mirror of
https://github.com/berkeleydb/je.git
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148 lines
6.1 KiB
HTML
148 lines
6.1 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>Adding and Removing 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="administration.html" title="Chapter 7. Administration" />
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<link rel="prev" href="backups.html" title="Running Backups" />
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<link rel="next" href="hotupgrade.html" title="Upgrading a JE Replication Group" />
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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">Adding and Removing 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="backups.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 7. Administration</th>
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<td width="20%" align="right"> <a accesskey="n" href="hotupgrade.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="addremovenodes"></a>Adding and Removing 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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As described in <a class="xref" href="utilities.html#node-addremove" title="Adding and Removing Nodes from the Group">Adding and Removing Nodes from the Group</a>,
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a node is added to the replication group simply by starting it up
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and allowing it to perform its start-up handshake with the
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Master. Once an electable node has been added to the replication
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group, it belongs to the replication group forever, or until you
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explicitly remove it. Also, the node is uniquely identified within
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the replication group by a name that you must give it when you start
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up the process.
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</p>
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<p>
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This is worth remembering, because if you have electable nodes that
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have been added to the replication group, but which you then
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shutdown for a long period of time, your replication group might not
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be able to perform a lot of tasks, such as:
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</p>
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<div class="orderedlist">
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<ol type="1">
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<li>
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<p>
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Elect a Master.
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</p>
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</li>
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<li>
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<p>
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Add a new node to the replicated group.
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</p>
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</li>
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<li>
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<p>
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Delete a node from the replication group.
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</p>
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</li>
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<li>
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<p>
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Successfully commit a transaction (this depends on the
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durability guarantees in place for your application).
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</p>
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</li>
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</ol>
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</div>
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<p>
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All of these actions might be adversely affected by a series of
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unavailable electable nodes because in order to do these things the
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Master must be in contact with a majority of the electable nodes
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belonging to the replication group (Monitor and Secondary nodes do
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not count). So if too many electable nodes are either shutdown or
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unavailable due to a network partition event, then these functions
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can become delayed or even completely unavailable.
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</p>
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<p>
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For this reason, if you have electable nodes that you want to
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shutdown for a long time, then you should remove those nodes from
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the replication group. JE provides a utility class that allows
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for node removal, so your application developer should have provided
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you with a tool of some kind that allows you to do this as a normal
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administrative function.
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</p>
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<p>
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When removing an electable node from the replication group, remember
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that:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p>
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for best results, shut down the node first.
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</p>
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</li>
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<li>
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<p>
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a majority of the nodes must currently be in contact with
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the Master in order to acknowledge the node removal.
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</p>
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</li>
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</ul>
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</div>
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<p>
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If at some later time you want to restart the node and have it
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join the replication group, you can do this using the normal
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procedure that your application uses when starting a node for
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the first time. Be aware, however, that you cannot reuse the
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unique name that the node was using when you removed it from
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the group as an electable node. Instead, give the node a
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completely new unique name before having it rejoin the
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replication group.
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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="backups.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="administration.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="hotupgrade.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">Running Backups </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"> Upgrading a JE Replication Group</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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