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 import org.apache.hadoop.conf.Configurable;
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.classification.InterfaceStability;
27 import org.apache.hadoop.hbase.master.MasterRpcServices;
28 import org.apache.hadoop.hbase.master.MasterServices;
29
30 /**
31 * Performs "normalization" of regions on the cluster, making sure that suboptimal
32 * choice of split keys doesn't leave cluster in a situation when some regions are
33 * substantially larger than others for considerable amount of time.
34 *
35 * Users who want to use this feature could either use default {@link SimpleRegionNormalizer}
36 * or plug in their own implementation. Please note that overly aggressive normalization rules
37 * (attempting to make all regions perfectly equal in size) could potentially lead to
38 * "split/merge storms".
39 */
40 @InterfaceAudience.Private
41 @InterfaceStability.Evolving
42 public interface RegionNormalizer extends Configurable {
43 /**
44 * Set the master service. Must be called before first call to
45 * {@link #computePlansForTable(TableName)}.
46 * @param masterServices master services to use
47 */
48 void setMasterServices(MasterServices masterServices);
49
50 /**
51 * Set the master RPC service. Must be called before first call to
52 * {@link #computePlansForTable(TableName)}.
53 * @param masterRpcServices master RPC services to use
54 */
55 void setMasterRpcServices(MasterRpcServices masterRpcServices);
56
57 /**
58 * Computes next optimal normalization plan.
59 * @param table table to normalize
60 * @return normalization actions to perform. Null if no action to take
61 */
62 List<NormalizationPlan> computePlansForTable(TableName table) throws HBaseIOException;
63 }