1 /** 2 * 3 * Licensed to the Apache Software Foundation (ASF) under one 4 * or more contributor license agreements. See the NOTICE file 5 * distributed with this work for additional information 6 * regarding copyright ownership. The ASF licenses this file 7 * to you under the Apache License, Version 2.0 (the 8 * "License"); you may not use this file except in compliance 9 * with the License. You may obtain a copy of the License at 10 * 11 * http://www.apache.org/licenses/LICENSE-2.0 12 * 13 * Unless required by applicable law or agreed to in writing, software 14 * distributed under the License is distributed on an "AS IS" BASIS, 15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 * See the License for the specific language governing permissions and 17 * limitations under the License. 18 */ 19 package org.apache.hadoop.hbase.master.normalizer; 20 21 import java.util.List; 22 23 import org.apache.hadoop.hbase.HBaseIOException; 24 import org.apache.hadoop.hbase.TableName; 25 import org.apache.hadoop.hbase.classification.InterfaceAudience; 26 import org.apache.hadoop.hbase.master.MasterServices; 27 28 /** 29 * Performs "normalization" of regions on the cluster, making sure that suboptimal 30 * choice of split keys doesn't leave cluster in a situation when some regions are 31 * substantially larger than others for considerable amount of time. 32 * 33 * Users who want to use this feature could either use default {@link SimpleRegionNormalizer} 34 * or plug in their own implementation. Please note that overly aggressive normalization rules 35 * (attempting to make all regions perfectly equal in size) could potentially lead to 36 * "split/merge storms". 37 */ 38 @InterfaceAudience.Private 39 public interface RegionNormalizer { 40 /** 41 * Set the master service. Must be called before first call to 42 * {@link #computePlanForTable(TableName)}. 43 * @param masterServices master services to use 44 */ 45 void setMasterServices(MasterServices masterServices); 46 47 /** 48 * Computes next optimal normalization plan. 49 * @param table table to normalize 50 * @return normalization actions to perform. Null if no action to take 51 */ 52 List<NormalizationPlan> computePlanForTable(TableName table) 53 throws HBaseIOException; 54 }