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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  package org.apache.hadoop.hbase.util;
20  
21  import java.io.IOException;
22  import java.util.ArrayList;
23  import java.util.List;
24  import java.util.NoSuchElementException;
25  import java.util.Random;
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.HConstants;
33  import org.apache.hadoop.hbase.HRegionInfo;
34  import org.apache.hadoop.hbase.HTableDescriptor;
35  import org.apache.hadoop.hbase.MetaTableAccessor;
36  import org.apache.hadoop.hbase.TableName;
37  import org.apache.hadoop.hbase.TableNotDisabledException;
38  import org.apache.hadoop.hbase.classification.InterfaceAudience;
39  import org.apache.hadoop.hbase.client.Admin;
40  import org.apache.hadoop.hbase.client.Connection;
41  import org.apache.hadoop.hbase.client.ConnectionFactory;
42  import org.apache.hadoop.hbase.client.Delete;
43  import org.apache.hadoop.hbase.client.HConnection;
44  import org.apache.hadoop.hbase.client.Result;
45  import org.apache.hadoop.hbase.client.ResultScanner;
46  import org.apache.hadoop.hbase.client.Table;
47  import org.apache.hadoop.hbase.regionserver.HRegion;
48  import org.apache.hadoop.hbase.wal.WALFactory;
49  import org.apache.hadoop.ipc.RemoteException;
50  
51  /**
52   * A non-instantiable class that has a static method capable of compacting
53   * a table by merging adjacent regions.
54   */
55  @InterfaceAudience.Private
56  class HMerge {
57    // TODO: Where is this class used?  How does it relate to Merge in same package?
58    private static final Log LOG = LogFactory.getLog(HMerge.class);
59    static final Random rand = new Random();
60  
61    /*
62     * Not instantiable
63     */
64    private HMerge() {
65      super();
66    }
67  
68    /**
69     * Scans the table and merges two adjacent regions if they are small. This
70     * only happens when a lot of rows are deleted.
71     *
72     * When merging the hbase:meta region, the HBase instance must be offline.
73     * When merging a normal table, the HBase instance must be online, but the
74     * table must be disabled.
75     *
76     * @param conf        - configuration object for HBase
77     * @param fs          - FileSystem where regions reside
78     * @param tableName   - Table to be compacted
79     * @throws IOException
80     */
81    public static void merge(Configuration conf, FileSystem fs,
82      final TableName tableName)
83    throws IOException {
84      merge(conf, fs, tableName, true);
85    }
86  
87    /**
88     * Scans the table and merges two adjacent regions if they are small. This
89     * only happens when a lot of rows are deleted.
90     *
91     * When merging the hbase:meta region, the HBase instance must be offline.
92     * When merging a normal table, the HBase instance must be online, but the
93     * table must be disabled.
94     *
95     * @param conf        - configuration object for HBase
96     * @param fs          - FileSystem where regions reside
97     * @param tableName   - Table to be compacted
98     * @param testMasterRunning True if we are to verify master is down before
99     * running merge
100    * @throws IOException
101    */
102   public static void merge(Configuration conf, FileSystem fs,
103     final TableName tableName, final boolean testMasterRunning)
104   throws IOException {
105     boolean masterIsRunning = false;
106     HConnection hConnection = null;
107     if (testMasterRunning) {
108       try {
109         hConnection = (HConnection) ConnectionFactory.createConnection(conf);
110         masterIsRunning = hConnection.isMasterRunning();
111       } finally {
112         if (hConnection != null) {
113           hConnection.close();
114         }
115       }
116     }
117     if (tableName.equals(TableName.META_TABLE_NAME)) {
118       if (masterIsRunning) {
119         throw new IllegalStateException(
120             "Can not compact hbase:meta table if instance is on-line");
121       }
122       // TODO reenable new OfflineMerger(conf, fs).process();
123     } else {
124       if(!masterIsRunning) {
125         throw new IllegalStateException(
126             "HBase instance must be running to merge a normal table");
127       }
128       try (Connection conn = ConnectionFactory.createConnection(conf);
