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Posted to commits@hbase.apache.org by gi...@apache.org on 2018/03/29 14:48:06 UTC
[18/41] hbase-site git commit: Published site at
d8b550fabcacf3050583b514c4081adf5d087d65.
http://git-wip-us.apache.org/repos/asf/hbase-site/blob/2a4c7d89/devapidocs/src-html/org/apache/hadoop/hbase/master/zksyncer/ClientZKSyncer.ClientZkUpdater.html
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+<!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.master.zksyncer;<a name="line.19"></a>
+<span class="sourceLineNo">020</span><a name="line.20"></a>
+<span class="sourceLineNo">021</span>import java.io.IOException;<a name="line.21"></a>
+<span class="sourceLineNo">022</span>import java.util.Collection;<a name="line.22"></a>
+<span class="sourceLineNo">023</span>import java.util.HashMap;<a name="line.23"></a>
+<span class="sourceLineNo">024</span>import java.util.Map;<a name="line.24"></a>
+<span class="sourceLineNo">025</span>import java.util.concurrent.ArrayBlockingQueue;<a name="line.25"></a>
+<span class="sourceLineNo">026</span>import java.util.concurrent.BlockingQueue;<a name="line.26"></a>
+<span class="sourceLineNo">027</span><a name="line.27"></a>
+<span class="sourceLineNo">028</span>import org.apache.commons.logging.Log;<a name="line.28"></a>
+<span class="sourceLineNo">029</span>import org.apache.commons.logging.LogFactory;<a name="line.29"></a>
+<span class="sourceLineNo">030</span>import org.apache.hadoop.hbase.HConstants;<a name="line.30"></a>
+<span class="sourceLineNo">031</span>import org.apache.hadoop.hbase.Server;<a name="line.31"></a>
+<span class="sourceLineNo">032</span>import org.apache.hadoop.hbase.util.Threads;<a name="line.32"></a>
+<span class="sourceLineNo">033</span>import org.apache.hadoop.hbase.zookeeper.ZKListener;<a name="line.33"></a>
+<span class="sourceLineNo">034</span>import org.apache.hadoop.hbase.zookeeper.ZKUtil;<a name="line.34"></a>
+<span class="sourceLineNo">035</span>import org.apache.hadoop.hbase.zookeeper.ZKWatcher;<a name="line.35"></a>
+<span class="sourceLineNo">036</span>import org.apache.yetus.audience.InterfaceAudience;<a name="line.36"></a>
+<span class="sourceLineNo">037</span>import org.apache.zookeeper.CreateMode;<a name="line.37"></a>
+<span class="sourceLineNo">038</span>import org.apache.zookeeper.KeeperException;<a name="line.38"></a>
+<span class="sourceLineNo">039</span><a name="line.39"></a>
+<span class="sourceLineNo">040</span>/**<a name="line.40"></a>
+<span class="sourceLineNo">041</span> * Tracks the target znode(s) on server ZK cluster and synchronize them to client ZK cluster if<a name="line.41"></a>
+<span class="sourceLineNo">042</span> * changed<a name="line.42"></a>
+<span class="sourceLineNo">043</span> * <p/><a name="line.43"></a>
+<span class="sourceLineNo">044</span> * The target znode(s) is given through {@link #getNodesToWatch()} method<a name="line.44"></a>
+<span class="sourceLineNo">045</span> */<a name="line.45"></a>
+<span class="sourceLineNo">046</span>@InterfaceAudience.Private<a name="line.46"></a>
+<span class="sourceLineNo">047</span>public abstract class ClientZKSyncer extends ZKListener {<a name="line.47"></a>
+<span class="sourceLineNo">048</span> private static final Log LOG = LogFactory.getLog(ClientZKSyncer.class);<a name="line.48"></a>
+<span class="sourceLineNo">049</span> private final Server server;<a name="line.49"></a>
+<span class="sourceLineNo">050</span> private final ZKWatcher clientZkWatcher;<a name="line.50"></a>
+<span class="sourceLineNo">051</span> // We use queues and daemon threads to synchronize the data to client ZK cluster<a name="line.51"></a>
+<span class="sourceLineNo">052</span> // to avoid blocking the single event thread for watchers<a name="line.52"></a>
+<span class="sourceLineNo">053</span> private final Map<String, BlockingQueue<byte[]>> queues;<a name="line.53"></a>
+<span class="sourceLineNo">054</span><a name="line.54"></a>
+<span class="sourceLineNo">055</span> public ClientZKSyncer(ZKWatcher watcher, ZKWatcher clientZkWatcher, Server server) {<a name="line.55"></a>
+<span class="sourceLineNo">056</span> super(watcher);<a name="line.56"></a>
+<span class="sourceLineNo">057</span> this.server = server;<a name="line.57"></a>
+<span class="sourceLineNo">058</span> this.clientZkWatcher = clientZkWatcher;<a name="line.58"></a>
+<span class="sourceLineNo">059</span> this.queues = new HashMap<>();<a name="line.59"></a>
+<span class="sourceLineNo">060</span> }<a name="line.60"></a>
+<span class="sourceLineNo">061</span><a name="line.61"></a>
+<span class="sourceLineNo">062</span> /**<a name="line.62"></a>
+<span class="sourceLineNo">063</span> * Starts the syncer<a name="line.63"></a>
+<span class="sourceLineNo">064</span> * @throws KeeperException if error occurs when trying to create base nodes on client ZK<a name="line.64"></a>
+<span class="sourceLineNo">065</span> */<a name="line.65"></a>
+<span class="sourceLineNo">066</span> public void start() throws KeeperException {<a name="line.66"></a>
+<span class="sourceLineNo">067</span> LOG.debug("Starting " + getClass().getSimpleName());<a name="line.67"></a>
+<span class="sourceLineNo">068</span> this.watcher.registerListener(this);<a name="line.68"></a>
+<span class="sourceLineNo">069</span> // create base znode on remote ZK<a name="line.69"></a>
+<span class="sourceLineNo">070</span> ZKUtil.createWithParents(clientZkWatcher, watcher.znodePaths.baseZNode);<a name="line.70"></a>
+<span class="sourceLineNo">071</span> // set meta znodes for client ZK<a name="line.71"></a>
+<span class="sourceLineNo">072</span> Collection<String> nodes = getNodesToWatch();<a name="line.72"></a>
