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.trogdor.workload;
  
  import org.apache.kafka.clients.producer.KafkaProducer;
  import org.apache.kafka.common.errors.InterruptException;
  
  import com.fasterxml.jackson.annotation.JsonCreator;
  import com.fasterxml.jackson.annotation.JsonProperty;
  
  import java.util.Random;
  
  /**
   * This generator will flush the producer after a specific number of messages, determined by a gaussian distribution.
   * This is useful to simulate a specific number of messages in a batch regardless of the message size, since batch
   * flushing is not exposed in the KafkaProducer.
   *
   * WARNING: This does not directly control when KafkaProducer will batch, this only makes best effort.  This also
   * cannot tell when a KafkaProducer batch is closed.  If the KafkaProducer sends a batch before this executes, this
   * will continue to execute on its own cadence.  To alleviate this, make sure to set `linger.ms` to allow for messages
   * to be generated up to your upper limit threshold, and make sure to set `batch.size` to allow for all these messages.
   *
   * Here is an example spec:
   *
   * {
   *    "type": "gaussian",
   *    "messagesPerFlushAverage": 16,
   *    "messagesPerFlushDeviation": 4
   * }
   *
   * This example will flush the producer on average every 16 messages, assuming `linger.ms` and `batch.size` allow for
   * it.  That average changes based on a normal distribution after each flush:
   *
   *    An average of the flushes will be at 16 messages.
   *    ~68% of the flushes are at between 12 and 20 messages.
   *    ~95% of the flushes are at between 8 and 24 messages.
   *    ~99% of the flushes are at between 4 and 28 messages.
   */
  
  public class GaussianFlushGenerator implements FlushGenerator {
      private final int messagesPerFlushAverage;
      private final double messagesPerFlushDeviation;
  
      private final Random random = new Random();
  
      private int messageTracker = 0;
      private int flushSize = 0;
  
      @JsonCreator
      public GaussianFlushGenerator(@JsonProperty("messagesPerFlushAverage") int messagesPerFlushAverage,
                                    @JsonProperty("messagesPerFlushDeviation") double messagesPerFlushDeviation) {
          this.messagesPerFlushAverage = messagesPerFlushAverage;
          this.messagesPerFlushDeviation = messagesPerFlushDeviation;
          calculateFlushSize();
      }
  
      @JsonProperty
      public int messagesPerFlushAverage() {
          return messagesPerFlushAverage;
      }
  
      @JsonProperty
      public double messagesPerFlushDeviation() {
          return messagesPerFlushDeviation;
      }
  
      private synchronized void calculateFlushSize() {
          flushSize = Math.max((int) (random.nextGaussian() * messagesPerFlushDeviation) + messagesPerFlushAverage, 1);
          messageTracker = 0;
      }
  
      @Override
      public synchronized <K, V> void increment(KafkaProducer<K, V> producer) {
          // Increment the message tracker.
          messageTracker += 1;
  
          // Compare the tracked message count with the throttle limits.
          if (messageTracker >= flushSize) {
              try {
                  producer.flush();
              } catch (InterruptException e) {
                  // Ignore flush interruption exceptions.
              }
              calculateFlushSize();
          }
      }
  }
  