org.apache.hadoop.hdfs.server.blockmanagement.Host2NodesMap 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.hdfs.server.blockmanagement;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
/** A map from host names to datanode descriptors. */
@InterfaceAudience.Private
@InterfaceStability.Evolving
class Host2NodesMap {
private HashMap mapHost = new HashMap();
private final HashMap map
= new HashMap();
private final ReadWriteLock hostmapLock = new ReentrantReadWriteLock();
/** Check if node is already in the map. */
boolean contains(DatanodeDescriptor node) {
if (node==null) {
return false;
}
String ipAddr = node.getIpAddr();
hostmapLock.readLock().lock();
try {
DatanodeDescriptor[] nodes = map.get(ipAddr);
if (nodes != null) {
for(DatanodeDescriptor containedNode:nodes) {
if (node==containedNode) {
return true;
}
}
}
} finally {
hostmapLock.readLock().unlock();
}
return false;
}
/** add node to the map
* return true if the node is added; false otherwise.
*/
boolean add(DatanodeDescriptor node) {
hostmapLock.writeLock().lock();
try {
if (node==null || contains(node)) {
return false;
}
String ipAddr = node.getIpAddr();
String hostname = node.getHostName();
mapHost.put(hostname, ipAddr);
DatanodeDescriptor[] nodes = map.get(ipAddr);
DatanodeDescriptor[] newNodes;
if (nodes==null) {
newNodes = new DatanodeDescriptor[1];
newNodes[0]=node;
} else { // rare case: more than one datanode on the host
newNodes = new DatanodeDescriptor[nodes.length+1];
System.arraycopy(nodes, 0, newNodes, 0, nodes.length);
newNodes[nodes.length] = node;
}
map.put(ipAddr, newNodes);
return true;
} finally {
hostmapLock.writeLock().unlock();
}
}
/** remove node from the map
* return true if the node is removed; false otherwise.
*/
boolean remove(DatanodeDescriptor node) {
if (node==null) {
return false;
}
String ipAddr = node.getIpAddr();
String hostname = node.getHostName();
hostmapLock.writeLock().lock();
try {
DatanodeDescriptor[] nodes = map.get(ipAddr);
if (nodes==null) {
return false;
}
if (nodes.length==1) {
if (nodes[0]==node) {
map.remove(ipAddr);
//remove hostname key since last datanode is removed
mapHost.remove(hostname);
return true;
} else {
return false;
}
}
//rare case
int i=0;
for(; i host: mapHost.entrySet()) {
DatanodeDescriptor[] e = map.get(host.getValue());
b.append("\n " + host.getKey() + " => "+host.getValue() + " => "
+ Arrays.asList(e));
}
return b.append("\n]").toString();
}
}