<?php
/**
- *
- */
-
-/**
- * Depends on the database object
+ * @file
+ * @ingroup Database
*/
-require_once( 'Database.php' );
-
-# Valid database indexes
-# Operation-based indexes
-define( 'DB_SLAVE', -1 ); # Read from the slave (or only server)
-define( 'DB_MASTER', -2 ); # Write to master (or only server)
-define( 'DB_LAST', -3 ); # Whatever database was used last
-
-# Obsolete aliases
-define( 'DB_READ', -1 );
-define( 'DB_WRITE', -2 );
-
-# Task-based indexes
-# ***NOT USED YET, EXPERIMENTAL***
-# These may be defined in $wgDBservers. If they aren't, the default reader or writer will be used
-# Even numbers are always readers, odd numbers are writers
-define( 'DB_TASK_FIRST', 1000 ); # First in list
-define( 'DB_SEARCH_R', 1000 ); # Search read
-define( 'DB_SEARCH_W', 1001 ); # Search write
-define( 'DB_ASKSQL_R', 1002 ); # Special:Asksql read
-define( 'DB_WATCHLIST_R', 1004 ); # Watchlist read
-define( 'DB_TASK_LAST', 1004) ; # Last in list
-
-define( 'MASTER_WAIT_TIMEOUT', 15 ); # Time to wait for a slave to synchronise
/**
* Database load balancing object
+ *
* @todo document
+ * @ingroup Database
*/
class LoadBalancer {
- /* private */ var $mServers, $mConnections, $mLoads;
- /* private */ var $mFailFunction;
- /* private */ var $mForce, $mReadIndex, $mLastIndex;
- /* private */ var $mWaitForFile, $mWaitForPos;
-
- function LoadBalancer()
- {
- $this->mServers = array();
- $this->mConnections = array();
- $this->mFailFunction = false;
- $this->mReadIndex = -1;
- $this->mForce = -1;
- $this->mLastIndex = -1;
- }
-
- function newFromParams( $servers, $failFunction = false )
- {
- $lb = new LoadBalancer;
- $lb->initialise( $servers, $failFunction = false );
- return $lb;
- }
-
- function initialise( $servers, $failFunction = false )
+ /* private */ var $mServers, $mConns, $mLoads, $mGroupLoads;
+ /* private */ var $mFailFunction, $mErrorConnection;
+ /* private */ var $mReadIndex, $mLastIndex, $mAllowLagged;
+ /* private */ var $mWaitForPos, $mWaitTimeout;
+ /* private */ var $mLaggedSlaveMode, $mLastError = 'Unknown error';
+ /* private */ var $mParentInfo, $mLagTimes;
+
+ function __construct( $servers, $failFunction = false, $waitTimeout = 10, $unused = false )
{
$this->mServers = $servers;
$this->mFailFunction = $failFunction;
$this->mReadIndex = -1;
$this->mWriteIndex = -1;
- $this->mForce = -1;
- $this->mConnections = array();
- $this->mLastIndex = 1;
+ $this->mConns = array(
+ 'local' => array(),
+ 'foreignUsed' => array(),
+ 'foreignFree' => 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;
+ }
+ }
}
}
-
+
+ static function newFromParams( $servers, $failFunction = false, $waitTimeout = 10 )
+ {
+ return new LoadBalancer( $servers, $failFunction, $waitTimeout );
+ }
+
+ /**
+ * Get or set arbitrary data used by the parent object, usually an LBFactory
+ */
+ function parentInfo( $x = null ) {
+ return wfSetVar( $this->mParentInfo, $x );
+ }
+
/**
* Given an array of non-normalised probabilities, this function will select
* an element and return the appropriate key
return false;
}
- $sum = 0;
- foreach ( $weights as $w ) {
- $sum += $w;
+ $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;
return $i;
}
- function getReaderIndex()
