content: /*
   * 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.kafka.common.metrics.stats;
  
  import org.apache.kafka.common.metrics.MetricConfig;
  import org.apache.kafka.common.utils.MockTime;
  import org.apache.kafka.common.utils.Time;
  
  import org.junit.jupiter.api.BeforeEach;
  import org.junit.jupiter.api.Test;
  
  import java.util.List;
  
  import static java.util.concurrent.TimeUnit.SECONDS;
  import static org.junit.jupiter.api.Assertions.assertEquals;
  
  class SampledStatTest {
  
      private SampledStat stat;
      private Time time;
  
      @BeforeEach
      public void setup() {
          stat = new SampleCount();
          time = new MockTime();
      }
  
      @Test
      public void testSampleIsPurgedIfDoesntOverlap() {
          MetricConfig config = new MetricConfig().timeWindow(1, SECONDS).samples(2);
  
          // Monitored window: 2s. Complete a sample and wait 2.5s after.
          completeSample(config);
          time.sleep(2500);
  
          double numSamples = stat.measure(config, time.milliseconds());
          assertEquals(0, numSamples, "Sample should be purged if doesn't overlap the window");
      }
  
      @Test
      public void testSampleIsKeptIfOverlaps() {
          MetricConfig config = new MetricConfig().timeWindow(1, SECONDS).samples(2);
  
          // Monitored window: 2s. Complete a sample and wait 1.5s after.
          completeSample(config);
          time.sleep(1500);
  
          double numSamples = stat.measure(config, time.milliseconds());
          assertEquals(1, numSamples, "Sample should be kept if overlaps the window");
      }
  
      @Test
      public void testSampleIsKeptIfOverlapsAndExtra() {
          MetricConfig config = new MetricConfig().timeWindow(1, SECONDS).samples(2);
  
          // Monitored window: 2s. Create 2 samples with gaps in between and
          // take a measurement at 2.2s from the start.
          completeSample(config);
          time.sleep(100);
          completeSample(config);
          time.sleep(100);
          stat.record(config, 1, time.milliseconds());
  
          double numSamples = stat.measure(config, time.milliseconds());
          assertEquals(3, numSamples, "Sample should be kept if overlaps the window and is n+1");
      }
  
      // Creates a sample with events at the start and at the end. Positions clock at the end.
      private void completeSample(MetricConfig config) {
          stat.record(config, 1, time.milliseconds());
          time.sleep(config.timeWindowMs() - 1);
          stat.record(config, 1, time.milliseconds());
          time.sleep(1);
      }
  
      // measure() of this impl returns the number of samples
      static class SampleCount extends SampledStat {
  
          SampleCount() {
              super(0);
          }
  
          @Override
          protected void update(Sample sample, MetricConfig config, double value, long timeMs) {
              sample.value = 1;
          }
  
          @Override
          public double combine(List<Sample> samples, MetricConfig config, long now) {
              return samples.stream().mapToDouble(s -> s.value).sum();
          }
      }
  }
  