hadoop Metrics2Util 源码
haddop Metrics2Util 代码
文件路径：/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/util/Metrics2Util.java
/**
* 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.metrics2.util;
import java.util.PriorityQueue;
import org.apache.hadoop.classification.InterfaceAudience;
/**
* Utility class to simplify creation of hadoop metrics2 source/sink.
*/
@InterfaceAudience.Private
public class Metrics2Util {
/**
* A pair of a name and its corresponding value. Defines a custom
* comparator so the TopN PriorityQueue sorts based on the count.
*/
@InterfaceAudience.Private
public static class NameValuePair implements Comparable<NameValuePair> {
private String name;
private long value;
public NameValuePair(String metricName, long value) {
this.name = metricName;
this.value = value;
}
public String getName() {
return name;
}
public long getValue() {
return value;
}
@Override
public int compareTo(NameValuePair other) {
return (int) (value - other.value);
}
@Override
public boolean equals(Object other) {
if (other instanceof NameValuePair) {
return compareTo((NameValuePair)other) == 0;
}
return false;
}
@Override
public int hashCode() {
return Long.valueOf(value).hashCode();
}
}
/**
* A fixed-size priority queue, used to retrieve top-n of offered entries.
*/
@InterfaceAudience.Private
public static class TopN extends PriorityQueue<NameValuePair> {
private static final long serialVersionUID = 5134028249611535803L;
private int n; // > 0
private long total = 0;
public TopN(int n) {
super(n);
this.n = n;
}
@Override
public boolean offer(NameValuePair entry) {
updateTotal(entry.value);
if (size() == n) {
NameValuePair smallest = peek();
if (smallest.value >= entry.value) {
return false;
}
poll(); // remove smallest
}
return super.offer(entry);
}
private void updateTotal(long value) {
total += value;
}
public long getTotal() {
return total;
}
}
}
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