+<span class="sourceLineNo">073</span> LOG.debug("Znodes to watch: " + nodes);<a name="line.73"></a>
+<span class="sourceLineNo">074</span> // initialize queues and threads<a name="line.74"></a>
+<span class="sourceLineNo">075</span> for (String node : nodes) {<a name="line.75"></a>
+<span class="sourceLineNo">076</span> BlockingQueue<byte[]> queue = new ArrayBlockingQueue<>(1);<a name="line.76"></a>
+<span class="sourceLineNo">077</span> queues.put(node, queue);<a name="line.77"></a>
+<span class="sourceLineNo">078</span> Thread updater = new ClientZkUpdater(node, queue);<a name="line.78"></a>
+<span class="sourceLineNo">079</span> updater.setDaemon(true);<a name="line.79"></a>
+<span class="sourceLineNo">080</span> updater.start();<a name="line.80"></a>
+<span class="sourceLineNo">081</span> watchAndCheckExists(node);<a name="line.81"></a>
+<span class="sourceLineNo">082</span> }<a name="line.82"></a>
+<span class="sourceLineNo">083</span> }<a name="line.83"></a>
+<span class="sourceLineNo">084</span><a name="line.84"></a>
+<span class="sourceLineNo">085</span> private void watchAndCheckExists(String node) {<a name="line.85"></a>
+<span class="sourceLineNo">086</span> try {<a name="line.86"></a>
+<span class="sourceLineNo">087</span> if (ZKUtil.watchAndCheckExists(watcher, node)) {<a name="line.87"></a>
+<span class="sourceLineNo">088</span> byte[] data = ZKUtil.getDataAndWatch(watcher, node);<a name="line.88"></a>
+<span class="sourceLineNo">089</span> if (data != null) {<a name="line.89"></a>
+<span class="sourceLineNo">090</span> // put the data into queue<a name="line.90"></a>
+<span class="sourceLineNo">091</span> upsertQueue(node, data);<a name="line.91"></a>
+<span class="sourceLineNo">092</span> } else {<a name="line.92"></a>
+<span class="sourceLineNo">093</span> // It existed but now does not, should has been tracked by our watcher, ignore<a name="line.93"></a>
+<span class="sourceLineNo">094</span> LOG.debug("Found no data from " + node);<a name="line.94"></a>
+<span class="sourceLineNo">095</span> watchAndCheckExists(node);<a name="line.95"></a>
+<span class="sourceLineNo">096</span> }<a name="line.96"></a>
+<span class="sourceLineNo">097</span> } else {<a name="line.97"></a>
+<span class="sourceLineNo">098</span> // cleanup stale ZNodes on client ZK to avoid invalid requests to server<a name="line.98"></a>
+<span class="sourceLineNo">099</span> ZKUtil.deleteNodeFailSilent(clientZkWatcher, node);<a name="line.99"></a>
+<span class="sourceLineNo">100</span> }<a name="line.100"></a>
+<span class="sourceLineNo">101</span> } catch (KeeperException e) {<a name="line.101"></a>
+<span class="sourceLineNo">102</span> server.abort("Unexpected exception during initialization, aborting", e);<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><a name="line.105"></a>
+<span class="sourceLineNo">106</span> /**<a name="line.106"></a>
+<span class="sourceLineNo">107</span> * Update the value of the single element in queue if any, or else insert.<a name="line.107"></a>
+<span class="sourceLineNo">108</span> * <p/><a name="line.108"></a>
+<span class="sourceLineNo">109</span> * We only need to synchronize the latest znode value to client ZK rather than synchronize each<a name="line.109"></a>
+<span class="sourceLineNo">110</span> * time<a name="line.110"></a>
+<span class="sourceLineNo">111</span> * @param data the data to write to queue<a name="line.111"></a>
+<span class="sourceLineNo">112</span> */<a name="line.112"></a>
+<span class="sourceLineNo">113</span> private void upsertQueue(String node, byte[] data) {<a name="line.113"></a>
+<span class="sourceLineNo">114</span> BlockingQueue<byte[]> queue = queues.get(node);<a name="line.114"></a>
+<span class="sourceLineNo">115</span> synchronized (queue) {<a name="line.115"></a>
+<span class="sourceLineNo">116</span> queue.poll();<a name="line.116"></a>
+<span class="sourceLineNo">117</span> queue.offer(data);<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><a name="line.120"></a>
+<span class="sourceLineNo">121</span> /**<a name="line.121"></a>
+<span class="sourceLineNo">122</span> * Set data for client ZK and retry until succeed. Be very careful to prevent dead loop when<a name="line.122"></a>
+<span class="sourceLineNo">123</span> * modifying this method<a name="line.123"></a>
+<span class="sourceLineNo">124</span> * @param node the znode to set on client ZK<a name="line.124"></a>
+<span class="sourceLineNo">125</span> * @param data the data to set to client ZK<a name="line.125"></a>
+<span class="sourceLineNo">126</span> * @throws InterruptedException if the thread is interrupted during process<a name="line.126"></a>
+<span class="sourceLineNo">127</span> */<a name="line.127"></a>
+<span class="sourceLineNo">128</span> private final void setDataForClientZkUntilSuccess(String node, byte[] data)<a name="line.128"></a>
+<span class="sourceLineNo">129</span> throws InterruptedException {<a name="line.129"></a>
+<span class="sourceLineNo">130</span> while (!server.isStopped()) {<a name="line.130"></a>
+<span class="sourceLineNo">131</span> try {<a name="line.131"></a>
+<span class="sourceLineNo">132</span> LOG.debug("Set data for remote " + node + ", client zk wather: " + clientZkWatcher);<a name="line.132"></a>
+<span class="sourceLineNo">133</span> ZKUtil.setData(clientZkWatcher, node, data);<a name="line.133"></a>
+<span class="sourceLineNo">134</span> break;<a name="line.134"></a>
+<span class="sourceLineNo">135</span> } catch (KeeperException.NoNodeException nne) {<a name="line.135"></a>
+<span class="sourceLineNo">136</span> // Node doesn't exist, create it and set value<a name="line.136"></a>
