View Javadoc

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  
20  package org.apache.hadoop.hbase.util;
21  
22  import java.io.IOException;
23  import java.util.Collections;
24  import java.util.Map;
25  import java.util.TreeMap;
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.hbase.HBaseConfiguration;
33  import org.apache.hadoop.hbase.HConstants;
34  import org.apache.hadoop.hbase.HRegionInfo;
35  import org.apache.hadoop.hbase.TableName;
36  import org.apache.hadoop.hbase.regionserver.HRegion;
37  import org.apache.hadoop.hbase.regionserver.wal.HLog;
38  import org.apache.hadoop.hbase.regionserver.wal.HLogFactory;
39  
40  /**
41   * Contains utility methods for manipulating HBase meta tables.
42   * Be sure to call {@link #shutdown()} when done with this class so it closes
43   * resources opened during meta processing (ROOT, META, etc.).  Be careful
44   * how you use this class.  If used during migrations, be careful when using
45   * this class to check whether migration is needed.
46   */
47  @InterfaceAudience.Private
48  public class MetaUtils {
49    private static final Log LOG = LogFactory.getLog(MetaUtils.class);
50    private final Configuration conf;
51    private final FSTableDescriptors descriptors;
52    private FileSystem fs;
53    private HLog log;
54    private HRegion metaRegion;
55    private Map<byte [], HRegion> metaRegions = Collections.synchronizedSortedMap(
56      new TreeMap<byte [], HRegion>(Bytes.BYTES_COMPARATOR));
57  
58    /** Default constructor
59     * @throws IOException e
60     */
61    public MetaUtils() throws IOException {
62      this(HBaseConfiguration.create());
63    }
64  
65    /**
66     * @param conf Configuration
67     * @throws IOException e
68     */
69    public MetaUtils(Configuration conf) throws IOException {
70      this.conf = conf;
71      conf.setInt(HConstants.HBASE_CLIENT_RETRIES_NUMBER, 1);
72      this.metaRegion = null;
73      this.descriptors = new FSTableDescriptors(conf);
74      initialize();
75    }
76  
77    /**
78     * Verifies that DFS is available and that HBase is off-line.
79     * @throws IOException e
80     */
81    private void initialize() throws IOException {
82      this.fs = FileSystem.get(this.conf);
83    }
84  
85    /**
86     * @return the HLog
87     * @throws IOException e
88     */
89    public synchronized HLog getLog() throws IOException {
90      if (this.log == null) {
91        String logName = 
92            HConstants.HREGION_LOGDIR_NAME + "_" + System.currentTimeMillis();
93        this.log = HLogFactory.createHLog(this.fs, this.fs.getHomeDirectory(),
94                                          logName, this.conf);
95      }
96      return this.log;
97    }
98  
99    /**
100    * @return HRegion for meta region
101    * @throws IOException e
102    */
103   public HRegion getMetaRegion() throws IOException {
104     if (this.metaRegion == null) {
105       openMetaRegion();
106     }
107     return this.metaRegion;
108   }
109 
110   /**
111    * Closes catalog regions if open. Also closes and deletes the HLog. You
112    * must call this method if you want to persist changes made during a
113    * MetaUtils edit session.
114    */
115   public void shutdown() {
116     if (this.metaRegion != null) {
117       try {
118         this.metaRegion.close();
119       } catch (IOException e) {
120         LOG.error("closing meta region", e);
121       } finally {
122         this.metaRegion = null;
123       }
124     }
125     try {
126       for (HRegion r: metaRegions.values()) {
127         LOG.info("CLOSING hbase:meta " + r.toString());
128         r.close();
129       }
130     } catch (IOException e) {
131       LOG.error("closing meta region", e);
132     } finally {
133       metaRegions.clear();
134     }
135     try {
136       if (this.log != null) {
137         this.log.rollWriter();
138         this.log.closeAndDelete();
139       }
140     } catch (IOException e) {
141       LOG.error("closing HLog", e);
142     } finally {
143       this.log = null;
144     }
145   }
146 
147   private synchronized HRegion openMetaRegion() throws IOException {
148     if (this.metaRegion != null) {
149       return this.metaRegion;
150     }
151     this.metaRegion = HRegion.openHRegion(HRegionInfo.FIRST_META_REGIONINFO,
152       descriptors.get(TableName.META_TABLE_NAME), getLog(), this.conf);
153     this.metaRegion.compactStores();
154     return this.metaRegion;
155   }
156 }