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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.procedure2;<a name="line.18"></a>
<span class="sourceLineNo">019</span><a name="line.19"></a>
<span class="sourceLineNo">020</span>import java.util.function.Function;<a name="line.20"></a>
<span class="sourceLineNo">021</span>import java.util.function.Predicate;<a name="line.21"></a>
<span class="sourceLineNo">022</span>import java.util.stream.Stream;<a name="line.22"></a>
<span class="sourceLineNo">023</span>import org.apache.yetus.audience.InterfaceAudience;<a name="line.23"></a>
<span class="sourceLineNo">024</span><a name="line.24"></a>
<span class="sourceLineNo">025</span>/**<a name="line.25"></a>
<span class="sourceLineNo">026</span> * Locking for mutual exclusion between procedures. Used only by procedure framework internally.<a name="line.26"></a>
<span class="sourceLineNo">027</span> * {@link LockAndQueue} has two purposes:<a name="line.27"></a>
<span class="sourceLineNo">028</span> * &lt;ol&gt;<a name="line.28"></a>
<span class="sourceLineNo">029</span> * &lt;li&gt;Acquire/release exclusive/shared locks.&lt;/li&gt;<a name="line.29"></a>
<span class="sourceLineNo">030</span> * &lt;li&gt;Maintains a list of procedures waiting on this lock. {@link LockAndQueue} extends<a name="line.30"></a>
<span class="sourceLineNo">031</span> * {@link ProcedureDeque} class. Blocked Procedures are added to our super Deque. Using inheritance<a name="line.31"></a>
<span class="sourceLineNo">032</span> * over composition to keep the Deque of waiting Procedures is unusual, but we do it this way<a name="line.32"></a>
<span class="sourceLineNo">033</span> * because in certain cases, there will be millions of regions. This layout uses less memory.<a name="line.33"></a>
<span class="sourceLineNo">034</span> * &lt;/ol&gt;<a name="line.34"></a>
<span class="sourceLineNo">035</span> * &lt;p/&gt;<a name="line.35"></a>
<span class="sourceLineNo">036</span> * NOT thread-safe. Needs external concurrency control: e.g. uses in MasterProcedureScheduler are<a name="line.36"></a>
<span class="sourceLineNo">037</span> * guarded by schedLock(). &lt;br/&gt;<a name="line.37"></a>
<span class="sourceLineNo">038</span> * There is no need of 'volatile' keyword for member variables because of memory synchronization<a name="line.38"></a>
<span class="sourceLineNo">039</span> * guarantees of locks (see 'Memory Synchronization',<a name="line.39"></a>
<span class="sourceLineNo">040</span> * http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/locks/Lock.html) &lt;br/&gt;<a name="line.40"></a>
<span class="sourceLineNo">041</span> * We do not implement Lock interface because we need exclusive and shared locking, and also because<a name="line.41"></a>
<span class="sourceLineNo">042</span> * try-lock functions require procedure id. &lt;br/&gt;<a name="line.42"></a>
<span class="sourceLineNo">043</span> * We do not use ReentrantReadWriteLock directly because of its high memory overhead.<a name="line.43"></a>
<span class="sourceLineNo">044</span> */<a name="line.44"></a>
<span class="sourceLineNo">045</span>@InterfaceAudience.Private<a name="line.45"></a>
<span class="sourceLineNo">046</span>public class LockAndQueue implements LockStatus {<a name="line.46"></a>
<span class="sourceLineNo">047</span><a name="line.47"></a>
<span class="sourceLineNo">048</span> private final Function&lt;Long, Procedure&lt;?&gt;&gt; procedureRetriever;<a name="line.48"></a>
<span class="sourceLineNo">049</span> private final ProcedureDeque queue = new ProcedureDeque();<a name="line.49"></a>
<span class="sourceLineNo">050</span> private Procedure&lt;?&gt; exclusiveLockOwnerProcedure = null;<a name="line.50"></a>
<span class="sourceLineNo">051</span> private int sharedLock = 0;<a name="line.51"></a>
<span class="sourceLineNo">052</span><a name="line.52"></a>
<span class="sourceLineNo">053</span> // ======================================================================<a name="line.53"></a>