- {
- $fname = 'LoadBalancer::getReaderIndex';
- wfProfileIn( $fname );
+ function getRandomNonLagged( $loads, $wiki = false ) {
+ # Unset excessively lagged servers
+ $lags = $this->getLagTimes( $wiki );
+ foreach ( $lags as $i => $lag ) {
+ if ( $i != 0 && isset( $this->mServers[$i]['max lag'] ) ) {
+ if ( $lag === false ) {
+ wfDebug( "Server #$i is not replicating\n" );
+ unset( $loads[$i] );
+ } elseif ( $lag > $this->mServers[$i]['max lag'] ) {
+ wfDebug( "Server #$i is excessively lagged ($lag seconds)\n" );
+ unset( $loads[$i] );
+ }
+ }
+ }
- $i = false;
- if ( $this->mForce >= 0 ) {
- $i = $this->mForce;
- } else {
- if ( $this->mReadIndex >= 0 ) {
- $i = $this->mReadIndex;
+ # 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( $group = false, $wiki = false ) {
+ global $wgReadOnly, $wgDBClusterTimeout, $wgDBAvgStatusPoll, $wgDBtype;
+
+ # FIXME: For now, only go through all this for mysql databases
+ if ($wgDBtype != 'mysql') {
+ return $this->getWriterIndex();
+ }
+
+ if ( count( $this->mServers ) == 1 ) {
+ # Skip the load balancing if there's only one server
+ return 0;
+ } elseif ( $group === false and $this->mReadIndex >= 0 ) {
+ # Shortcut if generic reader exists already
+ return $this->mReadIndex;
+ }
+
+ wfProfileIn( __METHOD__ );
+
+ $totalElapsed = 0;
+
+ # convert from seconds to microseconds
+ $timeout = $wgDBClusterTimeout * 1e6;
+
+ # Find the relevant load array
+ if ( $group !== false ) {
+ if ( isset( $this->mGroupLoads[$group] ) ) {
+ $nonErrorLoads = $this->mGroupLoads[$group];
} else {
- # $loads is $this->mLoads except with elements knocked out if they
- # don't work
- $loads = $this->mLoads;
- do {
- $i = $this->pickRandom( $loads );
- if ( $i !== false ) {
- wfDebug( "Using reader #$i: {$this->mServers[$i]['host']}\n" );
-
- $this->openConnection( $i );
-
- if ( !$this->isOpen( $i ) ) {
- unset( $loads[$i] );
- }
+ # No loads for this group, return false and the caller can use some other group
+ wfDebug( __METHOD__.": no loads for group $group\n" );
+ wfProfileOut( __METHOD__ );
+ return false;
+ }
+ } else {
+ $nonErrorLoads = $this->mLoads;
+ }
+
+ if ( !$nonErrorLoads ) {
+ throw new MWException( "Empty server array given to LoadBalancer" );
+ }
+
+ $i = false;
+ $found = false;
+ $laggedSlaveMode = false;
+
+ # First try quickly looking through the available servers for a server that
+ # meets our criteria
+ do {
+ $totalThreadsConnected = 0;
+ $overloadedServers = 0;
+ $currentLoads = $nonErrorLoads;
+ while ( count( $currentLoads ) ) {
+ if ( $wgReadOnly || $this->mAllowLagged || $laggedSlaveMode ) {
+ $i = $this->pickRandom( $currentLoads );
+ } else {
+ $i = $this->getRandomNonLagged( $currentLoads, $wiki );
+ if ( $i === false && count( $currentLoads ) != 0 ) {
+ # All slaves lagged. Switch to read-only mode
+ $wgReadOnly = wfMsgNoDBForContent( 'readonly_lag' );
+ $i = $this->pickRandom( $currentLoads );
+ $laggedSlaveMode = true;
}
- } while ( $i !== false && !$this->isOpen( $i ) );
+ }
+
+ if ( $i === false ) {
+ # pickRandom() returned false
+ # This is permanent and means the configuration wants us to return false
+ wfDebugLog( 'connect', __METHOD__.": pickRandom() returned false\n" );
+ wfProfileOut( __METHOD__ );
