loadbalancer.php

来自「php 开发的内容管理系统」· PHP 代码 · 共 667 行 · 第 1/2 页

	function &getConnection( $i, $fail = true, $groups = array() )
	{
		global $wgDBtype;
		$fname = 'LoadBalancer::getConnection';
		wfProfileIn( $fname );


		# Query groups
		if ( !is_array( $groups ) ) {
			$groupIndex = $this->getGroupIndex( $groups, $i );
			if ( $groupIndex !== false ) {
				$i = $groupIndex;
			}
		} else {
			foreach ( $groups as $group ) {
				$groupIndex = $this->getGroupIndex( $group, $i );
				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 );
		if ( !class_exists( $class ) ) {
			require_once( "$class.php" );
		}

		# 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() {
		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;
			}
		}
	}

	/**
	 * 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();
			}
		}
	}

	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() {
		global $wgDBname;

		$expiry = 5;
		$requestRate = 10;

		global $wgMemc;
		$times = $wgMemc->get( "$wgDBname: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'] );
				return $times;
			}
		}

		# 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();
		$wgMemc->set( "$wgDBname:lag_times", $times, $expiry );

		# But don't give the timestamp to the caller
		unset($times['timestamp']);
		return $times;
	}
}

?>