70f3afd548
An if body must not begin with an empty line Change-Id: I62b058be337fcc85a120fcd3dadce564db59a271
1277 lines
36 KiB
PHP
1277 lines
36 KiB
PHP
<?php
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/**
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* Database load balancing.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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* http://www.gnu.org/copyleft/gpl.html
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*
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* @file
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* @ingroup Database
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*/
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/**
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* Database load balancing object
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*
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* @todo document
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* @ingroup Database
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*/
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class LoadBalancer {
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/** @var array[] Map of (server index => server config array) */
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private $mServers;
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/** @var array[] Map of (local/foreignUsed/foreignFree => server index => DatabaseBase array) */
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private $mConns;
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/** @var array Map of (server index => weight) */
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private $mLoads;
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/** @var array[] Map of (group => server index => weight) */
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private $mGroupLoads;
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/** @var bool Whether to disregard slave lag as a factor in slave selection */
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private $mAllowLagged;
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/** @var integer Seconds to spend waiting on slave lag to resolve */
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private $mWaitTimeout;
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/** @var array LBFactory information */
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private $mParentInfo;
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/** @var string The LoadMonitor subclass name */
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private $mLoadMonitorClass;
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/** @var LoadMonitor */
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private $mLoadMonitor;
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/** @var bool|DatabaseBase Database connection that caused a problem */
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private $mErrorConnection;
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/** @var integer The generic (not query grouped) slave index (of $mServers) */
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private $mReadIndex;
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/** @var bool|DBMasterPos False if not set */
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private $mWaitForPos;
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/** @var bool Whether the generic reader fell back to a lagged slave */
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private $mLaggedSlaveMode;
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/** @var string The last DB selection or connection error */
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private $mLastError = 'Unknown error';
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/** @var integer Total connections opened */
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private $connsOpened = 0;
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/** @var ProcessCacheLRU */
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private $mProcCache;
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/** @var integer Warn when this many connection are held */
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const CONN_HELD_WARN_THRESHOLD = 10;
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/**
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* @param array $params Array with keys:
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* servers Required. Array of server info structures.
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* loadMonitor Name of a class used to fetch server lag and load.
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* @throws MWException
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*/
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public function __construct( array $params ) {
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if ( !isset( $params['servers'] ) ) {
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throw new MWException( __CLASS__ . ': missing servers parameter' );
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}
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$this->mServers = $params['servers'];
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$this->mWaitTimeout = 10;
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$this->mReadIndex = -1;
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$this->mWriteIndex = -1;
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$this->mConns = array(
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'local' => array(),
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'foreignUsed' => array(),
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'foreignFree' => array() );
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$this->mLoads = array();
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$this->mWaitForPos = false;
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$this->mLaggedSlaveMode = false;
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$this->mErrorConnection = false;
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$this->mAllowLagged = false;
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if ( isset( $params['loadMonitor'] ) ) {
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$this->mLoadMonitorClass = $params['loadMonitor'];
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} else {
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$master = reset( $params['servers'] );
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if ( isset( $master['type'] ) && $master['type'] === 'mysql' ) {
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$this->mLoadMonitorClass = 'LoadMonitorMySQL';
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} else {
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$this->mLoadMonitorClass = 'LoadMonitorNull';
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}
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}
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foreach ( $params['servers'] as $i => $server ) {
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$this->mLoads[$i] = $server['load'];
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if ( isset( $server['groupLoads'] ) ) {
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foreach ( $server['groupLoads'] as $group => $ratio ) {
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if ( !isset( $this->mGroupLoads[$group] ) ) {
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$this->mGroupLoads[$group] = array();
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}
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$this->mGroupLoads[$group][$i] = $ratio;
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}
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}
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}
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$this->mProcCache = new ProcessCacheLRU( 30 );
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}
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/**
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* Get a LoadMonitor instance
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*
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* @return LoadMonitor
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*/
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private function getLoadMonitor() {
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if ( !isset( $this->mLoadMonitor ) ) {
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$class = $this->mLoadMonitorClass;
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$this->mLoadMonitor = new $class( $this );
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}
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return $this->mLoadMonitor;
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}
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/**
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* Get or set arbitrary data used by the parent object, usually an LBFactory
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* @param mixed $x
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* @return mixed
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*/
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public function parentInfo( $x = null ) {
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return wfSetVar( $this->mParentInfo, $x );
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}
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/**
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* Given an array of non-normalised probabilities, this function will select
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* an element and return the appropriate key
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*
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* @deprecated since 1.21, use ArrayUtils::pickRandom()
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*
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* @param array $weights
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* @return bool|int|string
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*/
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public function pickRandom( array $weights ) {
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return ArrayUtils::pickRandom( $weights );
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}
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/**
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* @param array $loads
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* @param bool|string $wiki Wiki to get non-lagged for
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* @param float $maxLag Restrict the maximum allowed lag to this many seconds
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* @return bool|int|string
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*/
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private function getRandomNonLagged( array $loads, $wiki = false, $maxLag = INF ) {
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$lags = $this->getLagTimes( $wiki );
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# Unset excessively lagged servers
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foreach ( $lags as $i => $lag ) {
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if ( $i != 0 ) {
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$maxServerLag = $maxLag;
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if ( isset( $this->mServers[$i]['max lag'] ) ) {
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$maxServerLag = min( $maxServerLag, $this->mServers[$i]['max lag'] );
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}
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if ( $lag === false ) {
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wfDebugLog( 'replication', "Server #$i is not replicating" );
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unset( $loads[$i] );
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} elseif ( $lag > $maxServerLag ) {
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wfDebugLog( 'replication', "Server #$i is excessively lagged ($lag seconds)" );
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unset( $loads[$i] );
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}
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}
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}
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# Find out if all the slaves with non-zero load are lagged
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$sum = 0;
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foreach ( $loads as $load ) {
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$sum += $load;
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}
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if ( $sum == 0 ) {
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# No appropriate DB servers except maybe the master and some slaves with zero load
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# Do NOT use the master
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# Instead, this function will return false, triggering read-only mode,
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# and a lagged slave will be used instead.
