org.apache.hadoop.net.NetworkTopology Maven / Gradle / Ivy
/**
* 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.List;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Random;
import java.util.TreeMap;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import com.google.common.annotations.VisibleForTesting;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.CommonConfigurationKeysPublic;
import org.apache.hadoop.util.ReflectionUtils;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
/** 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.
*
*/
@InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})
@InterfaceStability.Unstable
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);
public static class InvalidTopologyException extends RuntimeException {
private static final long serialVersionUID = 1L;
public InvalidTopologyException(String msg) {
super(msg);
}
}
/**
* Get an instance of NetworkTopology based on the value of the configuration
* parameter net.topology.impl.
*
* @param conf the configuration to be used
* @return an instance of NetworkTopology
*/
public static NetworkTopology getInstance(Configuration conf){
return ReflectionUtils.newInstance(
conf.getClass(CommonConfigurationKeysPublic.NET_TOPOLOGY_IMPL_KEY,
NetworkTopology.class, NetworkTopology.class), conf);
}
/** InnerNode represents a switch/router of a data center or rack.
* Different from a leaf node, it has non-null children.
*/
static class InnerNode extends NodeBase {
protected List children=new ArrayList();
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);
}
/** @return its children */
List 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 n
*
* @param n a node
* @return true if this node is an ancestor of n
*/
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 n
*
* @param n a node
* @return true if this node is the parent of n
*/
boolean isParent(Node n) {
return n.getNetworkLocation().equals(getPath(this));
}
/* Return a child name of this node who is an ancestor of node n */
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 n 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; iTo be overridden in subclasses for specific InnerNode implementations,
* as alternative to overriding the full {@link #add(Node)} method.
*
* @param parentName The name of the parent node
* @return A new inner node
* @see InnerNode#InnerNode(String, String, InnerNode, int)
*/
protected InnerNode createParentNode(String parentName) {
return new InnerNode(parentName, getPath(this), this, this.getLevel()+1);
}
/** Remove node n 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; ileafIndex leaf of this subtree
* if it is not in the excludedNode
*
* @param leafIndex an indexed leaf of the node
* @param excludedNode an excluded node (can be null)
* @return
*/
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 (isLeafParent()) { // 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 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;
}
}
protected boolean isLeafParent() {
return isRack();
}
/**
* Determine if children a leaves, default implementation calls {@link #isRack()}
* To be overridden in subclasses for specific InnerNode implementations,
* as alternative to overriding the full {@link #getLeaf(int, Node)} method.
*
* @return true if children are leaves, false otherwise
*/
protected boolean areChildrenLeaves() {
return isRack();
}
/**
* Get number of leaves.
*/
int getNumOfLeaves() {
return numOfLeaves;
}
} // end of InnerNode
/**
* the root cluster map
*/
InnerNode clusterMap;
/** Depth of all leaf nodes */
private int depthOfAllLeaves = -1;
/** rack counter */
protected int numOfRacks = 0;
/**
* Whether or not this cluster has ever consisted of more than 1 rack,
* according to the NetworkTopology.
