ShuffleGroupingTest.java

// Copyright 2016 Twitter. All rights reserved.
//
// Licensed 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.twitter.heron.simulator.grouping;

import java.util.LinkedList;
import java.util.List;

import org.junit.After;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;

import com.twitter.heron.proto.system.HeronTuples;

public class ShuffleGroupingTest {

  @Before
  public void before() throws Exception {
  }

  @After
  public void after() throws Exception {
  }

  /**
   * Method: test round robin nature of shuffle grouping
   */
  @Test
  public void testRoundRobin() throws Exception {
    List<Integer> taskIds = new LinkedList<>();
    taskIds.add(0);
    taskIds.add(2);
    taskIds.add(4);
    taskIds.add(8);

    ShuffleGrouping g = new ShuffleGrouping(taskIds);
    HeronTuples.HeronDataTuple dummy = HeronTuples.HeronDataTuple.getDefaultInstance();
    List<Integer> dest = g.getListToSend(dummy);

    Assert.assertEquals(dest.size(), 1);
    int first = dest.get(0);
    int index = -1;
    for (int i = 0; i < taskIds.size(); ++i) {
      if (taskIds.get(i) == first) {
        index = i;
        break;
      }
    }
    dest.clear();

    for (int i = 0; i < 100; ++i) {
      dest = g.getListToSend(dummy);

      Assert.assertEquals(dest.size(), 1);
      int d = dest.get(0);
      index = (index + 1) % taskIds.size();
      Assert.assertEquals((Integer) d, taskIds.get(index));
      dest.clear();
    }
  }

  /**
   * Method: test random start
   */
  @Test
  public void testRandomStart() throws Exception {
    List<Integer> taskIds = new LinkedList<>();
    taskIds.add(0);
    taskIds.add(1);

    int zeros = 0;
    int ones = 0;
    int count = 1000;

    for (int i = 0; i < count; ++i) {
      ShuffleGrouping g = new ShuffleGrouping(taskIds);
      HeronTuples.HeronDataTuple dummy = HeronTuples.HeronDataTuple.getDefaultInstance();
      List<Integer> dest = g.getListToSend(dummy);

      Assert.assertEquals(dest.size(), 1);
      int first = dest.get(0);
      if (first == 0) {
        zeros++;
      } else {
        ones++;
      }
      dest.clear();
    }

    double variance = ((double) Math.abs(zeros - ones)) / count;
    Assert.assertTrue(variance <= 0.1);
  }
}