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return false;
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}
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if ( count( $loads ) == 0 ) {
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return false;
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}
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#wfDebugLog( 'connect', var_export( $loads, true ) );
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# Return a random representative of the remainder
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return ArrayUtils::pickRandom( $loads );
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}
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/**
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* Get the index of the reader connection, which may be a slave
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* This takes into account load ratios and lag times. It should
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* always return a consistent index during a given invocation
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*
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* Side effect: opens connections to databases
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* @param string|bool $group Query group, or false for the generic reader
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* @param string|bool $wiki Wiki ID, or false for the current wiki
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* @throws MWException
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* @return bool|int|string
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*/
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public function getReaderIndex( $group = false, $wiki = false ) {
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global $wgDBtype;
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# @todo FIXME: For now, only go through all this for mysql databases
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if ( $wgDBtype != 'mysql' ) {
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return $this->getWriterIndex();
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}
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if ( count( $this->mServers ) == 1 ) {
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# Skip the load balancing if there's only one server
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return 0;
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} elseif ( $group === false && $this->mReadIndex >= 0 ) {
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# Shortcut if generic reader exists already
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return $this->mReadIndex;
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}
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# Find the relevant load array
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if ( $group !== false ) {
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if ( isset( $this->mGroupLoads[$group] ) ) {
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$nonErrorLoads = $this->mGroupLoads[$group];
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} else {
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# No loads for this group, return false and the caller can use some other group
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wfDebug( __METHOD__ . ": no loads for group $group\n" );
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return false;
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}
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} else {
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$nonErrorLoads = $this->mLoads;
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}
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if ( !count( $nonErrorLoads ) ) {
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throw new MWException( "Empty server array given to LoadBalancer" );
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}
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# Scale the configured load ratios according to the dynamic load (if the load monitor supports it)
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$this->getLoadMonitor()->scaleLoads( $nonErrorLoads, $group, $wiki );
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$laggedSlaveMode = false;
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# No server found yet
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$i = false;
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# First try quickly looking through the available servers for a server that
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# meets our criteria
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$currentLoads = $nonErrorLoads;
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while ( count( $currentLoads ) ) {
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if ( $this->mAllowLagged || $laggedSlaveMode ) {
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$i = ArrayUtils::pickRandom( $currentLoads );
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} else {
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$i = false;
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if ( $this->mWaitForPos && $this->mWaitForPos->asOfTime() ) {
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# ChronologyProtecter causes mWaitForPos to be set via sessions.
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# This triggers doWait() after connect, so it's especially good to
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# avoid lagged servers so as to avoid just blocking in that method.
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$ago = microtime( true ) - $this->mWaitForPos->asOfTime();
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# Aim for <= 1 second of waiting (being too picky can backfire)
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$i = $this->getRandomNonLagged( $currentLoads, $wiki, $ago + 1 );
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}
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if ( $i === false ) {
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# Any server with less lag than it's 'max lag' param is preferable
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$i = $this->getRandomNonLagged( $currentLoads, $wiki );
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}
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if ( $i === false && count( $currentLoads ) != 0 ) {
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# All slaves lagged. Switch to read-only mode
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wfDebugLog( 'replication', "All slaves lagged. Switch to read-only mode" );
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$i = ArrayUtils::pickRandom( $currentLoads );
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$laggedSlaveMode = true;
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}
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}
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if ( $i === false ) {
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# pickRandom() returned false
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# This is permanent and means the configuration or the load monitor
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# wants us to return false.
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wfDebugLog( 'connect', __METHOD__ . ": pickRandom() returned false" );
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return false;
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}
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$serverName = $this->getServerName( $i );
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wfDebugLog( 'connect', __METHOD__ . ": Using reader #$i: $serverName..." );
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$conn = $this->openConnection( $i, $wiki );
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if ( !$conn ) {
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wfDebugLog( 'connect', __METHOD__ . ": Failed connecting to $i/$wiki" );
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unset( $nonErrorLoads[$i] );
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unset( $currentLoads[$i] );
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$i = false;
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continue;
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}
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// Decrement reference counter, we are finished with this connection.
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// It will be incremented for the caller later.
