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| <pre><span class="sourceLineNo">001</span>/**<a name="line.1"></a> |
| <span class="sourceLineNo">002</span> * Licensed to the Apache Software Foundation (ASF) under one<a name="line.2"></a> |
| <span class="sourceLineNo">003</span> * or more contributor license agreements. See the NOTICE file<a name="line.3"></a> |
| <span class="sourceLineNo">004</span> * distributed with this work for additional information<a name="line.4"></a> |
| <span class="sourceLineNo">005</span> * regarding copyright ownership. The ASF licenses this file<a name="line.5"></a> |
| <span class="sourceLineNo">006</span> * to you under the Apache License, Version 2.0 (the<a name="line.6"></a> |
| <span class="sourceLineNo">007</span> * "License"); you may not use this file except in compliance<a name="line.7"></a> |
| <span class="sourceLineNo">008</span> * with the License. You may obtain a copy of the License at<a name="line.8"></a> |
| <span class="sourceLineNo">009</span> *<a name="line.9"></a> |
| <span class="sourceLineNo">010</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.10"></a> |
| <span class="sourceLineNo">011</span> *<a name="line.11"></a> |
| <span class="sourceLineNo">012</span> * Unless required by applicable law or agreed to in writing, software<a name="line.12"></a> |
| <span class="sourceLineNo">013</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.13"></a> |
| <span class="sourceLineNo">014</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.14"></a> |
| <span class="sourceLineNo">015</span> * See the License for the specific language governing permissions and<a name="line.15"></a> |
| <span class="sourceLineNo">016</span> * limitations under the License.<a name="line.16"></a> |
| <span class="sourceLineNo">017</span> */<a name="line.17"></a> |
| <span class="sourceLineNo">018</span>package org.apache.hadoop.hbase.conf;<a name="line.18"></a> |
| <span class="sourceLineNo">019</span><a name="line.19"></a> |
| <span class="sourceLineNo">020</span>import java.util.Collections;<a name="line.20"></a> |
| <span class="sourceLineNo">021</span>import java.util.Set;<a name="line.21"></a> |
| <span class="sourceLineNo">022</span>import java.util.WeakHashMap;<a name="line.22"></a> |
| <span class="sourceLineNo">023</span>import org.apache.hadoop.conf.Configuration;<a name="line.23"></a> |
| <span class="sourceLineNo">024</span>import org.apache.hbase.thirdparty.com.google.common.annotations.VisibleForTesting;<a name="line.24"></a> |
| <span class="sourceLineNo">025</span>import org.apache.yetus.audience.InterfaceAudience;<a name="line.25"></a> |
| <span class="sourceLineNo">026</span>import org.apache.yetus.audience.InterfaceStability;<a name="line.26"></a> |
| <span class="sourceLineNo">027</span>import org.slf4j.Logger;<a name="line.27"></a> |
| <span class="sourceLineNo">028</span>import org.slf4j.LoggerFactory;<a name="line.28"></a> |
| <span class="sourceLineNo">029</span><a name="line.29"></a> |
| <span class="sourceLineNo">030</span>/**<a name="line.30"></a> |
| <span class="sourceLineNo">031</span> * Maintains the set of all the classes which would like to get notified<a name="line.31"></a> |
| <span class="sourceLineNo">032</span> * when the Configuration is reloaded from the disk in the Online Configuration<a name="line.32"></a> |
| <span class="sourceLineNo">033</span> * Change mechanism, which lets you update certain configuration properties<a name="line.33"></a> |
| <span class="sourceLineNo">034</span> * on-the-fly, without having to restart the cluster.<a name="line.34"></a> |
| <span class="sourceLineNo">035</span> *<a name="line.35"></a> |
| <span class="sourceLineNo">036</span> * If a class has configuration properties which you would like to be able to<a name="line.36"></a> |
