| <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> |
| <html lang="en"> |
| <head> |
| <title>Source code</title> |
| <link rel="stylesheet" type="text/css" href="../../../../../../stylesheet.css" title="Style"> |
| </head> |
| <body> |
| <div class="sourceContainer"> |
| <pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a> |
| <span class="sourceLineNo">002</span> *<a name="line.2"></a> |
| <span class="sourceLineNo">003</span> * Licensed to the Apache Software Foundation (ASF) under one<a name="line.3"></a> |
| <span class="sourceLineNo">004</span> * or more contributor license agreements. See the NOTICE file<a name="line.4"></a> |
| <span class="sourceLineNo">005</span> * distributed with this work for additional information<a name="line.5"></a> |
| <span class="sourceLineNo">006</span> * regarding copyright ownership. The ASF licenses this file<a name="line.6"></a> |
| <span class="sourceLineNo">007</span> * to you under the Apache License, Version 2.0 (the<a name="line.7"></a> |
| <span class="sourceLineNo">008</span> * "License"); you may not use this file except in compliance<a name="line.8"></a> |
| <span class="sourceLineNo">009</span> * with the License. You may obtain a copy of the License at<a name="line.9"></a> |
| <span class="sourceLineNo">010</span> *<a name="line.10"></a> |
| <span class="sourceLineNo">011</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.11"></a> |
| <span class="sourceLineNo">012</span> *<a name="line.12"></a> |
| <span class="sourceLineNo">013</span> * Unless required by applicable law or agreed to in writing, software<a name="line.13"></a> |
| <span class="sourceLineNo">014</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.14"></a> |
| <span class="sourceLineNo">015</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.15"></a> |
| <span class="sourceLineNo">016</span> * See the License for the specific language governing permissions and<a name="line.16"></a> |
| <span class="sourceLineNo">017</span> * limitations under the License.<a name="line.17"></a> |
| <span class="sourceLineNo">018</span> */<a name="line.18"></a> |
| <span class="sourceLineNo">019</span>package org.apache.hadoop.hbase.util;<a name="line.19"></a> |
| <span class="sourceLineNo">020</span><a name="line.20"></a> |
| <span class="sourceLineNo">021</span>import org.apache.yetus.audience.InterfaceAudience;<a name="line.21"></a> |
| <span class="sourceLineNo">022</span><a name="line.22"></a> |
| <span class="sourceLineNo">023</span>/**<a name="line.23"></a> |
| <span class="sourceLineNo">024</span> * Manages a singleton instance of the environment edge. This class shall<a name="line.24"></a> |
| <span class="sourceLineNo">025</span> * implement static versions of the interface {@link EnvironmentEdge}, then<a name="line.25"></a> |
| <span class="sourceLineNo">026</span> * defer to the delegate on invocation.<a name="line.26"></a> |
| <span class="sourceLineNo">027</span> * <br><a name="line.27"></a> |
| <span class="sourceLineNo">028</span> * <b>Original Motivation:</b><a name="line.28"></a> |
| <span class="sourceLineNo">029</span> * The main purpose of the Environment Edge Manager was to have better control<a name="line.29"></a> |
| <span class="sourceLineNo">030</span> * over the tests so that they behave the same when run in any system.<a name="line.30"></a> |
| <span class="sourceLineNo">031</span> * (Refer: <a href="https://issues.apache.org/jira/browse/HBASE-2578">HBASE-2578</a> - The issue<a name="line.31"></a> |
| <span class="sourceLineNo">032</span> * which added the {@link org.apache.hadoop.hbase.util.EnvironmentEdgeManager}).<a name="line.32"></a> |
| <span class="sourceLineNo">033</span> * The idea is to have a central place where time can be assigned in HBase. That makes<a name="line.33"></a> |
| <span class="sourceLineNo">034</span> * it easier to inject different implementations of time. The default environment edge is the Java<a name="line.34"></a> |