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if ( $wiki !== false ) {
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$this->reuseConnection( $conn );
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}
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# Return this server
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break;
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}
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# If all servers were down, quit now
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if ( !count( $nonErrorLoads ) ) {
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wfDebugLog( 'connect', "All servers down" );
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}
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if ( $i !== false ) {
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# Slave connection successful
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# Wait for the session master pos for a short time
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if ( $this->mWaitForPos && $i > 0 ) {
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if ( !$this->doWait( $i ) ) {
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$this->mServers[$i]['slave pos'] = $conn->getSlavePos();
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}
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}
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if ( $this->mReadIndex <= 0 && $this->mLoads[$i] > 0 && $group === false ) {
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$this->mReadIndex = $i;
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# Record if the generic reader index is in "lagged slave" mode
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if ( $laggedSlaveMode ) {
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$this->mLaggedSlaveMode = true;
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}
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}
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$serverName = $this->getServerName( $i );
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wfDebug( __METHOD__ . ": using server $serverName for group '$group'\n" );
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}
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return $i;
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}
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/**
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* Set the master wait position
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* If a DB_SLAVE connection has been opened already, waits
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* Otherwise sets a variable telling it to wait if such a connection is opened
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* @param DBMasterPos $pos
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*/
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public function waitFor( $pos ) {
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$this->mWaitForPos = $pos;
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$i = $this->mReadIndex;
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if ( $i > 0 ) {
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if ( !$this->doWait( $i ) ) {
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$this->mServers[$i]['slave pos'] = $this->getAnyOpenConnection( $i )->getSlavePos();
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$this->mLaggedSlaveMode = true;
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}
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}
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}
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/**
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* Set the master wait position and wait for a "generic" slave to catch up to it
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*
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* This can be used a faster proxy for waitForAll()
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*
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* @param DBMasterPos $pos
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* @param int $timeout Max seconds to wait; default is mWaitTimeout
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* @return bool Success (able to connect and no timeouts reached)
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* @since 1.26
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*/
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public function waitForOne( $pos, $timeout = null ) {
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$this->mWaitForPos = $pos;
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$i = $this->mReadIndex;
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if ( $i <= 0 ) {
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// Pick a generic slave if there isn't one yet
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$readLoads = $this->mLoads;
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unset( $readLoads[$this->getWriterIndex()] ); // slaves only
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$readLoads = array_filter( $readLoads ); // with non-zero load
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$i = ArrayUtils::pickRandom( $readLoads );
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}
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if ( $i > 0 ) {
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$ok = $this->doWait( $i, true, $timeout );
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} else {
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$ok = true; // no applicable loads
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}
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return $ok;
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}
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/**
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* Set the master wait position and wait for ALL slaves to catch up to it
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* @param DBMasterPos $pos
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* @param int $timeout Max seconds to wait; default is mWaitTimeout
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* @return bool Success (able to connect and no timeouts reached)
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*/
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public function waitForAll( $pos, $timeout = null ) {
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$this->mWaitForPos = $pos;
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$serverCount = count( $this->mServers );
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$ok = true;
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for ( $i = 1; $i < $serverCount; $i++ ) {
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if ( $this->mLoads[$i] > 0 ) {
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$ok = $this->doWait( $i, true, $timeout ) && $ok;
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}
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}
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return $ok;
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}
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/**
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* Get any open connection to a given server index, local or foreign
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* Returns false if there is no connection open
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*
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* @param int $i
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* @return DatabaseBase|bool False on failure
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*/
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public function getAnyOpenConnection( $i ) {
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foreach ( $this->mConns as $conns ) {
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if ( !empty( $conns[$i] ) ) {
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return reset( $conns[$i] );
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}
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}
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return false;
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}
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/**
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* Wait for a given slave to catch up to the master pos stored in $this
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* @param int $index Server index
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* @param bool $open Check the server even if a new connection has to be made
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* @param int $timeout Max seconds to wait; default is mWaitTimeout
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* @return bool
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*/
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protected function doWait( $index, $open = false, $timeout = null ) {
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$close = false; // close the connection afterwards
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# Find a connection to wait on, creating one if needed and allowed
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$conn = $this->getAnyOpenConnection( $index );
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if ( !$conn ) {
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if ( !$open ) {
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wfDebug( __METHOD__ . ": no connection open\n" );
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return false;
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} else {
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$conn = $this->openConnection( $index, '' );
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if ( !$conn ) {
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wfDebug( __METHOD__ . ": failed to open connection\n" );
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return false;
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}
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// Avoid connection spam in waitForAll() when connections
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// are made just for the sake of doing this lag check.
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$close = true;
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}
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}
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wfDebug( __METHOD__ . ": Waiting for slave #$index to catch up...\n" );
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$timeout = $timeout ?: $this->mWaitTimeout;
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$result = $conn->masterPosWait( $this->mWaitForPos, $timeout );
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if ( $result == -1 || is_null( $result ) ) {
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# Timed out waiting for slave, use master instead
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$server = $server = $this->getServerName( $index );
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$msg = __METHOD__ . ": Timed out waiting on $server pos {$this->mWaitForPos}";
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wfDebug( "$msg\n" );
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wfDebugLog( 'DBPerformance', "$msg:\n" . wfBacktrace( true ) );
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$ok = false;
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} else {
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wfDebug( __METHOD__ . ": Done\n" );
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$ok = true;
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}
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if ( $close ) {
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$this->closeConnection( $conn );
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}
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return $ok;
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}
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/**
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* Get a connection by index
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* This is the main entry point for this class.
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*
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* @param int $i Server index
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* @param array|string|bool $groups Query group(s), or false for the generic reader
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* @param string|bool $wiki Wiki ID, or false for the current wiki
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*
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* @throws MWException
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* @return DatabaseBase
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*/
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public function getConnection( $i, $groups = array(), $wiki = false ) {
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if ( $i === null || $i === false ) {
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throw new MWException( 'Attempt to call ' . __METHOD__ .
