includes/db/loadbalancer/LoadMonitor.php

   1 <?php
   2 /**
   3  * Database load monitoring.
   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  * @file
  21  * @ingroup Database
  22  */
  23
  24 /**
  25  * An interface for database load monitoring
  26  *
  27  * @ingroup Database
  28  */
  29 interface LoadMonitor {
  30         /**
  31          * Construct a new LoadMonitor with a given LoadBalancer parent
  32          *
  33          * @param LoadBalancer $parent
  34          */
  35         public function __construct( $parent );
  36
  37         /**
  38          * Perform pre-connection load ratio adjustment.
  39          * @param array &$loads
  40          * @param string|bool $group The selected query group. Default: false
  41          * @param string|bool $wiki Default: false
  42          */
  43         public function scaleLoads( &$loads, $group = false, $wiki = false );
  44
  45         /**
  46          * Get an estimate of replication lag (in seconds) for each server
  47          *
  48          * Values may be "false" if replication is too broken to estimate
  49          *
  50          * @param array $serverIndexes
  51          * @param string $wiki
  52          *
  53          * @return array Map of (server index => float|int|bool)
  54          */
  55         public function getLagTimes( $serverIndexes, $wiki );
  56
  57         /**
  58          * Clear any process and persistent cache of lag times
  59          * @since 1.27
  60          */
  61         public function clearCaches();
  62 }
  63
  64 class LoadMonitorNull implements LoadMonitor {
  65         public function __construct( $parent ) {
  66         }
  67
  68         public function scaleLoads( &$loads, $group = false, $wiki = false ) {
  69         }
  70
  71         public function getLagTimes( $serverIndexes, $wiki ) {
  72                 return array_fill_keys( $serverIndexes, 0 );
  73         }
  74
  75         public function clearCaches() {
  76
  77         }
  78 }