+<span class="sourceLineNo">137</span> try {<a name="line.137"></a>
+<span class="sourceLineNo">138</span> ZKUtil.createNodeIfNotExistsNoWatch(clientZkWatcher, node, data, CreateMode.PERSISTENT);<a name="line.138"></a>
+<span class="sourceLineNo">139</span> break;<a name="line.139"></a>
+<span class="sourceLineNo">140</span> } catch (KeeperException.ConnectionLossException<a name="line.140"></a>
+<span class="sourceLineNo">141</span> | KeeperException.SessionExpiredException ee) {<a name="line.141"></a>
+<span class="sourceLineNo">142</span> reconnectAfterExpiration();<a name="line.142"></a>
+<span class="sourceLineNo">143</span> } catch (KeeperException e) {<a name="line.143"></a>
+<span class="sourceLineNo">144</span> LOG.warn(<a name="line.144"></a>
+<span class="sourceLineNo">145</span> "Failed to create znode " + node + " due to: " + e.getMessage() + ", will retry later");<a name="line.145"></a>
+<span class="sourceLineNo">146</span> }<a name="line.146"></a>
+<span class="sourceLineNo">147</span> } catch (KeeperException.ConnectionLossException<a name="line.147"></a>
+<span class="sourceLineNo">148</span> | KeeperException.SessionExpiredException ee) {<a name="line.148"></a>
+<span class="sourceLineNo">149</span> reconnectAfterExpiration();<a name="line.149"></a>
+<span class="sourceLineNo">150</span> } catch (KeeperException e) {<a name="line.150"></a>
+<span class="sourceLineNo">151</span> LOG.debug("Failed to set data to client ZK, will retry later", e);<a name="line.151"></a>
+<span class="sourceLineNo">152</span> }<a name="line.152"></a>
+<span class="sourceLineNo">153</span> Threads.sleep(HConstants.SOCKET_RETRY_WAIT_MS);<a name="line.153"></a>
+<span class="sourceLineNo">154</span> }<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> private final void reconnectAfterExpiration() throws InterruptedException {<a name="line.157"></a>
+<span class="sourceLineNo">158</span> LOG.warn("ZK session expired or lost. Retry a new connection...");<a name="line.158"></a>
+<span class="sourceLineNo">159</span> try {<a name="line.159"></a>
+<span class="sourceLineNo">160</span> clientZkWatcher.reconnectAfterExpiration();<a name="line.160"></a>
+<span class="sourceLineNo">161</span> } catch (IOException | KeeperException e) {<a name="line.161"></a>
+<span class="sourceLineNo">162</span> LOG.warn("Failed to reconnect to client zk after session expiration, will retry later", e);<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><a name="line.165"></a>
+<span class="sourceLineNo">166</span> @Override<a name="line.166"></a>
+<span class="sourceLineNo">167</span> public void nodeCreated(String path) {<a name="line.167"></a>
+<span class="sourceLineNo">168</span> if (!validate(path)) {<a name="line.168"></a>
+<span class="sourceLineNo">169</span> return;<a name="line.169"></a>
+<span class="sourceLineNo">170</span> }<a name="line.170"></a>
+<span class="sourceLineNo">171</span> try {<a name="line.171"></a>
+<span class="sourceLineNo">172</span> byte[] data = ZKUtil.getDataAndWatch(watcher, path);<a name="line.172"></a>
+<span class="sourceLineNo">173</span> upsertQueue(path, data);<a name="line.173"></a>
+<span class="sourceLineNo">174</span> } catch (KeeperException e) {<a name="line.174"></a>
+<span class="sourceLineNo">175</span> LOG.warn("Unexpected exception handling nodeCreated event", e);<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><a name="line.178"></a>
+<span class="sourceLineNo">179</span> @Override<a name="line.179"></a>
+<span class="sourceLineNo">180</span> public void nodeDataChanged(String path) {<a name="line.180"></a>
+<span class="sourceLineNo">181</span> if (validate(path)) {<a name="line.181"></a>
+<span class="sourceLineNo">182</span> nodeCreated(path);<a name="line.182"></a>
+<span class="sourceLineNo">183</span> }<a name="line.183"></a>
+<span class="sourceLineNo">184</span> }<a name="line.184"></a>
+<span class="sourceLineNo">185</span><a name="line.185"></a>
+<span class="sourceLineNo">186</span> @Override<a name="line.186"></a>
+<span class="sourceLineNo">187</span> public synchronized void nodeDeleted(String path) {<a name="line.187"></a>
+<span class="sourceLineNo">188</span> if (validate(path)) {<a name="line.188"></a>
+<span class="sourceLineNo">189</span> try {<a name="line.189"></a>
+<span class="sourceLineNo">190</span> if (ZKUtil.watchAndCheckExists(watcher, path)) {<a name="line.190"></a>
+<span class="sourceLineNo">191</span> nodeCreated(path);<a name="line.191"></a>
+<span class="sourceLineNo">192</span> }<a name="line.192"></a>
+<span class="sourceLineNo">193</span> } catch (KeeperException e) {<a name="line.193"></a>
+<span class="sourceLineNo">194</span> LOG.warn("Unexpected exception handling nodeDeleted event for path: " + path, e);<a name="line.194"></a>
+<span class="sourceLineNo">195</span> }<a name="line.195"></a>
+<span class="sourceLineNo">196</span> }<a name="line.196"></a>
+<span class="sourceLineNo">197</span> }<a name="line.197"></a>
+<span class="sourceLineNo">198</span><a name="line.198"></a>
+<span class="sourceLineNo">199</span> /**<a name="line.199"></a>
+<span class="sourceLineNo">200</span> * Validate whether a znode path is watched by us<a name="line.200"></a>
+<span class="sourceLineNo">201</span> * @param path the path to validate<a name="line.201"></a>
+<span class="sourceLineNo">202</span> * @return true if the znode is watched by us<a name="line.202"></a>
+<span class="sourceLineNo">203</span> */<a name="line.203"></a>
+<span class="sourceLineNo">204</span> abstract boolean validate(String path);<a name="line.204"></a>
+<span class="sourceLineNo">205</span><a name="line.205"></a>