<span class="sourceLineNo">054</span> // Lock Status<a name="line.54"></a>
<span class="sourceLineNo">055</span> // ======================================================================<a name="line.55"></a>
<span class="sourceLineNo">056</span><a name="line.56"></a>
<span class="sourceLineNo">057</span> public LockAndQueue(Function&lt;Long, Procedure&lt;?&gt;&gt; procedureRetriever) {<a name="line.57"></a>
<span class="sourceLineNo">058</span> this.procedureRetriever = procedureRetriever;<a name="line.58"></a>
<span class="sourceLineNo">059</span> }<a name="line.59"></a>
<span class="sourceLineNo">060</span><a name="line.60"></a>
<span class="sourceLineNo">061</span> @Override<a name="line.61"></a>
<span class="sourceLineNo">062</span> public boolean hasExclusiveLock() {<a name="line.62"></a>
<span class="sourceLineNo">063</span> return this.exclusiveLockOwnerProcedure != null;<a name="line.63"></a>
<span class="sourceLineNo">064</span> }<a name="line.64"></a>
<span class="sourceLineNo">065</span><a name="line.65"></a>
<span class="sourceLineNo">066</span> @Override<a name="line.66"></a>
<span class="sourceLineNo">067</span> public boolean hasLockAccess(Procedure&lt;?&gt; proc) {<a name="line.67"></a>
<span class="sourceLineNo">068</span> if (exclusiveLockOwnerProcedure == null) {<a name="line.68"></a>
<span class="sourceLineNo">069</span> return false;<a name="line.69"></a>
<span class="sourceLineNo">070</span> }<a name="line.70"></a>
<span class="sourceLineNo">071</span> long lockOwnerId = exclusiveLockOwnerProcedure.getProcId();<a name="line.71"></a>
<span class="sourceLineNo">072</span> if (proc.getProcId() == lockOwnerId) {<a name="line.72"></a>
<span class="sourceLineNo">073</span> return true;<a name="line.73"></a>
<span class="sourceLineNo">074</span> }<a name="line.74"></a>
<span class="sourceLineNo">075</span> if (!proc.hasParent()) {<a name="line.75"></a>
<span class="sourceLineNo">076</span> return false;<a name="line.76"></a>
<span class="sourceLineNo">077</span> }<a name="line.77"></a>
<span class="sourceLineNo">078</span> // fast path to check root procedure<a name="line.78"></a>
<span class="sourceLineNo">079</span> if (proc.getRootProcId() == lockOwnerId) {<a name="line.79"></a>
<span class="sourceLineNo">080</span> return true;<a name="line.80"></a>
<span class="sourceLineNo">081</span> }<a name="line.81"></a>
<span class="sourceLineNo">082</span> // check ancestors<a name="line.82"></a>
<span class="sourceLineNo">083</span> for (Procedure&lt;?&gt; p = proc;;) {<a name="line.83"></a>
<span class="sourceLineNo">084</span> if (p.getParentProcId() == lockOwnerId) {<a name="line.84"></a>
<span class="sourceLineNo">085</span> return true;<a name="line.85"></a>
<span class="sourceLineNo">086</span> }<a name="line.86"></a>
<span class="sourceLineNo">087</span> p = procedureRetriever.apply(p.getParentProcId());<a name="line.87"></a>
<span class="sourceLineNo">088</span> if (p == null || !p.hasParent()) {<a name="line.88"></a>
<span class="sourceLineNo">089</span> return false;<a name="line.89"></a>
<span class="sourceLineNo">090</span> }<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> @Override<a name="line.94"></a>
<span class="sourceLineNo">095</span> public Procedure&lt;?&gt; getExclusiveLockOwnerProcedure() {<a name="line.95"></a>
<span class="sourceLineNo">096</span> return exclusiveLockOwnerProcedure;<a name="line.96"></a>
<span class="sourceLineNo">097</span> }<a name="line.97"></a>
<span class="sourceLineNo">098</span><a name="line.98"></a>
<span class="sourceLineNo">099</span> @Override<a name="line.99"></a>
<span class="sourceLineNo">100</span> public int getSharedLockCount() {<a name="line.100"></a>
<span class="sourceLineNo">101</span> return sharedLock;<a name="line.101"></a>
<span class="sourceLineNo">102</span> }<a name="line.102"></a>
<span class="sourceLineNo">103</span><a name="line.103"></a>
