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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.master;</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 edu.umd.cs.findbugs.annotations.NonNull;</span>
<span class="source-line-no">021</span><span id="line-21">import java.io.IOException;</span>
<span class="source-line-no">022</span><span id="line-22">import java.util.List;</span>
<span class="source-line-no">023</span><span id="line-23">import java.util.Map;</span>
<span class="source-line-no">024</span><span id="line-24">import org.apache.hadoop.conf.Configuration;</span>
<span class="source-line-no">025</span><span id="line-25">import org.apache.hadoop.hbase.ClusterMetrics;</span>
<span class="source-line-no">026</span><span id="line-26">import org.apache.hadoop.hbase.ServerName;</span>
<span class="source-line-no">027</span><span id="line-27">import org.apache.hadoop.hbase.Stoppable;</span>
<span class="source-line-no">028</span><span id="line-28">import org.apache.hadoop.hbase.TableName;</span>
<span class="source-line-no">029</span><span id="line-29">import org.apache.hadoop.hbase.client.RegionInfo;</span>
<span class="source-line-no">030</span><span id="line-30">import org.apache.hadoop.hbase.conf.ConfigurationObserver;</span>
<span class="source-line-no">031</span><span id="line-31">import org.apache.hadoop.hbase.master.balancer.ClusterInfoProvider;</span>
<span class="source-line-no">032</span><span id="line-32">import org.apache.yetus.audience.InterfaceAudience;</span>
<span class="source-line-no">033</span><span id="line-33"></span>
<span class="source-line-no">034</span><span id="line-34">/**</span>
<span class="source-line-no">035</span><span id="line-35"> * Makes decisions about the placement and movement of Regions across RegionServers.</span>
<span class="source-line-no">036</span><span id="line-36"> * &lt;p/&gt;</span>
<span class="source-line-no">037</span><span id="line-37"> * Cluster-wide load balancing will occur only when there are no regions in transition and according</span>
<span class="source-line-no">038</span><span id="line-38"> * to a fixed period of a time using {@link #balanceCluster(Map)}.</span>
<span class="source-line-no">039</span><span id="line-39"> * &lt;p/&gt;</span>
<span class="source-line-no">040</span><span id="line-40"> * On cluster startup, bulk assignment can be used to determine locations for all Regions in a</span>
<span class="source-line-no">041</span><span id="line-41"> * cluster.</span>
<span class="source-line-no">042</span><span id="line-42"> * &lt;p/&gt;</span>
<span class="source-line-no">043</span><span id="line-43"> * This class produces plans for the {@code AssignmentManager} to execute.</span>
<span class="source-line-no">044</span><span id="line-44"> * &lt;p/&gt;</span>
<span class="source-line-no">045</span><span id="line-45"> * About locking:</span>
<span class="source-line-no">046</span><span id="line-46"> * &lt;ul&gt;</span>
<span class="source-line-no">047</span><span id="line-47"> * &lt;li&gt;We will first call {@link #setClusterInfoProvider(ClusterInfoProvider)} and then</span>
<span class="source-line-no">048</span><span id="line-48"> * {@link #initialize()} to initialize the balancer, and before calling {@link #initialize()}, we</span>
<span class="source-line-no">049</span><span id="line-49"> * will never call any methods of this balancer. So these two methods do not need to be</span>
<span class="source-line-no">050</span><span id="line-50"> * synchronized.&lt;/li&gt;</span>
<span class="source-line-no">051</span><span id="line-51"> * &lt;li&gt;The {@link #balanceCluster(Map)} method will use the {@link ClusterMetrics} which is set by</span>
<span class="source-line-no">052</span><span id="line-52"> * {@link #updateClusterMetrics(ClusterMetrics)}, and also lots of configurations, which could be</span>
<span class="source-line-no">053</span><span id="line-53"> * changed by {@link #onConfigurationChange(Configuration)}, so the easier way is to make these</span>
<span class="source-line-no">054</span><span id="line-54"> * three methods synchronized. And since there will be only one balancing thread, this will not</span>
<span class="source-line-no">055</span><span id="line-55"> * impact performance too much.&lt;/li&gt;</span>
<span class="source-line-no">056</span><span id="line-56"> * &lt;li&gt;The {@link #roundRobinAssignment(List, List)}, {@link #retainAssignment(Map, List)} and</span>
<span class="source-line-no">057</span><span id="line-57"> * {@link #randomAssignment(RegionInfo, List)} could be called from multiple threads concurrently,</span>
<span class="source-line-no">058</span><span id="line-58"> * so these three methods should not be synchronized, the implementation classes need to make sure</span>
<span class="source-line-no">059</span><span id="line-59"> * that they are thread safe.&lt;/li&gt;</span>
