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109 lines
5 KiB
HTML
109 lines
5 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>Managing Heartbeats</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="fmwrkconnectretry.html" title="Managing Connection Retries" />
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<link rel="next" href="fwrkmasterreplica.html" title="Chapter 4. Replica versus Master Processes" />
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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 11.2.5.2</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">Managing Heartbeats</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="fmwrkconnectretry.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="fwrkmasterreplica.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="heartbeats"></a>Managing Heartbeats</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 your replicated application experiences few updates,
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it is possible for the replication group to lose a
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master without noticing it. This is because normally a
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replicated application only knows that a master has
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gone missing when update activity causes messages to be
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passed between the master and replicas.
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</p>
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<p>
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To guard against this, you can configure a heartbeat.
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The heartbeat must be configured for both the master
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and each of the replicas.
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</p>
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<p>
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On the master, you configure the application to send a
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heartbeat on a defined interval when it is otherwise
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idle. Do this by using the
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<span>
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<code class="literal">DB_REP_HEARTBEAT_SEND</code> value
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to the <code class="literal">which</code> parameter of the
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<code class="methodname">DB_ENV->rep_set_timeout()</code>
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method.
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</span>
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You must also provide the method a value representing the period between heartbeats in microseconds. Note that the heartbeat is sent only if the
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system is idle.
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</p>
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<p>
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On the replica, you configure the application to listen
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for a heartbeat. The time that you configure here is
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the amount of time the replica will wait for some
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message from the master (either the heartbeat or some
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other message) before concluding that the connection is
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lost. You do this using the
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<span>
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<code class="literal">DB_REP_HEARTBEAT_MONITOR</code> value
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to the <code class="literal">which</code> parameter of the
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<code class="methodname">DB_ENV->rep_set_timeout()</code>
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method and a timeout value in microseconds.
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</span>
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</p>
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<p>
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For best results, configure the heartbeat monitor for a
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longer time interval than the heartbeat send interval.
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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="fmwrkconnectretry.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="fwrkmasterreplica.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 Connection Retries </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 4. Replica versus Master Processes</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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