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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.zookeeper;</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.concurrent.atomic.AtomicBoolean;</span> |
| <span class="source-line-no">021</span><span id="line-21">import org.apache.hadoop.hbase.Stoppable;</span> |
| <span class="source-line-no">022</span><span id="line-22">import org.apache.hadoop.hbase.util.Bytes;</span> |
| <span class="source-line-no">023</span><span id="line-23">import org.apache.yetus.audience.InterfaceAudience;</span> |
| <span class="source-line-no">024</span><span id="line-24">import org.apache.zookeeper.KeeperException;</span> |
| <span class="source-line-no">025</span><span id="line-25">import org.slf4j.Logger;</span> |
| <span class="source-line-no">026</span><span id="line-26">import org.slf4j.LoggerFactory;</span> |
| <span class="source-line-no">027</span><span id="line-27"></span> |
| <span class="source-line-no">028</span><span id="line-28">/**</span> |
| <span class="source-line-no">029</span><span id="line-29"> * Handles coordination of a single "leader" instance among many possible candidates. The first</span> |
| <span class="source-line-no">030</span><span id="line-30"> * {@link ZKLeaderManager} to successfully create the given znode becomes the leader, allowing the</span> |
| <span class="source-line-no">031</span><span id="line-31"> * instance to continue with whatever processing must be protected. Other {@link ZKLeaderManager}</span> |
| <span class="source-line-no">032</span><span id="line-32"> * instances will wait to be notified of changes to the leader znode. If the current master instance</span> |
| <span class="source-line-no">033</span><span id="line-33"> * fails, the ephemeral leader znode will be removed, and all waiting instances will be notified,</span> |
| <span class="source-line-no">034</span><span id="line-34"> * with the race to claim the leader znode beginning all over again.</span> |
| <span class="source-line-no">035</span><span id="line-35"> * @deprecated Not used</span> |
| <span class="source-line-no">036</span><span id="line-36"> */</span> |
| <span class="source-line-no">037</span><span id="line-37">@Deprecated</span> |
| <span class="source-line-no">038</span><span id="line-38">@InterfaceAudience.Private</span> |
| <span class="source-line-no">039</span><span id="line-39">public class ZKLeaderManager extends ZKListener {</span> |
| <span class="source-line-no">040</span><span id="line-40"> private static final Logger LOG = LoggerFactory.getLogger(ZKLeaderManager.class);</span> |
| <span class="source-line-no">041</span><span id="line-41"></span> |
| <span class="source-line-no">042</span><span id="line-42"> private final Object lock = new Object();</span> |
| <span class="source-line-no">043</span><span id="line-43"> private final AtomicBoolean leaderExists = new AtomicBoolean();</span> |
| <span class="source-line-no">044</span><span id="line-44"> private final String leaderZNode;</span> |
| <span class="source-line-no">045</span><span id="line-45"> private final byte[] nodeId;</span> |
| <span class="source-line-no">046</span><span id="line-46"> private final Stoppable candidate;</span> |
| <span class="source-line-no">047</span><span id="line-47"></span> |
| <span class="source-line-no">048</span><span id="line-48"> public ZKLeaderManager(ZKWatcher watcher, String leaderZNode, byte[] identifier,</span> |
| <span class="source-line-no">049</span><span id="line-49"> Stoppable candidate) {</span> |
| <span class="source-line-no">050</span><span id="line-50"> super(watcher);</span> |
| <span class="source-line-no">051</span><span id="line-51"> this.leaderZNode = leaderZNode;</span> |
| <span class="source-line-no">052</span><span id="line-52"> this.nodeId = identifier;</span> |
| <span class="source-line-no">053</span><span id="line-53"> this.candidate = candidate;</span> |
| <span class="source-line-no">054</span><span id="line-54"> }</span> |
| <span class="source-line-no">055</span><span id="line-55"></span> |
