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 com.alibaba.jstorm.common.metric;
  
  import com.codahale.metrics.Gauge;
  
  /**
   * 
   * @author zhongyan.feng
   * @version $Id:
   */
  public class TimerRatio implements Gauge<Double> {
  
      private long lastUpdateTime = 0;
      private long sum = 0;
      private long lastGaugeTime = 0;
  
      public synchronized void start() {
          if (lastUpdateTime == 0) {
              lastUpdateTime = System.nanoTime();
          }
      }
  
      public synchronized void stop() {
          if (lastUpdateTime != 0) {
              long now = System.nanoTime();
              long cost = now - lastUpdateTime;
              lastUpdateTime = 0;
              sum += cost;
          }
  
      }
  
      @Override
      public Double getValue() {
          synchronized (this) {
              stop();
  
              long now = System.nanoTime();
              long cost = now - lastGaugeTime;
              if (cost == 0) {
                  return 1.0;
              }
  
              lastGaugeTime = now;
              double ratio = ((double) sum) / cost;
              sum = 0;
              return ratio;
  
          }
  
      }
  
  }
  