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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.hbase.classification.InterfaceAudience;
30  import org.apache.hadoop.conf.Configuration;
31  import org.apache.hadoop.fs.FileSystem;
32  import org.apache.hadoop.fs.Path;
33  import org.apache.hadoop.hbase.HConstants;
34  import org.apache.hadoop.hbase.HRegionInfo;
35  import org.apache.hadoop.hbase.HTableDescriptor;
36  import org.apache.hadoop.hbase.MetaTableAccessor;
37  import org.apache.hadoop.hbase.TableName;
38  import org.apache.hadoop.hbase.TableNotDisabledException;
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.HBaseAdmin;
44  import org.apache.hadoop.hbase.client.HConnectable;
45  import org.apache.hadoop.hbase.client.HConnection;
46  import org.apache.hadoop.hbase.client.HConnectionManager;
47  import org.apache.hadoop.hbase.client.Result;
48  import org.apache.hadoop.hbase.client.ResultScanner;
49  import org.apache.hadoop.hbase.client.Table;
50  import org.apache.hadoop.hbase.regionserver.HRegion;
51  import org.apache.hadoop.hbase.wal.WALFactory;
52  import org.apache.hadoop.ipc.RemoteException;
53  
54  /**
55   * A non-instantiable class that has a static method capable of compacting
56   * a table by merging adjacent regions.
57   */
58  @InterfaceAudience.Private
59  class HMerge {
60    // TODO: Where is this class used?  How does it relate to Merge in same package?
61    static final Log LOG = LogFactory.getLog(HMerge.class);
62    static final Random rand = new Random();
63  
64    /*
65     * Not instantiable
66     */
67    private HMerge() {
68      super();
69    }
70  
71    /**
72     * Scans the table and merges two adjacent regions if they are small. This
73     * only happens when a lot of rows are deleted.
74     *
75     * When merging the hbase:meta region, the HBase instance must be offline.
76     * When merging a normal table, the HBase instance must be online, but the
77     * table must be disabled.
78     *
79     * @param conf        - configuration object for HBase
80     * @param fs          - FileSystem where regions reside
81     * @param tableName   - Table to be compacted
82     * @throws IOException
83     */
84    public static void merge(Configuration conf, FileSystem fs,
85      final TableName tableName)
86    throws IOException {
87      merge(conf, fs, tableName, true);
88    }
89  
90    /**
91     * Scans the table and merges two adjacent regions if they are small. This
92     * only happens when a lot of rows are deleted.
93     *
94     * When merging the hbase:meta region, the HBase instance must be offline.
95     * When merging a normal table, the HBase instance must be online, but the
96     * table must be disabled.
97     *
98     * @param conf        - configuration object for HBase
99     * @param fs          - FileSystem where regions reside
100    * @param tableName   - Table to be compacted
101    * @param testMasterRunning True if we are to verify master is down before
102    * running merge
103    * @throws IOException
104    */
105   public static void merge(Configuration conf, FileSystem fs,
106     final TableName tableName, final boolean testMasterRunning)
107   throws IOException {
108     boolean masterIsRunning = false;
109     if (testMasterRunning) {
110       masterIsRunning = HConnectionManager
111           .execute(new HConnectable<Boolean>(conf) {
112             @Override
113             public Boolean connect(HConnection connection) throws IOException {
114               return connection.isMasterRunning();
115             }
116           });
117     }
118     if (tableName.equals(TableName.META_TABLE_NAME)) {
119       if (masterIsRunning) {
120         throw new IllegalStateException(
121             "Can not compact hbase:meta table if instance is on-line");
122       }
123       // TODO reenable new OfflineMerger(conf, fs).process();
124     } else {
125       if(!masterIsRunning) {
126         throw new IllegalStateException(
127             "HBase instance must be running to merge a normal table");
128       }
129       Admin admin = new HBaseAdmin(conf);
130       try {
131         if (!admin.isTableDisabled(tableName)) {