| <span class="source-line-no">056</span><span id="line-56"> public void start() {</span> |
| <span class="source-line-no">057</span><span id="line-57"> try {</span> |
| <span class="source-line-no">058</span><span id="line-58"> watcher.registerListener(this);</span> |
| <span class="source-line-no">059</span><span id="line-59"> String parent = ZKUtil.getParent(leaderZNode);</span> |
| <span class="source-line-no">060</span><span id="line-60"> if (ZKUtil.checkExists(watcher, parent) < 0) {</span> |
| <span class="source-line-no">061</span><span id="line-61"> ZKUtil.createWithParents(watcher, parent);</span> |
| <span class="source-line-no">062</span><span id="line-62"> }</span> |
| <span class="source-line-no">063</span><span id="line-63"> } catch (KeeperException ke) {</span> |
| <span class="source-line-no">064</span><span id="line-64"> watcher.abort("Unhandled zk exception when starting", ke);</span> |
| <span class="source-line-no">065</span><span id="line-65"> candidate.stop("Unhandled zk exception starting up: " + ke.getMessage());</span> |
| <span class="source-line-no">066</span><span id="line-66"> }</span> |
| <span class="source-line-no">067</span><span id="line-67"> }</span> |
| <span class="source-line-no">068</span><span id="line-68"></span> |
| <span class="source-line-no">069</span><span id="line-69"> @Override</span> |
| <span class="source-line-no">070</span><span id="line-70"> public void nodeCreated(String path) {</span> |
| <span class="source-line-no">071</span><span id="line-71"> if (leaderZNode.equals(path) && !candidate.isStopped()) {</span> |
| <span class="source-line-no">072</span><span id="line-72"> handleLeaderChange();</span> |
| <span class="source-line-no">073</span><span id="line-73"> }</span> |
| <span class="source-line-no">074</span><span id="line-74"> }</span> |
| <span class="source-line-no">075</span><span id="line-75"></span> |
| <span class="source-line-no">076</span><span id="line-76"> @Override</span> |
| <span class="source-line-no">077</span><span id="line-77"> public void nodeDeleted(String path) {</span> |
| <span class="source-line-no">078</span><span id="line-78"> if (leaderZNode.equals(path) && !candidate.isStopped()) {</span> |
| <span class="source-line-no">079</span><span id="line-79"> handleLeaderChange();</span> |
| <span class="source-line-no">080</span><span id="line-80"> }</span> |
| <span class="source-line-no">081</span><span id="line-81"> }</span> |
| <span class="source-line-no">082</span><span id="line-82"></span> |
| <span class="source-line-no">083</span><span id="line-83"> private void handleLeaderChange() {</span> |
| <span class="source-line-no">084</span><span id="line-84"> try {</span> |
| <span class="source-line-no">085</span><span id="line-85"> synchronized (lock) {</span> |
| <span class="source-line-no">086</span><span id="line-86"> if (ZKUtil.watchAndCheckExists(watcher, leaderZNode)) {</span> |
| <span class="source-line-no">087</span><span id="line-87"> LOG.info("Found new leader for znode: {}", leaderZNode);</span> |
| <span class="source-line-no">088</span><span id="line-88"> leaderExists.set(true);</span> |
| <span class="source-line-no">089</span><span id="line-89"> } else {</span> |
| <span class="source-line-no">090</span><span id="line-90"> LOG.info("Leader change, but no new leader found");</span> |
| <span class="source-line-no">091</span><span id="line-91"> leaderExists.set(false);</span> |
| <span class="source-line-no">092</span><span id="line-92"> lock.notifyAll();</span> |
| <span class="source-line-no">093</span><span id="line-93"> }</span> |
| <span class="source-line-no">094</span><span id="line-94"> }</span> |
| <span class="source-line-no">095</span><span id="line-95"> } catch (KeeperException ke) {</span> |
| <span class="source-line-no">096</span><span id="line-96"> watcher.abort("ZooKeeper error checking for leader znode", ke);</span> |
| <span class="source-line-no">097</span><span id="line-97"> candidate.stop("ZooKeeper error checking for leader: " + ke.getMessage());</span> |