+<span class="sourceLineNo">206</span> /**<a name="line.206"></a>
+<span class="sourceLineNo">207</span> * @return the znode(s) to watch<a name="line.207"></a>
+<span class="sourceLineNo">208</span> */<a name="line.208"></a>
+<span class="sourceLineNo">209</span> abstract Collection<String> getNodesToWatch();<a name="line.209"></a>
+<span class="sourceLineNo">210</span><a name="line.210"></a>
+<span class="sourceLineNo">211</span> /**<a name="line.211"></a>
+<span class="sourceLineNo">212</span> * Thread to synchronize znode data to client ZK cluster<a name="line.212"></a>
+<span class="sourceLineNo">213</span> */<a name="line.213"></a>
+<span class="sourceLineNo">214</span> class ClientZkUpdater extends Thread {<a name="line.214"></a>
+<span class="sourceLineNo">215</span> final String znode;<a name="line.215"></a>
+<span class="sourceLineNo">216</span> final BlockingQueue<byte[]> queue;<a name="line.216"></a>
+<span class="sourceLineNo">217</span><a name="line.217"></a>
+<span class="sourceLineNo">218</span> public ClientZkUpdater(String znode, BlockingQueue<byte[]> queue) {<a name="line.218"></a>
+<span class="sourceLineNo">219</span> this.znode = znode;<a name="line.219"></a>
+<span class="sourceLineNo">220</span> this.queue = queue;<a name="line.220"></a>
+<span class="sourceLineNo">221</span> setName("ClientZKUpdater-" + znode);<a name="line.221"></a>
+<span class="sourceLineNo">222</span> }<a name="line.222"></a>
+<span class="sourceLineNo">223</span><a name="line.223"></a>
+<span class="sourceLineNo">224</span> @Override<a name="line.224"></a>
+<span class="sourceLineNo">225</span> public void run() {<a name="line.225"></a>
+<span class="sourceLineNo">226</span> while (!server.isStopped()) {<a name="line.226"></a>
+<span class="sourceLineNo">227</span> try {<a name="line.227"></a>
+<span class="sourceLineNo">228</span> byte[] data = queue.take();<a name="line.228"></a>
+<span class="sourceLineNo">229</span> setDataForClientZkUntilSuccess(znode, data);<a name="line.229"></a>
+<span class="sourceLineNo">230</span> } catch (InterruptedException e) {<a name="line.230"></a>
+<span class="sourceLineNo">231</span> if (LOG.isDebugEnabled()) {<a name="line.231"></a>
+<span class="sourceLineNo">232</span> LOG.debug(<a name="line.232"></a>
+<span class="sourceLineNo">233</span> "Interrupted while checking whether need to update meta location to client zk");<a name="line.233"></a>
+<span class="sourceLineNo">234</span> }<a name="line.234"></a>
+<span class="sourceLineNo">235</span> Thread.currentThread().interrupt();<a name="line.235"></a>
+<span class="sourceLineNo">236</span> break;<a name="line.236"></a>
+<span class="sourceLineNo">237</span> }<a name="line.237"></a>
+<span class="sourceLineNo">238</span> }<a name="line.238"></a>
+<span class="sourceLineNo">239</span> }<a name="line.239"></a>
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+</html>
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+<!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.master.zksyncer;<a name="line.19"></a>
+<span class="sourceLineNo">020</span><a name="line.20"></a>
+<span class="sourceLineNo">021</span>import java.io.IOException;<a name="line.21"></a>
+<span class="sourceLineNo">022</span>import java.util.Collection;<a name="line.22"></a>
+<span class="sourceLineNo">023</span>import java.util.HashMap;<a name="line.23"></a>
+<span class="sourceLineNo">024</span>import java.util.Map;<a name="line.24"></a>
+<span class="sourceLineNo">025</span>import java.util.concurrent.ArrayBlockingQueue;<a name="line.25"></a>
+<span class="sourceLineNo">026</span>import java.util.concurrent.BlockingQueue;<a name="line.26"></a>
+<span class="sourceLineNo">027</span><a name="line.27"></a>
+<span class="sourceLineNo">028</span>import org.apache.commons.logging.Log;<a name="line.28"></a>
+<span class="sourceLineNo">029</span>import org.apache.commons.logging.LogFactory;<a name="line.29"></a>
+<span class="sourceLineNo">030</span>import org.apache.hadoop.hbase.HConstants;<a name="line.30"></a>
+<span class="sourceLineNo">031</span>import org.apache.hadoop.hbase.Server;<a name="line.31"></a>
+<span class="sourceLineNo">032</span>import org.apache.hadoop.hbase.util.Threads;<a name="line.32"></a>
+<span class="sourceLineNo">033</span>import org.apache.hadoop.hbase.zookeeper.ZKListener;<a name="line.33"></a>
+<span class="sourceLineNo">034</span>import org.apache.hadoop.hbase.zookeeper.ZKUtil;<a name="line.34"></a>
+<span class="sourceLineNo">035</span>import org.apache.hadoop.hbase.zookeeper.ZKWatcher;<a name="line.35"></a>
+<span class="sourceLineNo">036</span>import org.apache.yetus.audience.InterfaceAudience;<a name="line.36"></a>
+<span class="sourceLineNo">037</span>import org.apache.zookeeper.CreateMode;<a name="line.37"></a>
+<span class="sourceLineNo">038</span>import org.apache.zookeeper.KeeperException;<a name="line.38"></a>
+<span class="sourceLineNo">039</span><a name="line.39"></a>
+<span class="sourceLineNo">040</span>/**<a name="line.40"></a>
+<span class="sourceLineNo">041</span> * Tracks the target znode(s) on server ZK cluster and synchronize them to client ZK cluster if<a name="line.41"></a>
+<span class="sourceLineNo">042</span> * changed<a name="line.42"></a>
+<span class="sourceLineNo">043</span> * <p/><a name="line.43"></a>
+<span class="sourceLineNo">044</span> * The target znode(s) is given through {@link #getNodesToWatch()} method<a name="line.44"></a>
+<span class="sourceLineNo">045</span> */<a name="line.45"></a>
+<span class="sourceLineNo">046</span>@InterfaceAudience.Private<a name="line.46"></a>
