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-rw-r--r--includes/LoadBalancer.php653
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diff --git a/includes/LoadBalancer.php b/includes/LoadBalancer.php
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index 0cdadd1e..00000000
--- a/includes/LoadBalancer.php
+++ /dev/null
@@ -1,653 +0,0 @@
-<?php
-/**
- *
- */
-
-
-/**
- * Database load balancing object
- *
- * @todo document
- */
-class LoadBalancer {
- /* private */ var $mServers, $mConnections, $mLoads, $mGroupLoads;
- /* private */ var $mFailFunction, $mErrorConnection;
- /* private */ var $mForce, $mReadIndex, $mLastIndex, $mAllowLagged;
- /* private */ var $mWaitForFile, $mWaitForPos, $mWaitTimeout;
- /* private */ var $mLaggedSlaveMode, $mLastError = 'Unknown error';
-
- function __construct( $servers, $failFunction = false, $waitTimeout = 10, $waitForMasterNow = false )
- {
- $this->mServers = $servers;
- $this->mFailFunction = $failFunction;
- $this->mReadIndex = -1;
- $this->mWriteIndex = -1;
- $this->mForce = -1;
- $this->mConnections = array();
- $this->mLastIndex = -1;
- $this->mLoads = array();
- $this->mWaitForFile = false;
- $this->mWaitForPos = false;
- $this->mWaitTimeout = $waitTimeout;
- $this->mLaggedSlaveMode = false;
- $this->mErrorConnection = false;
- $this->mAllowLag = false;
-
- foreach( $servers as $i => $server ) {
- $this->mLoads[$i] = $server['load'];
- if ( isset( $server['groupLoads'] ) ) {
- foreach ( $server['groupLoads'] as $group => $ratio ) {
- if ( !isset( $this->mGroupLoads[$group] ) ) {
- $this->mGroupLoads[$group] = array();
- }
- $this->mGroupLoads[$group][$i] = $ratio;
- }
- }
- }
- if ( $waitForMasterNow ) {
- $this->loadMasterPos();
- }
- }
-
- static function newFromParams( $servers, $failFunction = false, $waitTimeout = 10 )
- {
- return new LoadBalancer( $servers, $failFunction, $waitTimeout );
- }
-
- /**
- * Given an array of non-normalised probabilities, this function will select
- * an element and return the appropriate key
- */
- function pickRandom( $weights )
- {
- if ( !is_array( $weights ) || count( $weights ) == 0 ) {
- return false;
- }
-
- $sum = array_sum( $weights );
- if ( $sum == 0 ) {
- # No loads on any of them
- # In previous versions, this triggered an unweighted random selection,
- # but this feature has been removed as of April 2006 to allow for strict
- # separation of query groups.
- return false;
- }
- $max = mt_getrandmax();
- $rand = mt_rand(0, $max) / $max * $sum;
-
- $sum = 0;
- foreach ( $weights as $i => $w ) {
- $sum += $w;
- if ( $sum >= $rand ) {
- break;
- }
- }
- return $i;
- }
-
- function getRandomNonLagged( $loads ) {
- # Unset excessively lagged servers
- $lags = $this->getLagTimes();
- foreach ( $lags as $i => $lag ) {
- if ( $i != 0 && isset( $this->mServers[$i]['max lag'] ) &&
- ( $lag === false || $lag > $this->mServers[$i]['max lag'] ) )
- {
- unset( $loads[$i] );
- }
- }
-
- # Find out if all the slaves with non-zero load are lagged
- $sum = 0;
- foreach ( $loads as $load ) {
- $sum += $load;
- }
- if ( $sum == 0 ) {
- # No appropriate DB servers except maybe the master and some slaves with zero load
- # Do NOT use the master
- # Instead, this function will return false, triggering read-only mode,
- # and a lagged slave will be used instead.
