/**
*
* 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.hbase;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.NavigableSet;
import java.util.TreeMap;
import java.util.TreeSet;
import org.apache.hadoop.classification.InterfaceAudience;
/**
* Data structure to describe the distribution of HDFS blocks amount hosts
*/
@InterfaceAudience.Private
public class HDFSBlocksDistribution {
private Map<String,HostAndWeight> hostAndWeights = null;
private long uniqueBlocksTotalWeight = 0;
/**
* Stores the hostname and weight for that hostname.
*
* This is used when determining the physical locations of the blocks making
* up a region.
*
* To make a prioritized list of the hosts holding the most data of a region,
* this class is used to count the total weight for each host. The weight is
* currently just the size of the file.
*/
public static class HostAndWeight {
private String host;
private long weight;
/**
* Constructor
* @param host the host name
* @param weight the weight
*/
public HostAndWeight(String host, long weight) {
this.host = host;
this.weight = weight;
}
/**
* add weight
* @param weight the weight
*/
public void addWeight(long weight) {
this.weight += weight;
}
/**
* @return the host name
*/
public String getHost() {
return host;
}
/**
* @return the weight
*/
public long getWeight() {
return weight;
}
/**
* comparator used to sort hosts based on weight
*/
public static class WeightComparator implements Comparator<HostAndWeight> {
@Override
public int compare(HostAndWeight l, HostAndWeight r) {
if(l.getWeight() == r.getWeight()) {
return l.getHost().compareTo(r.getHost());
}
return l.getWeight() < r.getWeight() ? -1 : 1;
}
}
}
/**
* Constructor
*/
public HDFSBlocksDistribution() {
this.hostAndWeights =
new TreeMap<String,HostAndWeight>();
}
/**
* @see java.lang.Object#toString()
*/
@Override
public synchronized String toString() {
return "number of unique hosts in the disribution=" +
this.hostAndWeights.size();
}
/**
* add some weight to a list of hosts, update the value of unique block weight
* @param hosts the list of the host
* @param weight the weight
*/
public void addHostsAndBlockWeight(String[] hosts, long weight) {
if (hosts == null || hosts.length == 0) {
throw new NullPointerException("empty hosts");
}
addUniqueWeight(weight);
for (String hostname : hosts) {
addHostAndBlockWeight(hostname, weight);
}
}
/**
* add some weight to the total unique weight
* @param weight the weight
*/
private void addUniqueWeight(long weight) {
uniqueBlocksTotalWeight += weight;
}
/**
* add some weight to a specific host
* @param host the host name
* @param weight the weight
*/
private void addHostAndBlockWeight(String host, long weight) {
if (host == null) {
throw new NullPointerException("Passed hostname is null");
}
HostAndWeight hostAndWeight = this.hostAndWeights.get(host);
if(hostAndWeight == null) {
hostAndWeight = new HostAndWeight(host, weight);
this.hostAndWeights.put(host, hostAndWeight);
} else {
hostAndWeight.addWeight(weight);
}
}
/**
* @return the hosts and their weights
*/
public Map<String,HostAndWeight> getHostAndWeights() {
return this.hostAndWeights;
}
/**
* return the weight for a specific host, that will be the total bytes of all
* blocks on the host
* @param host the host name
* @return the weight of the given host
*/
public long getWeight(String host) {
long weight = 0;
if (host != null) {
HostAndWeight hostAndWeight = this.hostAndWeights.get(host);
if(hostAndWeight != null) {
weight = hostAndWeight.getWeight();
}
}
return weight;
}
/**
* @return the sum of all unique blocks' weight
*/
public long getUniqueBlocksTotalWeight() {
return uniqueBlocksTotalWeight;
}
/**
* return the locality index of a given host
* @param host the host name
* @return the locality index of the given host
*/
public float getBlockLocalityIndex(String host) {
float localityIndex = 0;
HostAndWeight hostAndWeight = this.hostAndWeights.get(host);
if (hostAndWeight != null && uniqueBlocksTotalWeight != 0) {
localityIndex=(float)hostAndWeight.weight/(float)uniqueBlocksTotalWeight;
}
return localityIndex;
}
/**
* This will add the distribution from input to this object
* @param otherBlocksDistribution the other hdfs blocks distribution
*/
public void add(HDFSBlocksDistribution otherBlocksDistribution) {
Map<String,HostAndWeight> otherHostAndWeights =
otherBlocksDistribution.getHostAndWeights();
for (Map.Entry<String, HostAndWeight> otherHostAndWeight:
otherHostAndWeights.entrySet()) {
addHostAndBlockWeight(otherHostAndWeight.getValue().host,
otherHostAndWeight.getValue().weight);
}
addUniqueWeight(otherBlocksDistribution.getUniqueBlocksTotalWeight());
}
/**
* return the sorted list of hosts in terms of their weights
*/
public List<String> getTopHosts() {
NavigableSet<HostAndWeight> orderedHosts = new TreeSet<HostAndWeight>(
new HostAndWeight.WeightComparator());
orderedHosts.addAll(this.hostAndWeights.values());
List<String> topHosts = new ArrayList<String>(orderedHosts.size());
for(HostAndWeight haw : orderedHosts.descendingSet()) {
topHosts.add(haw.getHost());
}
return topHosts;
}
}