<span class="source-line-no">060</span><span id="line-60"> * &lt;/ul&gt;</span>
<span class="source-line-no">061</span><span id="line-61"> */</span>
<span class="source-line-no">062</span><span id="line-62">@InterfaceAudience.Private</span>
<span class="source-line-no">063</span><span id="line-63">public interface LoadBalancer extends Stoppable, ConfigurationObserver {</span>
<span class="source-line-no">064</span><span id="line-64"></span>
<span class="source-line-no">065</span><span id="line-65"> // Used to signal to the caller that the region(s) cannot be assigned</span>
<span class="source-line-no">066</span><span id="line-66"> // We deliberately use 'localhost' so the operation will fail fast</span>
<span class="source-line-no">067</span><span id="line-67"> ServerName BOGUS_SERVER_NAME = ServerName.valueOf("localhost,1,1");</span>
<span class="source-line-no">068</span><span id="line-68"></span>
<span class="source-line-no">069</span><span id="line-69"> /**</span>
<span class="source-line-no">070</span><span id="line-70"> * Config for pluggable load balancers.</span>
<span class="source-line-no">071</span><span id="line-71"> * @deprecated since 3.0.0, will be removed in 4.0.0. In the new implementation, as the base load</span>
<span class="source-line-no">072</span><span id="line-72"> * balancer will always be the rs group based one, you should just use</span>
<span class="source-line-no">073</span><span id="line-73"> * {@link org.apache.hadoop.hbase.HConstants#HBASE_MASTER_LOADBALANCER_CLASS} to</span>
<span class="source-line-no">074</span><span id="line-74"> * config the per group load balancer.</span>
<span class="source-line-no">075</span><span id="line-75"> */</span>
<span class="source-line-no">076</span><span id="line-76"> @Deprecated</span>
<span class="source-line-no">077</span><span id="line-77"> String HBASE_RSGROUP_LOADBALANCER_CLASS = "hbase.rsgroup.grouploadbalancer.class";</span>
<span class="source-line-no">078</span><span id="line-78"></span>
<span class="source-line-no">079</span><span id="line-79"> /**</span>
<span class="source-line-no">080</span><span id="line-80"> * Set the current cluster status. This allows a LoadBalancer to map host name to a server</span>
<span class="source-line-no">081</span><span id="line-81"> */</span>
<span class="source-line-no">082</span><span id="line-82"> void updateClusterMetrics(ClusterMetrics metrics);</span>
<span class="source-line-no">083</span><span id="line-83"></span>
<span class="source-line-no">084</span><span id="line-84"> /**</span>
<span class="source-line-no">085</span><span id="line-85"> * Set the cluster info provider. Usually it is just a wrapper of master.</span>
<span class="source-line-no">086</span><span id="line-86"> */</span>
<span class="source-line-no">087</span><span id="line-87"> void setClusterInfoProvider(ClusterInfoProvider provider);</span>
<span class="source-line-no">088</span><span id="line-88"></span>
<span class="source-line-no">089</span><span id="line-89"> /**</span>
<span class="source-line-no">090</span><span id="line-90"> * Perform the major balance operation for cluster.</span>
<span class="source-line-no">091</span><span id="line-91"> * @param loadOfAllTable region load of servers for all table</span>
<span class="source-line-no">092</span><span id="line-92"> * @return a list of regions to be moved, including source and destination, or null if cluster is</span>
<span class="source-line-no">093</span><span id="line-93"> * already balanced</span>
<span class="source-line-no">094</span><span id="line-94"> */</span>
<span class="source-line-no">095</span><span id="line-95"> List&lt;RegionPlan&gt; balanceCluster(Map&lt;TableName, Map&lt;ServerName, List&lt;RegionInfo&gt;&gt;&gt; loadOfAllTable)</span>
<span class="source-line-no">096</span><span id="line-96"> throws IOException;</span>
<span class="source-line-no">097</span><span id="line-97"></span>
<span class="source-line-no">098</span><span id="line-98"> /**</span>
<span class="source-line-no">099</span><span id="line-99"> * Perform a Round Robin assignment of regions.</span>
<span class="source-line-no">100</span><span id="line-100"> * @return Map of servername to regioninfos</span>
<span class="source-line-no">101</span><span id="line-101"> */</span>
<span class="source-line-no">102</span><span id="line-102"> @NonNull</span>
<span class="source-line-no">103</span><span id="line-103"> Map&lt;ServerName, List&lt;RegionInfo&gt;&gt; roundRobinAssignment(List&lt;RegionInfo&gt; regions,</span>
<span class="source-line-no">104</span><span id="line-104"> List&lt;ServerName&gt; servers) throws IOException;</span>
<span class="source-line-no">105</span><span id="line-105"></span>
<span class="source-line-no">106</span><span id="line-106"> /**</span>
