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141 lines
6.7 KiB
HTML
<?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>Converting Existing Environments for Replication</title>
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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="utilities.html" title="Chapter 4. Utilities" />
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<link rel="prev" href="dbbackup.html" title="Backing up a Replicated Application" />
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<link rel="next" href="monitors.html" title="Chapter 5. Writing Monitor Nodes" />
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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">Converting Existing Environments for Replication</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="dbbackup.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 4. Utilities</th>
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<td width="20%" align="right"> <a accesskey="n" href="monitors.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="enablerep"></a>Converting Existing Environments for Replication</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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JE HA environments log files contain information and data
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used only by replication. Non-replicated environments are
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lacking this information, so in order to use a
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previously-existing non-replicated environment in an HA
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application, it must undergo a one time conversion.
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</p>
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<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
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<h3 class="title">Note</h3>
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<p>
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If you try to open a non-replicated environment as a
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replicated environment, the operation will throw an
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<a class="ulink" href="http://java.sun.com/j2se/1.5.0/docs/api/java/lang/UnsupportedOperationException.html" target="_top">UnsupportedOperationException</a>. This is the only way your
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code can tell if an environment needs to be converted.
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</p>
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</div>
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<p>
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You use the <a class="ulink" href="../java/com/sleepycat/je/rep/util/DbEnableReplication.html" target="_top">DbEnableReplication</a> class to perform this
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one-time conversion. This class is particularly useful if you
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want to prototype a standalone transactional application, and
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then add in replication after the transactional application is
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working as desired.
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</p>
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<p>
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The conversion process is one-way; once an environment
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directory is converted, the rules that govern
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<a class="ulink" href="../java/com/sleepycat/je/rep/ReplicatedEnvironment.html" target="_top">ReplicatedEnvironment</a> apply. This means the environment can
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no longer be opened for writes by a standalone <a class="ulink" href="../java/com/sleepycat/je/Environment.html" target="_top">Environment</a> handle
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(however, it still can be opened by a standalone
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<a class="ulink" href="../java/com/sleepycat/je/Environment.html" target="_top">Environment</a> handle in read-only mode).
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</p>
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<p>
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Note that <a class="ulink" href="../java/com/sleepycat/je/rep/util/DbEnableReplication.html" target="_top">DbEnableReplication</a> only adds a minimum amount of
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replication metadata. The conversion process is not in any way
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dependent on the size of the environment you are converting.
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</p>
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<p>
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The converted environment can be used to start a new
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replication group. After conversion, the environment can be
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opened as a <a class="ulink" href="../java/com/sleepycat/je/rep/ReplicatedEnvironment.html" target="_top">ReplicatedEnvironment</a>. Additional nodes that join
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the group are then populated with data from the converted
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environment.
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</p>
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<p>
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For example:
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</p>
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<pre class="programlisting">// Create the first node using an existing environment
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DbEnableReplication converter =
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new DbEnableReplication(envDirMars, // env home dir
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"UniversalRepGroup", // group name
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"nodeMars", // node name
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"mars:5001"); // node host,port
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converter.convert();
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ReplicatedEnvironment nodeMars =
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new ReplicatedEnvironment(envDirMars, ...);
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// Bring up additional nodes, which will be initialized from
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// nodeMars.
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ReplicationConfig repConfig = new ReplicationConfig();
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try {
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repConfig.setGroupName("UniversalRepGroup");
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repConfig.setNodeName("nodeVenus");
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repConfig.setNodeHostPort("venus:5008");
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repConfig.setHelperHosts("mars:5001");
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nodeVenus = new ReplicatedEnvironment(envDirVenus,
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repConfig,
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envConfig);
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} catch (InsufficientLogException insufficientLogEx) {
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// log files will be copied from another node in the group
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NetworkRestore restore = new NetworkRestore();
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restore.execute(insufficientLogEx, new NetworkRestoreConfig());
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// try opening the node now
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nodeVenus = new ReplicatedEnvironment(envDirVenus,
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repConfig,
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envConfig);
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} </pre>
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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="dbbackup.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="utilities.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="monitors.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">Backing up a Replicated Application </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"> Chapter 5. Writing Monitor Nodes</td>
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</tr>
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</table>
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</body>
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</html>
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