*/
private boolean clusterEverBeenMultiRack = false;
/** the lock used to manage access */
protected ReadWriteLock netlock = new ReentrantReadWriteLock();
public NetworkTopology() {
clusterMap = new InnerNode(InnerNode.ROOT);
}
/** Add a leaf node
* Update node counter & rack counter if necessary
* @param node node to be added; can be null
* @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;
int newDepth = NodeBase.locationToDepth(node.getNetworkLocation()) + 1;
netlock.writeLock().lock();
try {
if( node instanceof InnerNode ) {
throw new IllegalArgumentException(
"Not allow to add an inner node: "+NodeBase.getPath(node));
}
if ((depthOfAllLeaves != -1) && (depthOfAllLeaves != newDepth)) {
LOG.error("Error: can't add leaf node " + NodeBase.getPath(node) +
" at depth " + newDepth + " to topology:\n" + this.toString());
throw new InvalidTopologyException("Failed to add " + NodeBase.getPath(node) +
": You cannot have a rack and a non-rack node at the same " +
"level of the network topology.");
}
Node rack = getNodeForNetworkLocation(node);
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) {
incrementRacks();
}
if (!(node instanceof InnerNode)) {
if (depthOfAllLeaves == -1) {
depthOfAllLeaves = node.getLevel();
}
}
}
if(LOG.isDebugEnabled()) {
LOG.debug("NetworkTopology became:\n" + this.toString());
}
} finally {
netlock.writeLock().unlock();
}
}
protected void incrementRacks() {
numOfRacks++;
if (!clusterEverBeenMultiRack && numOfRacks > 1) {
clusterEverBeenMultiRack = true;
}
}
/**
* Return a reference to the node given its string representation.
* Default implementation delegates to {@link #getNode(String)}.
*
*
To be overridden in subclasses for specific NetworkTopology
* implementations, as alternative to overriding the full {@link #add(Node)}
* method.
*
* @param node The string representation of this node's network location is
* used to retrieve a Node object.
* @return a reference to the node; null if the node is not in the tree
*
* @see #add(Node)
* @see #getNode(String)
*/
protected Node getNodeForNetworkLocation(Node node) {
return getNode(node.getNetworkLocation());
}
/**
* Given a string representation of a rack, return its children
* @param loc a path-like string representation of a rack
* @return a newly allocated list with all the node's children
*/
public List getDatanodesInRack(String loc) {
netlock.readLock().lock();
try {
loc = NodeBase.normalize(loc);
if (!NodeBase.ROOT.equals(loc)) {
loc = loc.substring(1);
}
InnerNode rack = (InnerNode) clusterMap.getLoc(loc);
if (rack == null) {
return null;
}
return new ArrayList(rack.getChildren());
} finally {
netlock.readLock().unlock();
}
}
/** Remove a node
* Update node counter and rack counter if necessary
* @param node node to be removed; can be null
*/
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--;
}
}
if(LOG.isDebugEnabled()) {
LOG.debug("NetworkTopology became:\n" + this.toString());
}
} finally {
netlock.writeLock().unlock();
}
}
/** Check if the tree contains node node
*
* @param node a node
* @return true if node 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 true if this cluster has ever consisted of multiple racks, even if
* it is not now a multi-rack cluster.
*/
public boolean hasClusterEverBeenMultiRack() {
return clusterEverBeenMultiRack;
}
/** Given a string representation of a rack for a specific network
* location
*
* To be overridden in subclasses for specific NetworkTopology
* implementations, as alternative to overriding the full
* {@link #getRack(String)} method.
* @param loc
* a path-like string representation of a network location
* @return a rack string
*/
public String getRack(String loc) {
return loc;
}
/** @return the total number of racks */
public int getNumOfRacks() {
netlock.readLock().lock();
try {
return numOfRacks;
} finally {
netlock.readLock().unlock();
}
}
/** @return the total number of leaf 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 which is zero if they are the same
* or {@link Integer#MAX_VALUE} if 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 (can be null)
* @param node2 another node (can be null)
* @return true if node1 and node2 are on 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 isSameParents(node1, node2);
} finally {
netlock.readLock().unlock();
}
}
/**
* Check if network topology is aware of NodeGroup
*/
public boolean isNodeGroupAware() {
return false;
}
/**
* Return false directly as not aware of NodeGroup, to be override in sub-class
*/
public boolean isOnSameNodeGroup(Node node1, Node node2) {
return false;
}
/**
* Compare the parents of each node for equality
*
* To be overridden in subclasses for specific NetworkTopology
* implementations, as alternative to overriding the full
* {@link #isOnSameRack(Node, Node)} method.
