org.apache.hadoop.net
Class NetworkTopology

java.lang.Object
  org.apache.hadoop.net.NetworkTopology

public class NetworkTopology
extends Object

The class represents a cluster of computer with a tree hierarchical network topology. For example, a cluster may be consists of many data centers filled with racks of computers. In a network topology, leaves represent data nodes (computers) and inner nodes represent switches/routers that manage traffic in/out of data centers or racks.

Author:

hairong

Field Summary

static String	DEFAULT_RACK
static org.apache.commons.logging.Log	LOG

Constructor Summary

NetworkTopology()

Method Summary

void	add(DatanodeDescriptor node) Add a data node Update data node counter & rack counter if neccessary
DatanodeDescriptor	chooseRandom(String scope) randomly choose one node from scope if scope starts with ~, choose one from the all datanodes except for the ones in scope; otherwise, choose one from scope
boolean	contains(DatanodeDescriptor node) Check if the tree contains data node node
int	countNumOfAvailableNodes(String scope, List<DatanodeDescriptor> excludedNodes) return the number of leaves in scope but not in excludedNodes if scope starts with ~, return the number of datanodes that are not in scope and excludedNodes;
int	getDistance(DatanodeDescriptor node1, DatanodeDescriptor node2) Return the distance between two data nodes It is assumed that the distance from one node to its parent is 1 The distance between two nodes is calculated by summing up their distances to their closest common ancestor.
Node	getNode(String loc) Given a string representation of a node, return its reference
int	getNumOfLeaves() Return the total number of data nodes
int	getNumOfRacks() Return the total number of racks
boolean	isOnSameRack(DatanodeDescriptor node1, DatanodeDescriptor node2) Check if two data nodes are on the same rack
void	remove(DatanodeDescriptor node) Remove a data node Update data node counter & rack counter if neccessary
void	sortByDistance(DatanodeDescriptor reader, DatanodeDescriptor[] nodes) Sorts nodes array by their distances to reader.
String	toString() convert a network tree to a string

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

DEFAULT_RACK

public static final String DEFAULT_RACK

See Also:

Constant Field Values

LOG

public static final org.apache.commons.logging.Log LOG

Constructor Detail

NetworkTopology

public NetworkTopology()

Method Detail

add

public void add(DatanodeDescriptor node)

Add a data node Update data node counter & rack counter if neccessary

Parameters:

node - data node to be added

Throws:

IllegalArgumentException - if add a data node to a leave

remove

public void remove(DatanodeDescriptor node)

Remove a data node Update data node counter & rack counter if neccessary

Parameters:

node - data node to be removed

contains

public boolean contains(DatanodeDescriptor node)

Check if the tree contains data node node

Parameters:

node - a data node

Returns:

true if node is already in the tree; false otherwise

getNode

public Node getNode(String loc)

Given a string representation of a node, return its reference

Parameters:

loc - a path-like string representation of a node

Returns:

a reference to the node; null if the node is not in the tree

getNumOfRacks

public int getNumOfRacks()

Return the total number of racks

getNumOfLeaves

public int getNumOfLeaves()

Return the total number of data nodes

getDistance

public int getDistance(DatanodeDescriptor node1,
                       DatanodeDescriptor node2)

Return the distance between two data nodes It is assumed that the distance from one node to its parent is 1 The distance between two nodes is calculated by summing up their distances to their closest common ancestor.

Parameters:

node1 - one data node

node2 - another data node

Returns:

the distance between node1 and node2 node1 or node2 do not belong to the cluster

isOnSameRack

public boolean isOnSameRack(DatanodeDescriptor node1,
                            DatanodeDescriptor node2)

Check if two data nodes are on the same rack

Parameters:

node1 - one data node

node2 - another data node

Returns:

true if node1 and node2 are pm the same rack; false otherwise

Throws:

IllegalArgumentException - when either node1 or node2 is null, or node1 or node2 do not belong to the cluster

chooseRandom

public DatanodeDescriptor chooseRandom(String scope)

randomly choose one node from scope if scope starts with ~, choose one from the all datanodes except for the ones in scope; otherwise, choose one from scope

Parameters:

scope - range of datanodes from which a node will be choosen

Returns:

the choosen data node

countNumOfAvailableNodes

public int countNumOfAvailableNodes(String scope,
                                    List<DatanodeDescriptor> excludedNodes)

return the number of leaves in scope but not in excludedNodes if scope starts with ~, return the number of datanodes that are not in scope and excludedNodes;

Parameters:

scope - a path string that may start with ~

excludedNodes - a list of data nodes

Returns:

number of available data nodes

toString

public String toString()

convert a network tree to a string

Overrides:

toString in class Object

sortByDistance

public void sortByDistance(DatanodeDescriptor reader,
                           DatanodeDescriptor[] nodes)

Sorts nodes array by their distances to reader.