| <span class="sourceLineNo">035</span> * Current Time in millis. The environment edge manager class is designed to be able<a name="line.35"></a> |
| <span class="sourceLineNo">036</span> * to plug in a new implementation of time by simply injecting an implementation<a name="line.36"></a> |
| <span class="sourceLineNo">037</span> * of {@link org.apache.hadoop.hbase.util.EnvironmentEdge} interface to<a name="line.37"></a> |
| <span class="sourceLineNo">038</span> * {@link org.apache.hadoop.hbase.util.EnvironmentEdgeManager}<a name="line.38"></a> |
| <span class="sourceLineNo">039</span><p><a name="line.39"></a> |
| <span class="sourceLineNo">040</span> <b>Problems with Environment Edge:</b><br><a name="line.40"></a> |
| <span class="sourceLineNo">041</span> 1. One of the major problems is the side effects of injecting an Environment Edge into<a name="line.41"></a> |
| <span class="sourceLineNo">042</span> Environment Edge Manager.<br><a name="line.42"></a> |
| <span class="sourceLineNo">043</span> For example, A test could inject an edge to fast forward time in order to avoid thread<a name="line.43"></a> |
| <span class="sourceLineNo">044</span> sleep to save time, but it could trigger a premature waking up of another thread waiting<a name="line.44"></a> |
| <span class="sourceLineNo">045</span> on a condition dependent on time lapse, which could potentially affect the normal<a name="line.45"></a> |
| <span class="sourceLineNo">046</span> working of the system leading to failure of tests.<br><a name="line.46"></a> |
| <span class="sourceLineNo">047</span> 2. Every test should ensure it is setting the Environment Edge it needs for the test to<a name="line.47"></a> |
| <span class="sourceLineNo">048</span> perform in an expected way. Because another test which might have run before the current test<a name="line.48"></a> |
| <span class="sourceLineNo">049</span> could have injected its own custom Environment Edge which may not be applicable to this<a name="line.49"></a> |
| <span class="sourceLineNo">050</span> test. This is still solvable but the problem is that the tests can run in parallel<a name="line.50"></a> |
| <span class="sourceLineNo">051</span> leading to different combinations of environment edges being injected causing unexpected<a name="line.51"></a> |
| <span class="sourceLineNo">052</span> results.<br><a name="line.52"></a> |
| <span class="sourceLineNo">053</span> 3. Another important issue with respect to injecting time through Environment Edge is that<a name="line.53"></a> |
| <span class="sourceLineNo">054</span> the milliseconds unit of time is ingrained throughout the codebase in the form of hardcoded<a name="line.54"></a> |
| <span class="sourceLineNo">055</span> sleep time or timeouts that any change of time unit or making it fast or slow can potentially<a name="line.55"></a> |
| <span class="sourceLineNo">056</span> trigger unexpected failures due to timeout or unintended flow of execution.<br><a name="line.56"></a> |
| <span class="sourceLineNo">057</span></p><a name="line.57"></a> |
| <span class="sourceLineNo">058</span> Because of the above issues, only {@link org.apache.hadoop.hbase.util.DefaultEnvironmentEdge}<a name="line.58"></a> |
| <span class="sourceLineNo">059</span> is being used, whose implementation of time returns the {@link System#currentTimeMillis()}. It<a name="line.59"></a> |
| <span class="sourceLineNo">060</span> is advised not to inject any other {@link org.apache.hadoop.hbase.util.EnvironmentEdge}.<a name="line.60"></a> |
| <span class="sourceLineNo">061</span> */<a name="line.61"></a> |
| <span class="sourceLineNo">062</span>@InterfaceAudience.Private<a name="line.62"></a> |
| <span class="sourceLineNo">063</span>public class EnvironmentEdgeManager {<a name="line.63"></a> |
| <span class="sourceLineNo">064</span> private static volatile EnvironmentEdge delegate = new DefaultEnvironmentEdge();<a name="line.64"></a> |
| <span class="sourceLineNo">065</span><a name="line.65"></a> |
