ShuffleGrouping.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.ArrayList;
import java.util.List;
import java.util.Random;

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

public class ShuffleGrouping extends Grouping {
  private final int taskIdsSize;
  private int nextTaskIndex;

  public ShuffleGrouping(List<Integer> taskIds) {
    super(taskIds);

    taskIdsSize = taskIds.size();

    nextTaskIndex = new Random().nextInt(taskIds.size());
  }

  @Override
  public List<Integer> getListToSend(HeronTuples.HeronDataTuple tuple) {
    List<Integer> res = new ArrayList<>(1);
    res.add(taskIds.get(nextTaskIndex));
    nextTaskIndex = getNextTaskIndex(nextTaskIndex);

    return res;
  }

  private int getNextTaskIndex(int index) {
    int dupIndex = index + 1;

    if (dupIndex == taskIdsSize) {
      dupIndex = 0;
    }

    return dupIndex;
  }
}