132           throw new TableNotDisabledException(tableName);
133         }
134       } finally {
135         admin.close();
136       }
137       new OnlineMerger(conf, fs, tableName).process();
138     }
139   }
140 
141   private static abstract class Merger {
142     protected final Configuration conf;
143     protected final FileSystem fs;
144     protected final Path rootDir;
145     protected final HTableDescriptor htd;
146     protected final WALFactory walFactory;
147     private final long maxFilesize;
148 
149 
150     protected Merger(Configuration conf, FileSystem fs, final TableName tableName)
151     throws IOException {
152       this.conf = conf;
153       this.fs = fs;
154       this.maxFilesize = conf.getLong(HConstants.HREGION_MAX_FILESIZE,
155           HConstants.DEFAULT_MAX_FILE_SIZE);
156 
157       this.rootDir = FSUtils.getRootDir(conf);
158       Path tabledir = FSUtils.getTableDir(this.rootDir, tableName);
159       this.htd = FSTableDescriptors.getTableDescriptorFromFs(this.fs, tabledir)
160           .getHTableDescriptor();
161       String logname = "merge_" + System.currentTimeMillis() + HConstants.HREGION_LOGDIR_NAME;
162 
163       final Configuration walConf = new Configuration(conf);
164       FSUtils.setRootDir(walConf, tabledir);
165       this.walFactory = new WALFactory(walConf, null, logname);
166     }
167 
168     void process() throws IOException {
169       try {
170         for (HRegionInfo[] regionsToMerge = next();
171             regionsToMerge != null;
172             regionsToMerge = next()) {
173           if (!merge(regionsToMerge)) {
174             return;
175           }
176         }
177       } finally {
178         try {
179           walFactory.close();
180         } catch(IOException e) {
181           LOG.error(e);
182         }
183       }
184     }
185 
186     protected boolean merge(final HRegionInfo[] info) throws IOException {
187       if (info.length < 2) {
188         LOG.info("only one region - nothing to merge");
189         return false;
190       }
191 
192       HRegion currentRegion = null;
193       long currentSize = 0;
194       HRegion nextRegion = null;
195       long nextSize = 0;
196       for (int i = 0; i < info.length - 1; i++) {
197         if (currentRegion == null) {
198           currentRegion = HRegion.openHRegion(conf, fs, this.rootDir, info[i], this.htd,
199               walFactory.getWAL(info[i].getEncodedNameAsBytes()));
200           currentSize = currentRegion.getLargestHStoreSize();
201         }
202         nextRegion = HRegion.openHRegion(conf, fs, this.rootDir, info[i + 1], this.htd,
203             walFactory.getWAL(info[i+1].getEncodedNameAsBytes()));
204         nextSize = nextRegion.getLargestHStoreSize();
205 
206         if ((currentSize + nextSize) <= (maxFilesize / 2)) {
207           // We merge two adjacent regions if their total size is less than
208           // one half of the desired maximum size
209           LOG.info("Merging regions " + currentRegion.getRegionNameAsString() +
210             " and " + nextRegion.getRegionNameAsString());
211           HRegion mergedRegion =
212             HRegion.mergeAdjacent(currentRegion, nextRegion);
213           updateMeta(currentRegion.getRegionName(), nextRegion.getRegionName(),
214               mergedRegion);
215           break;
216         }
217         LOG.info("not merging regions " + Bytes.toStringBinary(currentRegion.getRegionName())
218             + " and " + Bytes.toStringBinary(nextRegion.getRegionName()));
219         currentRegion.close();
220         currentRegion = nextRegion;
221         currentSize = nextSize;
222       }
223       if(currentRegion != null) {
224         currentRegion.close();
225       }
226       return true;
227     }
228 
229     protected abstract HRegionInfo[] next() throws IOException;
230 
231     protected abstract void updateMeta(final byte [] oldRegion1,
232       final byte [] oldRegion2, HRegion newRegion)
233     throws IOException;
234 
235   }
236 
237   /** Instantiated to compact a normal user table */
238   private static class OnlineMerger extends Merger {
239     private final TableName tableName;
240     private final Table table;