| <span class="sourceLineNo">037</span> * change on-the-fly, do the following:<a name="line.37"></a> |
| <span class="sourceLineNo">038</span> * 1. Implement the {@link ConfigurationObserver} interface. This would require<a name="line.38"></a> |
| <span class="sourceLineNo">039</span> * you to implement the<a name="line.39"></a> |
| <span class="sourceLineNo">040</span> * {@link ConfigurationObserver#onConfigurationChange(Configuration)}<a name="line.40"></a> |
| <span class="sourceLineNo">041</span> * method. This is a callback that is used to notify your class' instance<a name="line.41"></a> |
| <span class="sourceLineNo">042</span> * that the configuration has changed. In this method, you need to check<a name="line.42"></a> |
| <span class="sourceLineNo">043</span> * if the new values for the properties that are of interest to your class<a name="line.43"></a> |
| <span class="sourceLineNo">044</span> * are different from the cached values. If yes, update them.<a name="line.44"></a> |
| <span class="sourceLineNo">045</span> *<a name="line.45"></a> |
| <span class="sourceLineNo">046</span> * However, be careful with this. Certain properties might be trivially<a name="line.46"></a> |
| <span class="sourceLineNo">047</span> * mutable online, but others might not. Two properties might be trivially<a name="line.47"></a> |
| <span class="sourceLineNo">048</span> * mutable by themselves, but not when changed together. For example, if a<a name="line.48"></a> |
| <span class="sourceLineNo">049</span> * method uses properties "a" and "b" to make some decision, and is running<a name="line.49"></a> |
| <span class="sourceLineNo">050</span> * in parallel when the notifyOnChange() method updates "a", but hasn't<a name="line.50"></a> |
| <span class="sourceLineNo">051</span> * yet updated "b", it might make a decision on the basis of a new value of<a name="line.51"></a> |
| <span class="sourceLineNo">052</span> * "a", and an old value of "b". This might introduce subtle bugs. This<a name="line.52"></a> |
| <span class="sourceLineNo">053</span> * needs to be dealt on a case-by-case basis, and this class does not provide<a name="line.53"></a> |
| <span class="sourceLineNo">054</span> * any protection from such cases.<a name="line.54"></a> |
| <span class="sourceLineNo">055</span> *<a name="line.55"></a> |
| <span class="sourceLineNo">056</span> * 2. Register the appropriate instance of the class with the<a name="line.56"></a> |
| <span class="sourceLineNo">057</span> * {@link ConfigurationManager} instance, using the<a name="line.57"></a> |
| <span class="sourceLineNo">058</span> * {@link ConfigurationManager#registerObserver(ConfigurationObserver)}<a name="line.58"></a> |
| <span class="sourceLineNo">059</span> * method. Be careful not to do this in the constructor, as you might cause<a name="line.59"></a> |
| <span class="sourceLineNo">060</span> * the 'this' reference to escape. Use a factory method, or an initialize()<a name="line.60"></a> |
| <span class="sourceLineNo">061</span> * method which is called after the construction of the object.<a name="line.61"></a> |
| <span class="sourceLineNo">062</span> *<a name="line.62"></a> |
| <span class="sourceLineNo">063</span> * 3. Deregister the instance using the<a name="line.63"></a> |
| <span class="sourceLineNo">064</span> * {@link ConfigurationManager#deregisterObserver(ConfigurationObserver)}<a name="line.64"></a> |
| <span class="sourceLineNo">065</span> * method when it is going out of scope. In case you are not able to do that<a name="line.65"></a> |
| <span class="sourceLineNo">066</span> * for any reason, it is still okay, since entries for dead observers are<a name="line.66"></a> |
