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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  package org.apache.hadoop.hbase.trace;
19  
20  import java.io.IOException;
21  import java.util.Collection;
22  import java.util.HashSet;
23  
24  import org.apache.commons.logging.Log;
25  import org.apache.commons.logging.LogFactory;
26  import org.apache.hadoop.conf.Configuration;
27  import org.htrace.SpanReceiver;
28  import org.htrace.Trace;
29  
30  /**
31   * This class provides functions for reading the names of SpanReceivers from
32   * hbase-site.xml, adding those SpanReceivers to the Tracer, and closing those
33   * SpanReceivers when appropriate.
34   */
35  public class SpanReceiverHost {
36    public static final String SPAN_RECEIVERS_CONF_KEY = "hbase.trace.spanreceiver.classes";
37    private static final Log LOG = LogFactory.getLog(SpanReceiverHost.class);
38    private Collection<SpanReceiver> receivers;
39    private Configuration conf;
40    private boolean closed = false;
41  
42    private static enum SingletonHolder {
43      INSTANCE;
44      Object lock = new Object();
45      SpanReceiverHost host = null;
46    }
47  
48    public static SpanReceiverHost getInstance(Configuration conf) {
49      if (SingletonHolder.INSTANCE.host != null) {
50        return SingletonHolder.INSTANCE.host;
51      }
52      synchronized (SingletonHolder.INSTANCE.lock) {
53        if (SingletonHolder.INSTANCE.host != null) {
54          return SingletonHolder.INSTANCE.host;
55        }
56  
57        SpanReceiverHost host = new SpanReceiverHost(conf);
58        host.loadSpanReceivers();
59        SingletonHolder.INSTANCE.host = host;
60        return SingletonHolder.INSTANCE.host;
61      }
62  
63    }
64  
65    SpanReceiverHost(Configuration conf) {
66      receivers = new HashSet<SpanReceiver>();
67      this.conf = conf;
68    }
69  
70    /**
71     * Reads the names of classes specified in the
72     * "hbase.trace.spanreceiver.classes" property and instantiates and registers
73     * them with the Tracer as SpanReceiver's.
74     *
75     */
76    public void loadSpanReceivers() {
77      Class<?> implClass = null;
78      String[] receiverNames = conf.getStrings(SPAN_RECEIVERS_CONF_KEY);
79      if (receiverNames == null || receiverNames.length == 0) {
80        return;
81      }
82      for (String className : receiverNames) {
83        className = className.trim();
84  
85        try {
86          implClass = Class.forName(className);
87          SpanReceiver receiver = loadInstance(implClass);
88          if (receiver != null) {
89            receivers.add(receiver);
90            LOG.info("SpanReceiver " + className + " was loaded successfully.");
91          }
92  
93        } catch (ClassNotFoundException e) {
94          LOG.warn("Class " + className + " cannot be found. " + e.getMessage());
95        } catch (IOException e) {
96          LOG.warn("Load SpanReceiver " + className + " failed. "
97              + e.getMessage());
98        }
99      }
100     for (SpanReceiver rcvr : receivers) {
101       Trace.addReceiver(rcvr);
102     }
103   }
104 
105   private SpanReceiver loadInstance(Class<?> implClass)
106       throws IOException {
107     SpanReceiver impl = null;
108     try {
109       Object o = implClass.newInstance();
110       impl = (SpanReceiver)o;
111       impl.configure(new HBaseHTraceConfiguration(this.conf));
112     } catch (SecurityException e) {
113       throw new IOException(e);
114     } catch (IllegalArgumentException e) {
115       throw new IOException(e);
116     } catch (RuntimeException e) {
117       throw new IOException(e);
118     } catch (InstantiationException e) {
119       e.printStackTrace();
120     } catch (IllegalAccessException e) {
121       e.printStackTrace();
122     }
123 
124     return impl;
125   }
126 
127   /**
128    * Calls close() on all SpanReceivers created by this SpanReceiverHost.
129    */
130   public synchronized void closeReceivers() {
131     if (closed) return;
132     closed = true;
133     for (SpanReceiver rcvr : receivers) {
134       try {
135         rcvr.close();
136       } catch (IOException e) {
137         LOG.warn("Unable to close SpanReceiver correctly: " + e.getMessage(), e);
138       }
139     }
140   }
141 }