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
19 package org.apache.hadoop.hbase.client;
20
21 import java.io.IOException;
22 import java.util.ArrayList;
23 import java.util.Collections;
24 import java.util.List;
25 import java.util.UUID;
26
27 import org.apache.commons.logging.Log;
28 import org.apache.commons.logging.LogFactory;
29 import org.apache.hadoop.conf.Configuration;
30 import org.apache.hadoop.fs.FileSystem;
31 import org.apache.hadoop.fs.Path;
32 import org.apache.hadoop.hbase.CellUtil;
33 import org.apache.hadoop.hbase.HRegionInfo;
34 import org.apache.hadoop.hbase.HTableDescriptor;
35 import org.apache.hadoop.hbase.classification.InterfaceAudience;
36 import org.apache.hadoop.hbase.classification.InterfaceStability;
37 import org.apache.hadoop.hbase.snapshot.RestoreSnapshotHelper;
38 import org.apache.hadoop.hbase.util.FSUtils;
39
40 /**
41 * A Scanner which performs a scan over snapshot files. Using this class requires copying the
42 * snapshot to a temporary empty directory, which will copy the snapshot reference files into that
43 * directory. Actual data files are not copied.
44 *
45 * <p>
46 * This also allows one to run the scan from an
47 * online or offline hbase cluster. The snapshot files can be exported by using the
48 * {@link org.apache.hadoop.hbase.snapshot.ExportSnapshot} tool,
49 * to a pure-hdfs cluster, and this scanner can be used to
50 * run the scan directly over the snapshot files. The snapshot should not be deleted while there
51 * are open scanners reading from snapshot files.
52 *
53 * <p>
54 * An internal RegionScanner is used to execute the {@link Scan} obtained
55 * from the user for each region in the snapshot.
56 * <p>
57 * HBase owns all the data and snapshot files on the filesystem. Only the HBase user can read from
58 * snapshot files and data files. HBase also enforces security because all the requests are handled
59 * by the server layer, and the user cannot read from the data files directly. To read from snapshot
60 * files directly from the file system, the user who is running the MR job must have sufficient
61 * permissions to access snapshot and reference files. This means that to run mapreduce over
62 * snapshot files, the job has to be run as the HBase user or the user must have group or other
63 * priviledges in the filesystem (See HBASE-8369). Note that, given other users access to read from
64 * snapshot/data files will completely circumvent the access control enforced by HBase.
65 * @see org.apache.hadoop.hbase.mapreduce.TableSnapshotInputFormat
66 */
67 @InterfaceAudience.Public
68 @InterfaceStability.Evolving
69 public class TableSnapshotScanner extends AbstractClientScanner {
70
71 private static final Log LOG = LogFactory.getLog(TableSnapshotScanner.class);
72
73 private Configuration conf;
74 private String snapshotName;
75 private FileSystem fs;
76 private Path rootDir;
77 private Path restoreDir;
78 private Scan scan;
79 private ArrayList<HRegionInfo> regions;
80 private HTableDescriptor htd;
81
82 private ClientSideRegionScanner currentRegionScanner = null;
83 private int currentRegion = -1;
84
85 /**
86 * Creates a TableSnapshotScanner.
87 * @param conf the configuration
88 * @param restoreDir a temporary directory to copy the snapshot files into. Current user should
89 * have write permissions to this directory, and this should not be a subdirectory of rootdir.
90 * The scanner deletes the contents of the directory once the scanner is closed.
91 * @param snapshotName the name of the snapshot to read from
92 * @param scan a Scan representing scan parameters
93 * @throws IOException in case of error
94 */
95 public TableSnapshotScanner(Configuration conf, Path restoreDir,
96 String snapshotName, Scan scan) throws IOException {
97 this(conf, FSUtils.getRootDir(conf), restoreDir, snapshotName, scan);
98 }
99
100 /**
101 * Creates a TableSnapshotScanner.
102 * @param conf the configuration
103 * @param rootDir root directory for HBase.
104 * @param restoreDir a temporary directory to copy the snapshot files into. Current user should
105 * have write permissions to this directory, and this should not be a subdirectory of rootdir.
106 * The scanner deletes the contents of the directory once the scanner is closed.
107 * @param snapshotName the name of the snapshot to read from
108 * @param scan a Scan representing scan parameters
109 * @throws IOException in case of error
110 */
111 public TableSnapshotScanner(Configuration conf, Path rootDir,
112 Path restoreDir, String snapshotName, Scan scan) throws IOException {
113 this.conf = conf;
114 this.snapshotName = snapshotName;
115 this.rootDir = rootDir;
116 // restoreDir will be deleted in close(), use a unique sub directory
117 this.restoreDir = new Path(restoreDir, UUID.randomUUID().toString());
118 this.scan = scan;
119 this.fs = rootDir.getFileSystem(conf);
120 init();
121 }
122
123 private void init() throws IOException {
124 final RestoreSnapshotHelper.RestoreMetaChanges meta =
125 RestoreSnapshotHelper.copySnapshotForScanner(
126 conf, fs, rootDir, restoreDir, snapshotName);
127 final List<HRegionInfo> restoredRegions = meta.getRegionsToAdd();
128
129 htd = meta.getTableDescriptor();
130 regions = new ArrayList<HRegionInfo>(restoredRegions.size());
131 for (HRegionInfo hri: restoredRegions) {
132 if (hri.isOffline() && (hri.isSplit() || hri.isSplitParent())) {
133 continue;
134 }
135 if (CellUtil.overlappingKeys(scan.getStartRow(), scan.getStopRow(),
136 hri.getStartKey(), hri.getEndKey())) {
137 regions.add(hri);
138 }
139 }
140
141 // sort for regions according to startKey.
142 Collections.sort(regions);
143 initScanMetrics(scan);
144 }
145
146 @Override
147 public Result next() throws IOException {
148 Result result = null;
149 while (true) {
150 if (currentRegionScanner == null) {
151 currentRegion++;
152 if (currentRegion >= regions.size()) {
153 return null;
154 }
155
156 HRegionInfo hri = regions.get(currentRegion);
157 currentRegionScanner = new ClientSideRegionScanner(conf, fs,
158 restoreDir, htd, hri, scan, scanMetrics);
159 if (this.scanMetrics != null) {
160 this.scanMetrics.countOfRegions.incrementAndGet();
161 }
162 }
163
164 try {
165 result = currentRegionScanner.next();
166 if (result != null) {
167 return result;
168 }
169 } finally {
170 if (result == null) {
171 currentRegionScanner.close();
172 currentRegionScanner = null;
173 }
174 }
175 }
176 }
177
178 @Override
179 public void close() {
180 if (currentRegionScanner != null) {
181 currentRegionScanner.close();
182 }
183 try {
184 fs.delete(this.restoreDir, true);
185 } catch (IOException ex) {
186 LOG.warn("Could not delete restore directory for the snapshot:" + ex);
187 }
188 }
189
190 @Override
191 public boolean renewLease() {
192 throw new UnsupportedOperationException();
193 }
194
195 }