| <span class="sourceLineNo">067</span> * automatically collected during GC. But nonetheless, it is still a good<a name="line.67"></a> |
| <span class="sourceLineNo">068</span> * practice to deregister your observer, whenever possible.<a name="line.68"></a> |
| <span class="sourceLineNo">069</span> */<a name="line.69"></a> |
| <span class="sourceLineNo">070</span>@InterfaceAudience.Private<a name="line.70"></a> |
| <span class="sourceLineNo">071</span>@InterfaceStability.Evolving<a name="line.71"></a> |
| <span class="sourceLineNo">072</span>public class ConfigurationManager {<a name="line.72"></a> |
| <span class="sourceLineNo">073</span> private static final Logger LOG = LoggerFactory.getLogger(ConfigurationManager.class);<a name="line.73"></a> |
| <span class="sourceLineNo">074</span><a name="line.74"></a> |
| <span class="sourceLineNo">075</span> // The set of Configuration Observers. These classes would like to get<a name="line.75"></a> |
| <span class="sourceLineNo">076</span> // notified when the configuration is reloaded from disk. This is a set<a name="line.76"></a> |
| <span class="sourceLineNo">077</span> // constructed from a WeakHashMap, whose entries would be removed if the<a name="line.77"></a> |
| <span class="sourceLineNo">078</span> // observer classes go out of scope.<a name="line.78"></a> |
| <span class="sourceLineNo">079</span> private final Set<ConfigurationObserver> configurationObservers =<a name="line.79"></a> |
| <span class="sourceLineNo">080</span> Collections.newSetFromMap(new WeakHashMap<>());<a name="line.80"></a> |
| <span class="sourceLineNo">081</span><a name="line.81"></a> |
| <span class="sourceLineNo">082</span> /**<a name="line.82"></a> |
| <span class="sourceLineNo">083</span> * Register an observer class<a name="line.83"></a> |
| <span class="sourceLineNo">084</span> * @param observer observer to be registered.<a name="line.84"></a> |
| <span class="sourceLineNo">085</span> */<a name="line.85"></a> |
| <span class="sourceLineNo">086</span> public void registerObserver(ConfigurationObserver observer) {<a name="line.86"></a> |
| <span class="sourceLineNo">087</span> synchronized (configurationObservers) {<a name="line.87"></a> |
| <span class="sourceLineNo">088</span> configurationObservers.add(observer);<a name="line.88"></a> |
| <span class="sourceLineNo">089</span> if (observer instanceof PropagatingConfigurationObserver) {<a name="line.89"></a> |
| <span class="sourceLineNo">090</span> ((PropagatingConfigurationObserver) observer).registerChildren(this);<a name="line.90"></a> |
| <span class="sourceLineNo">091</span> }<a name="line.91"></a> |
| <span class="sourceLineNo">092</span> }<a name="line.92"></a> |
| <span class="sourceLineNo">093</span> }<a name="line.93"></a> |
| <span class="sourceLineNo">094</span><a name="line.94"></a> |
| <span class="sourceLineNo">095</span> /**<a name="line.95"></a> |
| <span class="sourceLineNo">096</span> * Deregister an observer class<a name="line.96"></a> |
| <span class="sourceLineNo">097</span> * @param observer to be deregistered.<a name="line.97"></a> |
| <span class="sourceLineNo">098</span> */<a name="line.98"></a> |
| <span class="sourceLineNo">099</span> public void deregisterObserver(ConfigurationObserver observer) {<a name="line.99"></a> |
| <span class="sourceLineNo">100</span> synchronized (configurationObservers) {<a name="line.100"></a> |
| <span class="sourceLineNo">101</span> configurationObservers.remove(observer);<a name="line.101"></a> |
| <span class="sourceLineNo">102</span> if (observer instanceof PropagatingConfigurationObserver) {<a name="line.102"></a> |
| <span class="sourceLineNo">103</span> ((PropagatingConfigurationObserver) observer).deregisterChildren(this);<a name="line.103"></a> |
| <span class="sourceLineNo">104</span> }<a name="line.104"></a> |