129           Admin admin = conn.getAdmin()) {
130         if (!admin.isTableDisabled(tableName)) {
131           throw new TableNotDisabledException(tableName);
132         }
133       }
134       new OnlineMerger(conf, fs, tableName).process();
135     }
136   }
137 
138   private static abstract class Merger {
139     protected final Configuration conf;
140     protected final FileSystem fs;
141     protected final Path rootDir;
142     protected final HTableDescriptor htd;
143     protected final WALFactory walFactory;
144     private final long maxFilesize;
145 
146 
147     protected Merger(Configuration conf, FileSystem fs, final TableName tableName)
148     throws IOException {
149       this.conf = conf;
150       this.fs = fs;
151       this.maxFilesize = conf.getLong(HConstants.HREGION_MAX_FILESIZE,
152           HConstants.DEFAULT_MAX_FILE_SIZE);
153 
154       this.rootDir = FSUtils.getRootDir(conf);
155       Path tabledir = FSUtils.getTableDir(this.rootDir, tableName);
156       this.htd = FSTableDescriptors.getTableDescriptorFromFs(this.fs, tabledir)
157           .getHTableDescriptor();
158       String logname = "merge_" + System.currentTimeMillis() + HConstants.HREGION_LOGDIR_NAME;
159 
160       final Configuration walConf = new Configuration(conf);
161       FSUtils.setRootDir(walConf, tabledir);
162       this.walFactory = new WALFactory(walConf, null, logname);
163     }
164 
165     void process() throws IOException {
166       try {
167         for (HRegionInfo[] regionsToMerge = next();
168             regionsToMerge != null;
169             regionsToMerge = next()) {
170           if (!merge(regionsToMerge)) {
171             return;
172           }
173         }
174       } finally {
175         try {
176           walFactory.close();
177         } catch(IOException e) {
178           LOG.error(e);
179         }
180       }
181     }
182 
183     protected boolean merge(final HRegionInfo[] info) throws IOException {
184       if (info.length < 2) {
185         LOG.info("only one region - nothing to merge");
186         return false;
187       }
188 
189       HRegion currentRegion = null;
190       long currentSize = 0;
191       HRegion nextRegion = null;
192       long nextSize = 0;
193       for (int i = 0; i < info.length - 1; i++) {
194         if (currentRegion == null) {
195           currentRegion = HRegion.openHRegion(conf, fs, this.rootDir, info[i], this.htd,
196               walFactory.getWAL(info[i].getEncodedNameAsBytes()));
197           currentSize = currentRegion.getLargestHStoreSize();
198         }
199         nextRegion = HRegion.openHRegion(conf, fs, this.rootDir, info[i + 1], this.htd,
200             walFactory.getWAL(info[i+1].getEncodedNameAsBytes()));
201         nextSize = nextRegion.getLargestHStoreSize();
202 
203         if ((currentSize + nextSize) <= (maxFilesize / 2)) {
204           // We merge two adjacent regions if their total size is less than
205           // one half of the desired maximum size
206           LOG.info("Merging regions " + currentRegion.getRegionInfo().getRegionNameAsString() +
207             " and " + nextRegion.getRegionInfo().getRegionNameAsString());
208           HRegion mergedRegion =
209             HRegion.mergeAdjacent(currentRegion, nextRegion);
210           updateMeta(currentRegion.getRegionInfo().getRegionName(),
211             nextRegion.getRegionInfo().getRegionName(), mergedRegion);
212           break;
213         }
214         LOG.info("not merging regions " +
215           Bytes.toStringBinary(currentRegion.getRegionInfo().getRegionName()) +
216             " and " + Bytes.toStringBinary(nextRegion.getRegionInfo().getRegionName()));
217         currentRegion.close();
218         currentRegion = nextRegion;
219         currentSize = nextSize;
220       }
221       if(currentRegion != null) {
222         currentRegion.close();
223       }
224       return true;
225     }
226 
227     protected abstract HRegionInfo[] next() throws IOException;
228 
229     protected abstract void updateMeta(final byte [] oldRegion1,
230       final byte [] oldRegion2, HRegion newRegion)
231     throws IOException;
232 
233   }
234 
235   /** Instantiated to compact a normal user table */
236   private static class OnlineMerger extends Merger {
