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