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107 lines
4.8 KiB
HTML
107 lines
4.8 KiB
HTML
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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>Secondary Nodes</title>
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<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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<link rel="start" href="index.html" title="Getting Started with Berkeley DB, Java Edition High Availability Applications" />
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<link rel="up" href="progoverview.html" title="Chapter 2. Replication API First Steps" />
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<link rel="prev" href="replicawrites.html" title="Managing Write Requests at a Replica" />
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<link rel="next" href="timesync.html" title="Time Synchronization" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 12.2.7.5</p>
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</div>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">Secondary Nodes</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="replicawrites.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 2. Replication API First Steps</th>
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<td width="20%" align="right"> <a accesskey="n" href="timesync.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="secondary"></a>Secondary Nodes</h2>
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</div>
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</div>
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</div>
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<p>
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If you are creating a replication group where there will be higher
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latency network connections between some nodes and the rest of the
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replication group, typically because the nodes are located in
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distant geographical regions, then it may be useful to create
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those distant nodes nodes as Secondary nodes. Secondary nodes are
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nodes that only serve as read-only Replicas. They cannot become
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Masters, participate in elections, or provide acknowledgements for
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commit operations. Secondary nodes can be used to provide a
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distant location with quick access to read-only data, although the
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data may be somewhat out of date due to replication delays over
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the high latency link. By using Secondary nodes for the nodes at a
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distance, the Electable nodes will be able to perform elections
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and provide acknowledgments without experiencing network delays
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associated with higher latency connections to the Secondary nodes.
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</p>
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<p>
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Here is an example of how to create a Secondary node that can join
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an existing group of Electable nodes:
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</p>
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<pre class="programlisting">EnvironmentConfig envConfig = new EnvironmentConfig();
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envConfig.setAllowCreate(true);
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envConfig.setTransactional(true);
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// Identify the secondary node
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ReplicationConfig electableRepConfig =
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new ReplicationConfig("PlanetaryRepGroup",
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"Mars",
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"mars.example.com:500");
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// Configure the node to be a secondary node
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repConfig.setNodeType(NodeType.SECONDARY);
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// Specify one of the electable nodes as a helper
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repConfig.setHelperHosts("jupiter.example.com:5002");
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ReplicatedEnvironment repEnv =
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new ReplicatedEnvironment(envHome, repConfig, envConfig);</pre>
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<p>
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Note that, if you have created an environment with
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NodeType.SECONDARY, it is possible to convert the node from a
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Secondary node to an Electable node by restarting the environment
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with NodeType.ELECTABLE. Once an environment has been used as an
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Electable node, though, it is not possible to convert to be a
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Secondary node.
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</p>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="replicawrites.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="progoverview.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="timesync.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">Managing Write Requests at a Replica </td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top"> Time Synchronization</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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