- return false;
- }
-
- if ( count( $loads ) == 0 ) {
- return false;
- }
-
- #wfDebugLog( 'connect', var_export( $loads, true ) );
-
- # Return a random representative of the remainder
- return $this->pickRandom( $loads );
- }
-
- /**
- * Get the index of the reader connection, which may be a slave
- * This takes into account load ratios and lag times. It should
- * always return a consistent index during a given invocation
- *
- * Side effect: opens connections to databases
- */
- function getReaderIndex() {
- global $wgReadOnly, $wgDBClusterTimeout, $wgDBAvgStatusPoll;
-
- $fname = 'LoadBalancer::getReaderIndex';
- wfProfileIn( $fname );
-
- $i = false;
- if ( $this->mForce >= 0 ) {
- $i = $this->mForce;
- } elseif ( count( $this->mServers ) == 1 ) {
- # Skip the load balancing if there's only one server
- $i = 0;
- } else {
- if ( $this->mReadIndex >= 0 ) {
- $i = $this->mReadIndex;
- } else {
- # $loads is $this->mLoads except with elements knocked out if they
- # don't work
- $loads = $this->mLoads;
- $done = false;
- $totalElapsed = 0;
- do {
- if ( $wgReadOnly or $this->mAllowLagged ) {
- $i = $this->pickRandom( $loads );
- } else {
- $i = $this->getRandomNonLagged( $loads );
- if ( $i === false && count( $loads ) != 0 ) {
- # All slaves lagged. Switch to read-only mode
- $wgReadOnly = wfMsgNoDBForContent( 'readonly_lag' );
- $i = $this->pickRandom( $loads );
- }
- }
- $serverIndex = $i;
- if ( $i !== false ) {
- wfDebugLog( 'connect', "$fname: Using reader #$i: {$this->mServers[$i]['host']}...\n" );
- $this->openConnection( $i );
-
- if ( !$this->isOpen( $i ) ) {
- wfDebug( "$fname: Failed\n" );
- unset( $loads[$i] );
- $sleepTime = 0;
- } else {
- if ( isset( $this->mServers[$i]['max threads'] ) ) {
- $status = $this->mConnections[$i]->getStatus("Thread%");
- if ( $status['Threads_running'] > $this->mServers[$i]['max threads'] ) {
- # Too much load, back off and wait for a while.
- # The sleep time is scaled by the number of threads connected,
- # to produce a roughly constant global poll rate.
- $sleepTime = $wgDBAvgStatusPoll * $status['Threads_connected'];
-
- # If we reach the timeout and exit the loop, don't use it
- $i = false;
- } else {
- $done = true;
- $sleepTime = 0;
- }
- } else {
- $done = true;
- $sleepTime = 0;
- }
- }
- } else {
- $sleepTime = 500000;
- }
- if ( $sleepTime ) {
- $totalElapsed += $sleepTime;
- $x = "{$this->mServers[$serverIndex]['host']} [$serverIndex]";
- wfProfileIn( "$fname-sleep $x" );
- usleep( $sleepTime );
- wfProfileOut( "$fname-sleep $x" );
- }
- } while ( count( $loads ) && !$done && $totalElapsed / 1e6 < $wgDBClusterTimeout );
-
- if ( $totalElapsed / 1e6 >= $wgDBClusterTimeout ) {
- $this->mErrorConnection = false;
- $this->mLastError = 'All servers busy';
- }
-
- if ( $i !== false && $this->isOpen( $i ) ) {
- # Wait for the session master pos for a short time
- if ( $this->mWaitForFile ) {
- if ( !$this->doWait( $i ) ) {
- $this->mServers[$i]['slave pos'] = $this->mConnections[$i]->getSlavePos();
- }
- }
- if ( $i !== false ) {
- $this->mReadIndex = $i;
- }
- } else {
- $i = false;
- }
- }
- }
- wfProfileOut( $fname );
- return $i;
- }
-
- /**
- * Get a random server to use in a query group
- */
- function getGroupIndex( $group ) {
- if ( isset( $this->mGroupLoads[$group] ) ) {
- $i = $this->pickRandom( $this->mGroupLoads[$group] );
- } else {
- $i = false;
- }
- wfDebug( "Query group $group => $i\n" );
- return $i;
- }
-
- /**
- * Set the master wait position
- * If a DB_SLAVE connection has been opened already, waits
- * Otherwise sets a variable telling it to wait if such a connection is opened
- */
- function waitFor( $file, $pos ) {
- $fname = 'LoadBalancer::waitFor';
- wfProfileIn( $fname );
-
- wfDebug( "User master pos: $file $pos\n" );
- $this->mWaitForFile = false;
- $this->mWaitForPos = false;
-
- if ( count( $this->mServers ) > 1 ) {
- $this->mWaitForFile = $file;
- $this->mWaitForPos = $pos;
- $i = $this->mReadIndex;
-
- if ( $i > 0 ) {
- if ( !$this->doWait( $i ) ) {
- $this->mServers[$i]['slave pos'] = $this->mConnections[$i]->getSlavePos();
- $this->mLaggedSlaveMode = true;
- }
- }
- }
- wfProfileOut( $fname );
- }
-
- /**
- * Wait for a given slave to catch up to the master pos stored in $this
- */
- function doWait( $index ) {
- global $wgMemc;
-
- $retVal = false;
-
- # Debugging hacks
- if ( isset( $this->mServers[$index]['lagged slave'] ) ) {
- return false;
- } elseif ( isset( $this->mServers[$index]['fake slave'] ) ) {
- return true;
- }
-
- $key = 'masterpos:' . $index;
- $memcPos = $wgMemc->get( $key );
- if ( $memcPos ) {
- list( $file, $pos ) = explode( ' ', $memcPos );
- # If the saved position is later than the requested position, return now
- if ( $file == $this->mWaitForFile && $this->mWaitForPos <= $pos ) {
- $retVal = true;
- }
- }
-
- if ( !$retVal && $this->isOpen( $index ) ) {
