888 lines
25 KiB
PHP
888 lines
25 KiB
PHP
<?php
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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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*/
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class LoadBalancer {
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/* private */ var $mServers, $mConns, $mLoads, $mGroupLoads;
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/* private */ var $mFailFunction, $mErrorConnection;
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/* private */ var $mReadIndex, $mLastIndex, $mAllowLagged;
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/* private */ var $mWaitForPos, $mWaitTimeout;
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/* private */ var $mLaggedSlaveMode, $mLastError = 'Unknown error';
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/* private */ var $mParentInfo, $mLagTimes;
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function __construct( $servers, $failFunction = false, $waitTimeout = 10, $unused = false )
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{
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$this->mServers = $servers;
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$this->mFailFunction = $failFunction;
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$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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$this->mLastIndex = -1;
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$this->mLoads = array();
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$this->mWaitForPos = false;
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$this->mWaitTimeout = $waitTimeout;
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$this->mLaggedSlaveMode = false;
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$this->mErrorConnection = false;
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$this->mAllowLag = false;
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foreach( $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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}
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static function newFromParams( $servers, $failFunction = false, $waitTimeout = 10 )
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{
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return new LoadBalancer( $servers, $failFunction, $waitTimeout );
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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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*/
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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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function pickRandom( $weights )
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{
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if ( !is_array( $weights ) || count( $weights ) == 0 ) {
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return false;
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}
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$sum = array_sum( $weights );
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if ( $sum == 0 ) {
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# No loads on any of them
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# In previous versions, this triggered an unweighted random selection,
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# but this feature has been removed as of April 2006 to allow for strict
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# separation of query groups.
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return false;
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}
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$max = mt_getrandmax();
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$rand = mt_rand(0, $max) / $max * $sum;
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$sum = 0;
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foreach ( $weights as $i => $w ) {
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$sum += $w;
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if ( $sum >= $rand ) {
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break;
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}
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}
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return $i;
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}
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function getRandomNonLagged( $loads, $wiki = false ) {
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# Unset excessively lagged servers
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$lags = $this->getLagTimes( $wiki );
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foreach ( $lags as $i => $lag ) {
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if ( $i != 0 && isset( $this->mServers[$i]['max lag'] ) ) {
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if ( $lag === false ) {
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wfDebug( "Server #$i is not replicating\n" );
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unset( $loads[$i] );
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} elseif ( $lag > $this->mServers[$i]['max lag'] ) {
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wfDebug( "Server #$i is excessively lagged ($lag seconds)\n" );
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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 $this->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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*/
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function getReaderIndex( $group = false, $wiki = false ) {
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global $wgReadOnly, $wgDBClusterTimeout, $wgDBAvgStatusPoll, $wgDBtype;
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# FIXME: For now, only go through all this for mysql databases
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if ($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 and $this->mReadIndex >= 0 ) {
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# Shortcut if generic reader exists already
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return $this->mReadIndex;
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}
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wfProfileIn( __METHOD__ );
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$totalElapsed = 0;
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# convert from seconds to microseconds
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$timeout = $wgDBClusterTimeout * 1e6;
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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 $group\n" );
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wfProfileOut( __METHOD__ );
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return false;
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}
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} else {
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$nonErrorLoads = $this->mLoads;
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}
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if ( !$nonErrorLoads ) {
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throw new MWException( "Empty server array given to LoadBalancer" );
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}
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$i = false;
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$found = false;
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$laggedSlaveMode = false;
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# First try quickly looking through the available servers for a server that
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# meets our criteria
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do {
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$totalThreadsConnected = 0;
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$overloadedServers = 0;
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$currentLoads = $nonErrorLoads;
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while ( count( $currentLoads ) ) {
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if ( $wgReadOnly || $this->mAllowLagged || $laggedSlaveMode ) {
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$i = $this->pickRandom( $currentLoads );
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} else {
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$i = $this->getRandomNonLagged( $currentLoads, $wiki );
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if ( $i === false && count( $currentLoads ) != 0 ) {
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# All slaves lagged. Switch to read-only mode
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$wgReadOnly = wfMsgNoDBForContent( 'readonly_lag' );
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$i = $this->pickRandom( $currentLoads );
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$laggedSlaveMode = true;
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}
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}
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if ( $i === false ) {
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# pickRandom() returned false
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# This is permanent and means the configuration wants us to return false
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wfDebugLog( 'connect', __METHOD__.": pickRandom() returned false\n" );
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wfProfileOut( __METHOD__ );
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return false;
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}
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wfDebugLog( 'connect', __METHOD__.": Using reader #$i: {$this->mServers[$i]['host']}...\n" );
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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\n" );
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unset( $nonErrorLoads[$i] );
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unset( $currentLoads[$i] );
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continue;
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}
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if ( isset( $this->mServers[$i]['max threads'] ) ) {
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$status = $conn->getStatus("Thread%");
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if ( $wiki !== false ) {
