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<pre><span class="source-line-no">001</span><span id="line-1">/*</span>
<span class="source-line-no">002</span><span id="line-2"> * Licensed to the Apache Software Foundation (ASF) under one</span>
<span class="source-line-no">003</span><span id="line-3"> * or more contributor license agreements. See the NOTICE file</span>
<span class="source-line-no">004</span><span id="line-4"> * distributed with this work for additional information</span>
<span class="source-line-no">005</span><span id="line-5"> * regarding copyright ownership. The ASF licenses this file</span>
<span class="source-line-no">006</span><span id="line-6"> * to you under the Apache License, Version 2.0 (the</span>
<span class="source-line-no">007</span><span id="line-7"> * "License"); you may not use this file except in compliance</span>
<span class="source-line-no">008</span><span id="line-8"> * with the License. You may obtain a copy of the License at</span>
<span class="source-line-no">009</span><span id="line-9"> *</span>
<span class="source-line-no">010</span><span id="line-10"> * http://www.apache.org/licenses/LICENSE-2.0</span>
<span class="source-line-no">011</span><span id="line-11"> *</span>
<span class="source-line-no">012</span><span id="line-12"> * Unless required by applicable law or agreed to in writing, software</span>
<span class="source-line-no">013</span><span id="line-13"> * distributed under the License is distributed on an "AS IS" BASIS,</span>
<span class="source-line-no">014</span><span id="line-14"> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.</span>
<span class="source-line-no">015</span><span id="line-15"> * See the License for the specific language governing permissions and</span>
<span class="source-line-no">016</span><span id="line-16"> * limitations under the License.</span>
<span class="source-line-no">017</span><span id="line-17"> */</span>
<span class="source-line-no">018</span><span id="line-18">package org.apache.hadoop.hbase.coprocessor;</span>
<span class="source-line-no">019</span><span id="line-19"></span>
<span class="source-line-no">020</span><span id="line-20">import java.util.Optional;</span>
<span class="source-line-no">021</span><span id="line-21">import org.apache.hadoop.hbase.CoprocessorEnvironment;</span>
<span class="source-line-no">022</span><span id="line-22">import org.apache.hadoop.hbase.HBaseInterfaceAudience;</span>
<span class="source-line-no">023</span><span id="line-23">import org.apache.hadoop.hbase.security.User;</span>
<span class="source-line-no">024</span><span id="line-24">import org.apache.yetus.audience.InterfaceAudience;</span>
<span class="source-line-no">025</span><span id="line-25">import org.apache.yetus.audience.InterfaceStability;</span>
<span class="source-line-no">026</span><span id="line-26"></span>
<span class="source-line-no">027</span><span id="line-27">/**</span>
<span class="source-line-no">028</span><span id="line-28"> * Carries the execution state for a given invocation of an Observer coprocessor</span>
<span class="source-line-no">029</span><span id="line-29"> * ({@link RegionObserver}, {@link MasterObserver}, or {@link WALObserver}) method. The same</span>
<span class="source-line-no">030</span><span id="line-30"> * ObserverContext instance is passed sequentially to all loaded coprocessors for a given Observer</span>
<span class="source-line-no">031</span><span id="line-31"> * method trigger, with the &lt;code&gt;CoprocessorEnvironment&lt;/code&gt; reference set appropriately for each</span>
<span class="source-line-no">032</span><span id="line-32"> * Coprocessor type: e.g. the RegionCoprocessorEnvironment is passed to RegionCoprocessors, and so</span>
<span class="source-line-no">033</span><span id="line-33"> * on.</span>
<span class="source-line-no">034</span><span id="line-34"> * @param &lt;E&gt; The {@link CoprocessorEnvironment} subclass applicable to the revelant Observer</span>
<span class="source-line-no">035</span><span id="line-35"> * interface.</span>
<span class="source-line-no">036</span><span id="line-36"> */</span>
<span class="source-line-no">037</span><span id="line-37">@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)</span>
<span class="source-line-no">038</span><span id="line-38">@InterfaceStability.Evolving</span>
<span class="source-line-no">039</span><span id="line-39">public interface ObserverContext&lt;E extends CoprocessorEnvironment&gt; {</span>
<span class="source-line-no">040</span><span id="line-40"> E getEnvironment();</span>
<span class="source-line-no">041</span><span id="line-41"></span>
<span class="source-line-no">042</span><span id="line-42"> /**</span>