+<span class="sourceLineNo">047</span>public abstract class ClientZKSyncer extends ZKListener {<a name="line.47"></a>
+<span class="sourceLineNo">048</span> private static final Log LOG = LogFactory.getLog(ClientZKSyncer.class);<a name="line.48"></a>
+<span class="sourceLineNo">049</span> private final Server server;<a name="line.49"></a>
+<span class="sourceLineNo">050</span> private final ZKWatcher clientZkWatcher;<a name="line.50"></a>
+<span class="sourceLineNo">051</span> // We use queues and daemon threads to synchronize the data to client ZK cluster<a name="line.51"></a>
+<span class="sourceLineNo">052</span> // to avoid blocking the single event thread for watchers<a name="line.52"></a>
+<span class="sourceLineNo">053</span> private final Map<String, BlockingQueue<byte[]>> queues;<a name="line.53"></a>
+<span class="sourceLineNo">054</span><a name="line.54"></a>
+<span class="sourceLineNo">055</span> public ClientZKSyncer(ZKWatcher watcher, ZKWatcher clientZkWatcher, Server server) {<a name="line.55"></a>
+<span class="sourceLineNo">056</span> super(watcher);<a name="line.56"></a>
+<span class="sourceLineNo">057</span> this.server = server;<a name="line.57"></a>
+<span class="sourceLineNo">058</span> this.clientZkWatcher = clientZkWatcher;<a name="line.58"></a>
+<span class="sourceLineNo">059</span> this.queues = new HashMap<>();<a name="line.59"></a>
+<span class="sourceLineNo">060</span> }<a name="line.60"></a>
+<span class="sourceLineNo">061</span><a name="line.61"></a>
+<span class="sourceLineNo">062</span> /**<a name="line.62"></a>
+<span class="sourceLineNo">063</span> * Starts the syncer<a name="line.63"></a>
+<span class="sourceLineNo">064</span> * @throws KeeperException if error occurs when trying to create base nodes on client ZK<a name="line.64"></a>
+<span class="sourceLineNo">065</span> */<a name="line.65"></a>
+<span class="sourceLineNo">066</span> public void start() throws KeeperException {<a name="line.66"></a>
+<span class="sourceLineNo">067</span> LOG.debug("Starting " + getClass().getSimpleName());<a name="line.67"></a>
+<span class="sourceLineNo">068</span> this.watcher.registerListener(this);<a name="line.68"></a>
+<span class="sourceLineNo">069</span> // create base znode on remote ZK<a name="line.69"></a>
+<span class="sourceLineNo">070</span> ZKUtil.createWithParents(clientZkWatcher, watcher.znodePaths.baseZNode);<a name="line.70"></a>
+<span class="sourceLineNo">071</span> // set meta znodes for client ZK<a name="line.71"></a>
+<span class="sourceLineNo">072</span> Collection<String> nodes = getNodesToWatch();<a name="line.72"></a>
+<span class="sourceLineNo">073</span> LOG.debug("Znodes to watch: " + nodes);<a name="line.73"></a>
+<span class="sourceLineNo">074</span> // initialize queues and threads<a name="line.74"></a>
+<span class="sourceLineNo">075</span> for (String node : nodes) {<a name="line.75"></a>
+<span class="sourceLineNo">076</span> BlockingQueue<byte[]> queue = new ArrayBlockingQueue<>(1);<a name="line.76"></a>
+<span class="sourceLineNo">077</span> queues.put(node, queue);<a name="line.77"></a>
+<span class="sourceLineNo">078</span> Thread updater = new ClientZkUpdater(node, queue);<a name="line.78"></a>
+<span class="sourceLineNo">079</span> updater.setDaemon(true);<a name="line.79"></a>
+<span class="sourceLineNo">080</span> updater.start();<a name="line.80"></a>
+<span class="sourceLineNo">081</span> watchAndCheckExists(node);<a name="line.81"></a>
+<span class="sourceLineNo">082</span> }<a name="line.82"></a>
+<span class="sourceLineNo">083</span> }<a name="line.83"></a>
+<span class="sourceLineNo">084</span><a name="line.84"></a>
+<span class="sourceLineNo">085</span> private void watchAndCheckExists(String node) {<a name="line.85"></a>
+<span class="sourceLineNo">086</span> try {<a name="line.86"></a>
+<span class="sourceLineNo">087</span> if (ZKUtil.watchAndCheckExists(watcher, node)) {<a name="line.87"></a>
+<span class="sourceLineNo">088</span> byte[] data = ZKUtil.getDataAndWatch(watcher, node);<a name="line.88"></a>
+<span class="sourceLineNo">089</span> if (data != null) {<a name="line.89"></a>
+<span class="sourceLineNo">090</span> // put the data into queue<a name="line.90"></a>
+<span class="sourceLineNo">091</span> upsertQueue(node, data);<a name="line.91"></a>
+<span class="sourceLineNo">092</span> } else {<a name="line.92"></a>
+<span class="sourceLineNo">093</span> // It existed but now does not, should has been tracked by our watcher, ignore<a name="line.93"></a>
+<span class="sourceLineNo">094</span> LOG.debug("Found no data from " + node);<a name="line.94"></a>
+<span class="sourceLineNo">095</span> watchAndCheckExists(node);<a name="line.95"></a>
+<span class="sourceLineNo">096</span> }<a name="line.96"></a>
+<span class="sourceLineNo">097</span> } else {<a name="line.97"></a>
+<span class="sourceLineNo">098</span> // cleanup stale ZNodes on client ZK to avoid invalid requests to server<a name="line.98"></a>
+<span class="sourceLineNo">099</span> ZKUtil.deleteNodeFailSilent(clientZkWatcher, node);<a name="line.99"></a>
+<span class="sourceLineNo">100</span> }<a name="line.100"></a>
+<span class="sourceLineNo">101</span> } catch (KeeperException e) {<a name="line.101"></a>
+<span class="sourceLineNo">102</span> server.abort("Unexpected exception during initialization, aborting", e);<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><a name="line.105"></a>
+<span class="sourceLineNo">106</span> /**<a name="line.106"></a>
+<span class="sourceLineNo">107</span> * Update the value of the single element in queue if any, or else insert.<a name="line.107"></a>
+<span class="sourceLineNo">108</span> * <p/><a name="line.108"></a>
