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.raft.internals;
  
  import org.apache.kafka.common.metrics.MeasurableStat;
  import org.apache.kafka.common.metrics.MetricConfig;
  
  /**
   * Maintains an approximate ratio of the duration of a specific event
   * over all time. For example, this can be used to compute the ratio of
   * time that a thread is busy or idle. The value is approximate since the
   * measurement and recording intervals may not be aligned.
   *
   * Note that the duration of the event is assumed to be small relative to
   * the interval of measurement.
   *
   */
  public class TimeRatio implements MeasurableStat {
      private long intervalStartTimestampMs = -1;
      private long lastRecordedTimestampMs = -1;
      private double totalRecordedDurationMs = 0;
  
      private final double defaultRatio;
  
      public TimeRatio(double defaultRatio) {
          if (defaultRatio < 0.0 || defaultRatio > 1.0) {
              throw new IllegalArgumentException("Invalid ratio: value " + defaultRatio + " is not between 0 and 1.");
          }
  
          this.defaultRatio = defaultRatio;
      }
  
      @Override
      public double measure(MetricConfig config, long currentTimestampMs) {
          if (lastRecordedTimestampMs < 0) {
              // Return the default value if no recordings have been captured.
              return defaultRatio;
          } else {
              // We measure the ratio over the
              double intervalDurationMs = Math.max(lastRecordedTimestampMs - intervalStartTimestampMs, 0);
              final double ratio;
              if (intervalDurationMs == 0) {
                  ratio = defaultRatio;
              } else if (totalRecordedDurationMs > intervalDurationMs) {
                  ratio = 1.0;
              } else {
                  ratio = totalRecordedDurationMs / intervalDurationMs;
              }
  
              // The next interval begins at the
              intervalStartTimestampMs = lastRecordedTimestampMs;
              totalRecordedDurationMs = 0;
              return ratio;
          }
      }
  
      @Override
      public void record(MetricConfig config, double value, long currentTimestampMs) {
          if (intervalStartTimestampMs < 0) {
              // Discard the initial value since the value occurred prior to the interval start
              intervalStartTimestampMs = currentTimestampMs;
          } else {
              totalRecordedDurationMs += value;
              lastRecordedTimestampMs = currentTimestampMs;
          }
      }
  
  }
  