+ return false;
+ }
+
+ wfDebugLog( 'connect', __METHOD__.": Using reader #$i: {$this->mServers[$i]['host']}...\n" );
+ $conn = $this->openConnection( $i, $wiki );
+
+ if ( !$conn ) {
+ wfDebugLog( 'connect', __METHOD__.": Failed connecting to $i/$wiki\n" );
+ unset( $nonErrorLoads[$i] );
+ unset( $currentLoads[$i] );
+ continue;
+ }
- if ( $this->isOpen( $i ) ) {
- $this->mReadIndex = $i;
+ if ( isset( $this->mServers[$i]['max threads'] ) ) {
+ $status = $conn->getStatus("Thread%");
+ if ( $wiki !== false ) {
+ $this->reuseConnection( $conn );
+ }
+ if ( $status['Threads_running'] > $this->mServers[$i]['max threads'] ) {
+ $totalThreadsConnected += $status['Threads_connected'];
+ $overloadedServers++;
+ unset( $currentLoads[$i] );
+ } else {
+ # Max threads satisfied, return this server
+ break 2;
+ }
} else {
- $i = false;
+ # No maximum, return this server
+ if ( $wiki !== false ) {
+ $this->reuseConnection( $conn );
+ }
+ $found = true;
+ break 2;
}
}
+
+ # No server found yet
+ $i = false;
+
+ # If all servers were down, quit now
+ if ( !count( $nonErrorLoads ) ) {
+ wfDebugLog( 'connect', "All servers down\n" );
+ break;
+ }
+
+ # Some servers must have been overloaded
+ if ( $overloadedServers == 0 ) {
+ throw new MWException( __METHOD__.": unexpectedly found no overloaded servers" );
+ }
+ # Back off for a while
+ # Scale the sleep time by the number of connected threads, to produce a
+ # roughly constant global poll rate
+ $avgThreads = $totalThreadsConnected / $overloadedServers;
+ $totalElapsed += $this->sleep( $wgDBAvgStatusPoll * $avgThreads );
+ } while ( $totalElapsed < $timeout );
+
+ if ( $totalElapsed >= $timeout ) {
+ wfDebugLog( 'connect', "All servers busy\n" );
+ $this->mErrorConnection = false;
+ $this->mLastError = 'All servers busy';
+ }
+
+ if ( $i !== false ) {
+ # Wait for the session master pos for a short time
+ if ( $this->mWaitForPos && $i > 0 ) {
+ if ( !$this->doWait( $i ) ) {
+ $this->mServers[$i]['slave pos'] = $conn->getSlavePos();
+ }
+ }
+ if ( $this->mReadIndex <=0 && $this->mLoads[$i]>0 && $i !== false ) {
+ $this->mReadIndex = $i;
+ }
}
- wfProfileOut( $fname );
+ wfProfileOut( __METHOD__ );
return $i;
}
+ /**
+ * Wait for a specified number of microseconds, and return the period waited
+ */
+ function sleep( $t ) {
+ wfProfileIn( __METHOD__ );
+ wfDebug( __METHOD__.": waiting $t us\n" );
+ usleep( $t );
+ wfProfileOut( __METHOD__ );
+ return $t;
+ }
+
+ /**
+ * Get a random server to use in a query group
+ * @deprecated use getReaderIndex
+ */
+ function getGroupIndex( $group ) {
+ return $this->getReaderIndex( $group );
+ }
+
/**
* 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;
+ public function waitFor( $pos ) {
+ wfProfileIn( __METHOD__ );
+ $this->mWaitForPos = $pos;
+ $i = $this->mReadIndex;
+
+ if ( $i > 0 ) {
+ if ( !$this->doWait( $i ) ) {
+ $this->mServers[$i]['slave pos'] = $this->getAnyOpenConnection( $i )->getSlavePos();
+ $this->mLaggedSlaveMode = true;
+ }
+ }
+ wfProfileOut( __METHOD__ );
+ }
- if ( $this->mReadIndex > 0 ) {
- if ( !$this->doWait( $this->mReadIndex ) ) {
- # Use master instead
- $this->mReadIndex = 0;
- }
- }
+ /**
+ * Get any open connection to a given server index, local or foreign
