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.utils;
  
  import java.util.Random;
  import java.util.concurrent.atomic.AtomicInteger;
  import java.util.concurrent.atomic.AtomicLong;
  
  /**
   * statistics tuples: sampling event
   *
   * @author yannian/Longda
   */
  public class EventSampler {
      private volatile int freq;
      private AtomicInteger i = new AtomicInteger(0);
      private volatile int target;
      private Random r = new Random();
  
      public EventSampler(int freq) {
          this.freq = freq;
          this.target = r.nextInt(freq);
  
          if (freq / 4 > 1) {
              intervalCheck.setInterval(freq / 4);
          }
      }
  
      /**
       * select 1/freq
       */
      public boolean countCheck() {
          i.incrementAndGet();
          if (i.get() > freq) {
              target = r.nextInt(freq);
              i.set(0);
          }
          return i.get() == target;
      }
  
      private AtomicInteger counter = new AtomicInteger(0);
      private AtomicLong sum = new AtomicLong(0);
      private IntervalCheck intervalCheck = new IntervalCheck();
  
      public Integer tpsCheck() {
          int send = counter.incrementAndGet();
  
          Double pastSeconds = intervalCheck.checkAndGet();
          if (pastSeconds != null) {
              counter.set(0);
              return (int) (send / pastSeconds);
          }
          return null;
      }
  
      public Integer timesCheck() {
          int send = counter.incrementAndGet();
  
          Double pastSeconds = intervalCheck.checkAndGet();
          if (pastSeconds != null) {
              counter.set(0);
              return send;
          }
          return null;
      }
  
      public Pair<Integer, Double> avgCheck(long one) {
          int send = counter.incrementAndGet();
          long total = sum.addAndGet(one);
  
          Double pastSeconds = intervalCheck.checkAndGet();
          if (pastSeconds != null) {
              counter.set(0);
              sum.set(0);
  
              Double avg = (double) 0;
              if (send != 0) {
                  avg = ((double) total) / send;
              }
              return new Pair<>(send, avg);
          }
          return null;
      }
  }
  