mirror of
https://github.com/berkeleydb/libdb.git
synced 2024-11-17 01:26:25 +00:00
171 lines
7.7 KiB
HTML
171 lines
7.7 KiB
HTML
|
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
|
|||
|
|
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
|||
|
|
<html xmlns="http://www.w3.org/1999/xhtml">
|
|||
|
|
<head>
|
|||
|
|
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
|
|||
|
|
<title>Managing Election Times</title>
|
|||
|
|
<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
|
|||
|
|
<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
|
|||
|
|
<link rel="start" href="index.html" title="Getting Started with Replicated Berkeley DB Applications" />
|
|||
|
|
<link rel="up" href="repapp.html" title="Chapter 3. The DB Replication Manager" />
|
|||
|
|
<link rel="prev" href="fwrkpermmessage.html" title="Permanent Message Handling" />
|
|||
|
|
<link rel="next" href="fmwrkconnectretry.html" title="Managing Connection Retries" />
|
|||
|
|
</head>
|
|||
|
|
<body>
|
|||
|
|
<div xmlns="" class="navheader">
|
|||
|
|
<div class="libver">
|
|||
|
|
<p>Library Version 11.2.5.2</p>
|
|||
|
|
</div>
|
|||
|
|
<table width="100%" summary="Navigation header">
|
|||
|
|
<tr>
|
|||
|
|
<th colspan="3" align="center">Managing Election Times</th>
|
|||
|
|
</tr>
|
|||
|
|
<tr>
|
|||
|
|
<td width="20%" align="left"><a accesskey="p" href="fwrkpermmessage.html">Prev</a> </td>
|
|||
|
|
<th width="60%" align="center">Chapter 3. The DB Replication Manager</th>
|
|||
|
|
<td width="20%" align="right"> <a accesskey="n" href="fmwrkconnectretry.html">Next</a></td>
|
|||
|
|
</tr>
|
|||
|
|
</table>
|
|||
|
|
<hr />
|
|||
|
|
</div>
|
|||
|
|
<div class="sect1" lang="en" xml:lang="en">
|
|||
|
|
<div class="titlepage">
|
|||
|
|
<div>
|
|||
|
|
<div>
|
|||
|
|
<h2 class="title" style="clear: both"><a id="electiontimes"></a>Managing Election Times</h2>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<div class="toc">
|
|||
|
|
<dl>
|
|||
|
|
<dt>
|
|||
|
|
<span class="sect2">
|
|||
|
|
<a href="electiontimes.html#electiontimeout">Managing Election Timeouts</a>
|
|||
|
|
</span>
|
|||
|
|
</dt>
|
|||
|
|
<dt>
|
|||
|
|
<span class="sect2">
|
|||
|
|
<a href="electiontimes.html#electretrytime">Managing Election Retry Times</a>
|
|||
|
|
</span>
|
|||
|
|
</dt>
|
|||
|
|
</dl>
|
|||
|
|
</div>
|
|||
|
|
<p>
|
|||
|
|
Where it comes to elections, there are two timeout
|
|||
|
|
values with which you should be concerned: election
|
|||
|
|
timeouts and election retries.
