1 /*
2 * Copyright 2010 The Apache Software Foundation
3 *
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing, software
15 * distributed under the License is distributed on an "AS IS" BASIS,
16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17 * See the License for the specific language governing permissions and
18 * limitations under the License.
19 */
20
21 package org.apache.hadoop.hbase.rest;
22
23 import java.io.IOException;
24
25 import org.apache.hadoop.conf.Configuration;
26 import org.apache.hadoop.hbase.client.HTablePool;
27 import org.apache.hadoop.hbase.rest.metrics.RESTMetrics;
28
29 /**
30 * Singleton class encapsulating global REST servlet state and functions.
31 */
32 public class RESTServlet implements Constants {
33 private static RESTServlet INSTANCE;
34 private final Configuration conf;
35 private final HTablePool pool;
36 private final RESTMetrics metrics = new RESTMetrics();
37
38 /**
39 * @return the RESTServlet singleton instance
40 * @throws IOException
41 */
42 public synchronized static RESTServlet getInstance() throws IOException {
43 assert(INSTANCE != null);
44 return INSTANCE;
45 }
46
47 /**
48 * @param conf Existing configuration to use in rest servlet
49 * @return the RESTServlet singleton instance
50 * @throws IOException
51 */
52 public synchronized static RESTServlet getInstance(Configuration conf)
53 throws IOException {
54 if (INSTANCE == null) {
55 INSTANCE = new RESTServlet(conf);
56 }
57 return INSTANCE;
58 }
59
60 public synchronized static void stop() {
61 if (INSTANCE != null) INSTANCE = null;
62 }
63
64 /**
65 * Constructor with existing configuration
66 * @param conf existing configuration
67 * @throws IOException.
68 */
69 RESTServlet(Configuration conf) throws IOException {
70 this.conf = conf;
71 this.pool = new HTablePool(conf, 10);
72 }
73
74 HTablePool getTablePool() {
75 return pool;
76 }
77
78 Configuration getConfiguration() {
79 return conf;
80 }
81
82 RESTMetrics getMetrics() {
83 return metrics;
84 }
85
86 /**
87 * Helper method to determine if server should
88 * only respond to GET HTTP method requests.
89 * @return boolean for server read-only state
90 */
91 boolean isReadOnly() {
92 return getConfiguration().getBoolean("hbase.rest.readonly", false);
93 }
94 }