| <span class="source-line-no">098</span><span id="line-98"> }</span> |
| <span class="source-line-no">099</span><span id="line-99"> }</span> |
| <span class="source-line-no">100</span><span id="line-100"></span> |
| <span class="source-line-no">101</span><span id="line-101"> /**</span> |
| <span class="source-line-no">102</span><span id="line-102"> * Blocks until this instance has claimed the leader ZNode in ZooKeeper</span> |
| <span class="source-line-no">103</span><span id="line-103"> */</span> |
| <span class="source-line-no">104</span><span id="line-104"> public void waitToBecomeLeader() {</span> |
| <span class="source-line-no">105</span><span id="line-105"> while (!candidate.isStopped()) {</span> |
| <span class="source-line-no">106</span><span id="line-106"> try {</span> |
| <span class="source-line-no">107</span><span id="line-107"> if (ZKUtil.createEphemeralNodeAndWatch(watcher, leaderZNode, nodeId)) {</span> |
| <span class="source-line-no">108</span><span id="line-108"> // claimed the leader znode</span> |
| <span class="source-line-no">109</span><span id="line-109"> leaderExists.set(true);</span> |
| <span class="source-line-no">110</span><span id="line-110"> if (LOG.isDebugEnabled()) {</span> |
| <span class="source-line-no">111</span><span id="line-111"> LOG.debug("Claimed the leader znode as '" + Bytes.toStringBinary(nodeId) + "'");</span> |
| <span class="source-line-no">112</span><span id="line-112"> }</span> |
| <span class="source-line-no">113</span><span id="line-113"> return;</span> |
| <span class="source-line-no">114</span><span id="line-114"> }</span> |
| <span class="source-line-no">115</span><span id="line-115"></span> |
| <span class="source-line-no">116</span><span id="line-116"> // if claiming the node failed, there should be another existing node</span> |
| <span class="source-line-no">117</span><span id="line-117"> byte[] currentId = ZKUtil.getDataAndWatch(watcher, leaderZNode);</span> |
| <span class="source-line-no">118</span><span id="line-118"> if (currentId != null && Bytes.equals(currentId, nodeId)) {</span> |
| <span class="source-line-no">119</span><span id="line-119"> // claimed with our ID, but we didn't grab it, possibly restarted?</span> |
| <span class="source-line-no">120</span><span id="line-120"> LOG.info(</span> |
| <span class="source-line-no">121</span><span id="line-121"> "Found existing leader with our ID (" + Bytes.toStringBinary(nodeId) + "), removing");</span> |
| <span class="source-line-no">122</span><span id="line-122"> ZKUtil.deleteNode(watcher, leaderZNode);</span> |
| <span class="source-line-no">123</span><span id="line-123"> leaderExists.set(false);</span> |
| <span class="source-line-no">124</span><span id="line-124"> } else {</span> |
| <span class="source-line-no">125</span><span id="line-125"> LOG.info("Found existing leader with ID: {}", Bytes.toStringBinary(currentId));</span> |
| <span class="source-line-no">126</span><span id="line-126"> leaderExists.set(true);</span> |
| <span class="source-line-no">127</span><span id="line-127"> }</span> |
| <span class="source-line-no">128</span><span id="line-128"> } catch (KeeperException ke) {</span> |
| <span class="source-line-no">129</span><span id="line-129"> watcher.abort("Unexpected error from ZK, stopping candidate", ke);</span> |
| <span class="source-line-no">130</span><span id="line-130"> candidate.stop("Unexpected error from ZK: " + ke.getMessage());</span> |
| <span class="source-line-no">131</span><span id="line-131"> return;</span> |
| <span class="source-line-no">132</span><span id="line-132"> }</span> |
| <span class="source-line-no">133</span><span id="line-133"></span> |
| <span class="source-line-no">134</span><span id="line-134"> // wait for next chance</span> |
| <span class="source-line-no">135</span><span id="line-135"> synchronized (lock) {</span> |
| <span class="source-line-no">136</span><span id="line-136"> while (leaderExists.get() && !candidate.isStopped()) {</span> |
| <span class="source-line-no">137</span><span id="line-137"> try {</span> |
