| /** |
| * 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.distributedlog.common.rate; |
| |
| import com.google.common.base.Ticker; |
| import java.util.concurrent.LinkedBlockingDeque; |
| import java.util.concurrent.TimeUnit; |
| import java.util.concurrent.atomic.AtomicLong; |
| import org.apache.commons.lang3.tuple.Pair; |
| |
| /** |
| * Sampled {@link MovingAverageRate}. |
| */ |
| class SampledMovingAverageRate implements MovingAverageRate { |
| |
| private static final long NANOS_PER_SEC = TimeUnit.SECONDS.toNanos(1); |
| |
| private final AtomicLong total; |
| private final Ticker ticker; |
| private final double scaleFactor; |
| private final LinkedBlockingDeque<Pair<Long, Long>> samples; |
| |
| private double value; |
| |
| public SampledMovingAverageRate(int intervalSecs) { |
| this(intervalSecs, 1, Ticker.systemTicker()); |
| } |
| |
| SampledMovingAverageRate(int intervalSecs, |
| double scaleFactor, |
| Ticker ticker) { |
| this.value = 0; |
| this.total = new AtomicLong(0); |
| this.scaleFactor = scaleFactor; |
| this.ticker = ticker; |
| this.samples = new LinkedBlockingDeque<>(intervalSecs); |
| } |
| |
| @Override |
| public double get() { |
| return value; |
| } |
| |
| @Override |
| public void add(long amount) { |
| total.getAndAdd(amount); |
| } |
| |
| @Override |
| public void inc() { |
| add(1); |
| } |
| |
| void sample() { |
| value = doSample(); |
| } |
| |
| private double doSample() { |
| long newSample = total.get(); |
| long newTimestamp = ticker.read(); |
| |
| double rate = 0; |
| if (!samples.isEmpty()) { |
| Pair<Long, Long> oldestSample = samples.peekLast(); |
| |
| double dy = newSample - oldestSample.getRight(); |
| double dt = newTimestamp - oldestSample.getLeft(); |
| |
| rate = (dt == 0) ? 0 : (NANOS_PER_SEC * scaleFactor * dy) / dt; |
| } |
| |
| if (samples.remainingCapacity() == 0) { |
| samples.removeLast(); |
| } else { |
| samples.addFirst(Pair.of(newTimestamp, newSample)); |
| } |
| |
| return rate; |
| } |
| } |