241     private final ResultScanner metaScanner;
242     private HRegionInfo latestRegion;
243 
244     OnlineMerger(Configuration conf, FileSystem fs,
245       final TableName tableName)
246     throws IOException {
247       super(conf, fs, tableName);
248       this.tableName = tableName;
249       Connection connection = ConnectionFactory.createConnection(conf);
250       this.table = connection.getTable(TableName.META_TABLE_NAME);
251       this.metaScanner = table.getScanner(HConstants.CATALOG_FAMILY,
252           HConstants.REGIONINFO_QUALIFIER);
253       this.latestRegion = null;
254     }
255 
256     private HRegionInfo nextRegion() throws IOException {
257       try {
258         Result results = getMetaRow();
259         if (results == null) {
260           return null;
261         }
262         HRegionInfo region = HRegionInfo.getHRegionInfo(results);
263         if (region == null) {
264           throw new NoSuchElementException("meta region entry missing " +
265               Bytes.toString(HConstants.CATALOG_FAMILY) + ":" +
266               Bytes.toString(HConstants.REGIONINFO_QUALIFIER));
267         }
268         if (!region.getTable().equals(this.tableName)) {
269           return null;
270         }
271         return region;
272       } catch (IOException e) {
273         e = e instanceof RemoteException ? ((RemoteException) e).unwrapRemoteException() : e;
274         LOG.error("meta scanner error", e);
275         metaScanner.close();
276         throw e;
277       }
278     }
279 
280     /*
281      * Check current row has a HRegionInfo.  Skip to next row if HRI is empty.
282      * @return A Map of the row content else null if we are off the end.
283      * @throws IOException
284      */
285     private Result getMetaRow() throws IOException {
286       Result currentRow = metaScanner.next();
287       boolean foundResult = false;
288       while (currentRow != null) {
289         LOG.info("Row: <" + Bytes.toStringBinary(currentRow.getRow()) + ">");
290         byte[] regionInfoValue = currentRow.getValue(HConstants.CATALOG_FAMILY,
291             HConstants.REGIONINFO_QUALIFIER);
292         if (regionInfoValue == null || regionInfoValue.length == 0) {
293           currentRow = metaScanner.next();
294           continue;
295         }
296         HRegionInfo region = HRegionInfo.getHRegionInfo(currentRow);
297         if (!region.getTable().equals(this.tableName)) {
298           currentRow = metaScanner.next();
299           continue;
300         }
301         foundResult = true;
302         break;
303       }
304       return foundResult ? currentRow : null;
305     }
306 
307     @Override
308     protected HRegionInfo[] next() throws IOException {
309       List<HRegionInfo> regions = new ArrayList<HRegionInfo>();
310       if(latestRegion == null) {
311         latestRegion = nextRegion();
312       }
313       if(latestRegion != null) {
314         regions.add(latestRegion);
315       }
316       latestRegion = nextRegion();
317       if(latestRegion != null) {
318         regions.add(latestRegion);
319       }
320       return regions.toArray(new HRegionInfo[regions.size()]);
321     }
322 
323     @Override
324     protected void updateMeta(final byte [] oldRegion1,
325         final byte [] oldRegion2,
326       HRegion newRegion)
327     throws IOException {
328       byte[][] regionsToDelete = {oldRegion1, oldRegion2};
329       for (int r = 0; r < regionsToDelete.length; r++) {
330         if(Bytes.equals(regionsToDelete[r], latestRegion.getRegionName())) {
331           latestRegion = null;
332         }
333         Delete delete = new Delete(regionsToDelete[r]);
334         table.delete(delete);
335         if(LOG.isDebugEnabled()) {
336           LOG.debug("updated columns in row: " + Bytes.toStringBinary(regionsToDelete[r]));
337         }
338       }
339       newRegion.getRegionInfo().setOffline(true);
340 
341       MetaTableAccessor.addRegionToMeta(table, newRegion.getRegionInfo());
342 
343       if(LOG.isDebugEnabled()) {
344         LOG.debug("updated columns in row: "
345             + Bytes.toStringBinary(newRegion.getRegionName()));
346       }
347     }
348   }
349 }