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' with invalid server index' );
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}
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if ( $wiki === wfWikiID() ) {
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$wiki = false;
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}
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$groups = ( $groups === false || $groups === array() )
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? array( false ) // check one "group": the generic pool
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: (array)$groups;
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$masterOnly = ( $i == DB_MASTER || $i == $this->getWriterIndex() );
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$oldConnsOpened = $this->connsOpened; // connections open now
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if ( $i == DB_MASTER ) {
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$i = $this->getWriterIndex();
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|
} else {
|
|
# Try to find an available server in any the query groups (in order)
|
|
foreach ( $groups as $group ) {
|
|
$groupIndex = $this->getReaderIndex( $group, $wiki );
|
|
if ( $groupIndex !== false ) {
|
|
$i = $groupIndex;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
# Operation-based index
|
|
if ( $i == DB_SLAVE ) {
|
|
$this->mLastError = 'Unknown error'; // reset error string
|
|
# Try the general server pool if $groups are unavailable.
|
|
$i = in_array( false, $groups, true )
|
|
? false // don't bother with this if that is what was tried above
|
|
: $this->getReaderIndex( false, $wiki );
|
|
# Couldn't find a working server in getReaderIndex()?
|
|
if ( $i === false ) {
|
|
$this->mLastError = 'No working slave server: ' . $this->mLastError;
|
|
|
|
return $this->reportConnectionError();
|
|
}
|
|
}
|
|
|
|
# Now we have an explicit index into the servers array
|
|
$conn = $this->openConnection( $i, $wiki );
|
|
if ( !$conn ) {
|
|
return $this->reportConnectionError();
|
|
}
|
|
|
|
# Profile any new connections that happen
|
|
if ( $this->connsOpened > $oldConnsOpened ) {
|
|
$host = $conn->getServer();
|
|
$dbname = $conn->getDBname();
|
|
$trxProf = Profiler::instance()->getTransactionProfiler();
|
|
$trxProf->recordConnection( $host, $dbname, $masterOnly );
|
|
}
|
|
|
|
return $conn;
|
|
}
|
|
|
|
/**
|
|
* Mark a foreign connection as being available for reuse under a different
|
|
* DB name or prefix. This mechanism is reference-counted, and must be called
|
|
* the same number of times as getConnection() to work.
|
|
*
|
|
* @param DatabaseBase $conn
|
|
* @throws MWException
|
|
*/
|
|
public function reuseConnection( $conn ) {
|
|
$serverIndex = $conn->getLBInfo( 'serverIndex' );
|
|
$refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
|
|
if ( $serverIndex === null || $refCount === null ) {
|
|
wfDebug( __METHOD__ . ": this connection was not opened as a foreign connection\n" );
|
|
|
|
/**
|
|
* This can happen in code like:
|
|
* foreach ( $dbs as $db ) {
|
|
* $conn = $lb->getConnection( DB_SLAVE, array(), $db );
|
|
* ...
|
|
* $lb->reuseConnection( $conn );
|
|
* }
|
|
* When a connection to the local DB is opened in this way, reuseConnection()
|
|
* should be ignored
|
|
*/
|
|
|
|
return;
|
|
}
|
|
|
|
$dbName = $conn->getDBname();
|
|
$prefix = $conn->tablePrefix();
|
|
if ( strval( $prefix ) !== '' ) {
|
|
$wiki = "$dbName-$prefix";
|
|
} else {
|
|
$wiki = $dbName;
|
|
}
|
|
if ( $this->mConns['foreignUsed'][$serverIndex][$wiki] !== $conn ) {
|
|
throw new MWException( __METHOD__ . ": connection not found, has " .
|
|
"the connection been freed already?" );
|
|
}
|
|
$conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
|
|
if ( $refCount <= 0 ) {
|
|
$this->mConns['foreignFree'][$serverIndex][$wiki] = $conn;
|
|
unset( $this->mConns['foreignUsed'][$serverIndex][$wiki] );
|
|
wfDebug( __METHOD__ . ": freed connection $serverIndex/$wiki\n" );
|
|
} else {
|
|
wfDebug( __METHOD__ . ": reference count for $serverIndex/$wiki reduced to $refCount\n" );
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Get a database connection handle reference
|
|
*
|
|
* The handle's methods wrap simply wrap those of a DatabaseBase handle
|
|
*
|
|
* @see LoadBalancer::getConnection() for parameter information
|
|
*
|
|
* @param int $db
|
|
* @param array|string|bool $groups Query group(s), or false for the generic reader
|
|
* @param string|bool $wiki Wiki ID, or false for the current wiki
|
|
* @return DBConnRef
|
|
*/
|
|
public function getConnectionRef( $db, $groups = array(), $wiki = false ) {
|
|
return new DBConnRef( $this, $this->getConnection( $db, $groups, $wiki ) );
|
|
}
|
|
|
|
/**
|
|
* Get a database connection handle reference without connecting yet
|
|
*
|
|
* The handle's methods wrap simply wrap those of a DatabaseBase handle
|
|
*
|
|
* @see LoadBalancer::getConnection() for parameter information
|
|
*
|
|
* @param int $db
|
|
* @param array|string|bool $groups Query group(s), or false for the generic reader
|
|
* @param string|bool $wiki Wiki ID, or false for the current wiki
|
|
* @return DBConnRef
|
|
*/
|
|
public function getLazyConnectionRef( $db, $groups = array(), $wiki = false ) {
|
|
return new DBConnRef( $this, array( $db, $groups, $wiki ) );
|
|
}
|
|
|
|
/**
|
|
* Open a connection to the server given by the specified index
|
|
* Index must be an actual index into the array.
|
|
* If the server is already open, returns it.
|
|
*
|
|
* On error, returns false, and the connection which caused the
|
|
* error will be available via $this->mErrorConnection.
