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
20 package org.apache.hadoop.hbase.coprocessor;
21
22 import org.apache.hadoop.hbase.classification.InterfaceAudience;
23 import org.apache.hadoop.hbase.classification.InterfaceStability;
24 import org.apache.hadoop.hbase.Coprocessor;
25 import org.apache.hadoop.hbase.HBaseInterfaceAudience;
26 import org.apache.hadoop.hbase.HRegionInfo;
27 import org.apache.hadoop.hbase.regionserver.wal.HLogKey;
28 import org.apache.hadoop.hbase.regionserver.wal.WALEdit;
29
30 import java.io.IOException;
31
32 /**
33 * It's provided to have a way for coprocessors to observe, rewrite,
34 * or skip WALEdits as they are being written to the WAL.
35 *
36 * {@link org.apache.hadoop.hbase.coprocessor.RegionObserver} provides
37 * hooks for adding logic for WALEdits in the region context during reconstruction,
38 *
39 * Defines coprocessor hooks for interacting with operations on the
40 * {@link org.apache.hadoop.hbase.regionserver.wal.HLog}.
41 */
42 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
43 @InterfaceStability.Evolving
44 public interface WALObserver extends Coprocessor {
45
46 /**
47 * Called before a {@link org.apache.hadoop.hbase.regionserver.wal.WALEdit}
48 * is writen to WAL.
49 *
50 * @param ctx
51 * @param info
52 * @param logKey
53 * @param logEdit
54 * @return true if default behavior should be bypassed, false otherwise
55 * @throws IOException
56 */
57 // TODO: return value is not used
58 boolean preWALWrite(ObserverContext<WALCoprocessorEnvironment> ctx,
59 HRegionInfo info, HLogKey logKey, WALEdit logEdit) throws IOException;
60
61 /**
62 * Called after a {@link org.apache.hadoop.hbase.regionserver.wal.WALEdit}
63 * is writen to WAL.
64 *
65 * @param ctx
66 * @param info
67 * @param logKey
68 * @param logEdit
69 * @throws IOException
70 */
71 void postWALWrite(ObserverContext<WALCoprocessorEnvironment> ctx,
72 HRegionInfo info, HLogKey logKey, WALEdit logEdit) throws IOException;
73 }