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$this->reuseConnection( $conn );
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}
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if ( $status['Threads_running'] > $this->mServers[$i]['max threads'] ) {
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$totalThreadsConnected += $status['Threads_connected'];
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$overloadedServers++;
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unset( $currentLoads[$i] );
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} else {
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# Max threads satisfied, return this server
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break 2;
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}
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} else {
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# No maximum, return this server
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if ( $wiki !== false ) {
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$this->reuseConnection( $conn );
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}
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$found = true;
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break 2;
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}
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}
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# No server found yet
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$i = false;
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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\n" );
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break;
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}
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# Some servers must have been overloaded
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if ( $overloadedServers == 0 ) {
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throw new MWException( __METHOD__.": unexpectedly found no overloaded servers" );
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}
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# Back off for a while
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# Scale the sleep time by the number of connected threads, to produce a
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# roughly constant global poll rate
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$avgThreads = $totalThreadsConnected / $overloadedServers;
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$totalElapsed += $this->sleep( $wgDBAvgStatusPoll * $avgThreads );
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} while ( $totalElapsed < $timeout );
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if ( $totalElapsed >= $timeout ) {
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wfDebugLog( 'connect', "All servers busy\n" );
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$this->mErrorConnection = false;
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$this->mLastError = 'All servers busy';
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}
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if ( $i !== false ) {
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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 && $i !== false ) {
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$this->mReadIndex = $i;
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}
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}
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wfProfileOut( __METHOD__ );
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return $i;
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}
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/**
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* Wait for a specified number of microseconds, and return the period waited
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*/
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function sleep( $t ) {
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wfProfileIn( __METHOD__ );
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wfDebug( __METHOD__.": waiting $t us\n" );
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usleep( $t );
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wfProfileOut( __METHOD__ );
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return $t;
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}
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/**
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* Get a random server to use in a query group
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* @deprecated use getReaderIndex
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*/
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function getGroupIndex( $group ) {
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return $this->getReaderIndex( $group );
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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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*/
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public function waitFor( $pos ) {
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wfProfileIn( __METHOD__ );
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$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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wfProfileOut( __METHOD__ );
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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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function getAnyOpenConnection( $i ) {
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foreach ( $this->mConns as $type => $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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*/
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function doWait( $index ) {
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# Find a connection to wait on
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$conn = $this->getAnyOpenConnection( $index );
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if ( !$conn ) {
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wfDebug( __METHOD__ . ": no connection open\n" );
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return false;
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}
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wfDebug( __METHOD__.": Waiting for slave #$index to catch up...\n" );
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$result = $conn->masterPosWait( $this->mWaitForPos, $this->mWaitTimeout );
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if ( $result == -1 || is_null( $result ) ) {
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# Timed out waiting for slave, use master instead
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wfDebug( __METHOD__.": Timed out waiting for slave #$index pos {$this->mWaitForPos}\n" );
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return false;
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} else {
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wfDebug( __METHOD__.": Done\n" );
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return true;
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}
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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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public function &getConnection( $i, $groups = array(), $wiki = false ) {
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global $wgDBtype;
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wfProfileIn( __METHOD__ );
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if ( $wiki === wfWikiID() ) {
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$wiki = false;
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}
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# Query groups
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if ( $i == DB_MASTER ) {
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$i = $this->getWriterIndex();
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} elseif ( !is_array( $groups ) ) {
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$groupIndex = $this->getReaderIndex( $groups, $wiki );
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if ( $groupIndex !== false ) {
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$serverName = $this->getServerName( $groupIndex );
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wfDebug( __METHOD__.": using server $serverName for group $groups\n" );
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$i = $groupIndex;
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}
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} else {
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foreach ( $groups as $group ) {
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$groupIndex = $this->getReaderIndex( $group, $wiki );
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if ( $groupIndex !== false ) {
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$serverName = $this->getServerName( $groupIndex );
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wfDebug( __METHOD__.": using server $serverName for group $group\n" );
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$i = $groupIndex;
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break;
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}
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}
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}
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# Operation-based index
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if ( $i == DB_SLAVE ) {
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$i = $this->getReaderIndex( false, $wiki );
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} elseif ( $i == DB_LAST ) {
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# Just use $this->mLastIndex, which should already be set
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$i = $this->mLastIndex;
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if ( $i === -1 ) {
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# Oh dear, not set, best to use the writer for safety
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wfDebug( "Warning: DB_LAST used when there was no previous index\n" );
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$i = $this->getWriterIndex();
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}
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}
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# Couldn't find a working server in getReaderIndex()?