|
|
*
|
|
* @param int $i Server index
|
|
* @param string|bool $wiki Wiki ID, or false for the current wiki
|
|
* @return DatabaseBase
|
|
*
|
|
* @access private
|
|
*/
|
|
public function openConnection( $i, $wiki = false ) {
|
|
if ( $wiki !== false ) {
|
|
$conn = $this->openForeignConnection( $i, $wiki );
|
|
|
|
return $conn;
|
|
}
|
|
if ( isset( $this->mConns['local'][$i][0] ) ) {
|
|
$conn = $this->mConns['local'][$i][0];
|
|
} else {
|
|
$server = $this->mServers[$i];
|
|
$server['serverIndex'] = $i;
|
|
$conn = $this->reallyOpenConnection( $server, false );
|
|
$serverName = $this->getServerName( $i );
|
|
if ( $conn->isOpen() ) {
|
|
wfDebug( "Connected to database $i at $serverName\n" );
|
|
$this->mConns['local'][$i][0] = $conn;
|
|
} else {
|
|
wfDebug( "Failed to connect to database $i at $serverName\n" );
|
|
$this->mErrorConnection = $conn;
|
|
$conn = false;
|
|
}
|
|
}
|
|
|
|
return $conn;
|
|
}
|
|
|
|
/**
|
|
* Open a connection to a foreign DB, or return one if it is already open.
|
|
*
|
|
* Increments a reference count on the returned connection which locks the
|
|
* connection to the requested wiki. This reference count can be
|
|
* decremented by calling reuseConnection().
|
|
*
|
|
* If a connection is open to the appropriate server already, but with the wrong
|
|
* database, it will be switched to the right database and returned, as long as
|
|
* it has been freed first with reuseConnection().
|
|
*
|
|
* On error, returns false, and the connection which caused the
|
|
* error will be available via $this->mErrorConnection.
|
|
*
|
|
* @param int $i Server index
|
|
* @param string $wiki Wiki ID to open
|
|
* @return DatabaseBase
|
|
*/
|
|
private function openForeignConnection( $i, $wiki ) {
|
|
list( $dbName, $prefix ) = wfSplitWikiID( $wiki );
|
|
if ( isset( $this->mConns['foreignUsed'][$i][$wiki] ) ) {
|
|
// Reuse an already-used connection
|
|
$conn = $this->mConns['foreignUsed'][$i][$wiki];
|
|
wfDebug( __METHOD__ . ": reusing connection $i/$wiki\n" );
|
|
} elseif ( isset( $this->mConns['foreignFree'][$i][$wiki] ) ) {
|
|
// Reuse a free connection for the same wiki
|
|
$conn = $this->mConns['foreignFree'][$i][$wiki];
|
|
unset( $this->mConns['foreignFree'][$i][$wiki] );
|
|
$this->mConns['foreignUsed'][$i][$wiki] = $conn;
|
|
wfDebug( __METHOD__ . ": reusing free connection $i/$wiki\n" );
|
|
} elseif ( !empty( $this->mConns['foreignFree'][$i] ) ) {
|
|
// Reuse a connection from another wiki
|
|
$conn = reset( $this->mConns['foreignFree'][$i] );
|
|
$oldWiki = key( $this->mConns['foreignFree'][$i] );
|
|
|
|
// The empty string as a DB name means "don't care".
|
|
// DatabaseMysqlBase::open() already handle this on connection.
|
|
if ( $dbName !== '' && !$conn->selectDB( $dbName ) ) {
|
|
$this->mLastError = "Error selecting database $dbName on server " .
|
|
$conn->getServer() . " from client host " . wfHostname() . "\n";
|
|
$this->mErrorConnection = $conn;
|
|
$conn = false;
|
|
} else {
|
|
$conn->tablePrefix( $prefix );
|
|
unset( $this->mConns['foreignFree'][$i][$oldWiki] );
|
|
$this->mConns['foreignUsed'][$i][$wiki] = $conn;
|
|
wfDebug( __METHOD__ . ": reusing free connection from $oldWiki for $wiki\n" );
|
|
}
|
|
} else {
|
|
// Open a new connection
|
|
$server = $this->mServers[$i];
|
|
$server['serverIndex'] = $i;
|
|
$server['foreignPoolRefCount'] = 0;
|
|
$server['foreign'] = true;
|
|
$conn = $this->reallyOpenConnection( $server, $dbName );
|
|
if ( !$conn->isOpen() ) {
|
|
wfDebug( __METHOD__ . ": error opening connection for $i/$wiki\n" );
|
|
$this->mErrorConnection = $conn;
|
|
$conn = false;
|
|
} else {
|
|
$conn->tablePrefix( $prefix );
|
|
$this->mConns['foreignUsed'][$i][$wiki] = $conn;
|
|
wfDebug( __METHOD__ . ": opened new connection for $i/$wiki\n" );
|
|
}
|
|
}
|
|
|
|
// Increment reference count
|
|
if ( $conn ) {
|
|
$refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
|
|
$conn->setLBInfo( 'foreignPoolRefCount', $refCount + 1 );
|
|
}
|
|
|
|
return $conn;
|
|
}
|
|
|
|
/**
|
|
* Test if the specified index represents an open connection
|
|
*
|
|
* @param int $index Server index
|
|
* @access private
|
|
* @return bool
|
|
*/
|
|
private function isOpen( $index ) {
|
|
if ( !is_integer( $index ) ) {
|
|
return false;
|
|
}
|
|
|
|
return (bool)$this->getAnyOpenConnection( $index );
|
|
}
|
|
|
|
/**
|
|
* Really opens a connection. Uncached.
|
|
* Returns a Database object whether or not the connection was successful.
|
|
* @access private
|
|
*
|
|
* @param array $server
|
|
* @param bool $dbNameOverride
|
|
* @throws MWException
|
|
* @return DatabaseBase
|
|
*/
|
|
protected function reallyOpenConnection( $server, $dbNameOverride = false ) {
|
|
if ( !is_array( $server ) ) {
|
|
throw new MWException( 'You must update your load-balancing configuration. ' .
