/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.net;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Random;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/** 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.
*
*/
public class NetworkTopology {
public final static String DEFAULT_RACK = "/default-rack";
public final static int DEFAULT_HOST_LEVEL = 2;
public static final Log LOG =
LogFactory.getLog(NetworkTopology.class);
/* Inner Node represent a switch/router of a data center or rack.
* Different from a leave node, it has non-null children.
*/
private class InnerNode extends NodeBase {
private ArrayList<Node> children=new ArrayList<Node>();
private int numOfLeaves;
/** Construct an InnerNode from a path-like string */
InnerNode(String path) {
super(path);
}
/** Construct an InnerNode from its name and its network location */
InnerNode(String name, String location) {
super(name, location);
}
/** Construct an InnerNode
* from its name, its network location, its parent, and its level */
InnerNode(String name, String location, InnerNode parent, int level) {
super(name, location, parent, level);
}
/** Get its children */
Collection<Node> getChildren() {return children;}
/** Return the number of children this node has */
int getNumOfChildren() {
return children.size();
}
/** Judge if this node represents a rack
* Return true if it has no child or its children are not InnerNodes
*/
boolean isRack() {
if (children.isEmpty()) {
return true;
}
Node firstChild = children.get(0);
if (firstChild instanceof InnerNode) {
return false;
}
return true;
}
/** Judge if this node is an ancestor of node <i>n</i>
*
* @param n a node
* @return true if this node is an ancestor of <i>n</i>
*/
boolean isAncestor(Node n) {
return getPath(this).equals(NodeBase.PATH_SEPARATOR_STR) ||
(n.getNetworkLocation()+NodeBase.PATH_SEPARATOR_STR).
startsWith(getPath(this)+NodeBase.PATH_SEPARATOR_STR);
}
/** Judge if this node is the parent of node <i>n</i>
*
* @param n a node
* @return true if this node is the parent of <i>n</i>
*/
boolean isParent(Node n) {
return n.getNetworkLocation().equals(getPath(this));
}
/* Return a child name of this node who is an ancestor of node <i>n</i> */
private String getNextAncestorName(Node n) {
if (!isAncestor(n)) {
throw new IllegalArgumentException(
this + "is not an ancestor of " + n);
}
String name = n.getNetworkLocation().substring(getPath(this).length());
if (name.charAt(0) == PATH_SEPARATOR) {
name = name.substring(1);
}
int index=name.indexOf(PATH_SEPARATOR);
if (index !=-1)
name = name.substring(0, index);
return name;
}
/** Add node <i>n</i> to the subtree of this node
* @param n node to be added
* @return true if the node is added; false otherwise
*/
boolean add(Node n) {
if (!isAncestor(n))
throw new IllegalArgumentException(n.getName()+", which is located at "
+n.getNetworkLocation()+", is not a decendent of "
+getPath(this));
if (isParent(n)) {
// this node is the parent of n; add n directly
n.setParent(this);
n.setLevel(this.level+1);
for(int i=0; i<children.size(); i++) {
if (children.get(i).getName().equals(n.getName())) {
children.set(i, n);
return false;
}
}
children.add(n);
numOfLeaves++;
return true;
} else {
// find the next ancestor node
String parentName = getNextAncestorName(n);
InnerNode parentNode = null;
for(int i=0; i<children.size(); i++) {
if (children.get(i).getName().equals(parentName)) {
parentNode = (InnerNode)children.get(i);
break;
}
}
if (parentNode == null) {
// create a new InnerNode
parentNode = new InnerNode(parentName, getPath(this),
this, this.getLevel()+1);
children.add(parentNode);
}
// add n to the subtree of the next ancestor node
if (parentNode.add(n)) {
numOfLeaves++;
return true;
} else {
return false;
}
}
}
/** Remove node <i>n</i> from the subtree of this node
* @param n node to be deleted
* @return true if the node is deleted; false otherwise
*/
boolean remove(Node n) {
String parent = n.getNetworkLocation();
String currentPath = getPath(this);