| <span class="sourceLineNo">105</span> }<a name="line.105"></a> |
| <span class="sourceLineNo">106</span> }<a name="line.106"></a> |
| <span class="sourceLineNo">107</span><a name="line.107"></a> |
| <span class="sourceLineNo">108</span> /**<a name="line.108"></a> |
| <span class="sourceLineNo">109</span> * The conf object has been repopulated from disk, and we have to notify<a name="line.109"></a> |
| <span class="sourceLineNo">110</span> * all the observers that are expressed interest to do that.<a name="line.110"></a> |
| <span class="sourceLineNo">111</span> */<a name="line.111"></a> |
| <span class="sourceLineNo">112</span> public void notifyAllObservers(Configuration conf) {<a name="line.112"></a> |
| <span class="sourceLineNo">113</span> LOG.info("Starting to notify all observers that config changed.");<a name="line.113"></a> |
| <span class="sourceLineNo">114</span> synchronized (configurationObservers) {<a name="line.114"></a> |
| <span class="sourceLineNo">115</span> for (ConfigurationObserver observer : configurationObservers) {<a name="line.115"></a> |
| <span class="sourceLineNo">116</span> try {<a name="line.116"></a> |
| <span class="sourceLineNo">117</span> if (observer != null) {<a name="line.117"></a> |
| <span class="sourceLineNo">118</span> observer.onConfigurationChange(conf);<a name="line.118"></a> |
| <span class="sourceLineNo">119</span> }<a name="line.119"></a> |
| <span class="sourceLineNo">120</span> } catch (Throwable t) {<a name="line.120"></a> |
| <span class="sourceLineNo">121</span> LOG.error("Encountered a throwable while notifying observers: " + " of type : " +<a name="line.121"></a> |
| <span class="sourceLineNo">122</span> observer.getClass().getCanonicalName() + "(" + observer + ")", t);<a name="line.122"></a> |
| <span class="sourceLineNo">123</span> }<a name="line.123"></a> |
| <span class="sourceLineNo">124</span> }<a name="line.124"></a> |
| <span class="sourceLineNo">125</span> }<a name="line.125"></a> |
| <span class="sourceLineNo">126</span> }<a name="line.126"></a> |
| <span class="sourceLineNo">127</span><a name="line.127"></a> |
| <span class="sourceLineNo">128</span> /**<a name="line.128"></a> |
| <span class="sourceLineNo">129</span> * @return the number of observers. <a name="line.129"></a> |
| <span class="sourceLineNo">130</span> */<a name="line.130"></a> |
| <span class="sourceLineNo">131</span> public int getNumObservers() {<a name="line.131"></a> |
| <span class="sourceLineNo">132</span> synchronized (configurationObservers) {<a name="line.132"></a> |
| <span class="sourceLineNo">133</span> return configurationObservers.size();<a name="line.133"></a> |
| <span class="sourceLineNo">134</span> }<a name="line.134"></a> |
| <span class="sourceLineNo">135</span> }<a name="line.135"></a> |
| <span class="sourceLineNo">136</span><a name="line.136"></a> |
| <span class="sourceLineNo">137</span> /**<a name="line.137"></a> |
| <span class="sourceLineNo">138</span> * @return true if contains the observer, for unit test only<a name="line.138"></a> |
| <span class="sourceLineNo">139</span> */<a name="line.139"></a> |
| <span class="sourceLineNo">140</span> @VisibleForTesting<a name="line.140"></a> |
| <span class="sourceLineNo">141</span> public boolean containsObserver(ConfigurationObserver observer) {<a name="line.141"></a> |
| <span class="sourceLineNo">142</span> synchronized (configurationObservers) {<a name="line.142"></a> |
| <span class="sourceLineNo">143</span> return configurationObservers.contains(observer);<a name="line.143"></a> |
| <span class="sourceLineNo">144</span> }<a name="line.144"></a> |
| <span class="sourceLineNo">145</span> }<a name="line.145"></a> |
| <span class="sourceLineNo">146</span>}<a name="line.146"></a> |
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