001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.master.balancer;
019
020import java.util.Collections;
021import java.util.List;
022import org.apache.hadoop.hbase.master.RegionPlan;
023import org.apache.yetus.audience.InterfaceAudience;
024
025/**
026 * An action to move or swap a region
027 */
028@InterfaceAudience.Private
029abstract class BalanceAction {
030  enum Type {
031    ASSIGN_REGION,
032    MOVE_REGION,
033    SWAP_REGIONS,
034    MOVE_BATCH,
035    NULL,
036  }
037
038  static final BalanceAction NULL_ACTION = new NullBalanceAction();
039
040  private final Type type;
041
042  BalanceAction(Type type) {
043    this.type = type;
044  }
045
046  /**
047   * Returns an Action which would undo this action
048   */
049  abstract BalanceAction undoAction();
050
051  /**
052   * Returns the Action represented as RegionPlans
053   */
054  abstract List<RegionPlan> toRegionPlans(BalancerClusterState cluster);
055
056  Type getType() {
057    return type;
058  }
059
060  long getStepCount() {
061    return 1;
062  }
063
064  @Override
065  public String toString() {
066    return type + ":";
067  }
068
069  private static final class NullBalanceAction extends BalanceAction {
070    private NullBalanceAction() {
071      super(Type.NULL);
072    }
073
074    @Override
075    BalanceAction undoAction() {
076      return this;
077    }
078
079    @Override
080    List<RegionPlan> toRegionPlans(BalancerClusterState cluster) {
081      return Collections.emptyList();
082    }
083  }
084}