<span class="sourceLineNo">104</span> // ======================================================================<a name="line.104"></a>
<span class="sourceLineNo">105</span> // try/release Shared/Exclusive lock<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> /** Returns whether we have succesfully acquired the shared lock. */<a name="line.108"></a>
<span class="sourceLineNo">109</span> public boolean trySharedLock(Procedure&lt;?&gt; proc) {<a name="line.109"></a>
<span class="sourceLineNo">110</span> if (hasExclusiveLock() &amp;&amp; !hasLockAccess(proc)) {<a name="line.110"></a>
<span class="sourceLineNo">111</span> return false;<a name="line.111"></a>
<span class="sourceLineNo">112</span> }<a name="line.112"></a>
<span class="sourceLineNo">113</span> // If no one holds the xlock, then we are free to hold the sharedLock<a name="line.113"></a>
<span class="sourceLineNo">114</span> // If the parent proc or we have already held the xlock, then we return true here as<a name="line.114"></a>
<span class="sourceLineNo">115</span> // xlock is more powerful then shared lock.<a name="line.115"></a>
<span class="sourceLineNo">116</span> sharedLock++;<a name="line.116"></a>
<span class="sourceLineNo">117</span> return true;<a name="line.117"></a>
<span class="sourceLineNo">118</span> }<a name="line.118"></a>
<span class="sourceLineNo">119</span><a name="line.119"></a>
<span class="sourceLineNo">120</span> /** Returns whether we should wake the procedures waiting on the lock here. */<a name="line.120"></a>
<span class="sourceLineNo">121</span> public boolean releaseSharedLock() {<a name="line.121"></a>
<span class="sourceLineNo">122</span> // hasExclusiveLock could be true, it usually means we acquire shared lock while we or our<a name="line.122"></a>
<span class="sourceLineNo">123</span> // parent have held the xlock. And since there is still an exclusive lock, we do not need to<a name="line.123"></a>
<span class="sourceLineNo">124</span> // wake any procedures.<a name="line.124"></a>
<span class="sourceLineNo">125</span> return --sharedLock == 0 &amp;&amp; !hasExclusiveLock();<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> public boolean tryExclusiveLock(Procedure&lt;?&gt; proc) {<a name="line.128"></a>
<span class="sourceLineNo">129</span> if (isLocked()) {<a name="line.129"></a>
<span class="sourceLineNo">130</span> return hasLockAccess(proc);<a name="line.130"></a>
<span class="sourceLineNo">131</span> }<a name="line.131"></a>
<span class="sourceLineNo">132</span> exclusiveLockOwnerProcedure = proc;<a name="line.132"></a>
<span class="sourceLineNo">133</span> return true;<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> /** Returns whether we should wake the procedures waiting on the lock here. */<a name="line.136"></a>
<span class="sourceLineNo">137</span> public boolean releaseExclusiveLock(Procedure&lt;?&gt; proc) {<a name="line.137"></a>
<span class="sourceLineNo">138</span> if (<a name="line.138"></a>
<span class="sourceLineNo">139</span> exclusiveLockOwnerProcedure == null<a name="line.139"></a>
<span class="sourceLineNo">140</span> || exclusiveLockOwnerProcedure.getProcId() != proc.getProcId()<a name="line.140"></a>
<span class="sourceLineNo">141</span> ) {<a name="line.141"></a>
<span class="sourceLineNo">142</span> // We are not the lock owner, it is probably inherited from the parent procedures.<a name="line.142"></a>
<span class="sourceLineNo">143</span> return false;<a name="line.143"></a>
<span class="sourceLineNo">144</span> }<a name="line.144"></a>
<span class="sourceLineNo">145</span> exclusiveLockOwnerProcedure = null;<a name="line.145"></a>
<span class="sourceLineNo">146</span> // This maybe a bit strange so let me explain. We allow acquiring shared lock while the parent<a name="line.146"></a>
<span class="sourceLineNo">147</span> // proc or we have already held the xlock, and also allow releasing the locks in any order, so<a name="line.147"></a>