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if ( $i === false ) {
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$this->reportConnectionError( $this->mErrorConnection );
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}
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# Now we have an explicit index into the servers array
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$conn = $this->openConnection( $i, $wiki );
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if ( !$conn ) {
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$this->reportConnectionError( $this->mErrorConnection );
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}
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wfProfileOut( __METHOD__ );
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return $conn;
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}
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/**
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* Mark a foreign connection as being available for reuse under a different
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* DB name or prefix. This mechanism is reference-counted, and must be called
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* the same number of times as getConnection() to work.
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*/
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public function reuseConnection( $conn ) {
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$serverIndex = $conn->getLBInfo('serverIndex');
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$refCount = $conn->getLBInfo('foreignPoolRefCount');
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$dbName = $conn->getDBname();
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$prefix = $conn->tablePrefix();
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if ( strval( $prefix ) !== '' ) {
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$wiki = "$dbName-$prefix";
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} else {
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$wiki = $dbName;
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}
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if ( $serverIndex === null || $refCount === null ) {
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wfDebug( __METHOD__.": this connection was not opened as a foreign connection\n" );
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/**
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* This can happen in code like:
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* foreach ( $dbs as $db ) {
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* $conn = $lb->getConnection( DB_SLAVE, array(), $db );
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* ...
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* $lb->reuseConnection( $conn );
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* }
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* When a connection to the local DB is opened in this way, reuseConnection()
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* should be ignored
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*/
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return;
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}
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if ( $this->mConns['foreignUsed'][$serverIndex][$wiki] !== $conn ) {
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throw new MWException( __METHOD__.": connection not found, has the connection been freed already?" );
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}
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$conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
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if ( $refCount <= 0 ) {
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$this->mConns['foreignFree'][$serverIndex][$wiki] = $conn;
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unset( $this->mConns['foreignUsed'][$serverIndex][$wiki] );
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wfDebug( __METHOD__.": freed connection $serverIndex/$wiki\n" );
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} else {
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wfDebug( __METHOD__.": reference count for $serverIndex/$wiki reduced to $refCount\n" );
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}
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}
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/**
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* Open a connection to the server given by the specified index
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* Index must be an actual index into the array.
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* If the server is already open, returns it.
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*
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* On error, returns false, and the connection which caused the
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* error will be available via $this->mErrorConnection.
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*
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* @param integer $i Server index
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* @param string $wiki Wiki ID to open
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* @return Database
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*
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* @access private
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*/
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function openConnection( $i, $wiki = false ) {
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wfProfileIn( __METHOD__ );
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if ( $wiki !== false ) {
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$conn = $this->openForeignConnection( $i, $wiki );
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wfProfileOut( __METHOD__);
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return $conn;
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}
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if ( isset( $this->mConns['local'][$i][0] ) ) {
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$conn = $this->mConns['local'][$i][0];
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} else {
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$server = $this->mServers[$i];
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$server['serverIndex'] = $i;
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$conn = $this->reallyOpenConnection( $server );
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if ( $conn->isOpen() ) {
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$this->mConns['local'][$i][0] = $conn;
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} else {
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wfDebug( "Failed to connect to database $i at {$this->mServers[$i]['host']}\n" );
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$this->mErrorConnection = $conn;
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$conn = false;
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}
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}
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$this->mLastIndex = $i;
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wfProfileOut( __METHOD__ );
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return $conn;
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}
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/**
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* Open a connection to a foreign DB, or return one if it is already open.
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*
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* Increments a reference count on the returned connection which locks the
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* connection to the requested wiki. This reference count can be
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* decremented by calling reuseConnection().
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*
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* If a connection is open to the appropriate server already, but with the wrong
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* database, it will be switched to the right database and returned, as long as
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* it has been freed first with reuseConnection().