+ * Returns false if there is no connection open
+ */
+ function getAnyOpenConnection( $i ) {
+ foreach ( $this->mConns as $type => $conns ) {
+ if ( !empty( $conns[$i] ) ) {
+ return reset( $conns[$i] );
+ }
}
- wfProfileOut( $fname );
+ return false;
}
/**
* Wait for a given slave to catch up to the master pos stored in $this
*/
function doWait( $index ) {
- global $wgMemc;
-
- $retVal = false;
-
- $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;
- }
+ # Find a connection to wait on
+ $conn = $this->getAnyOpenConnection( $index );
+ if ( !$conn ) {
+ wfDebug( __METHOD__ . ": no connection open\n" );
+ return false;
}
- if ( !$retVal && $this->isOpen( $index ) ) {
- $conn =& $this->mConnections( $index );
- wfDebug( "Waiting for slave #$index to catch up...\n" );
- $result = $conn->masterPosWait( $this->mWaitForFile, $this->mWaitForPos, MASTER_WAIT_TIMEOUT );
+ wfDebug( __METHOD__.": Waiting for slave #$index to catch up...\n" );
+ $result = $conn->masterPosWait( $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" );
- }
+ if ( $result == -1 || is_null( $result ) ) {
+ # Timed out waiting for slave, use master instead
+ wfDebug( __METHOD__.": Timed out waiting for slave #$index pos {$this->mWaitForPos}\n" );
+ return false;
+ } else {
+ wfDebug( __METHOD__.": Done\n" );
+ return true;
}
- return $retVal;
- }
+ }
/**
* Get a connection by index
+ * This is the main entry point for this class.
*/
- function &getConnection( $i, $fail = true )
- {
- $fname = 'LoadBalancer::getConnection';
- wfProfileIn( $fname );
- /*
- # Task-based index
- if ( $i >= DB_TASK_FIRST && $i < DB_TASK_LAST ) {
- if ( $i % 2 ) {
- # Odd index use writer
- $i = DB_MASTER;
- } else {
- # Even index use reader
- $i = DB_SLAVE;
+ public function &getConnection( $i, $groups = array(), $wiki = false ) {
+ global $wgDBtype;
+ wfProfileIn( __METHOD__ );
+
+ if ( $wiki === wfWikiID() ) {
+ $wiki = false;
+ }
+
+ # Query groups
+ if ( $i == DB_MASTER ) {
+ $i = $this->getWriterIndex();
+ } elseif ( !is_array( $groups ) ) {
+ $groupIndex = $this->getReaderIndex( $groups, $wiki );
+ if ( $groupIndex !== false ) {
+ $serverName = $this->getServerName( $groupIndex );
+ wfDebug( __METHOD__.": using server $serverName for group $groups\n" );
+ $i = $groupIndex;
+ }
+ } else {
+ foreach ( $groups as $group ) {
+ $groupIndex = $this->getReaderIndex( $group, $wiki );
+ if ( $groupIndex !== false ) {
+ $serverName = $this->getServerName( $groupIndex );
+ wfDebug( __METHOD__.": using server $serverName for group $group\n" );
+ $i = $groupIndex;
+ break;
+ }
}
- }*/
+ }
# Operation-based index
- if ( $i == DB_SLAVE ) {
- $i = $this->getReaderIndex();
- } elseif ( $i == DB_MASTER ) {
- $i = $this->getWriterIndex();
+ if ( $i == DB_SLAVE ) {
+ $i = $this->getReaderIndex( false, $wiki );
} elseif ( $i == DB_LAST ) {
# Just use $this->mLastIndex, which should already be set
$i = $this->mLastIndex;
$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];
+ $conn = $this->openConnection( $i, $wiki );
+ if ( !$conn ) {
+ $this->reportConnectionError( $this->mErrorConnection );
+ }
+
+ wfProfileOut( __METHOD__ );
+ 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.
