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.common.utils.Time;
  
  import com.fasterxml.jackson.annotation.JsonCreator;
  import com.fasterxml.jackson.annotation.JsonProperty;
  
  import java.nio.ByteBuffer;
  import java.nio.ByteOrder;
  import java.util.Random;
  
  /**
   * A PayloadGenerator which generates a timestamped uniform random payload.
   *
   * This generator generates pseudo-random payloads that can be reproduced from run to run.
   * The guarantees are the same as those of java.util.Random.
   *
   * The timestamp used for this class is in milliseconds since epoch, encoded directly to the first several bytes of the
   * payload.
   *
   * This should be used in conjunction with TimestampRecordProcessor in the Consumer to measure true end-to-end latency
   * of a system.
   *
   * `size` - The size in bytes of each message.
   * `seed` - Used to initialize Random() to remove some non-determinism.
   *
   * Here is an example spec:
   *
   * {
   *    "type": "timestampRandom",
   *    "size": 512
   * }
   *
   * This will generate a 512-byte random message with the first several bytes encoded with the timestamp.
   */
  public class TimestampRandomPayloadGenerator implements PayloadGenerator {
      private final int size;
      private final long seed;
  
      private final byte[] randomBytes;
      private final ByteBuffer buffer;
  
      private final Random random = new Random();
  
      @JsonCreator
      public TimestampRandomPayloadGenerator(@JsonProperty("size") int size,
                                             @JsonProperty("seed") long seed) {
          this.size = size;
          this.seed = seed;
          if (size < Long.BYTES) {
              throw new RuntimeException("The size of the payload must be greater than or equal to " + Long.BYTES + ".");
          }
          random.setSeed(seed);
          this.randomBytes = new byte[size - Long.BYTES];
          buffer = ByteBuffer.allocate(Long.BYTES);
          buffer.order(ByteOrder.LITTLE_ENDIAN);
      }
  
      @JsonProperty
      public int size() {
          return size;
      }
  
      @JsonProperty
      public long seed() {
          return seed;
      }
  
      @Override
      public synchronized byte[] generate(long position) {
          // Generate out of order to prevent inclusion of random number generation in latency numbers.
          byte[] result = new byte[size];
          if (randomBytes.length > 0) {
              random.setSeed(seed + position);
              random.nextBytes(randomBytes);
              System.arraycopy(randomBytes, 0, result, Long.BYTES, randomBytes.length);
          }
  
          // Do the timestamp generation as the very last task.
          buffer.clear();
          buffer.putLong(Time.SYSTEM.milliseconds());
          buffer.rewind();
          System.arraycopy(buffer.array(), 0, result, 0, Long.BYTES);
          return result;
      }
  }
  