+<span class="sourceLineNo">109</span> * We only need to synchronize the latest znode value to client ZK rather than synchronize each<a name="line.109"></a>
+<span class="sourceLineNo">110</span> * time<a name="line.110"></a>
+<span class="sourceLineNo">111</span> * @param data the data to write to queue<a name="line.111"></a>
+<span class="sourceLineNo">112</span> */<a name="line.112"></a>
+<span class="sourceLineNo">113</span> private void upsertQueue(String node, byte[] data) {<a name="line.113"></a>
+<span class="sourceLineNo">114</span> BlockingQueue<byte[]> queue = queues.get(node);<a name="line.114"></a>
+<span class="sourceLineNo">115</span> synchronized (queue) {<a name="line.115"></a>
+<span class="sourceLineNo">116</span> queue.poll();<a name="line.116"></a>
+<span class="sourceLineNo">117</span> queue.offer(data);<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><a name="line.120"></a>
+<span class="sourceLineNo">121</span> /**<a name="line.121"></a>
+<span class="sourceLineNo">122</span> * Set data for client ZK and retry until succeed. Be very careful to prevent dead loop when<a name="line.122"></a>
+<span class="sourceLineNo">123</span> * modifying this method<a name="line.123"></a>
+<span class="sourceLineNo">124</span> * @param node the znode to set on client ZK<a name="line.124"></a>
+<span class="sourceLineNo">125</span> * @param data the data to set to client ZK<a name="line.125"></a>
+<span class="sourceLineNo">126</span> * @throws InterruptedException if the thread is interrupted during process<a name="line.126"></a>
+<span class="sourceLineNo">127</span> */<a name="line.127"></a>
+<span class="sourceLineNo">128</span> private final void setDataForClientZkUntilSuccess(String node, byte[] data)<a name="line.128"></a>
+<span class="sourceLineNo">129</span> throws InterruptedException {<a name="line.129"></a>
+<span class="sourceLineNo">130</span> while (!server.isStopped()) {<a name="line.130"></a>
+<span class="sourceLineNo">131</span> try {<a name="line.131"></a>
+<span class="sourceLineNo">132</span> LOG.debug("Set data for remote " + node + ", client zk wather: " + clientZkWatcher);<a name="line.132"></a>
+<span class="sourceLineNo">133</span> ZKUtil.setData(clientZkWatcher, node, data);<a name="line.133"></a>
+<span class="sourceLineNo">134</span> break;<a name="line.134"></a>
+<span class="sourceLineNo">135</span> } catch (KeeperException.NoNodeException nne) {<a name="line.135"></a>
+<span class="sourceLineNo">136</span> // Node doesn't exist, create it and set value<a name="line.136"></a>
+<span class="sourceLineNo">137</span> try {<a name="line.137"></a>
+<span class="sourceLineNo">138</span> ZKUtil.createNodeIfNotExistsNoWatch(clientZkWatcher, node, data, CreateMode.PERSISTENT);<a name="line.138"></a>
+<span class="sourceLineNo">139</span> break;<a name="line.139"></a>
+<span class="sourceLineNo">140</span> } catch (KeeperException.ConnectionLossException<a name="line.140"></a>
+<span class="sourceLineNo">141</span> | KeeperException.SessionExpiredException ee) {<a name="line.141"></a>
+<span class="sourceLineNo">142</span> reconnectAfterExpiration();<a name="line.142"></a>
+<span class="sourceLineNo">143</span> } catch (KeeperException e) {<a name="line.143"></a>
+<span class="sourceLineNo">144</span> LOG.warn(<a name="line.144"></a>
+<span class="sourceLineNo">145</span> "Failed to create znode " + node + " due to: " + e.getMessage() + ", will retry later");<a name="line.145"></a>
+<span class="sourceLineNo">146</span> }<a name="line.146"></a>
+<span class="sourceLineNo">147</span> } catch (KeeperException.ConnectionLossException<a name="line.147"></a>
+<span class="sourceLineNo">148</span> | KeeperException.SessionExpiredException ee) {<a name="line.148"></a>
+<span class="sourceLineNo">149</span> reconnectAfterExpiration();<a name="line.149"></a>
+<span class="sourceLineNo">150</span> } catch (KeeperException e) {<a name="line.150"></a>
+<span class="sourceLineNo">151</span> LOG.debug("Failed to set data to client ZK, will retry later", e);<a name="line.151"></a>
+<span class="sourceLineNo">152</span> }<a name="line.152"></a>
+<span class="sourceLineNo">153</span> Threads.sleep(HConstants.SOCKET_RETRY_WAIT_MS);<a name="line.153"></a>
+<span class="sourceLineNo">154</span> }<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> private final void reconnectAfterExpiration() throws InterruptedException {<a name="line.157"></a>
+<span class="sourceLineNo">158</span> LOG.warn("ZK session expired or lost. Retry a new connection...");<a name="line.158"></a>
+<span class="sourceLineNo">159</span> try {<a name="line.159"></a>
+<span class="sourceLineNo">160</span> clientZkWatcher.reconnectAfterExpiration();<a name="line.160"></a>
+<span class="sourceLineNo">161</span> } catch (IOException | KeeperException e) {<a name="line.161"></a>
+<span class="sourceLineNo">162</span> LOG.warn("Failed to reconnect to client zk after session expiration, will retry later", e);<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><a name="line.165"></a>
+<span class="sourceLineNo">166</span> @Override<a name="line.166"></a>
+<span class="sourceLineNo">167</span> public void nodeCreated(String path) {<a name="line.167"></a>
+<span class="sourceLineNo">168</span> if (!validate(path)) {<a name="line.168"></a>
+<span class="sourceLineNo">169</span> return;<a name="line.169"></a>
+<span class="sourceLineNo">170</span> }<a name="line.170"></a>
+<span class="sourceLineNo">171</span> try {<a name="line.171"></a>
+<span class="sourceLineNo">172</span> byte[] data = ZKUtil.getDataAndWatch(watcher, path);<a name="line.172"></a>