+ */
+ public function reuseConnection( $conn ) {
+ $serverIndex = $conn->getLBInfo('serverIndex');
+ $refCount = $conn->getLBInfo('foreignPoolRefCount');
+ $dbName = $conn->getDBname();
+ $prefix = $conn->tablePrefix();
+ if ( strval( $prefix ) !== '' ) {
+ $wiki = "$dbName-$prefix";
+ } else {
+ $wiki = $dbName;
+ }
+ 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;
+ }
+ 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" );
+ }
}
/**
* Open a connection to the server given by the specified index
- * Index must be an actual index into the array
- * @private
+ * 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 integer $i Server index
+ * @param string $wiki Wiki ID to open
+ * @return Database
+ *
+ * @access private
*/
- function openConnection( $i, $fail = false ) {
- $fname = 'LoadBalancer::openConnection';
- wfProfileIn( $fname );
-
- if ( !$this->isOpen( $i ) ) {
- $this->mConnections[$i] = $this->reallyOpenConnection( $this->mServers[$i] );
-
- if ( $i != 0 && $this->mWaitForFile ) {
- if ( !$this->doWait( $i ) ) {
- # Error waiting for this slave, use master instead
- $this->mReadIndex = 0;
- $i = 0;
- if ( !$this->isOpen( 0 ) ) {
- $this->mConnections[0] = $this->reallyOpenConnection( $this->mServers[0] );
- }
- wfDebug( "Failed over to {$this->mConnections[0]->mServer}\n" );
- }
- }
+ function openConnection( $i, $wiki = false ) {
+ wfProfileIn( __METHOD__ );
+ if ( $wiki !== false ) {
+ $conn = $this->openForeignConnection( $i, $wiki );
+ wfProfileOut( __METHOD__);
+ return $conn;
}
- if ( !$this->isOpen( $i ) ) {
- wfDebug( "Failed to connect to database $i at {$this->mServers[$i]['host']}\n" );
- if ( $fail ) {
- $this->reportConnectionError( $this->mConnections[$i] );
+ 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 );
+ if ( $conn->isOpen() ) {
+ $this->mConns['local'][$i][0] = $conn;
+ } else {
+ wfDebug( "Failed to connect to database $i at {$this->mServers[$i]['host']}\n" );
+ $this->mErrorConnection = $conn;
+ $conn = false;
}
- $this->mConnections[$i] = false;
}
$this->mLastIndex = $i;
- wfProfileOut( $fname );
+ wfProfileOut( __METHOD__ );
+ 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 integer $i Server index
+ * @param string $wiki Wiki ID to open
+ * @return Database
+ */
+ function openForeignConnection( $i, $wiki ) {
+ wfProfileIn(__METHOD__);
+ 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] );
+
+ if ( !$conn->selectDB( $dbName ) ) {
+ global $wguname;
+ $this->mLastError = "Error selecting database $dbName on server " .
+ $conn->getServer() . " from client host {$wguname['nodename']}\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;
+ $conn = $this->reallyOpenConnection( $server, $dbName );
+ if ( !$conn->isOpen() ) {
+ wfDebug( __METHOD__.": error opening connection for $i/$wiki\n" );
+ $this->mErrorConnection = $conn;
+ $conn = false;
+ } else {
+ $this->mConns['foreignUsed'][$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 );
+ }
+ wfProfileOut(__METHOD__);
+ return $conn;
}
/**
* Test if the specified index represents an open connection
- * @private
+ * @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;
- }
+ return (bool)$this->getAnyOpenConnection( $index );
}
-
+
/**
- * Really opens a connection
- * @private
+ * Really opens a connection. Uncached.
+ * Returns a Database object whether or not the connection was successful.