<span class="source-line-no">107</span><span id="line-107"> * Assign regions to the previously hosting region server</span>
<span class="source-line-no">108</span><span id="line-108"> * @return List of plans</span>
<span class="source-line-no">109</span><span id="line-109"> */</span>
<span class="source-line-no">110</span><span id="line-110"> @NonNull</span>
<span class="source-line-no">111</span><span id="line-111"> Map&lt;ServerName, List&lt;RegionInfo&gt;&gt; retainAssignment(Map&lt;RegionInfo, ServerName&gt; regions,</span>
<span class="source-line-no">112</span><span id="line-112"> List&lt;ServerName&gt; servers) throws IOException;</span>
<span class="source-line-no">113</span><span id="line-113"></span>
<span class="source-line-no">114</span><span id="line-114"> /**</span>
<span class="source-line-no">115</span><span id="line-115"> * Get a random region server from the list</span>
<span class="source-line-no">116</span><span id="line-116"> * @param regionInfo Region for which this selection is being done.</span>
<span class="source-line-no">117</span><span id="line-117"> */</span>
<span class="source-line-no">118</span><span id="line-118"> ServerName randomAssignment(RegionInfo regionInfo, List&lt;ServerName&gt; servers) throws IOException;</span>
<span class="source-line-no">119</span><span id="line-119"></span>
<span class="source-line-no">120</span><span id="line-120"> /**</span>
<span class="source-line-no">121</span><span id="line-121"> * Initialize the load balancer. Must be called after setters.</span>
<span class="source-line-no">122</span><span id="line-122"> */</span>
<span class="source-line-no">123</span><span id="line-123"> void initialize() throws IOException;</span>
<span class="source-line-no">124</span><span id="line-124"></span>
<span class="source-line-no">125</span><span id="line-125"> /**</span>
<span class="source-line-no">126</span><span id="line-126"> * Marks the region as online at balancer.</span>
<span class="source-line-no">127</span><span id="line-127"> */</span>
<span class="source-line-no">128</span><span id="line-128"> void regionOnline(RegionInfo regionInfo, ServerName sn);</span>
<span class="source-line-no">129</span><span id="line-129"></span>
<span class="source-line-no">130</span><span id="line-130"> /**</span>
<span class="source-line-no">131</span><span id="line-131"> * Marks the region as offline at balancer.</span>
<span class="source-line-no">132</span><span id="line-132"> */</span>
<span class="source-line-no">133</span><span id="line-133"> void regionOffline(RegionInfo regionInfo);</span>
<span class="source-line-no">134</span><span id="line-134"></span>
<span class="source-line-no">135</span><span id="line-135"> /**</span>
<span class="source-line-no">136</span><span id="line-136"> * Notification that config has changed</span>
<span class="source-line-no">137</span><span id="line-137"> */</span>
<span class="source-line-no">138</span><span id="line-138"> @Override</span>
<span class="source-line-no">139</span><span id="line-139"> void onConfigurationChange(Configuration conf);</span>
<span class="source-line-no">140</span><span id="line-140"></span>
<span class="source-line-no">141</span><span id="line-141"> /**</span>
<span class="source-line-no">142</span><span id="line-142"> * If balancer needs to do initialization after Master has started up, lets do that here.</span>
<span class="source-line-no">143</span><span id="line-143"> */</span>
<span class="source-line-no">144</span><span id="line-144"> void postMasterStartupInitialize();</span>
<span class="source-line-no">145</span><span id="line-145"></span>
<span class="source-line-no">146</span><span id="line-146"> /* Updates balancer status tag reported to JMX */</span>
<span class="source-line-no">147</span><span id="line-147"> void updateBalancerStatus(boolean status);</span>
<span class="source-line-no">148</span><span id="line-148"></span>
<span class="source-line-no">149</span><span id="line-149"> /**</span>
<span class="source-line-no">150</span><span id="line-150"> * In some scenarios, Balancer needs to update internal status or information according to the</span>
<span class="source-line-no">151</span><span id="line-151"> * current tables load</span>
<span class="source-line-no">152</span><span id="line-152"> * @param loadOfAllTable region load of servers for all table</span>
<span class="source-line-no">153</span><span id="line-153"> */</span>
<span class="source-line-no">154</span><span id="line-154"> default void</span>
<span class="source-line-no">155</span><span id="line-155"> updateBalancerLoadInfo(Map&lt;TableName, Map&lt;ServerName, List&lt;RegionInfo&gt;&gt;&gt; loadOfAllTable) {</span>
<span class="source-line-no">156</span><span id="line-156"> }</span>
<span class="source-line-no">157</span><span id="line-157">}</span>
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