1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
17 */
18 package org.apache.hadoop.hbase.regionserver;
19
20 import org.apache.hadoop.conf.Configurable;
21 import org.apache.hadoop.conf.Configuration;
22 import org.apache.hadoop.hbase.HBaseInterfaceAudience;
23 import org.apache.hadoop.hbase.classification.InterfaceAudience;
24 import org.apache.hadoop.hbase.classification.InterfaceStability;
25 import org.apache.hadoop.hbase.util.ReflectionUtils;
26
27 /**
28 * A factory for creating RegionMergeTransactions, which execute region split as a "transaction".
29 * See {@link RegionMergeTransactionImpl}
30 */
31 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
32 @InterfaceStability.Evolving
33 public class RegionMergeTransactionFactory implements Configurable {
34
35 public static final String MERGE_TRANSACTION_IMPL_KEY =
36 "hbase.regionserver.merge.transaction.impl";
37
38 private Configuration conf;
39
40 public RegionMergeTransactionFactory(Configuration conf) {
41 this.conf = conf;
42 }
43
44 @Override
45 public Configuration getConf() {
46 return conf;
47 }
48
49 @Override
50 public void setConf(Configuration conf) {
51 this.conf = conf;
52 }
53
54 /**
55 * Create a merge transaction
56 * @param a region a to merge
57 * @param b region b to merge
58 * @param forcible if false, we will only merge adjacent regions
59 * @return transaction instance
60 */
61 public RegionMergeTransactionImpl create(final Region a, final Region b,
62 final boolean forcible) {
63 // The implementation class must extend RegionMergeTransactionImpl, not only
64 // implement the RegionMergeTransaction interface like you might expect,
65 // because various places such as AssignmentManager use static methods
66 // from RegionMergeTransactionImpl. Whatever we use for implementation must
67 // be compatible, so it's safest to require ? extends RegionMergeTransactionImpl.
68 // If not compatible we will throw a runtime exception from here.
69 return ReflectionUtils.instantiateWithCustomCtor(
70 conf.getClass(MERGE_TRANSACTION_IMPL_KEY, RegionMergeTransactionImpl.class,
71 RegionMergeTransactionImpl.class).getName(),
72 new Class[] { Region.class, Region.class, boolean.class },
73 new Object[] { a, b, forcible });
74 }
75
76 }