| <span class="source-line-no">138</span><span id="line-138"> lock.wait();</span> |
| <span class="source-line-no">139</span><span id="line-139"> } catch (InterruptedException ie) {</span> |
| <span class="source-line-no">140</span><span id="line-140"> LOG.debug("Interrupted waiting on leader", ie);</span> |
| <span class="source-line-no">141</span><span id="line-141"> }</span> |
| <span class="source-line-no">142</span><span id="line-142"> }</span> |
| <span class="source-line-no">143</span><span id="line-143"> }</span> |
| <span class="source-line-no">144</span><span id="line-144"> }</span> |
| <span class="source-line-no">145</span><span id="line-145"> }</span> |
| <span class="source-line-no">146</span><span id="line-146"></span> |
| <span class="source-line-no">147</span><span id="line-147"> /**</span> |
| <span class="source-line-no">148</span><span id="line-148"> * Removes the leader znode, if it is currently claimed by this instance.</span> |
| <span class="source-line-no">149</span><span id="line-149"> */</span> |
| <span class="source-line-no">150</span><span id="line-150"> public void stepDownAsLeader() {</span> |
| <span class="source-line-no">151</span><span id="line-151"> try {</span> |
| <span class="source-line-no">152</span><span id="line-152"> synchronized (lock) {</span> |
| <span class="source-line-no">153</span><span id="line-153"> if (!leaderExists.get()) {</span> |
| <span class="source-line-no">154</span><span id="line-154"> return;</span> |
| <span class="source-line-no">155</span><span id="line-155"> }</span> |
| <span class="source-line-no">156</span><span id="line-156"> byte[] leaderId = ZKUtil.getData(watcher, leaderZNode);</span> |
| <span class="source-line-no">157</span><span id="line-157"> if (leaderId != null && Bytes.equals(nodeId, leaderId)) {</span> |
| <span class="source-line-no">158</span><span id="line-158"> LOG.info("Stepping down as leader");</span> |
| <span class="source-line-no">159</span><span id="line-159"> ZKUtil.deleteNodeFailSilent(watcher, leaderZNode);</span> |
| <span class="source-line-no">160</span><span id="line-160"> leaderExists.set(false);</span> |
| <span class="source-line-no">161</span><span id="line-161"> } else {</span> |
| <span class="source-line-no">162</span><span id="line-162"> LOG.info("Not current leader, no need to step down");</span> |
| <span class="source-line-no">163</span><span id="line-163"> }</span> |
| <span class="source-line-no">164</span><span id="line-164"> }</span> |
| <span class="source-line-no">165</span><span id="line-165"> } catch (KeeperException ke) {</span> |
| <span class="source-line-no">166</span><span id="line-166"> watcher.abort("Unhandled zookeeper exception removing leader node", ke);</span> |
| <span class="source-line-no">167</span><span id="line-167"> candidate.stop("Unhandled zookeeper exception removing leader node: " + ke.getMessage());</span> |
| <span class="source-line-no">168</span><span id="line-168"> } catch (InterruptedException e) {</span> |
| <span class="source-line-no">169</span><span id="line-169"> watcher.abort("Unhandled zookeeper exception removing leader node", e);</span> |
| <span class="source-line-no">170</span><span id="line-170"> candidate.stop("Unhandled zookeeper exception removing leader node: " + e.getMessage());</span> |
| <span class="source-line-no">171</span><span id="line-171"> }</span> |
| <span class="source-line-no">172</span><span id="line-172"> }</span> |
| <span class="source-line-no">173</span><span id="line-173"></span> |
| <span class="source-line-no">174</span><span id="line-174"> public boolean hasLeader() {</span> |
| <span class="source-line-no">175</span><span id="line-175"> return leaderExists.get();</span> |
| <span class="source-line-no">176</span><span id="line-176"> }</span> |
| <span class="source-line-no">177</span><span id="line-177">}</span> |
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| </pre> |
| </div> |
| </main> |
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