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*
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* On error, returns false, and the connection which caused the
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* error will be available via $this->mErrorConnection.
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*
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* @param integer $i Server index
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* @param string $wiki Wiki ID to open
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|
* @return Database
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*/
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function openForeignConnection( $i, $wiki ) {
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wfProfileIn(__METHOD__);
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list( $dbName, $prefix ) = wfSplitWikiID( $wiki );
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if ( isset( $this->mConns['foreignUsed'][$i][$wiki] ) ) {
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// Reuse an already-used connection
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$conn = $this->mConns['foreignUsed'][$i][$wiki];
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wfDebug( __METHOD__.": reusing connection $i/$wiki\n" );
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} elseif ( isset( $this->mConns['foreignFree'][$i][$wiki] ) ) {
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// Reuse a free connection for the same wiki
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$conn = $this->mConns['foreignFree'][$i][$wiki];
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unset( $this->mConns['foreignFree'][$i][$wiki] );
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$this->mConns['foreignUsed'][$i][$wiki] = $conn;
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wfDebug( __METHOD__.": reusing free connection $i/$wiki\n" );
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} elseif ( !empty( $this->mConns['foreignFree'][$i] ) ) {
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// Reuse a connection from another wiki
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$conn = reset( $this->mConns['foreignFree'][$i] );
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$oldWiki = key( $this->mConns['foreignFree'][$i] );
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if ( !$conn->selectDB( $dbName ) ) {
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global $wguname;
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$this->mLastError = "Error selecting database $dbName on server " .
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$conn->getServer() . " from client host {$wguname['nodename']}\n";
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$this->mErrorConnection = $conn;
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$conn = false;
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} else {
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$conn->tablePrefix( $prefix );
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unset( $this->mConns['foreignFree'][$i][$oldWiki] );
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$this->mConns['foreignUsed'][$i][$wiki] = $conn;
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wfDebug( __METHOD__.": reusing free connection from $oldWiki for $wiki\n" );
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}
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} else {
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// Open a new connection
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$server = $this->mServers[$i];
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$server['serverIndex'] = $i;
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$server['foreignPoolRefCount'] = 0;
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$conn = $this->reallyOpenConnection( $server, $dbName );
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if ( !$conn->isOpen() ) {
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wfDebug( __METHOD__.": error opening connection for $i/$wiki\n" );
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$this->mErrorConnection = $conn;
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$conn = false;
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} else {
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$this->mConns['foreignUsed'][$i][$wiki] = $conn;
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wfDebug( __METHOD__.": opened new connection for $i/$wiki\n" );
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}
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}
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// Increment reference count
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if ( $conn ) {
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$refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
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$conn->setLBInfo( 'foreignPoolRefCount', $refCount + 1 );
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}
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wfProfileOut(__METHOD__);
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return $conn;
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}
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/**
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* Test if the specified index represents an open connection
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* @access private
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*/
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function isOpen( $index ) {
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if( !is_integer( $index ) ) {
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return false;
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}
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return (bool)$this->getAnyOpenConnection( $index );
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}
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/**
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* Really opens a connection. Uncached.
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* Returns a Database object whether or not the connection was successful.
