com.alibaba.metrics.RatioGauge 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 com.alibaba.metrics;
import static com.alibaba.metrics.Constants.NOT_AVAILABLE;
import static java.lang.Double.isInfinite;
import static java.lang.Double.isNaN;
/**
* A gauge which measures the ratio of one value to another.
*
* If the denominator is zero, not a number, or infinite, the resulting ratio is not a number.
*
* 一种衡量比率的度量器，传入分子和分母，该度量器会自动计算比率
*/
public abstract class RatioGauge implements Gauge {
private long lastUpdated = System.currentTimeMillis();
/**
* A ratio of one quantity to another.
*/
public static class Ratio {
/**
* Creates a new ratio with the given numerator and denominator.
*
* @param numerator the numerator of the ratio
* @param denominator the denominator of the ratio
* @return {@code numerator:denominator}
*/
public static Ratio of(double numerator, double denominator) {
return new Ratio(numerator, denominator);
}
private final double numerator;
private final double denominator;
private Ratio(double numerator, double denominator) {
this.numerator = numerator;
this.denominator = denominator;
}
/**
* Returns the ratio, which is either a {@code double} between 0 and 1 (inclusive) or
* {@code NaN}.
*
* @return the ratio
*/
public double getValue() {
final double d = denominator;
if (isNaN(d) || isInfinite(d) || d == 0) {
return Double.NaN;
}
return numerator / d;
}
@Override
public String toString() {
return numerator + ":" + denominator;
}
}
/**
* Returns the {@link Ratio} which is the gauge's current value.
*
* @return the {@link Ratio} which is the gauge's current value
*/
protected abstract Ratio getRatio();
public Double getValue() {
try {
Ratio r = getRatio();
if (r == null) {
return (double)NOT_AVAILABLE;
}
double result = r.getValue();
lastUpdated = System.currentTimeMillis();
return result;
} catch (Exception e) {
return (double)NOT_AVAILABLE;
}
}
@Override
public long lastUpdateTime() {
return lastUpdated;
}
}