001/*
002 *
003 * Licensed to the Apache Software Foundation (ASF) under one
004 * or more contributor license agreements.  See the NOTICE file
005 * distributed with this work for additional information
006 * regarding copyright ownership.  The ASF licenses this file
007 * to you under the Apache License, Version 2.0 (the
008 * "License"); you may not use this file except in compliance
009 * with the License.  You may obtain a copy of the License at
010 *
011 *     http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing, software
014 * distributed under the License is distributed on an "AS IS" BASIS,
015 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
016 * See the License for the specific language governing permissions and
017 * limitations under the License.
018 */
019package org.apache.hadoop.hbase.master.normalizer;
020
021import java.util.List;
022import org.apache.hadoop.conf.Configurable;
023import org.apache.hadoop.hbase.TableName;
024import org.apache.hadoop.hbase.master.MasterServices;
025import org.apache.yetus.audience.InterfaceAudience;
026
027/**
028 * Performs "normalization" of regions of a table, making sure that suboptimal
029 * choice of split keys doesn't leave cluster in a situation when some regions are
030 * substantially larger than others for considerable amount of time.
031 *
032 * Users who want to use this feature could either use default {@link SimpleRegionNormalizer}
033 * or plug in their own implementation. Please note that overly aggressive normalization rules
034 * (attempting to make all regions perfectly equal in size) could potentially lead to
035 * "split/merge storms".
036 */
037@InterfaceAudience.Private
038interface RegionNormalizer extends Configurable {
039  /**
040   * Set the master service. Must be called before first call to
041   * {@link #computePlansForTable(TableName)}.
042   * @param masterServices master services to use
043   */
044  void setMasterServices(MasterServices masterServices);
045
046  /**
047   * Computes a list of normalizer actions to perform on the target table. This is the primary
048   * entry-point from the Master driving a normalization activity.
049   * @param table table to normalize
050   * @return A list of the normalization actions to perform, or an empty list
051   *   if there's nothing to do.
052   */
053  List<NormalizationPlan> computePlansForTable(TableName table);
054}