+ * @access private
*/
- function reallyOpenConnection( &$server ) {
- extract( $server );
- # Get class for this database type
- $class = 'Database' . ucfirst( $type );
- if ( !class_exists( $class ) ) {
- require_once( "$class.php" );
- }
+ 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.' );
+ }
+
+ extract( $server );
+ if ( $dbNameOverride !== false ) {
+ $dbname = $dbNameOverride;
+ }
+
+ # Get class for this database type
+ $class = 'Database' . ucfirst( $type );
- # Create object
- return new $class( $host, $user, $password, $dbname, 1, $flags );
+ # Create object
+ wfDebug( "Connecting to $host $dbname...\n" );
+ $db = new $class( $host, $user, $password, $dbname, 1, $flags );
+ if ( $db->isOpen() ) {
+ wfDebug( "Connected\n" );
+ } else {
+ wfDebug( "Failed\n" );
+ }
+ $db->setLBInfo( $server );
+ if ( isset( $server['fakeSlaveLag'] ) ) {
+ $db->setFakeSlaveLag( $server['fakeSlaveLag'] );
+ }
+ if ( isset( $server['fakeMaster'] ) ) {
+ $db->setFakeMaster( true );
+ }
+ return $db;
}
-
- function reportConnectionError( &$conn )
- {
- $fname = 'LoadBalancer::reportConnectionError';
- wfProfileIn( $fname );
+
+ function reportConnectionError( &$conn ) {
+ wfProfileIn( __METHOD__ );
# 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 );
+ 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 {
- $conn->failFunction( 'wfEmergencyAbort' );
+ if ( $this->mFailFunction ) {
+ $conn->failFunction( $this->mFailFunction );
+ } else {
+ $conn->failFunction( false );
+ }
+ $server = $conn->getProperty( 'mServer' );
+ $conn->reportConnectionError( "{$this->mLastError} ({$server})" );
}
- $conn->reportConnectionError();
$reporting = false;
}
- wfProfileOut( $fname );
+ wfProfileOut( __METHOD__ );
}
-
- function getWriterIndex()
- {
+
+ function getWriterIndex() {
return 0;
}
- 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 );
}
- 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;
}
/**
}
/**
- * Save master pos to the session and to memcached, if the session exists
+ * Get the host name or IP address of the server with the specified index
*/
- function saveMasterPos() {
- global $wgSessionStarted;
- if ( $wgSessionStarted && 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;
- }
+ function getServerName( $i ) {
+ if ( isset( $this->mServers[$i]['hostName'] ) ) {
+ return $this->mServers[$i]['hostName'];
+ } elseif ( isset( $this->mServers[$i]['host'] ) ) {
+ return $this->mServers[$i]['host'];
+ } else {
+ return '';
}
}
/**
- * Loads the master pos from the session, waits for it if necessary
+ * Get the current master position for chronology control purposes
+ * @return mixed
*/
- function loadMasterPos() {
- if ( isset( $_SESSION['master_log_file'] ) && isset( $_SESSION['master_pos'] ) ) {
- $this->waitFor( $_SESSION['master_log_file'], $_SESSION['master_pos'] );
+ 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 ) {
+ for ( $i = 1; $i < count( $this->mServers ); $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
*/
function closeAll() {
- foreach( $this->mConnections as $i => $conn ) {
- if ( $this->isOpen( $i ) ) {
- $conn->close();
+ foreach ( $this->mConns as $conns2 ) {
+ foreach ( $conns2 as $conns3 ) {
+ foreach ( $conns3 as $conn ) {
+ $conn->close();
+ }
}
}
+ $this->mConns = array(
+ 'local' => array(),
+ 'foreignFree' => array(),
+ 'foreignUsed' => array(),
+ );
}
+ /**
+ * 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.
+ */
+ function closeConnecton( $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] );
+ $done = true;
+ break;
+ }
+ }
+ }
+ }
+ if ( !$done ) {
+ $conn->close();
+ }
+ }
+
+ /**
+ * Commit transactions on all open connections
+ */
function commitAll() {
- foreach( $this->mConnections as $i => $conn ) {
- if ( $this->isOpen( $i ) ) {
- $conn->immediateCommit();
+ foreach ( $this->mConns as $conns2 ) {
+ foreach ( $conns2 as $conns3 ) {
+ foreach ( $conns3 as $conn ) {
+ $conn->immediateCommit();
+ }
}
}
}
+
+ /* 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] ) ) {
+ continue;
+ }
+ foreach ( $conns2[$masterIndex] as $conn ) {
+ if ( $conn->lastQuery() != '' ) {
+ $conn->commit();
+ }
+ }
+ }
+ }
+
+ 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;
+ }
}
dépôts / lhc / web / wiklou.git / blobdiff