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* @access private
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*/
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function reallyOpenConnection( $server, $dbNameOverride = false ) {
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if( !is_array( $server ) ) {
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throw new MWException( 'You must update your load-balancing configuration. See DefaultSettings.php entry for $wgDBservers.' );
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}
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extract( $server );
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if ( $dbNameOverride !== false ) {
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$dbname = $dbNameOverride;
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}
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# Get class for this database type
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$class = 'Database' . ucfirst( $type );
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# Create object
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wfDebug( "Connecting to $host $dbname...\n" );
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$db = new $class( $host, $user, $password, $dbname, 1, $flags );
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if ( $db->isOpen() ) {
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wfDebug( "Connected\n" );
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} else {
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wfDebug( "Failed\n" );
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}
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$db->setLBInfo( $server );
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if ( isset( $server['fakeSlaveLag'] ) ) {
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$db->setFakeSlaveLag( $server['fakeSlaveLag'] );
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}
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if ( isset( $server['fakeMaster'] ) ) {
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$db->setFakeMaster( true );
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}
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return $db;
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}
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|
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function reportConnectionError( &$conn ) {
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wfProfileIn( __METHOD__ );
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# Prevent infinite recursion
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|
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static $reporting = false;
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if ( !$reporting ) {
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$reporting = true;
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if ( !is_object( $conn ) ) {
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// No last connection, probably due to all servers being too busy
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$conn = new Database;
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if ( $this->mFailFunction ) {
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$conn->failFunction( $this->mFailFunction );
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$conn->reportConnectionError( $this->mLastError );
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} else {
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// If all servers were busy, mLastError will contain something sensible
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throw new DBConnectionError( $conn, $this->mLastError );
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}
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} else {
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if ( $this->mFailFunction ) {
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$conn->failFunction( $this->mFailFunction );
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} else {
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$conn->failFunction( false );
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}
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$server = $conn->getProperty( 'mServer' );
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$conn->reportConnectionError( "{$this->mLastError} ({$server})" );
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}
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$reporting = false;
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}
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wfProfileOut( __METHOD__ );
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|
}
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|
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function getWriterIndex() {
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return 0;
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}
|
|
|
|
/**
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* Returns true if the specified index is a valid server index
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|
*/
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|
function haveIndex( $i ) {
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return array_key_exists( $i, $this->mServers );
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}
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|
|
|
/**
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* Returns true if the specified index is valid and has non-zero load
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*/
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|
function isNonZeroLoad( $i ) {
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return array_key_exists( $i, $this->mServers ) && $this->mLoads[$i] != 0;
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}
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|
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/**
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* Get the number of defined servers (not the number of open connections)
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*/
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function getServerCount() {
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return count( $this->mServers );
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}
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|
/**
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* Get the host name or IP address of the server with the specified index
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*/
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|
function getServerName( $i ) {
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if ( isset( $this->mServers[$i]['hostName'] ) ) {
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return $this->mServers[$i]['hostName'];
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|
} elseif ( isset( $this->mServers[$i]['host'] ) ) {
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|
return $this->mServers[$i]['host'];
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} else {
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return '';
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|
}
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|
}
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|
|
/**
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|
* Get the current master position for chronology control purposes
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|
* @return mixed
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|
*/
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|
function getMasterPos() {
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|
# If this entire request was served from a slave without opening a connection to the
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# master (however unlikely that may be), then we can fetch the position from the slave.
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|
$masterConn = $this->getAnyOpenConnection( 0 );
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if ( !$masterConn ) {
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for ( $i = 1; $i < count( $this->mServers ); $i++ ) {
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$conn = $this->getAnyOpenConnection( $i );
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if ( $conn ) {
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|
wfDebug( "Master pos fetched from slave\n" );
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return $conn->getSlavePos();
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}
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|
}
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|
} else {
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|
wfDebug( "Master pos fetched from master\n" );
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|
return $masterConn->getMasterPos();
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|
}
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|
return false;
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|
}
|
|
|
|
/**
|
|
* Close all open connections
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|
*/
|
|
function closeAll() {
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|
foreach ( $this->mConns as $conns2 ) {
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|
foreach ( $conns2 as $conns3 ) {
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|
foreach ( $conns3 as $conn ) {
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|
$conn->close();
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|
}
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|
}
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|
}
|
|
$this->mConns = array(
|
|
'local' => array(),
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|
'foreignFree' => array(),
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|
'foreignUsed' => array(),
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|
);
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|
}
|
|
|
|
/**
|
|
* 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.
