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.bookkeeper.common.util;
  
  import com.google.common.primitives.Longs;
  import java.security.SecureRandom;
  import java.util.Random;
  import lombok.extern.slf4j.Slf4j;
  import org.junit.Assert;
  import org.junit.Test;
  
  /**
   * Test how even is the distribution of ledgers across the threads of OrderedExecutor.
   */
  @Slf4j
  public class TestThreadSelection {
  
      public static final long MAX_KEY = 1_000_000L;
      public static final int MAX_THREADS = 96;
      public static final double MAX_DISPARITY = 1.25d;
  
      private final Random rnd = new SecureRandom();
  
      /**
       * Only even keys.
       */
      @Test
      public void testThreadSelectionEvenKeys() {
          runTest(0L, 2L);
      }
  
      /**
       * Only odd keys.
       */
      @Test
      public void testThreadSelectionOddKeys() {
          runTest(1L, 2L);
      }
  
      /**
       * All keys.
       */
      @Test
      public void testThreadSelectionAllKeys() {
          runTest(0L, 1L);
      }
  
      /**
       * Random keys.
       */
      @Test
      public void testThreadSelectionRandKeys() {
          for (int numThreads = 2; numThreads <= MAX_THREADS; numThreads++) {
              long[] placement = new long[numThreads];
  
              log.info("testing {} threads", numThreads);
              for (long key = 0L; key < MAX_KEY; key += 1L) {
                  int threadId = OrderedExecutor.chooseThreadIdx(rnd.nextLong(), numThreads);
                  placement[threadId]++;
              }
              validateTest(placement, numThreads);
          }
      }
  
      /**
       * Confirm the same key assigned to the same thread on consequent calls.
       */
      @Test
      public void testKeyAssignedToTheSameThread() {
          for (int numThreads = 2; numThreads <= MAX_THREADS; numThreads++) {
  
              log.info("testing {} threads", numThreads);
              for (long key = 0L; key < MAX_KEY; key += 1L) {
                  int threadId = OrderedExecutor.chooseThreadIdx(key, numThreads);
                  for (int i = 0; i < 10; i++) {
                      Assert.assertEquals("must be assigned to the same thread",
                              threadId, OrderedExecutor.chooseThreadIdx(key, numThreads));
                  }
              }
          }
      }
  
  
      private void runTest(long start, long step) {
          for (int numThreads = 2; numThreads <= MAX_THREADS; numThreads++) {
              long[] placement = new long[numThreads];
  
              log.info("testing {} threads", numThreads);
              for (long key = start; key < MAX_KEY; key += step) {
                  int threadId = OrderedExecutor.chooseThreadIdx(key, numThreads);
                  placement[threadId]++;
              }
              validateTest(placement, numThreads);
          }
      }
  
      private void validateTest(long[] placement, int numThreads) {
          long min = Longs.min(placement);
          long max = Longs.max(placement);
          log.info("got min={}, max={} (disparity: {}) for {} threads with {} ids",
                  min, max, max - min, numThreads, MAX_KEY);
          Assert.assertTrue("all threads were used [numThreads: " + numThreads + "]",
                  min > 0);
          log.info("disparity = {}", String.format("%,.2f", (double) max / min));
          Assert.assertTrue("no large disparity found [numThreads: " + numThreads + "], got "
                          + (double) max / min,
                  (double) max / min <= MAX_DISPARITY);
      }
  
  }
  