2011-09-13 17:44:24 +00:00
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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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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>Managing Election Times</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 Replicated Berkeley DB Applications" />
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<link rel="up" href="repapp.html" title="Chapter 3. The DB Replication Manager" />
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<link rel="prev" href="fwrkpermmessage.html" title="Permanent Message Handling" />
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<link rel="next" href="fmwrkconnectretry.html" title="Managing Connection Retries" />
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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2012-11-14 21:35:20 +00:00
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<p>Library Version 11.2.5.3</p>
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2011-09-13 17:44:24 +00:00
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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">Managing Election Times</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="fwrkpermmessage.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 3. The DB Replication Manager</th>
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<td width="20%" align="right"> <a accesskey="n" href="fmwrkconnectretry.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="electiontimes"></a>Managing Election Times</h2>
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</div>
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</div>
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</div>
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<div class="toc">
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<dl>
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<dt>
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<span class="sect2">
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<a href="electiontimes.html#electiontimeout">Managing Election Timeouts</a>
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</span>
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</dt>
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<dt>
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<span class="sect2">
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<a href="electiontimes.html#electretrytime">Managing Election Retry Times</a>
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</span>
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</dt>
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</dl>
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</div>
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<p>
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Where it comes to elections, there are two timeout
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values with which you should be concerned: election
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timeouts and election retries.
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</p>
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<div class="sect2" 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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<h3 class="title"><a id="electiontimeout"></a>Managing Election Timeouts</h3>
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</div>
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</div>
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</div>
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<p>
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When an environment calls for an election, it will wait
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some amount of time for the other replicas in the
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replication group to respond. The amount of time
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that the environment will wait before declaring the
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election completed is the <span class="emphasis"><em>election timeout</em></span>.
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</p>
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<p>
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If the environment hears from all other known replicas before
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the election timeout occurs, the election is considered
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a success and a master is elected.
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</p>
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<p>
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If only a subset of replicas respond, then the success
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or failure of the election is determined by
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how many replicas have participated in the
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election. It only takes a simple
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majority of replicas to elect a master. If
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there are enough votes for a given environment to
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meet that standard, then the master has been
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elected and the election is considered a
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success.
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</p>
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<p>
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However, if not enough replicas have participated in
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the election when the election timeout value is
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reached, the election is considered a failure
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and a master is not elected. At this point,
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your replication group is operating without a
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master, which means that, essentially,
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your replicated application has been placed in
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read-only mode.
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</p>
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<p>
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Note, however, that the Replication Manager will attempt a
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new election after a given amount of time has
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passed. See the next section for details.
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</p>
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<p>
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You set the election timeout value using
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<code class="methodname">Environment.setReplicationTimeout()</code>.
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You pass this method the
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<code class="methodname">ReplicationTimeoutType.ELECTION_TIMEOUT</code>
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constant and a timeout value in microseconds.
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</p>
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</div>
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<div class="sect2" 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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<h3 class="title"><a id="electretrytime"></a>Managing Election Retry Times</h3>
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</div>
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</div>
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</div>
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<p>
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In the event that a election fails (see the
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previous section), an election will not be
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attempted again until the election retry
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timeout value has expired.
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</p>
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<p>
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You set the election timeout value using
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<code class="methodname">Environment.setReplicationTimeout()</code>.
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You pass this method the
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<code class="methodname">ReplicationTimeoutType.ELECTION_RETRY</code>
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constant and a retry value in microseconds.
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</p>
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<p>
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Note that this
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<span>constant</span> is only
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valid when you are using the Replication Manager. If you are
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using the Base APIs, then this
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<span>constant</span> is
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ignored.
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</p>
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</div>
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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="fwrkpermmessage.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="repapp.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="fmwrkconnectretry.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">Permanent Message Handling </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"> Managing Connection Retries</td>
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</tr>
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</table>
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</div>
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</html>
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