- $conn =& $this->mConnections[$index];
- wfDebug( "Waiting for slave #$index to catch up...\n" );
- $result = $conn->masterPosWait( $this->mWaitForFile, $this->mWaitForPos, $this->mWaitTimeout );
-
- if ( $result == -1 || is_null( $result ) ) {
- # Timed out waiting for slave, use master instead
- wfDebug( "Timed out waiting for slave #$index pos {$this->mWaitForFile} {$this->mWaitForPos}\n" );
- $retVal = false;
- } else {
- $retVal = true;
- wfDebug( "Done\n" );
- }
- }
- return $retVal;
- }
-
- /**
- * Get a connection by index
- */
- function &getConnection( $i, $fail = true, $groups = array() )
- {
- global $wgDBtype;
- $fname = 'LoadBalancer::getConnection';
- wfProfileIn( $fname );
-
-
- # Query groups
- if ( !is_array( $groups ) ) {
- $groupIndex = $this->getGroupIndex( $groups );
- if ( $groupIndex !== false ) {
- $i = $groupIndex;
- }
- } else {
- foreach ( $groups as $group ) {
- $groupIndex = $this->getGroupIndex( $group );
- if ( $groupIndex !== false ) {
- $i = $groupIndex;
- break;
- }
- }
- }
-
- # For now, only go through all this for mysql databases
- if ($wgDBtype != 'mysql') {
- $i = $this->getWriterIndex();
- }
- # Operation-based index
- elseif ( $i == DB_SLAVE ) {
- $i = $this->getReaderIndex();
- } elseif ( $i == DB_MASTER ) {
- $i = $this->getWriterIndex();
- } elseif ( $i == DB_LAST ) {
- # Just use $this->mLastIndex, which should already be set
- $i = $this->mLastIndex;
- if ( $i === -1 ) {
- # Oh dear, not set, best to use the writer for safety
- wfDebug( "Warning: DB_LAST used when there was no previous index\n" );
- $i = $this->getWriterIndex();
- }
- }
- # Couldn't find a working server in getReaderIndex()?
- if ( $i === false ) {
- $this->reportConnectionError( $this->mErrorConnection );
- }
- # Now we have an explicit index into the servers array
- $this->openConnection( $i, $fail );
-
- wfProfileOut( $fname );
- return $this->mConnections[$i];
- }
-
- /**
- * Open a connection to the server given by the specified index
- * Index must be an actual index into the array
- * Returns success
- * @access private
- */
- function openConnection( $i, $fail = false ) {
- $fname = 'LoadBalancer::openConnection';
- wfProfileIn( $fname );
- $success = true;
-
- if ( !$this->isOpen( $i ) ) {
- $this->mConnections[$i] = $this->reallyOpenConnection( $this->mServers[$i] );
- }
-
- if ( !$this->isOpen( $i ) ) {
- wfDebug( "Failed to connect to database $i at {$this->mServers[$i]['host']}\n" );
- if ( $fail ) {
- $this->reportConnectionError( $this->mConnections[$i] );
- }
- $this->mErrorConnection = $this->mConnections[$i];
- $this->mConnections[$i] = false;
- $success = false;
- }
- $this->mLastIndex = $i;
- wfProfileOut( $fname );
- return $success;
- }
-
- /**
- * Test if the specified index represents an open connection
- * @access private
- */
- function isOpen( $index ) {
- if( !is_integer( $index ) ) {
- return false;
- }
- if ( array_key_exists( $index, $this->mConnections ) && is_object( $this->mConnections[$index] ) &&
- $this->mConnections[$index]->isOpen() )
- {
- return true;
- } else {
- return false;
- }
- }
-
- /**
- * Really opens a connection
- * @access private
- */
- function reallyOpenConnection( &$server ) {
- if( !is_array( $server ) ) {
- throw new MWException( 'You must update your load-balancing configuration. See DefaultSettings.php entry for $wgDBservers.' );
- }
-
- extract( $server );
- # Get class for this database type
- $class = 'Database' . ucfirst( $type );
-
- # Create object
- $db = new $class( $host, $user, $password, $dbname, 1, $flags );
- $db->setLBInfo( $server );
- return $db;
- }
-
- function reportConnectionError( &$conn ) {
- $fname = 'LoadBalancer::reportConnectionError';
- wfProfileIn( $fname );
- # Prevent infinite recursion
-
- static $reporting = false;
- if ( !$reporting ) {
- $reporting = true;
- if ( !is_object( $conn ) ) {
- // No last connection, probably due to all servers being too busy
- $conn = new Database;
- if ( $this->mFailFunction ) {
- $conn->failFunction( $this->mFailFunction );
- $conn->reportConnectionError( $this->mLastError );
- } else {
- // If all servers were busy, mLastError will contain something sensible
- throw new DBConnectionError( $conn, $this->mLastError );
- }
- } else {
- if ( $this->mFailFunction ) {
- $conn->failFunction( $this->mFailFunction );
- } else {
- $conn->failFunction( false );
- }
- $server = $conn->getProperty( 'mServer' );
- $conn->reportConnectionError( "{$this->mLastError} ({$server})" );
- }
- $reporting = false;
- }
- wfProfileOut( $fname );
- }
-
- function getWriterIndex() {
- return 0;
- }
-
- /**
- * Force subsequent calls to getConnection(DB_SLAVE) to return the
- * given index. Set to -1 to restore the original load balancing
- * behaviour. I thought this was a good idea when I originally
- * wrote this class, but it has never been used.