<span class="source-line-no">043</span><span id="line-43"> * Call to indicate that the current coprocessor's return value (or parameter -- depends on the</span>
<span class="source-line-no">044</span><span id="line-44"> * call-type) should be used in place of the value that would be obtained via normal processing;</span>
<span class="source-line-no">045</span><span id="line-45"> * i.e. bypass the core call and return the Coprocessor's result instead. DOES NOT work for all</span>
<span class="source-line-no">046</span><span id="line-46"> * Coprocessor invocations, only on a small subset of methods, mostly preXXX calls in</span>
<span class="source-line-no">047</span><span id="line-47"> * RegionObserver. Check javadoc on the pertinent Coprocessor Observer to see if</span>
<span class="source-line-no">048</span><span id="line-48"> * &lt;code&gt;bypass&lt;/code&gt; is supported.</span>
<span class="source-line-no">049</span><span id="line-49"> * &lt;p&gt;</span>
<span class="source-line-no">050</span><span id="line-50"> * This behavior of honoring only a subset of methods is new since hbase-2.0.0.</span>
<span class="source-line-no">051</span><span id="line-51"> * &lt;p&gt;</span>
<span class="source-line-no">052</span><span id="line-52"> * Where bypass is supported what is being bypassed is all of the core code implementing the</span>
<span class="source-line-no">053</span><span id="line-53"> * remainder of the operation. In order to understand what calling bypass() will skip, a</span>
<span class="source-line-no">054</span><span id="line-54"> * coprocessor implementer should read and understand all of the remaining code and its nuances.</span>
<span class="source-line-no">055</span><span id="line-55"> * Although this is good practice for coprocessor developers in general, it demands a lot. What is</span>
<span class="source-line-no">056</span><span id="line-56"> * skipped is extremely version dependent. The core code will vary, perhaps significantly, even</span>
<span class="source-line-no">057</span><span id="line-57"> * between point releases. We do not provide the promise of consistent behavior even between point</span>
<span class="source-line-no">058</span><span id="line-58"> * releases for the bypass semantic. To achieve that we could not change any code between hook</span>
<span class="source-line-no">059</span><span id="line-59"> * points. Therefore the coprocessor implementer becomes an HBase core developer in practice as</span>
<span class="source-line-no">060</span><span id="line-60"> * soon as they rely on bypass(). Every release of HBase may break the assumption that the</span>
<span class="source-line-no">061</span><span id="line-61"> * replacement for the bypassed code takes care of all necessary skipped concerns. Because those</span>
<span class="source-line-no">062</span><span id="line-62"> * concerns can change at any point, such an assumption is never safe.</span>
<span class="source-line-no">063</span><span id="line-63"> * &lt;/p&gt;</span>
<span class="source-line-no">064</span><span id="line-64"> * &lt;p&gt;</span>
<span class="source-line-no">065</span><span id="line-65"> * As of hbase2, when bypass has been set, we will NOT call any Coprocessors follow the bypassing</span>
<span class="source-line-no">066</span><span id="line-66"> * Coprocessor; we cut short the processing and return the bypassing Coprocessors response (this</span>
<span class="source-line-no">067</span><span id="line-67"> * used be a separate 'complete' option that has been folded into the 'bypass' in hbase2.</span>
<span class="source-line-no">068</span><span id="line-68"> * &lt;/p&gt;</span>
<span class="source-line-no">069</span><span id="line-69"> */</span>
<span class="source-line-no">070</span><span id="line-70"> void bypass();</span>
<span class="source-line-no">071</span><span id="line-71"></span>
<span class="source-line-no">072</span><span id="line-72"> /**</span>
<span class="source-line-no">073</span><span id="line-73"> * Returns the active user for the coprocessor call. If an explicit {@code User} instance was</span>
<span class="source-line-no">074</span><span id="line-74"> * provided to the constructor, that will be returned, otherwise if we are in the context of an</span>
<span class="source-line-no">075</span><span id="line-75"> * RPC call, the remote user is used. May not be present if the execution is outside of an RPC</span>
<span class="source-line-no">076</span><span id="line-76"> * context.</span>
<span class="source-line-no">077</span><span id="line-77"> */</span>
<span class="source-line-no">078</span><span id="line-78"> Optional&lt;User&gt; getCaller();</span>
<span class="source-line-no">079</span><span id="line-79">}</span>
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