|
|||
|
|
</p>
|
|||
|
|
<div class="sect2" lang="en" xml:lang="en">
|
|||
|
|
<div class="titlepage">
|
|||
|
|
<div>
|
|||
|
|
<div>
|
|||
|
|
<h3 class="title"><a id="electiontimeout"></a>Managing Election Timeouts</h3>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<p>
|
|||
|
|
When an environment calls for an election, it will wait
|
|||
|
|
some amount of time for the other replicas in the
|
|||
|
|
replication group to respond. The amount of time
|
|||
|
|
that the environment will wait before declaring the
|
|||
|
|
election completed is the <span class="emphasis"><em>election timeout</em></span>.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
If the environment hears from all other known replicas before
|
|||
|
|
the election timeout occurs, the election is considered
|
|||
|
|
a success and a master is elected.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
If only a subset of replicas respond, then the success
|
|||
|
|
or failure of the election is determined by
|
|||
|
|
how many replicas have participated in the
|
|||
|
|
election. It only takes a simple
|
|||
|
|
majority of replicas to elect a master. If
|
|||
|
|
there are enough votes for a given environment to
|
|||
|
|
meet that standard, then the master has been
|
|||
|
|
elected and the election is considered a
|
|||
|
|
success.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
However, if not enough replicas have participated in
|
|||
|
|
the election when the election timeout value is
|
|||
|
|
reached, the election is considered a failure
|
|||
|
|
and a master is not elected. At this point,
|
|||
|
|
your replication group is operating without a
|
|||
|
|
master, which means that, essentially,
|
|||
|
|
your replicated application has been placed in
|
|||
|
|
read-only mode.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Note, however, that the Replication Manager will attempt a
|
|||
|
|
new election after a given amount of time has
|
|||
|
|
passed. See the next section for details.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
You set the election timeout value using
|
|||
|
|
|
|||
|
|
<span><code class="methodname">DbEnv::rep_set_timeout()</code>.</span>
|
|||
|
|
To do so, specify the
|
|||
|
|
<code class="literal">DB_REP_ELECTION_TIMEOUT</code>
|
|||
|
|
value to the <code class="literal">which</code> parameter and then a
|
|||
|
|
timeout value in microseconds to the
|
|||
|
|
<code class="literal">timeout</code> parameter.
|
|||
|
|
</p>
|
|||
|
|
</div>
|
|||
|
|
<div class="sect2" lang="en" xml:lang="en">
|
|||
|
|
<div class="titlepage">
|
|||
|
|
<div>
|
|||
|
|
<div>
|
|||
|
|
<h3 class="title"><a id="electretrytime"></a>Managing Election Retry Times</h3>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<p>
|
|||
|
|
In the event that a election fails (see the
|
|||
|
|
previous section), an election will not be
|
|||
|
|
attempted again until the election retry
|
|||
|
|
timeout value has expired.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
You set the retry timeout value using
|
|||
|
|
|
|||
|
|
<span><code class="methodname">DbEnv::rep_set_timeout()</code>.</span>
|
|||
|
|
To do so, specify the
|
|||
|
|
<code class="literal">DB_REP_ELECTION_RETRY</code>
|
|||
|
|
value to the <code class="literal">which</code> parameter and then a
|
|||
|
|
retry value in microseconds to the
|
|||
|
|
<code class="literal">timeout</code> parameter.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Note that this <span>flag</span>
|
|||
|
|
is only
|
|||
|
|
valid when you are using the Replication Manager. If you are
|
|||
|
|
using the Base APIs, then this
|
|||
|
|
<span>flag</span>
|
|||
|
|
is
|
|||
|
|
ignored.
|
|||
|
|
</p>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<div class="navfooter">
|
|||
|
|
<hr />
|
|||
|
|
<table width="100%" summary="Navigation footer">
|
|||
|
|
<tr>
|
|||
|
|
<td width="40%" align="left"><a accesskey="p" href="fwrkpermmessage.html">Prev</a> </td>
|
|||
|
|
<td width="20%" align="center">
|
|||
|
|
<a accesskey="u" href="repapp.html">Up</a>
|
|||
|
|
</td>
|
|||
|
|
<td width="40%" align="right"> <a accesskey="n" href="fmwrkconnectretry.html">Next</a></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr>
|
|||
|
|
<td width="40%" align="left" valign="top">Permanent Message Handling </td>
|
|||
|
|
<td width="20%" align="center">
|
|||
|
|
<a accesskey="h" href="index.html">Home</a>
|
|||
|
|
</td>
|
|||
|
|
<td width="40%" align="right" valign="top"> Managing Connection Retries</td>
|
|||
|
|
</tr>
|
|||
|
|
</table>
|
|||
|
|
</div>
|
|||
|
|
</body>
|
|||
|
|
</html>
|