- */
- function force( $i ) {
- $this->mForce = $i;
- }
-
- /**
- * Returns true if the specified index is a valid server index
- */
- function haveIndex( $i ) {
- return array_key_exists( $i, $this->mServers );
- }
-
- /**
- * Returns true if the specified index is valid and has non-zero load
- */
- 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)
- */
- function getServerCount() {
- return count( $this->mServers );
- }
-
- /**
- * Save master pos to the session and to memcached, if the session exists
- */
- function saveMasterPos() {
- if ( session_id() != '' && count( $this->mServers ) > 1 ) {
- # 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.
- if ( empty( $this->mConnections[0] ) ) {
- $conn =& $this->getConnection( DB_SLAVE );
- list( $file, $pos ) = $conn->getSlavePos();
- wfDebug( "Saving master pos fetched from slave: $file $pos\n" );
- } else {
- $conn =& $this->getConnection( 0 );
- list( $file, $pos ) = $conn->getMasterPos();
- wfDebug( "Saving master pos: $file $pos\n" );
- }
- if ( $file !== false ) {
- $_SESSION['master_log_file'] = $file;
- $_SESSION['master_pos'] = $pos;
- }
- }
- }
-
- /**
- * Loads the master pos from the session, waits for it if necessary
- */
- function loadMasterPos() {
- if ( isset( $_SESSION['master_log_file'] ) && isset( $_SESSION['master_pos'] ) ) {
- $this->waitFor( $_SESSION['master_log_file'], $_SESSION['master_pos'] );
- }
- }
-
- /**
- * Close all open connections
- */
- function closeAll() {
- foreach( $this->mConnections as $i => $conn ) {
- if ( $this->isOpen( $i ) ) {
- // Need to use this syntax because $conn is a copy not a reference
- $this->mConnections[$i]->close();
- }
- }
- }
-
- function commitAll() {
- foreach( $this->mConnections as $i => $conn ) {
- if ( $this->isOpen( $i ) ) {
- // Need to use this syntax because $conn is a copy not a reference
- $this->mConnections[$i]->immediateCommit();
- }
- }
- }
-
- /* Issue COMMIT only on master, only if queries were done on connection */
- function commitMasterChanges() {
- // Always 0, but who knows.. :)
- $i = $this->getWriterIndex();
- if (array_key_exists($i,$this->mConnections)) {
- if ($this->mConnections[$i]->lastQuery() != '') {
- $this->mConnections[$i]->immediateCommit();
- }
- }
- }
-
- 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->mConnections as $i => $conn ) {
- if ( $this->isOpen( $i ) ) {
- if ( !$this->mConnections[$i]->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
- */
- function getMaxLag() {
- $maxLag = -1;
- $host = '';
- foreach ( $this->mServers as $i => $conn ) {
- if ( $this->openConnection( $i ) ) {
- $lag = $this->mConnections[$i]->getLag();
- if ( $lag > $maxLag ) {
- $maxLag = $lag;
- $host = $this->mServers[$i]['host'];
- }
- }
- }
- return array( $host, $maxLag );
- }
-
- /**
- * Get lag time for each DB
- * Results are cached for a short time in memcached
- */
- function getLagTimes() {
- wfProfileIn( __METHOD__ );
- $expiry = 5;
- $requestRate = 10;
-
- global $wgMemc;
- $times = $wgMemc->get( wfMemcKey( 'lag_times' ) );
- 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 ( $this->openConnection( $i ) ) {
- $times[$i] = $this->mConnections[$i]->getLag();
- }
- }
-
- # Add a timestamp key so we know when it was cached
- $times['timestamp'] = time();
- $wgMemc->set( wfMemcKey( 'lag_times' ), $times, $expiry );
-
- # But don't give the timestamp to the caller
- unset($times['timestamp']);
- wfProfileOut( __METHOD__ );
- return $times;
- }
-}
-
-
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2024-11-17 06:18:59 +0000