<span class="sourceLineNo">148</span> // it could happen that the xlock is released but there are still some procs holding the shared<a name="line.148"></a>
<span class="sourceLineNo">149</span> // lock.<a name="line.149"></a>
<span class="sourceLineNo">150</span> // In HBase, this could happen when a proc which holdLock is false and schedules sub procs which<a name="line.150"></a>
<span class="sourceLineNo">151</span> // acquire the shared lock on the same lock. This is because we will schedule the sub proces<a name="line.151"></a>
<span class="sourceLineNo">152</span> // before releasing the lock, so the sub procs could call acquire lock before we releasing the<a name="line.152"></a>
<span class="sourceLineNo">153</span> // xlock.<a name="line.153"></a>
<span class="sourceLineNo">154</span> return sharedLock == 0;<a name="line.154"></a>
<span class="sourceLineNo">155</span> }<a name="line.155"></a>
<span class="sourceLineNo">156</span><a name="line.156"></a>
<span class="sourceLineNo">157</span> public boolean isWaitingQueueEmpty() {<a name="line.157"></a>
<span class="sourceLineNo">158</span> return queue.isEmpty();<a name="line.158"></a>
<span class="sourceLineNo">159</span> }<a name="line.159"></a>
<span class="sourceLineNo">160</span><a name="line.160"></a>
<span class="sourceLineNo">161</span> public Procedure&lt;?&gt; removeFirst() {<a name="line.161"></a>
<span class="sourceLineNo">162</span> return queue.removeFirst();<a name="line.162"></a>
<span class="sourceLineNo">163</span> }<a name="line.163"></a>
<span class="sourceLineNo">164</span><a name="line.164"></a>
<span class="sourceLineNo">165</span> public void addLast(Procedure&lt;?&gt; proc) {<a name="line.165"></a>
<span class="sourceLineNo">166</span> queue.addLast(proc);<a name="line.166"></a>
<span class="sourceLineNo">167</span> }<a name="line.167"></a>
<span class="sourceLineNo">168</span><a name="line.168"></a>
<span class="sourceLineNo">169</span> public int wakeWaitingProcedures(ProcedureScheduler scheduler) {<a name="line.169"></a>
<span class="sourceLineNo">170</span> int count = queue.size();<a name="line.170"></a>
<span class="sourceLineNo">171</span> // wakeProcedure adds to the front of queue, so we start from last in the waitQueue' queue, so<a name="line.171"></a>
<span class="sourceLineNo">172</span> // that the procedure which was added first goes in the front for the scheduler queue.<a name="line.172"></a>
<span class="sourceLineNo">173</span> scheduler.addFront(queue.descendingIterator());<a name="line.173"></a>
<span class="sourceLineNo">174</span> queue.clear();<a name="line.174"></a>
<span class="sourceLineNo">175</span> return count;<a name="line.175"></a>
<span class="sourceLineNo">176</span> }<a name="line.176"></a>
<span class="sourceLineNo">177</span><a name="line.177"></a>
<span class="sourceLineNo">178</span> @SuppressWarnings("rawtypes")<a name="line.178"></a>
<span class="sourceLineNo">179</span> public Stream&lt;Procedure&gt; filterWaitingQueue(Predicate&lt;Procedure&gt; predicate) {<a name="line.179"></a>
<span class="sourceLineNo">180</span> return queue.stream().filter(predicate);<a name="line.180"></a>
<span class="sourceLineNo">181</span> }<a name="line.181"></a>
<span class="sourceLineNo">182</span><a name="line.182"></a>
<span class="sourceLineNo">183</span> @Override<a name="line.183"></a>
<span class="sourceLineNo">184</span> public String toString() {<a name="line.184"></a>
<span class="sourceLineNo">185</span> return "exclusiveLockOwner=" + (hasExclusiveLock() ? getExclusiveLockProcIdOwner() : "NONE")<a name="line.185"></a>
<span class="sourceLineNo">186</span> + ", sharedLockCount=" + getSharedLockCount() + ", waitingProcCount=" + queue.size();<a name="line.186"></a>
<span class="sourceLineNo">187</span> }<a name="line.187"></a>
<span class="sourceLineNo">188</span>}<a name="line.188"></a>
</pre>
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