| <span class="sourceLineNo">066</span> private EnvironmentEdgeManager() {<a name="line.66"></a> |
| <span class="sourceLineNo">067</span><a name="line.67"></a> |
| <span class="sourceLineNo">068</span> }<a name="line.68"></a> |
| <span class="sourceLineNo">069</span><a name="line.69"></a> |
| <span class="sourceLineNo">070</span> /**<a name="line.70"></a> |
| <span class="sourceLineNo">071</span> * Retrieves the singleton instance of the {@link EnvironmentEdge} that is<a name="line.71"></a> |
| <span class="sourceLineNo">072</span> * being managed.<a name="line.72"></a> |
| <span class="sourceLineNo">073</span> *<a name="line.73"></a> |
| <span class="sourceLineNo">074</span> * @return the edge.<a name="line.74"></a> |
| <span class="sourceLineNo">075</span> */<a name="line.75"></a> |
| <span class="sourceLineNo">076</span> public static EnvironmentEdge getDelegate() {<a name="line.76"></a> |
| <span class="sourceLineNo">077</span> return delegate;<a name="line.77"></a> |
| <span class="sourceLineNo">078</span> }<a name="line.78"></a> |
| <span class="sourceLineNo">079</span><a name="line.79"></a> |
| <span class="sourceLineNo">080</span> /**<a name="line.80"></a> |
| <span class="sourceLineNo">081</span> * Resets the managed instance to the default instance: {@link<a name="line.81"></a> |
| <span class="sourceLineNo">082</span> * DefaultEnvironmentEdge}.<a name="line.82"></a> |
| <span class="sourceLineNo">083</span> */<a name="line.83"></a> |
| <span class="sourceLineNo">084</span> public static void reset() {<a name="line.84"></a> |
| <span class="sourceLineNo">085</span> injectEdge(new DefaultEnvironmentEdge());<a name="line.85"></a> |
| <span class="sourceLineNo">086</span> }<a name="line.86"></a> |
| <span class="sourceLineNo">087</span><a name="line.87"></a> |
| <span class="sourceLineNo">088</span> /**<a name="line.88"></a> |
| <span class="sourceLineNo">089</span> * Injects the given edge such that it becomes the managed entity. If null is<a name="line.89"></a> |
| <span class="sourceLineNo">090</span> * passed to this method, the default type is assigned to the delegate.<a name="line.90"></a> |
| <span class="sourceLineNo">091</span> *<a name="line.91"></a> |
| <span class="sourceLineNo">092</span> * @param edge the new edge.<a name="line.92"></a> |
| <span class="sourceLineNo">093</span> */<a name="line.93"></a> |
| <span class="sourceLineNo">094</span> public static void injectEdge(EnvironmentEdge edge) {<a name="line.94"></a> |
| <span class="sourceLineNo">095</span> if (edge == null) {<a name="line.95"></a> |
| <span class="sourceLineNo">096</span> reset();<a name="line.96"></a> |
| <span class="sourceLineNo">097</span> } else {<a name="line.97"></a> |
| <span class="sourceLineNo">098</span> delegate = edge;<a name="line.98"></a> |
| <span class="sourceLineNo">099</span> }<a name="line.99"></a> |
| <span class="sourceLineNo">100</span> }<a name="line.100"></a> |
| <span class="sourceLineNo">101</span><a name="line.101"></a> |
| <span class="sourceLineNo">102</span> /**<a name="line.102"></a> |
| <span class="sourceLineNo">103</span> * Defers to the delegate and calls the<a name="line.103"></a> |
| <span class="sourceLineNo">104</span> * {@link EnvironmentEdge#currentTime()} method.<a name="line.104"></a> |
| <span class="sourceLineNo">105</span> *<a name="line.105"></a> |
| <span class="sourceLineNo">106</span> * @return current time in millis according to the delegate.<a name="line.106"></a> |
| <span class="sourceLineNo">107</span> */<a name="line.107"></a> |
| <span class="sourceLineNo">108</span> public static long currentTime() {<a name="line.108"></a> |
| <span class="sourceLineNo">109</span> return getDelegate().currentTime();<a name="line.109"></a> |
| <span class="sourceLineNo">110</span> }<a name="line.110"></a> |
| <span class="sourceLineNo">111</span>}<a name="line.111"></a> |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| </pre> |
| </div> |
| </body> |
| </html> |
