| /* |
| * 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.dubbo.metrics.aggregate; |
| |
| import com.tdunning.math.stats.TDigest; |
| |
| import java.util.concurrent.TimeUnit; |
| |
| /** |
| * Wrapper around TDigest. |
| * <p> |
| * Maintains a ring buffer of TDigest to provide quantiles over a sliding windows of time. |
| */ |
| public class TimeWindowQuantile { |
| private final double compression; |
| private final TDigest[] ringBuffer; |
| private int currentBucket; |
| private long lastRotateTimestampMillis; |
| private final long durationBetweenRotatesMillis; |
| |
| public TimeWindowQuantile(double compression, int bucketNum, int timeWindowSeconds) { |
| this.compression = compression; |
| this.ringBuffer = new TDigest[bucketNum]; |
| for (int i = 0; i < bucketNum; i++) { |
| this.ringBuffer[i] = TDigest.createDigest(compression); |
| } |
| |
| this.currentBucket = 0; |
| this.lastRotateTimestampMillis = System.currentTimeMillis(); |
| this.durationBetweenRotatesMillis = TimeUnit.SECONDS.toMillis(timeWindowSeconds) / bucketNum; |
| } |
| |
| public synchronized double quantile(double q) { |
| TDigest currentBucket = rotate(); |
| |
| // This may return Double.NaN, and it's correct behavior. |
| // see: https://github.com/prometheus/client_golang/issues/85 |
| return currentBucket.quantile(q); |
| } |
| |
| public synchronized void add(double value) { |
| rotate(); |
| for (TDigest bucket : ringBuffer) { |
| bucket.add(value); |
| } |
| } |
| |
| private TDigest rotate() { |
| long timeSinceLastRotateMillis = System.currentTimeMillis() - lastRotateTimestampMillis; |
| while (timeSinceLastRotateMillis > durationBetweenRotatesMillis) { |
| ringBuffer[currentBucket] = TDigest.createDigest(compression); |
| if (++currentBucket >= ringBuffer.length) { |
| currentBucket = 0; |
| } |
| timeSinceLastRotateMillis -= durationBetweenRotatesMillis; |
| lastRotateTimestampMillis += durationBetweenRotatesMillis; |
| } |
| return ringBuffer[currentBucket]; |
| } |
| } |