|
|
'See DefaultSettings.php entry for $wgDBservers.' );
|
|
}
|
|
|
|
if ( $dbNameOverride !== false ) {
|
|
$server['dbname'] = $dbNameOverride;
|
|
}
|
|
|
|
// Log when many connection are made on requests
|
|
if ( ++$this->connsOpened >= self::CONN_HELD_WARN_THRESHOLD ) {
|
|
$masterAddr = $this->getServerName( 0 );
|
|
wfDebugLog( 'DBPerformance', __METHOD__ . ": " .
|
|
"{$this->connsOpened}+ connections made (master=$masterAddr)\n" .
|
|
wfBacktrace( true ) );
|
|
}
|
|
|
|
# Create object
|
|
try {
|
|
$db = DatabaseBase::factory( $server['type'], $server );
|
|
} catch ( DBConnectionError $e ) {
|
|
// FIXME: This is probably the ugliest thing I have ever done to
|
|
// PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
|
|
$db = $e->db;
|
|
}
|
|
|
|
$db->setLBInfo( $server );
|
|
if ( isset( $server['fakeSlaveLag'] ) ) {
|
|
$db->setFakeSlaveLag( $server['fakeSlaveLag'] );
|
|
}
|
|
if ( isset( $server['fakeMaster'] ) ) {
|
|
$db->setFakeMaster( true );
|
|
}
|
|
|
|
return $db;
|
|
}
|
|
|
|
/**
|
|
* @throws DBConnectionError
|
|
* @return bool
|
|
*/
|
|
private function reportConnectionError() {
|
|
$conn = $this->mErrorConnection; // The connection which caused the error
|
|
$context = array(
|
|
'method' => __METHOD__,
|
|
'last_error' => $this->mLastError,
|
|
);
|
|
|
|
if ( !is_object( $conn ) ) {
|
|
// No last connection, probably due to all servers being too busy
|
|
wfLogDBError(
|
|
"LB failure with no last connection. Connection error: {last_error}",
|
|
$context
|
|
);
|
|
|
|
// If all servers were busy, mLastError will contain something sensible
|
|
throw new DBConnectionError( null, $this->mLastError );
|
|
} else {
|
|
$context['db_server'] = $conn->getProperty( 'mServer' );
|
|
wfLogDBError(
|
|
"Connection error: {last_error} ({db_server})",
|
|
$context
|
|
);
|
|
$conn->reportConnectionError( "{$this->mLastError} ({$context['db_server']})" ); // throws DBConnectionError
|
|
}
|
|
|
|
return false; /* not reached */
|
|
}
|
|
|
|
/**
|
|
* @return int
|
|
* @since 1.26
|
|
*/
|
|
public function getWriterIndex() {
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* Returns true if the specified index is a valid server index
|
|
*
|
|
* @param string $i
|
|
* @return bool
|
|
*/
|
|
public function haveIndex( $i ) {
|
|
return array_key_exists( $i, $this->mServers );
|
|
}
|
|
|
|
/**
|
|
* Returns true if the specified index is valid and has non-zero load
|
|
*
|
|
* @param string $i
|
|
* @return bool
|
|
*/
|
|
public function isNonZeroLoad( $i ) {
|
|
return array_key_exists( $i, $this->mServers ) && $this->mLoads[$i] != 0;
|
|
}
|
|
|
|
/**
|
|
* Get the number of defined servers (not the number of open connections)
|
|
*
|
|
* @return int
|
|
*/
|
|
public function getServerCount() {
|
|
return count( $this->mServers );
|
|
}
|
|
|
|
/**
|
|
* Get the host name or IP address of the server with the specified index
|
|
* Prefer a readable name if available.
|
|
* @param string $i
|
|
* @return string
|
|
*/
|
|
public function getServerName( $i ) {
|
|
if ( isset( $this->mServers[$i]['hostName'] ) ) {
|
|
$name = $this->mServers[$i]['hostName'];
|
|
} elseif ( isset( $this->mServers[$i]['host'] ) ) {
|
|
$name = $this->mServers[$i]['host'];
|
|
} else {
|
|
$name = '';
|
|
}
|
|
|
|
return ( $name != '' ) ? $name : 'localhost';
|
|
}
|
|
|
|
/**
|
|
* Return the server info structure for a given index, or false if the index is invalid.
|
|
* @param int $i
|
|
* @return array|bool
|
|
*/
|
|
public function getServerInfo( $i ) {
|
|
if ( isset( $this->mServers[$i] ) ) {
|
|
return $this->mServers[$i];
|
|
} else {
|
|
return false;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Sets the server info structure for the given index. Entry at index $i
|
|
* is created if it doesn't exist
|
|
* @param int $i
|
|
* @param array $serverInfo
|
|
*/
|
|
public function setServerInfo( $i, array $serverInfo ) {
|
|
$this->mServers[$i] = $serverInfo;
