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.MetricName;
  import org.apache.kafka.common.metrics.CompoundStat.NamedMeasurable;
  import org.apache.kafka.common.metrics.MetricConfig;
  
  import org.junit.jupiter.api.Test;
  
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  
  public class MeterTest {
  
      private static final double EPS = 0.0000001d;
  
      @Test
      public void testMeter() {
          Map<String, String> emptyTags = Collections.emptyMap();
          MetricName rateMetricName = new MetricName("rate", "test", "", emptyTags);
          MetricName totalMetricName = new MetricName("total", "test", "", emptyTags);
          Meter meter = new Meter(rateMetricName, totalMetricName);
          List<NamedMeasurable> stats = meter.stats();
          assertEquals(2, stats.size());
          NamedMeasurable total = stats.get(0);
          NamedMeasurable rate = stats.get(1);
          assertEquals(rateMetricName, rate.name());
          assertEquals(totalMetricName, total.name());
          Rate rateStat = (Rate) rate.stat();
          CumulativeSum totalStat = (CumulativeSum) total.stat();
  
          MetricConfig config = new MetricConfig();
          double nextValue = 0.0;
          double expectedTotal = 0.0;
          long now = 0;
          int intervalMs = 100;
          double delta = 5.0;
  
          // Record values in multiple windows and verify that rates are reported
          // for time windows and that the total is cumulative.
          for (int i = 1; i <= 100; i++) {
              for (; now < i * 1000; now += intervalMs, nextValue += delta) {
                  expectedTotal += nextValue;
                  meter.record(config, nextValue, now);
              }
              assertEquals(expectedTotal, totalStat.measure(config, now), EPS);
              long windowSizeMs = rateStat.windowSize(config, now);
              long windowStartMs = Math.max(now - windowSizeMs, 0);
              double sampledTotal = 0.0;
              double prevValue = nextValue - delta;
              for (long timeMs = now - 100; timeMs >= windowStartMs; timeMs -= intervalMs, prevValue -= delta)
                  sampledTotal += prevValue;
              assertEquals(sampledTotal * 1000 / windowSizeMs, rateStat.measure(config, now), EPS);
          }
      }
  }
  