ? $conn->fetchObject( $res ) : false;
  56                         if ( $s === false ) {
  57                                 $host = $this->parent->getServerName( $index );
  58                                 $this->replLogger->error( __METHOD__ . ": could not get status for $host" );
  59                         } else {
  60                                 // https://dev.mysql.com/doc/refman/5.7/en/server-status-variables.html
  61                                 if ( $s->Innodb_buffer_pool_pages_total > 0 ) {
  62                                         $ratio = $s->Innodb_buffer_pool_pages_data / $s->Innodb_buffer_pool_pages_total;
  63                                 } else {
  64                                         $ratio = 1.0;
  65                                 }
  66                                 // Stop caring once $ratio >= $this->warmCacheRatio
  67                                 $weight *= min( $ratio / $this->warmCacheRatio, 1.0 );
  68                         }
  69                 }
  70
  71                 return $weight;
  72         }
  73 }