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.classification.InterfaceAudience;
23 import org.apache.hadoop.classification.InterfaceStability;
24 import org.apache.hadoop.hbase.Coprocessor;
25 import org.apache.hadoop.hbase.HRegionInfo;
26 import org.apache.hadoop.hbase.regionserver.wal.HLogKey;
27 import org.apache.hadoop.hbase.regionserver.wal.WALEdit;
28
29 import java.io.IOException;
30
31 /**
32 * It's provided to have a way for coprocessors to observe, rewrite,
33 * or skip WALEdits as they are being written to the WAL.
34 *
35 * {@link org.apache.hadoop.hbase.coprocessor.RegionObserver} provides
36 * hooks for adding logic for WALEdits in the region context during reconstruction,
37 *
38 * Defines coprocessor hooks for interacting with operations on the
39 * {@link org.apache.hadoop.hbase.regionserver.wal.HLog}.
40 */
41 @InterfaceAudience.Public
42 @InterfaceStability.Evolving
43 public interface WALObserver extends Coprocessor {
44
45 /**
46 * Called before a {@link org.apache.hadoop.hbase.regionserver.wal.WALEdit}
47 * is writen to WAL.
48 *
49 * @param ctx
50 * @param info
51 * @param logKey
52 * @param logEdit
53 * @return true if default behavior should be bypassed, false otherwise
54 * @throws IOException
55 */
56 boolean preWALWrite(ObserverContext<WALCoprocessorEnvironment> ctx,
57 HRegionInfo info, HLogKey logKey, WALEdit logEdit) throws IOException;
58
59 /**
60 * Called after a {@link org.apache.hadoop.hbase.regionserver.wal.WALEdit}
61 * is writen to WAL.
62 *
63 * @param ctx
64 * @param info
65 * @param logKey
66 * @param logEdit
67 * @throws IOException
68 */
69 void postWALWrite(ObserverContext<WALCoprocessorEnvironment> ctx,
70 HRegionInfo info, HLogKey logKey, WALEdit logEdit) throws IOException;
71 }