if (!isAncestor(n))
throw new IllegalArgumentException(n.getName()
+", which is located at "
+parent+", is not a descendent of "+currentPath);
if (isParent(n)) {
// this node is the parent of n; remove n directly
for(int i=0; i<children.size(); i++) {
if (children.get(i).getName().equals(n.getName())) {
children.remove(i);
numOfLeaves--;
n.setParent(null);
return true;
}
}
return false;
} else {
// find the next ancestor node: the parent node
String parentName = getNextAncestorName(n);
InnerNode parentNode = null;
int i;
for(i=0; i<children.size(); i++) {
if (children.get(i).getName().equals(parentName)) {
parentNode = (InnerNode)children.get(i);
break;
}
}
if (parentNode==null) {
return false;
}
// remove n from the parent node
boolean isRemoved = parentNode.remove(n);
// if the parent node has no children, remove the parent node too
if (isRemoved) {
if (parentNode.getNumOfChildren() == 0) {
children.remove(i);
}
numOfLeaves--;
}
return isRemoved;
}
} // end of remove
/** Given a node's string representation, return a reference to the node */
private Node getLoc(String loc) {
if (loc == null || loc.length() == 0) return this;
String[] path = loc.split(PATH_SEPARATOR_STR, 2);
Node childnode = null;
for(int i=0; i<children.size(); i++) {
if (children.get(i).getName().equals(path[0])) {
childnode = children.get(i);
}
}
if (childnode == null) return null; // non-existing node
if (path.length == 1) return childnode;
if (childnode instanceof InnerNode) {
return ((InnerNode)childnode).getLoc(path[1]);
} else {
return null;
}
}
/** get <i>leafIndex</i> leaf of this subtree
* if it is not in the <i>excludedNode</i>*/
private Node getLeaf(int leafIndex, Node excludedNode) {
int count=0;
// check if the excluded node a leaf
boolean isLeaf =
excludedNode == null || !(excludedNode instanceof InnerNode);
// calculate the total number of excluded leaf nodes
int numOfExcludedLeaves =
isLeaf ? 1 : ((InnerNode)excludedNode).getNumOfLeaves();
if (isRack()) { // children are leaves
if (isLeaf) { // excluded node is a leaf node
int excludedIndex = children.indexOf(excludedNode);
if (excludedIndex != -1 && leafIndex >= 0) {
// excluded node is one of the children so adjust the leaf index
leafIndex = leafIndex>=excludedIndex ? leafIndex+1 : leafIndex;
}
}
// range check
if (leafIndex<0 || leafIndex>=this.getNumOfChildren()) {
return null;
}
return children.get(leafIndex);
} else {
for(int i=0; i<children.size(); i++) {
InnerNode child = (InnerNode)children.get(i);
if (excludedNode == null || excludedNode != child) {
// not the excludedNode
int numOfLeaves = child.getNumOfLeaves();
if (excludedNode != null && child.isAncestor(excludedNode)) {
numOfLeaves -= numOfExcludedLeaves;
}
if (count+numOfLeaves > leafIndex) {
// the leaf is in the child subtree
return child.getLeaf(leafIndex-count, excludedNode);
} else {
// go to the next child
count = count+numOfLeaves;
}
} else { // it is the excluededNode
// skip it and set the excludedNode to be null
excludedNode = null;
}
}
return null;
}
}
int getNumOfLeaves() {
return numOfLeaves;
}
} // end of InnerNode
InnerNode clusterMap = new InnerNode(InnerNode.ROOT); // the root
private int numOfRacks = 0; // rack counter
private ReadWriteLock netlock;
public NetworkTopology() {
netlock = new ReentrantReadWriteLock();
}
/** Add a leaf node
* Update node counter & rack counter if neccessary
* @param node
* node to be added
* @exception IllegalArgumentException if add a node to a leave
or node to be added is not a leaf
*/
public void add(Node node) {
if (node==null) return;
if( node instanceof InnerNode ) {
throw new IllegalArgumentException(
"Not allow to add an inner node: "+NodeBase.getPath(node));
}
netlock.writeLock().lock();
try {
Node rack = getNode(node.getNetworkLocation());
if (rack != null && !(rack instanceof InnerNode)) {
throw new IllegalArgumentException("Unexpected data node "
+ node.toString()
+ " at an illegal network location");
}
if (clusterMap.add(node)) {
