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.MasterRpcServices;
27 import org.apache.hadoop.hbase.master.MasterServices;
28
29 /**
30 * Performs "normalization" of regions on the cluster, making sure that suboptimal
31 * choice of split keys doesn't leave cluster in a situation when some regions are
32 * substantially larger than others for considerable amount of time.
33 *
34 * Users who want to use this feature could either use default {@link SimpleRegionNormalizer}
35 * or plug in their own implementation. Please note that overly aggressive normalization rules
36 * (attempting to make all regions perfectly equal in size) could potentially lead to
37 * "split/merge storms".
38 */
39 @InterfaceAudience.Private
40 public interface RegionNormalizer {
41 /**
42 * Set the master service. Must be called before first call to
43 * {@link #computePlanForTable(TableName)}.
44 * @param masterServices master services to use
45 */
46 void setMasterServices(MasterServices masterServices);
47
48 /**
49 * Set the master RPC service. Must be called before first call to
50 * {@link #computePlanForTable(TableName)}.
51 * @param masterRpcServices master RPC services to use
52 */
53 void setMasterRpcServices(MasterRpcServices masterRpcServices);
54
55 /**
56 * Computes next optimal normalization plan.
57 * @param table table to normalize
58 * @return normalization actions to perform. Null if no action to take
59 */
60 List<NormalizationPlan> computePlanForTable(TableName table)
61 throws HBaseIOException;
62 }