+<span class="sourceLineNo">173</span> upsertQueue(path, data);<a name="line.173"></a>
+<span class="sourceLineNo">174</span> } catch (KeeperException e) {<a name="line.174"></a>
+<span class="sourceLineNo">175</span> LOG.warn("Unexpected exception handling nodeCreated event", e);<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><a name="line.178"></a>
+<span class="sourceLineNo">179</span> @Override<a name="line.179"></a>
+<span class="sourceLineNo">180</span> public void nodeDataChanged(String path) {<a name="line.180"></a>
+<span class="sourceLineNo">181</span> if (validate(path)) {<a name="line.181"></a>
+<span class="sourceLineNo">182</span> nodeCreated(path);<a name="line.182"></a>
+<span class="sourceLineNo">183</span> }<a name="line.183"></a>
+<span class="sourceLineNo">184</span> }<a name="line.184"></a>
+<span class="sourceLineNo">185</span><a name="line.185"></a>
+<span class="sourceLineNo">186</span> @Override<a name="line.186"></a>
+<span class="sourceLineNo">187</span> public synchronized void nodeDeleted(String path) {<a name="line.187"></a>
+<span class="sourceLineNo">188</span> if (validate(path)) {<a name="line.188"></a>
+<span class="sourceLineNo">189</span> try {<a name="line.189"></a>
+<span class="sourceLineNo">190</span> if (ZKUtil.watchAndCheckExists(watcher, path)) {<a name="line.190"></a>
+<span class="sourceLineNo">191</span> nodeCreated(path);<a name="line.191"></a>
+<span class="sourceLineNo">192</span> }<a name="line.192"></a>
+<span class="sourceLineNo">193</span> } catch (KeeperException e) {<a name="line.193"></a>
+<span class="sourceLineNo">194</span> LOG.warn("Unexpected exception handling nodeDeleted event for path: " + path, e);<a name="line.194"></a>
+<span class="sourceLineNo">195</span> }<a name="line.195"></a>
+<span class="sourceLineNo">196</span> }<a name="line.196"></a>
+<span class="sourceLineNo">197</span> }<a name="line.197"></a>
+<span class="sourceLineNo">198</span><a name="line.198"></a>
+<span class="sourceLineNo">199</span> /**<a name="line.199"></a>
+<span class="sourceLineNo">200</span> * Validate whether a znode path is watched by us<a name="line.200"></a>
+<span class="sourceLineNo">201</span> * @param path the path to validate<a name="line.201"></a>
+<span class="sourceLineNo">202</span> * @return true if the znode is watched by us<a name="line.202"></a>
+<span class="sourceLineNo">203</span> */<a name="line.203"></a>
+<span class="sourceLineNo">204</span> abstract boolean validate(String path);<a name="line.204"></a>
+<span class="sourceLineNo">205</span><a name="line.205"></a>
+<span class="sourceLineNo">206</span> /**<a name="line.206"></a>
+<span class="sourceLineNo">207</span> * @return the znode(s) to watch<a name="line.207"></a>
+<span class="sourceLineNo">208</span> */<a name="line.208"></a>
+<span class="sourceLineNo">209</span> abstract Collection<String> getNodesToWatch();<a name="line.209"></a>
+<span class="sourceLineNo">210</span><a name="line.210"></a>
+<span class="sourceLineNo">211</span> /**<a name="line.211"></a>
+<span class="sourceLineNo">212</span> * Thread to synchronize znode data to client ZK cluster<a name="line.212"></a>
+<span class="sourceLineNo">213</span> */<a name="line.213"></a>
+<span class="sourceLineNo">214</span> class ClientZkUpdater extends Thread {<a name="line.214"></a>
+<span class="sourceLineNo">215</span> final String znode;<a name="line.215"></a>
+<span class="sourceLineNo">216</span> final BlockingQueue<byte[]> queue;<a name="line.216"></a>
+<span class="sourceLineNo">217</span><a name="line.217"></a>
+<span class="sourceLineNo">218</span> public ClientZkUpdater(String znode, BlockingQueue<byte[]> queue) {<a name="line.218"></a>
+<span class="sourceLineNo">219</span> this.znode = znode;<a name="line.219"></a>
+<span class="sourceLineNo">220</span> this.queue = queue;<a name="line.220"></a>
+<span class="sourceLineNo">221</span> setName("ClientZKUpdater-" + znode);<a name="line.221"></a>
+<span class="sourceLineNo">222</span> }<a name="line.222"></a>
+<span class="sourceLineNo">223</span><a name="line.223"></a>
+<span class="sourceLineNo">224</span> @Override<a name="line.224"></a>
+<span class="sourceLineNo">225</span> public void run() {<a name="line.225"></a>
+<span class="sourceLineNo">226</span> while (!server.isStopped()) {<a name="line.226"></a>
+<span class="sourceLineNo">227</span> try {<a name="line.227"></a>
+<span class="sourceLineNo">228</span> byte[] data = queue.take();<a name="line.228"></a>
+<span class="sourceLineNo">229</span> setDataForClientZkUntilSuccess(znode, data);<a name="line.229"></a>
+<span class="sourceLineNo">230</span> } catch (InterruptedException e) {<a name="line.230"></a>
+<span class="sourceLineNo">231</span> if (LOG.isDebugEnabled()) {<a name="line.231"></a>
+<span class="sourceLineNo">232</span> LOG.debug(<a name="line.232"></a>
+<span class="sourceLineNo">233</span> "Interrupted while checking whether need to update meta location to client zk");<a name="line.233"></a>
+<span class="sourceLineNo">234</span> }<a name="line.234"></a>
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+</html>
http://git-wip-us.apache.org/repos/asf/hbase-site/blob/2a4c7d89/devapidocs/src-html/org/apache/hadoop/hbase/master/zksyncer/MasterAddressSyncer.html
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diff --git a/devapidocs/src-html/org/apache/hadoop/hbase/master/zksyncer/MasterAddressSyncer.html b/devapidocs/src-html/org/apache/hadoop/hbase/master/zksyncer/MasterAddressSyncer.html
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+<!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.master.zksyncer;<a name="line.19"></a>
+<span class="sourceLineNo">020</span><a name="line.20"></a>