237     private final TableName tableName;
238     private final Table table;
239     private final ResultScanner metaScanner;
240     private HRegionInfo latestRegion;
241 
242     OnlineMerger(Configuration conf, FileSystem fs,
243       final TableName tableName)
244     throws IOException {
245       super(conf, fs, tableName);
246       this.tableName = tableName;
247       Connection connection = ConnectionFactory.createConnection(conf);
248       this.table = connection.getTable(TableName.META_TABLE_NAME);
249       this.metaScanner = table.getScanner(HConstants.CATALOG_FAMILY,
250           HConstants.REGIONINFO_QUALIFIER);
251       this.latestRegion = null;
252     }
253 
254     private HRegionInfo nextRegion() throws IOException {
255       try {
256         Result results = getMetaRow();
257         if (results == null) {
258           return null;
259         }
260         HRegionInfo region = HRegionInfo.getHRegionInfo(results);
261         if (region == null) {
262           throw new NoSuchElementException("meta region entry missing " +
263               Bytes.toString(HConstants.CATALOG_FAMILY) + ":" +
264               Bytes.toString(HConstants.REGIONINFO_QUALIFIER));
265         }
266         if (!region.getTable().equals(this.tableName)) {
267           return null;
268         }
269         return region;
270       } catch (IOException e) {
271         e = e instanceof RemoteException ? ((RemoteException) e).unwrapRemoteException() : e;
272         LOG.error("meta scanner error", e);
273         metaScanner.close();
274         throw e;
275       }
276     }
277 
278     /*
279      * Check current row has a HRegionInfo.  Skip to next row if HRI is empty.
280      * @return A Map of the row content else null if we are off the end.
281      * @throws IOException
282      */
283     private Result getMetaRow() throws IOException {
284       Result currentRow = metaScanner.next();
285       boolean foundResult = false;
286       while (currentRow != null) {
287         LOG.info("Row: <" + Bytes.toStringBinary(currentRow.getRow()) + ">");
288         byte[] regionInfoValue = currentRow.getValue(HConstants.CATALOG_FAMILY,
289             HConstants.REGIONINFO_QUALIFIER);
290         if (regionInfoValue == null || regionInfoValue.length == 0) {
291           currentRow = metaScanner.next();
292           continue;
293         }
294         HRegionInfo region = HRegionInfo.getHRegionInfo(currentRow);
295         if (!region.getTable().equals(this.tableName)) {
296           currentRow = metaScanner.next();
297           continue;
298         }
299         foundResult = true;
300         break;
301       }
302       return foundResult ? currentRow : null;
303     }
304 
305     @Override
306     protected HRegionInfo[] next() throws IOException {
307       List<HRegionInfo> regions = new ArrayList<HRegionInfo>();
308       if(latestRegion == null) {
309         latestRegion = nextRegion();
310       }
311       if(latestRegion != null) {
312         regions.add(latestRegion);
313       }
314       latestRegion = nextRegion();
315       if(latestRegion != null) {
316         regions.add(latestRegion);
317       }
318       return regions.toArray(new HRegionInfo[regions.size()]);
319     }
320 
321     @Override
322     protected void updateMeta(final byte [] oldRegion1,
323         final byte [] oldRegion2,
324       HRegion newRegion)
325     throws IOException {
326       byte[][] regionsToDelete = {oldRegion1, oldRegion2};
327       for (int r = 0; r < regionsToDelete.length; r++) {
328         if(Bytes.equals(regionsToDelete[r], latestRegion.getRegionName())) {
329           latestRegion = null;
330         }
331         Delete delete = new Delete(regionsToDelete[r]);
332         table.delete(delete);
333         if(LOG.isDebugEnabled()) {
334           LOG.debug("updated columns in row: " + Bytes.toStringBinary(regionsToDelete[r]));
335         }
336       }
337       newRegion.getRegionInfo().setOffline(true);
338 
339       MetaTableAccessor.addRegionToMeta(table, newRegion.getRegionInfo());
340 
341       if(LOG.isDebugEnabled()) {
342         LOG.debug("updated columns in row: "
343             + Bytes.toStringBinary(newRegion.getRegionInfo().getRegionName()));
344       }
345     }
346   }
347 }