| /* |
| * 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.flink.metrics; |
| |
| /** |
| * A MeterView provides an average rate of events per second over a given time period. |
| * |
| * <p>The primary advantage of this class is that the rate is neither updated by the computing |
| * thread nor for every event. Instead, a history of counts is maintained that is updated in regular |
| * intervals by a background thread. From this history a rate is derived on demand, which represents |
| * the average rate of events over the given time span. |
| * |
| * <p>Setting the time span to a low value reduces memory-consumption and will more accurately |
| * report short-term changes. The minimum value possible is {@link View#UPDATE_INTERVAL_SECONDS}. A |
| * high value in turn increases memory-consumption, since a longer history has to be maintained, but |
| * will result in smoother transitions between rates. |
| * |
| * <p>The events are counted by a {@link Counter}. |
| */ |
| public class MeterView implements Meter, View { |
| |
| private static final int DEFAULT_TIME_SPAN_IN_SECONDS = 60; |
| |
| /** The underlying counter maintaining the count. */ |
| private final Counter counter; |
| /** The time-span over which the average is calculated. */ |
| private final int timeSpanInSeconds; |
| /** Circular array containing the history of values. */ |
| private final long[] values; |
| /** The index in the array for the current time. */ |
| private int time = 0; |
| /** The last rate we computed. */ |
| private double currentRate = 0; |
| |
| public MeterView(int timeSpanInSeconds) { |
| this(new SimpleCounter(), timeSpanInSeconds); |
| } |
| |
| public MeterView(Counter counter) { |
| this(counter, DEFAULT_TIME_SPAN_IN_SECONDS); |
| } |
| |
| public MeterView(Counter counter, int timeSpanInSeconds) { |
| this.counter = counter; |
| // the time-span must be larger than the update-interval as otherwise the array has a size |
| // of 1, |
| // for which no rate can be computed as no distinct before/after measurement exists. |
| this.timeSpanInSeconds = |
| Math.max( |
| timeSpanInSeconds - (timeSpanInSeconds % UPDATE_INTERVAL_SECONDS), |
| UPDATE_INTERVAL_SECONDS); |
| this.values = new long[this.timeSpanInSeconds / UPDATE_INTERVAL_SECONDS + 1]; |
| } |
| |
| @Override |
| public void markEvent() { |
| this.counter.inc(); |
| } |
| |
| @Override |
| public void markEvent(long n) { |
| this.counter.inc(n); |
| } |
| |
| @Override |
| public long getCount() { |
| return counter.getCount(); |
| } |
| |
| @Override |
| public double getRate() { |
| return currentRate; |
| } |
| |
| @Override |
| public void update() { |
| time = (time + 1) % values.length; |
| values[time] = counter.getCount(); |
| currentRate = |
| ((double) (values[time] - values[(time + 1) % values.length]) / timeSpanInSeconds); |
| } |
| } |