+<span class="sourceLineNo">021</span>import java.util.ArrayList;<a name="line.21"></a>
+<span class="sourceLineNo">022</span>import java.util.Collection;<a name="line.22"></a>
+<span class="sourceLineNo">023</span><a name="line.23"></a>
+<span class="sourceLineNo">024</span>import org.apache.hadoop.hbase.Server;<a name="line.24"></a>
+<span class="sourceLineNo">025</span>import org.apache.hadoop.hbase.zookeeper.ZKWatcher;<a name="line.25"></a>
+<span class="sourceLineNo">026</span>import org.apache.yetus.audience.InterfaceAudience;<a name="line.26"></a>
+<span class="sourceLineNo">027</span><a name="line.27"></a>
+<span class="sourceLineNo">028</span>/**<a name="line.28"></a>
+<span class="sourceLineNo">029</span> * Tracks the active master address on server ZK cluster and synchronize them to client ZK cluster<a name="line.29"></a>
+<span class="sourceLineNo">030</span> * if changed<a name="line.30"></a>
+<span class="sourceLineNo">031</span> */<a name="line.31"></a>
+<span class="sourceLineNo">032</span>@InterfaceAudience.Private<a name="line.32"></a>
+<span class="sourceLineNo">033</span>public class MasterAddressSyncer extends ClientZKSyncer {<a name="line.33"></a>
+<span class="sourceLineNo">034</span> private final String masterAddressZNode;<a name="line.34"></a>
+<span class="sourceLineNo">035</span><a name="line.35"></a>
+<span class="sourceLineNo">036</span> public MasterAddressSyncer(ZKWatcher watcher, ZKWatcher clientZkWatcher, Server server) {<a name="line.36"></a>
+<span class="sourceLineNo">037</span> super(watcher, clientZkWatcher, server);<a name="line.37"></a>
+<span class="sourceLineNo">038</span> masterAddressZNode = watcher.znodePaths.masterAddressZNode;<a name="line.38"></a>
+<span class="sourceLineNo">039</span> }<a name="line.39"></a>
+<span class="sourceLineNo">040</span><a name="line.40"></a>
+<span class="sourceLineNo">041</span> @Override<a name="line.41"></a>
+<span class="sourceLineNo">042</span> boolean validate(String path) {<a name="line.42"></a>
+<span class="sourceLineNo">043</span> return path.equals(masterAddressZNode);<a name="line.43"></a>
+<span class="sourceLineNo">044</span> }<a name="line.44"></a>
+<span class="sourceLineNo">045</span><a name="line.45"></a>
+<span class="sourceLineNo">046</span> @Override<a name="line.46"></a>
+<span class="sourceLineNo">047</span> Collection<String> getNodesToWatch() {<a name="line.47"></a>
+<span class="sourceLineNo">048</span> ArrayList<String> toReturn = new ArrayList<>();<a name="line.48"></a>
+<span class="sourceLineNo">049</span> toReturn.add(masterAddressZNode);<a name="line.49"></a>
+<span class="sourceLineNo">050</span> return toReturn;<a name="line.50"></a>
+<span class="sourceLineNo">051</span> }<a name="line.51"></a>
+<span class="sourceLineNo">052</span>}<a name="line.52"></a>
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+</pre>
+</div>
+</body>
+</html>
http://git-wip-us.apache.org/repos/asf/hbase-site/blob/2a4c7d89/devapidocs/src-html/org/apache/hadoop/hbase/master/zksyncer/MetaLocationSyncer.html
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@@ -0,0 +1,118 @@
+<!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.master.zksyncer;<a name="line.19"></a>
+<span class="sourceLineNo">020</span><a name="line.20"></a>
+<span class="sourceLineNo">021</span>import java.util.Collection;<a name="line.21"></a>
+<span class="sourceLineNo">022</span><a name="line.22"></a>
+<span class="sourceLineNo">023</span>import org.apache.hadoop.hbase.Server;<a name="line.23"></a>
+<span class="sourceLineNo">024</span>import org.apache.hadoop.hbase.zookeeper.ZKWatcher;<a name="line.24"></a>
+<span class="sourceLineNo">025</span>import org.apache.yetus.audience.InterfaceAudience;<a name="line.25"></a>
+<span class="sourceLineNo">026</span><a name="line.26"></a>
+<span class="sourceLineNo">027</span>/**<a name="line.27"></a>
+<span class="sourceLineNo">028</span> * Tracks the meta region locations on server ZK cluster and synchronize them to client ZK cluster<a name="line.28"></a>
+<span class="sourceLineNo">029</span> * if changed<a name="line.29"></a>
+<span class="sourceLineNo">030</span> */<a name="line.30"></a>
+<span class="sourceLineNo">031</span>@InterfaceAudience.Private<a name="line.31"></a>
+<span class="sourceLineNo">032</span>public class MetaLocationSyncer extends ClientZKSyncer {<a name="line.32"></a>
+<span class="sourceLineNo">033</span> public MetaLocationSyncer(ZKWatcher watcher, ZKWatcher clientZkWatcher, Server server) {<a name="line.33"></a>
+<span class="sourceLineNo">034</span> super(watcher, clientZkWatcher, server);<a name="line.34"></a>
+<span class="sourceLineNo">035</span> }<a name="line.35"></a>
+<span class="sourceLineNo">036</span><a name="line.36"></a>
+<span class="sourceLineNo">037</span> @Override<a name="line.37"></a>
+<span class="sourceLineNo">038</span> boolean validate(String path) {<a name="line.38"></a>
+<span class="sourceLineNo">039</span> return watcher.znodePaths.isAnyMetaReplicaZNode(path);<a name="line.39"></a>
+<span class="sourceLineNo">040</span> }<a name="line.40"></a>
+<span class="sourceLineNo">041</span><a name="line.41"></a>
+<span class="sourceLineNo">042</span> @Override<a name="line.42"></a>
+<span class="sourceLineNo">043</span> Collection<String> getNodesToWatch() {<a name="line.43"></a>
+<span class="sourceLineNo">044</span> return watcher.znodePaths.metaReplicaZNodes.values();<a name="line.44"></a>
+<span class="sourceLineNo">045</span> }<a name="line.45"></a>
+<span class="sourceLineNo">046</span>}<a name="line.46"></a>
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+</body>
+</html>