LOG.info("Adding a new node: "+NodeBase.getPath(node));
if (rack == null) {
numOfRacks++;
}
}
LOG.debug("NetworkTopology became:\n" + this.toString());
} finally {
netlock.writeLock().unlock();
}
}
/** Remove a node
* Update node counter & rack counter if neccessary
* @param node
* node to be removed
*/
public void remove(Node node) {
if (node==null) return;
if( node instanceof InnerNode ) {
throw new IllegalArgumentException(
"Not allow to remove an inner node: "+NodeBase.getPath(node));
}
LOG.info("Removing a node: "+NodeBase.getPath(node));
netlock.writeLock().lock();
try {
if (clusterMap.remove(node)) {
InnerNode rack = (InnerNode)getNode(node.getNetworkLocation());
if (rack == null) {
numOfRacks--;
}
}
LOG.debug("NetworkTopology became:\n" + this.toString());
} finally {
netlock.writeLock().unlock();
}
}
/** Check if the tree contains node <i>node</i>
*
* @param node
* a node
* @return true if <i>node</i> is already in the tree; false otherwise
*/
public boolean contains(Node node) {
if (node == null) return false;
netlock.readLock().lock();
try {
Node parent = node.getParent();
for(int level=node.getLevel(); parent!=null&&level>0;
parent=parent.getParent(), level--) {
if (parent == clusterMap)
return true;
}
} finally {
netlock.readLock().unlock();
}
return false;
}
/** Given a string representation of a node, return its reference
*
* @param loc
* a path-like string representation of a node
* @return a reference to the node; null if the node is not in the tree
*/
public Node getNode(String loc) {
netlock.readLock().lock();
try {
loc = NodeBase.normalize(loc);
if (!NodeBase.ROOT.equals(loc))
loc = loc.substring(1);
return clusterMap.getLoc(loc);
} finally {
netlock.readLock().unlock();
}
}
/** Return the total number of racks */
public int getNumOfRacks() {
netlock.readLock().lock();
try {
return numOfRacks;
} finally {
netlock.readLock().unlock();
}
}
/** Return the total number of nodes */
public int getNumOfLeaves() {
netlock.readLock().lock();
try {
return clusterMap.getNumOfLeaves();
} finally {
netlock.readLock().unlock();
}
}
/** Return the distance between two 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.
* @param node1 one node
* @param node2 another node
* @return the distance between node1 and node2
* node1 or node2 do not belong to the cluster
*/
public int getDistance(Node node1, Node node2) {
if (node1 == node2) {
return 0;
}
Node n1=node1, n2=node2;
int dis = 0;
netlock.readLock().lock();
try {
int level1=node1.getLevel(), level2=node2.getLevel();
while(n1!=null && level1>level2) {
n1 = n1.getParent();
level1--;
dis++;
}
while(n2!=null && level2>level1) {
n2 = n2.getParent();
level2--;
dis++;
}
while(n1!=null && n2!=null && n1.getParent()!=n2.getParent()) {
n1=n1.getParent();
n2=n2.getParent();
dis+=2;
}
} finally {
netlock.readLock().unlock();
}
if (n1==null) {
LOG.warn("The cluster does not contain node: "+NodeBase.getPath(node1));
return Integer.MAX_VALUE;
}
if (n2==null) {
LOG.warn("The cluster does not contain node: "+NodeBase.getPath(node2));
return Integer.MAX_VALUE;
}
return dis+2;
}
/** Check if two nodes are on the same rack
* @param node1 one node
* @param node2 another node
* @return true if node1 and node2 are pm the same rack; false otherwise
* @exception IllegalArgumentException when either node1 or node2 is null, or
* node1 or node2 do not belong to the cluster
*/
public boolean isOnSameRack( Node node1, Node node2) {
if (node1 == null || node2 == null) {
return false;
}
netlock.readLock().lock();
try {
return node1.getParent()==node2.getParent();
} finally {
netlock.readLock().unlock();
}
}
final private static Random r = new Random();
/** randomly choose one node from <i>scope</i>
* if scope starts with ~, choose one from the all nodes except for the
* ones in <i>scope</i>; otherwise, choose one from <i>scope</i>
* @param scope range of nodes from which a node will be choosen
* @return the choosen node
*/
public Node chooseRandom(String scope) {