*
* @param node1 the first node to compare
* @param node2 the second node to compare
* @return true if their parents are equal, false otherwise
*
* @see #isOnSameRack(Node, Node)
*/
protected boolean isSameParents(Node node1, Node node2) {
return node1.getParent()==node2.getParent();
}
private static final Random r = new Random();
@VisibleForTesting
void setRandomSeed(long seed) {
r.setSeed(seed);
}
/** randomly choose one node from scope
* if scope starts with ~, choose one from the all nodes except for the
* ones in scope; otherwise, choose one from scope
* @param scope range of nodes from which a node will be chosen
* @return the chosen 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();
}
}
if (numOfDatanodes == 0) {
throw new InvalidTopologyException(
"Failed to find datanode (scope=\"" + String.valueOf(scope) +
"\" excludedScope=\"" + String.valueOf(excludedScope) + "\").");
}
int leaveIndex = r.nextInt(numOfDatanodes);
return innerNode.getLeaf(leaveIndex, node);
}
/** return leaves in scope
* @param scope a path string
* @return leaves nodes under specific scope
*/
public List getLeaves(String scope) {
Node node = getNode(scope);
List leafNodes = new ArrayList();
if (!(node instanceof InnerNode)) {
leafNodes.add(node);
} else {
InnerNode innerNode = (InnerNode) node;
for (int i=0;iscope but not in excludedNodes
* if scope starts with ~, return the number of nodes that are not
* in scope and excludedNodes;
* @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,
Collection excludedNodes) {
boolean isExcluded=false;
if (scope.startsWith("~")) {
isExcluded=true;
scope=scope.substring(1);
}
scope = NodeBase.normalize(scope);
int excludedCountInScope = 0; // the number of nodes in both scope & excludedNodes
int excludedCountOffScope = 0; // the number of nodes outside scope & excludedNodes
netlock.readLock().lock();
try {
for (Node node : excludedNodes) {
node = getNode(NodeBase.getPath(node));
if (node == null) {
continue;
}
if ((NodeBase.getPath(node) + NodeBase.PATH_SEPARATOR_STR)
.startsWith(scope + NodeBase.PATH_SEPARATOR_STR)) {
excludedCountInScope++;
} else {
excludedCountOffScope++;
}
}
Node n = getNode(scope);
int scopeNodeCount = 0;
if (n != null) {
scopeNodeCount++;
}
if (n instanceof InnerNode) {
scopeNodeCount=((InnerNode)n).getNumOfLeaves();
}
if (isExcluded) {
return clusterMap.getNumOfLeaves() - scopeNodeCount
- excludedCountOffScope;
} else {
return scopeNodeCount - excludedCountInScope;
}
} finally {
netlock.readLock().unlock();
}
}
/** convert a network tree to a string */
@Override
public String toString() {
// print the number of racks
StringBuilder tree = new StringBuilder();
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; ireader.
*
* In a three-level topology, a node can be either local, on the same rack,
* or on a different rack from the reader. Sorting the nodes based on network
* distance from the reader reduces network traffic and improves
* performance.
*
* As an additional twist, we also randomize the nodes at each network
* distance. This helps with load balancing when there is data skew.
*
* @param reader Node where data will be read
* @param nodes Available replicas with the requested data
* @param activeLen Number of active nodes at the front of the array
*/
public void sortByDistance(Node reader, Node[] nodes, int activeLen) {
/** Sort weights for the nodes array */
int[] weights = new int[activeLen];
for (int i=0; i> tree = new TreeMap>();
for (int i=0; i list = tree.get(weight);
if (list == null) {
list = Lists.newArrayListWithExpectedSize(1);
tree.put(weight, list);
}
list.add(node);
}
int idx = 0;
for (List list: tree.values()) {
if (list != null) {
Collections.shuffle(list, r);
for (Node n: list) {
nodes[idx] = n;
idx++;
}
}
}
Preconditions.checkState(idx == activeLen,
"Sorted the wrong number of nodes!");
}
}