geode-core/src/main/java/org/apache/geode/internal/cache/partitioned/rebalance/MoveBuckets.java

/*
 * 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.geode.internal.cache.partitioned.rebalance;

import org.apache.geode.internal.cache.partitioned.rebalance.model.Move;
import org.apache.geode.internal.cache.partitioned.rebalance.model.PartitionedRegionLoadModel;

/**
 * A director to move buckets to improve the load balance of a PR. This is most commonly used as an
 * element of the composite director.
 *
 */
public class MoveBuckets extends RebalanceDirectorAdapter {

  private PartitionedRegionLoadModel model;

  @Override
  public void initialize(PartitionedRegionLoadModel model) {
    this.model = model;
  }

  @Override
  public void membershipChanged(PartitionedRegionLoadModel model) {
    initialize(model);
  }

  @Override
  public boolean nextStep() {
    // TODO Auto-generated method stub
    return moveBuckets();
  }

  /**
   * Move a single bucket from one member to another.
   *
   * @return true if we could move the bucket
   */
  private boolean moveBuckets() {
    Move bestMove = model.findBestBucketMove();

    if (bestMove == null) {
      return false;
    }

    model.moveBucket(bestMove);

    return true;
  }

}