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 BagOStuff;
  25
  26 /**
  27  * Basic MySQL load monitor with no external dependencies
  28  * Uses memcached to cache the replication lag for a short time
  29  *
  30  * @ingroup Database
  31  */
  32 class LoadMonitorMySQL extends LoadMonitor {
  33         /** @var float What buffer pool use ratio counts as "warm" (e.g. 0.5 for 50% usage) */
  34         private $warmCacheRatio;
  35
  36         public function __construct(
  37                 ILoadBalancer $lb, BagOStuff $srvCache, BagOStuff $cache, array $options = []
  38         ) {
  39                 parent::__construct( $lb, $srvCache, $cache, $options );
  40
  41                 $this->warmCacheRatio = isset( $options['warmCacheRatio'] )
  42                         ? $options['warmCacheRatio']
  43                         : 0.0;
  44         }
  45
  46         protected function getWeightScale( $index, IDatabase $conn = null ) {
  47                 if ( !$conn ) {
  48                         return 0.0;
  49                 }
  50
  51                 $weight = 1.0;
  52                 if ( $this->warmCacheRatio > 0 ) {
  53                         $res = $conn->query( 'SHOW STATUS', false );
  54                         $s = $res ? $conn->fetchObject( $res ) : false;
  55                         if ( $s === false ) {
  56                                 $host = $this->parent->getServerName( $index );
  57                                 $this->replLogger->error( __METHOD__ . ": could not get status for $host" );
  58                         } else {
  59                                 // https://dev.mysql.com/doc/refman/5.7/en/server-status-variables.html
  60                                 if ( $s->Innodb_buffer_pool_pages_total > 0 ) {
  61                                         $ratio = $s->Innodb_buffer_pool_pages_data / $s->Innodb_buffer_pool_pages_total;
  62                                 } else {
  63                                         $ratio = 1.0;
  64                                 }
  65                                 // Stop caring once $ratio >= $this->warmCacheRatio
  66                                 $weight *= min( $ratio / $this->warmCacheRatio, 1.0 );
  67                         }
  68                 }
  69
  70                 return $weight;
  71         }
  72 }