|
|
}
|
|
|
|
/**
|
|
* Get the current master position for chronology control purposes
|
|
* @return mixed
|
|
*/
|
|
public function getMasterPos() {
|
|
# If this entire request was served from a slave without opening a connection to the
|
|
# master (however unlikely that may be), then we can fetch the position from the slave.
|
|
$masterConn = $this->getAnyOpenConnection( 0 );
|
|
if ( !$masterConn ) {
|
|
$serverCount = count( $this->mServers );
|
|
for ( $i = 1; $i < $serverCount; $i++ ) {
|
|
$conn = $this->getAnyOpenConnection( $i );
|
|
if ( $conn ) {
|
|
wfDebug( "Master pos fetched from slave\n" );
|
|
|
|
return $conn->getSlavePos();
|
|
}
|
|
}
|
|
} else {
|
|
wfDebug( "Master pos fetched from master\n" );
|
|
|
|
return $masterConn->getMasterPos();
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* Close all open connections
|
|
*/
|
|
public function closeAll() {
|
|
foreach ( $this->mConns as $conns2 ) {
|
|
foreach ( $conns2 as $conns3 ) {
|
|
/** @var DatabaseBase $conn */
|
|
foreach ( $conns3 as $conn ) {
|
|
$conn->close();
|
|
}
|
|
}
|
|
}
|
|
$this->mConns = array(
|
|
'local' => array(),
|
|
'foreignFree' => array(),
|
|
'foreignUsed' => array(),
|
|
);
|
|
$this->connsOpened = 0;
|
|
}
|
|
|
|
/**
|
|
* Close a connection
|
|
* Using this function makes sure the LoadBalancer knows the connection is closed.
|
|
* If you use $conn->close() directly, the load balancer won't update its state.
|
|
* @param DatabaseBase $conn
|
|
*/
|
|
public function closeConnection( $conn ) {
|
|
$done = false;
|
|
foreach ( $this->mConns as $i1 => $conns2 ) {
|
|
foreach ( $conns2 as $i2 => $conns3 ) {
|
|
foreach ( $conns3 as $i3 => $candidateConn ) {
|
|
if ( $conn === $candidateConn ) {
|
|
$conn->close();
|
|
unset( $this->mConns[$i1][$i2][$i3] );
|
|
--$this->connsOpened;
|
|
$done = true;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
if ( !$done ) {
|
|
$conn->close();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Commit transactions on all open connections
|
|
*/
|
|
public function commitAll() {
|
|
foreach ( $this->mConns as $conns2 ) {
|
|
foreach ( $conns2 as $conns3 ) {
|
|
/** @var DatabaseBase[] $conns3 */
|
|
foreach ( $conns3 as $conn ) {
|
|
if ( $conn->trxLevel() ) {
|
|
$conn->commit( __METHOD__, 'flush' );
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Issue COMMIT only on master, only if queries were done on connection
|
|
*/
|
|
public function commitMasterChanges() {
|
|
$masterIndex = $this->getWriterIndex();
|
|
foreach ( $this->mConns as $conns2 ) {
|
|
if ( empty( $conns2[$masterIndex] ) ) {
|
|
continue;
|
|
}
|
|
/** @var DatabaseBase $conn */
|
|
foreach ( $conns2[$masterIndex] as $conn ) {
|
|
if ( $conn->trxLevel() && $conn->writesOrCallbacksPending() ) {
|
|
$conn->commit( __METHOD__, 'flush' );
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Issue ROLLBACK only on master, only if queries were done on connection
|
|
* @since 1.23
|
|
*/
|
|
public function rollbackMasterChanges() {
|
|
$failedServers = array();
|
|
|
|
$masterIndex = $this->getWriterIndex();
|
|
foreach ( $this->mConns as $conns2 ) {
|
|
if ( empty( $conns2[$masterIndex] ) ) {
|
|
continue;
|
|
}
|
|
/** @var DatabaseBase $conn */
|
|
foreach ( $conns2[$masterIndex] as $conn ) {
|
|
if ( $conn->trxLevel() && $conn->writesOrCallbacksPending() ) {
|
|
try {
|
|
$conn->rollback( __METHOD__, 'flush' );
|
|
} catch ( DBError $e ) {
|
|
MWExceptionHandler::logException( $e );
|
|
$failedServers[] = $conn->getServer();
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
if ( $failedServers ) {
|
|
throw new DBExpectedError( null, "Rollback failed on server(s) " .
|
|
implode( ', ', array_unique( $failedServers ) ) );
|
|
}
|
|
}
|
|
|
|
/**
|
|
* @return bool Whether a master connection is already open
|
|
* @since 1.24
|
|
*/
|
|
public function hasMasterConnection() {
|
|
return $this->isOpen( $this->getWriterIndex() );
|
|
}
|
|
|
|
/**
|
|
* Determine if there are pending changes in a transaction by this thread
|
|
* @since 1.23
|
|
* @return bool
|
|
*/
|
|
public function hasMasterChanges() {
|
|
$masterIndex = $this->getWriterIndex();
|
|
foreach ( $this->mConns as $conns2 ) {
|
|
if ( empty( $conns2[$masterIndex] ) ) {
|
|
continue;
|
|
}
|
|
/** @var DatabaseBase $conn */
|
|
foreach ( $conns2[$masterIndex] as $conn ) {
|
|
if ( $conn->trxLevel() && $conn->writesOrCallbacksPending() ) {
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* Get the timestamp of the latest write query done by this thread
|
|
* @since 1.25
|
|
* @return float|bool UNIX timestamp or false
|
|
*/
|
|
public function lastMasterChangeTimestamp() {
|
|
$lastTime = false;
|
|
$masterIndex = $this->getWriterIndex();
|
|
foreach ( $this->mConns as $conns2 ) {
|
|
if ( empty( $conns2[$masterIndex] ) ) {
|
|
continue;
|
|
}
|
|
/** @var DatabaseBase $conn */
|
|