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|
*/
|
|
function closeConnecton( $conn ) {
|
|
$done = false;
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|
foreach ( $this->mConns as $i1 => $conns2 ) {
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|
foreach ( $conns2 as $i2 => $conns3 ) {
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|
foreach ( $conns3 as $i3 => $candidateConn ) {
|
|
if ( $conn === $candidateConn ) {
|
|
$conn->close();
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|
unset( $this->mConns[$i1][$i2][$i3] );
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|
$done = true;
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|
break;
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|
}
|
|
}
|
|
}
|
|
}
|
|
if ( !$done ) {
|
|
$conn->close();
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|
}
|
|
}
|
|
|
|
/**
|
|
* Commit transactions on all open connections
|
|
*/
|
|
function commitAll() {
|
|
foreach ( $this->mConns as $conns2 ) {
|
|
foreach ( $conns2 as $conns3 ) {
|
|
foreach ( $conns3 as $conn ) {
|
|
$conn->immediateCommit();
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|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Issue COMMIT only on master, only if queries were done on connection */
|
|
function commitMasterChanges() {
|
|
// Always 0, but who knows.. :)
|
|
$masterIndex = $this->getWriterIndex();
|
|
foreach ( $this->mConns as $type => $conns2 ) {
|
|
if ( empty( $conns2[$masterIndex] ) ) {
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|
continue;
|
|
}
|
|
foreach ( $conns2[$masterIndex] as $conn ) {
|
|
if ( $conn->lastQuery() != '' ) {
|
|
$conn->commit();
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|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
function waitTimeout( $value = NULL ) {
|
|
return wfSetVar( $this->mWaitTimeout, $value );
|
|
}
|
|
|
|
function getLaggedSlaveMode() {
|
|
return $this->mLaggedSlaveMode;
|
|
}
|
|
|
|
/* Disables/enables lag checks */
|
|
function allowLagged($mode=null) {
|
|
if ($mode===null)
|
|
return $this->mAllowLagged;
|
|
$this->mAllowLagged=$mode;
|
|
}
|
|
|
|
function pingAll() {
|
|
$success = true;
|
|
foreach ( $this->mConns as $conns2 ) {
|
|
foreach ( $conns2 as $conns3 ) {
|
|
foreach ( $conns3 as $conn ) {
|
|
if ( !$conn->ping() ) {
|
|
$success = false;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
return $success;
|
|
}
|
|
|
|
/**
|
|
* 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.
|
|
*/
|
|
function getMaxLag() {
|
|
$maxLag = -1;
|
|
$host = '';
|
|
foreach ( $this->mServers as $i => $conn ) {
|
|
$conn = $this->getAnyOpenConnection( $i );
|
|
if ( !$conn ) {
|
|
$conn = $this->openConnection( $i );
|
|
}
|
|
if ( !$conn ) {
|
|
continue;
|
|
}
|
|
$lag = $conn->getLag();
|
|
if ( $lag > $maxLag ) {
|
|
$maxLag = $lag;
|
|
$host = $this->mServers[$i]['host'];
|
|
}
|
|
}
|
|
return array( $host, $maxLag );
|
|
}
|
|
|
|
/**
|
|
* Get lag time for each server
|
|
* Results are cached for a short time in memcached, and indefinitely in the process cache
|
|
*/
|
|
function getLagTimes( $wiki = false ) {
|
|
wfProfileIn( __METHOD__ );
|
|
|
|
if ( !isset( $this->mLagTimes ) ) {
|
|
$expiry = 5;
|
|
$requestRate = 10;
|
|
|
|
global $wgMemc;
|
|
$masterName = $this->getServerName( 0 );
|
|
$memcKey = wfMemcKey( 'lag_times', $masterName );
|
|
$times = $wgMemc->get( $memcKey );
|
|
if ( $times ) {
|
|
# Randomly recache with probability rising over $expiry
|
|
$elapsed = time() - $times['timestamp'];
|
|
$chance = max( 0, ( $expiry - $elapsed ) * $requestRate );
|
|
if ( mt_rand( 0, $chance ) != 0 ) {
|
|
unset( $times['timestamp'] );
|
|
wfProfileOut( __METHOD__ );
|
|
return $times;
|
|
}
|
|
wfIncrStats( 'lag_cache_miss_expired' );
|
|
} else {
|
|
wfIncrStats( 'lag_cache_miss_absent' );
|
|
}
|
|
|
|
# Cache key missing or expired
|
|
|
|
$times = array();
|
|
foreach ( $this->mServers as $i => $conn ) {
|
|
if ($i == 0) { # Master
|
|
$times[$i] = 0;
|
|
} elseif ( false !== ( $conn = $this->getAnyOpenConnection( $i ) ) ) {
|
|
$times[$i] = $conn->getLag();
|
|
} elseif ( false !== ( $conn = $this->openConnection( $i, $wiki ) ) ) {
|
|
$times[$i] = $conn->getLag();
|
|
}
|
|
}
|
|
|
|
# Add a timestamp key so we know when it was cached
|
|
$times['timestamp'] = time();
|
|
$wgMemc->set( $memcKey, $times, $expiry );
|
|
|
|
# But don't give the timestamp to the caller
|
|
unset($times['timestamp']);
|
|
$this->mLagTimes = $times;
|
|
}
|
|
wfProfileOut( __METHOD__ );
|
|
return $this->mLagTimes;
|
|
}
|
|
}
|