netlock.readLock().lock();
try {
if (scope.startsWith("~")) {
return chooseRandom(NodeBase.ROOT, scope.substring(1));
} else {
return chooseRandom(scope, null);
}
} finally {
netlock.readLock().unlock();
}
}
private Node chooseRandom(String scope, String excludedScope){
if (excludedScope != null) {
if (scope.startsWith(excludedScope)) {
return null;
}
if (!excludedScope.startsWith(scope)) {
excludedScope = null;
}
}
Node node = getNode(scope);
if (!(node instanceof InnerNode)) {
return node;
}
InnerNode innerNode = (InnerNode)node;
int numOfDatanodes = innerNode.getNumOfLeaves();
if (excludedScope == null) {
node = null;
} else {
node = getNode(excludedScope);
if (!(node instanceof InnerNode)) {
numOfDatanodes -= 1;
} else {
numOfDatanodes -= ((InnerNode)node).getNumOfLeaves();
}
}
int leaveIndex = r.nextInt(numOfDatanodes);
return innerNode.getLeaf(leaveIndex, node);
}
/** return the number of leaves in <i>scope</i> but not in <i>excludedNodes</i>
* if scope starts with ~, return the number of nodes that are not
* in <i>scope</i> and <i>excludedNodes</i>;
* @param scope a path string that may start with ~
* @param excludedNodes a list of nodes
* @return number of available nodes
*/
public int countNumOfAvailableNodes(String scope,
List<Node> excludedNodes) {
boolean isExcluded=false;
if (scope.startsWith("~")) {
isExcluded=true;
scope=scope.substring(1);
}
scope = NodeBase.normalize(scope);
int count=0; // the number of nodes in both scope & excludedNodes
netlock.readLock().lock();
try {
for(Node node:excludedNodes) {
if ((NodeBase.getPath(node)+NodeBase.PATH_SEPARATOR_STR).
startsWith(scope+NodeBase.PATH_SEPARATOR_STR)) {
count++;
}
}
Node n=getNode(scope);
int scopeNodeCount=1;
if (n instanceof InnerNode) {
scopeNodeCount=((InnerNode)n).getNumOfLeaves();
}
if (isExcluded) {
return clusterMap.getNumOfLeaves()-
scopeNodeCount-excludedNodes.size()+count;
} else {
return scopeNodeCount-count;
}
} finally {
netlock.readLock().unlock();
}
}
/** convert a network tree to a string */
public String toString() {
// print the number of racks
StringBuffer tree = new StringBuffer();
tree.append("Number of racks: ");
tree.append(numOfRacks);
tree.append("\n");
// print the number of leaves
int numOfLeaves = getNumOfLeaves();
tree.append("Expected number of leaves:");
tree.append(numOfLeaves);
tree.append("\n");
// print nodes
for(int i=0; i<numOfLeaves; i++) {
tree.append(NodeBase.getPath(clusterMap.getLeaf(i, null)));
tree.append("\n");
}
return tree.toString();
}
/* swap two array items */
static private void swap(Node[] nodes, int i, int j) {
Node tempNode;
tempNode = nodes[j];
nodes[j] = nodes[i];
nodes[i] = tempNode;
}
/** Sort nodes array by their distances to <i>reader</i>
* It linearly scans the array, if a local node is found, swap it with
* the first element of the array.
* If a local rack node is found, swap it with the first element following
* the local node.
* If neither local node or local rack node is found, put a random replica
* location at postion 0.
* It leaves the rest nodes untouched.
*/
public void pseudoSortByDistance( Node reader, Node[] nodes ) {
int tempIndex = 0;
if (reader != null ) {
int localRackNode = -1;
//scan the array to find the local node & local rack node
for(int i=0; i<nodes.length; i++) {
if(tempIndex == 0 && reader == nodes[i]) { //local node
//swap the local node and the node at position 0
if( i != 0 ) {
swap(nodes, tempIndex, i);
}
tempIndex=1;
if(localRackNode != -1 ) {
if(localRackNode == 0) {
localRackNode = i;
}
break;
}
} else if(localRackNode == -1 && isOnSameRack(reader, nodes[i])) {
//local rack
localRackNode = i;
if(tempIndex != 0 ) break;
}
}
// swap the local rack node and the node at position tempIndex
if(localRackNode != -1 && localRackNode != tempIndex ) {
swap(nodes, tempIndex, localRackNode);
tempIndex++;
}
}
// put a random node at position 0 if it is not a local/local-rack node
if(tempIndex == 0 && nodes.length != 0) {
swap(nodes, 0, r.nextInt(nodes.length));
}
}
}