foreach ( $conns2[$masterIndex] as $conn ) {
|
|
$lastTime = max( $lastTime, $conn->lastDoneWrites() );
|
|
}
|
|
}
|
|
return $lastTime;
|
|
}
|
|
|
|
/**
|
|
* Check if this load balancer object had any recent or still
|
|
* pending writes issued against it by this PHP thread
|
|
*
|
|
* @param float $age How many seconds ago is "recent" [defaults to mWaitTimeout]
|
|
* @return bool
|
|
* @since 1.25
|
|
*/
|
|
public function hasOrMadeRecentMasterChanges( $age = null ) {
|
|
$age = ( $age === null ) ? $this->mWaitTimeout : $age;
|
|
|
|
return ( $this->hasMasterChanges()
|
|
|| $this->lastMasterChangeTimestamp() > microtime( true ) - $age );
|
|
}
|
|
|
|
/**
|
|
* @param mixed $value
|
|
* @return mixed
|
|
*/
|
|
public function waitTimeout( $value = null ) {
|
|
return wfSetVar( $this->mWaitTimeout, $value );
|
|
}
|
|
|
|
/**
|
|
* @return bool Whether the generic connection for reads is highly "lagged"
|
|
*/
|
|
public function getLaggedSlaveMode() {
|
|
# Get a generic reader connection
|
|
$this->getConnection( DB_SLAVE );
|
|
|
|
return $this->mLaggedSlaveMode;
|
|
}
|
|
|
|
/**
|
|
* Disables/enables lag checks
|
|
* @param null|bool $mode
|
|
* @return bool
|
|
*/
|
|
public function allowLagged( $mode = null ) {
|
|
if ( $mode === null ) {
|
|
return $this->mAllowLagged;
|
|
}
|
|
$this->mAllowLagged = $mode;
|
|
|
|
return $this->mAllowLagged;
|
|
}
|
|
|
|
/**
|
|
* @return bool
|
|
*/
|
|
public function pingAll() {
|
|
$success = true;
|
|
foreach ( $this->mConns as $conns2 ) {
|
|
foreach ( $conns2 as $conns3 ) {
|
|
/** @var DatabaseBase[] $conns3 */
|
|
foreach ( $conns3 as $conn ) {
|
|
if ( !$conn->ping() ) {
|
|
$success = false;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
return $success;
|
|
}
|
|
|
|
/**
|
|
* Call a function with each open connection object
|
|
* @param callable $callback
|
|
* @param array $params
|
|
*/
|
|
public function forEachOpenConnection( $callback, array $params = array() ) {
|
|
foreach ( $this->mConns as $conns2 ) {
|
|
foreach ( $conns2 as $conns3 ) {
|
|
foreach ( $conns3 as $conn ) {
|
|
$mergedParams = array_merge( array( $conn ), $params );
|
|
call_user_func_array( $callback, $mergedParams );
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Get the hostname and lag time of the most-lagged slave
|
|
*
|
|
* This is useful for maintenance scripts that need to throttle their updates.
|
|
* May attempt to open connections to slaves on the default DB. If there is
|
|
* no lag, the maximum lag will be reported as -1.
|
|
*
|
|
* @param bool|string $wiki Wiki ID, or false for the default database
|
|
* @return array ( host, max lag, index of max lagged host )
|
|
*/
|
|
public function getMaxLag( $wiki = false ) {
|
|
$maxLag = -1;
|
|
$host = '';
|
|
$maxIndex = 0;
|
|
|
|
if ( $this->getServerCount() <= 1 ) {
|
|
return array( $host, $maxLag, $maxIndex ); // no replication = no lag
|
|
}
|
|
|
|
$lagTimes = $this->getLagTimes( $wiki );
|
|
foreach ( $lagTimes as $i => $lag ) {
|
|
if ( $lag > $maxLag ) {
|
|
$maxLag = $lag;
|
|
$host = $this->mServers[$i]['host'];
|
|
$maxIndex = $i;
|
|
}
|
|
}
|
|
|
|
return array( $host, $maxLag, $maxIndex );
|
|
}
|
|
|
|
/**
|
|
* Get lag time for each server
|
|
*
|
|
* Results are cached for a short time in memcached/process cache
|
|
*
|
|
* @param string|bool $wiki
|
|
* @return int[] Map of (server index => seconds)
|
|
*/
|
|
public function getLagTimes( $wiki = false ) {
|
|
if ( $this->getServerCount() <= 1 ) {
|
|
return array( 0 => 0 ); // no replication = no lag
|
|
}
|
|
|
|
if ( $this->mProcCache->has( 'slave_lag', 'times', 1 ) ) {
|
|
return $this->mProcCache->get( 'slave_lag', 'times' );
|
|
}
|
|
|
|
# Send the request to the load monitor
|
|
$times = $this->getLoadMonitor()->getLagTimes( array_keys( $this->mServers ), $wiki );
|
|
|
|
$this->mProcCache->set( 'slave_lag', 'times', $times );
|
|
|
|
return $times;
|
|
}
|
|
|
|
/**
|
|
* Get the lag in seconds for a given connection, or zero if this load
|
|
* balancer does not have replication enabled.
|
|
*
|
|
* This should be used in preference to Database::getLag() in cases where
|
|
* replication may not be in use, since there is no way to determine if
|
|
* replication is in use at the connection level without running
|
|
* potentially restricted queries such as SHOW SLAVE STATUS. Using this
|
|
* function instead of Database::getLag() avoids a fatal error in this
|
|
* case on many installations.
|
|
*
|
|
* @param DatabaseBase $conn
|
|
* @return int
|
|
*/
|
|
public function safeGetLag( $conn ) {
|
|
if ( $this->getServerCount() == 1 ) {
|
|
return 0;
|
|
} else {
|
|
return $conn->getLag();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Clear the cache for slag lag delay times
|
|
*/
|
|
public function clearLagTimeCache() {
|
|
$this->mProcCache->clear( 'slave_lag' );
|
|
}
|
|
}
|