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doc: expand repmgrd configuration section
This commit is contained in:
Ian Barwick
@@ -36,96 +36,205 @@
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<sect2 id="repmgrd-automatic-failover-configuration">
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<title>Automatic failover configuration</title>
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<title>Required configuration for automatic failover</title>
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<para>
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If using automatic failover, the following <application>repmgrd</application> options *must* be set in
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<filename>repmgr.conf</filename> :
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The following <application>repmgrd</application> options <emphasis>must</emphasis> be set in
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<filename>repmgr.conf</filename>:
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<itemizedlist spacing="compact" mark="bullet">
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<listitem>
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<simpara><option>failover</option></simpara>
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</listitem>
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<listitem>
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<simpara><option>promote_command</option></simpara>
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</listitem>
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<listitem>
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<simpara><option>follow_command</option></simpara>
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</listitem>
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</itemizedlist>
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</para>
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<para>
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Example:
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<programlisting>
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failover=automatic
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promote_command='/usr/bin/repmgr standby promote -f /etc/repmgr.conf --log-to-file'
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follow_command='/usr/bin/repmgr standby follow -f /etc/repmgr.conf --log-to-file --upstream-node-id=%n'</programlisting>
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</para>
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<para>
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Adjust file paths as appropriate; alway specify the full path to the &repmgr; binary.
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Details of each option are as follows:
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</para>
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<variablelist>
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<varlistentry>
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<note>
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<para>
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&repmgr; will not apply <option>pg_bindir</option> when executing <option>promote_command</option>
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or <option>follow_command</option>; these can be user-defined scripts so must always be
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specified with the full path.
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</para>
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</note>
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<indexterm>
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<primary>failover</primary>
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</indexterm>
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<term><option>failover</option></term>
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<listitem>
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<para>
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<option>failover</option> can be one of <literal>automatic</literal> or <literal>manual</literal>.
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</para>
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<note>
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<para>
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If <option>failover</option> is set to <literal>manual</literal>, <application>repmgrd</application>
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will not take any action if a failover situation is detected, and the node may need to
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be modified manually (e.g. by executing <command><link linkend="repmgr-standby-follow">repmgr standby follow</link></command>).
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</para>
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</note>
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</listitem>
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</varlistentry>
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<varlistentry>
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<indexterm>
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<primary>promote_command</primary>
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</indexterm>
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<term><option>promote_command</option></term>
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<listitem>
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<para>
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The program or script defined in <option>promote_command</option> will be executed
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in a failover situation when <application>repmgrd</application> determines that
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the current node is to become the new primary node.
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</para>
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<para>
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Normally <option>promote_command</option> is set as &repmgr;'s
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<command><link linkend="repmgr-standby-promote">repmgr standby promote</link></command> command.
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</para>
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<para>
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It is also possible to provide e.g. a shell script to e.g. perform user-defined tasks
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before promoting the current node. In this case the script <emphasis>must</emphasis>
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at some point execute <command><link linkend="repmgr-standby-promote">repmgr standby promote</link></command>
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to promote the node; if this is not done, &repmgr; metadata will not be updated and
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&repmgr; will no longer function reliably.
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</para>
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<para>
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Example:
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<programlisting>
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promote_command='/usr/bin/repmgr standby promote -f /etc/repmgr.conf --log-to-file'</programlisting>
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</para>
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<para>
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Note that the <literal>--log-to-file</literal> option will cause
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output generated by the &repmgr; command, when executed by <application>repmgrd</application>,
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to be logged to the same destination configured to receive log output for <application>repmgrd</application>.
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</para>
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<note>
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<para>
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&repmgr; will not apply <option>pg_bindir</option> when executing <option>promote_command</option>
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or <option>follow_command</option>; these can be user-defined scripts so must always be
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specified with the full path.
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</para>
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</note>
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</listitem>
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</varlistentry>
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<varlistentry>
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<indexterm>
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<primary>follow_command</primary>
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</indexterm>
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<term><option>follow_command</option></term>
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<listitem>
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<para>
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The program or script defined in <option>follow_command</option> will be executed
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in a failover situation when <application>repmgrd</application> determines that
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the current node is to follow the new primary node.
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</para>
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<para>
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Normally <option>follow_command</option> is set as &repmgr;'s
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<command><link linkend="repmgr-standby-follow">repmgr standby promote</link></command> command.
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</para>
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<para>
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The <option>follow_command</option> parameter
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should provide the <literal>--upstream-node-id=%n</literal>
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option to <command>repmgr standby follow</command>; the <literal>%n</literal> will be replaced by
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<application>repmgrd</application> with the ID of the new primary node. If this is not provided,
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<command>repmgr standby follow</command> will attempt to determine the new primary by itself, but if the
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original primary comes back online after the new primary is promoted, there is a risk that
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<command>repmgr standby follow</command> will result in the node continuing to follow
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the original primary.
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</para>
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<para>
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It is also possible to provide e.g. a shell script to e.g. perform user-defined tasks
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before promoting the current node. In this case the script <emphasis>must</emphasis>
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at some point execute <command><link linkend="repmgr-standby-follow">repmgr standby follow</link></command>
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to promote the node; if this is not done, &repmgr; metadata will not be updated and
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&repmgr; will no longer function reliably.
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</para>
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<para>
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Example:
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<programlisting>
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follow_command='/usr/bin/repmgr standby follow -f /etc/repmgr.conf --log-to-file --upstream-node-id=%n'</programlisting>
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</para>
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<para>
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Note that the <literal>--log-to-file</literal> option will cause
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output generated by the &repmgr; command, when executed by <application>repmgrd</application>,
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to be logged to the same destination configured to receive log output for <application>repmgrd</application>.
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</para>
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<note>
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<para>
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&repmgr; will not apply <option>pg_bindir</option> when executing <option>promote_command</option>
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or <option>follow_command</option>; these can be user-defined scripts so must always be
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specified with the full path.
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</para>
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</note>
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</listitem>
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</varlistentry>
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</variablelist>
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</sect2>
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<sect2 id="repmgrd-automatic-failover-configuration-optionanl">
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<title>Optional configuration for automatic failover</title>
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<para>
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The following configuraton options can be used to fine-tune automatic failove:
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</para>
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<variablelist>
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<varlistentry>
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<indexterm>
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<primary>connection_check_type</primary>
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</indexterm>
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<term><option>connection_check_type</option></term>
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<listitem>
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<para>
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The option <option>connection_check_type</option> is used to select the method
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<application>repmgrd</application> uses to determine whether the upstream node is available.
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</para>
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<para>
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Possible values are:
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<itemizedlist spacing="compact" mark="bullet">
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<listitem>
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<simpara>
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<literal>ping</literal> (default) - uses <command>PQping()</command> to
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determine server availability
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</simpara>
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</listitem>
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<listitem>
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<simpara>
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<literal>connection</literal> - determines server availability
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by executing an SQL statement on the node via the existing connection
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</simpara>
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</listitem>
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</itemizedlist>
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>
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Note that the <literal>--log-to-file</literal> option will cause
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output generated by the &repmgr; command, when executed by <application>repmgrd</application>,
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to be logged to the same destination configured to receive log output for <application>repmgrd</application>.
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See <filename><ulink url="https://raw.githubusercontent.com/2ndQuadrant/repmgr/master/repmgr.conf.sample">repmgr.conf.sample</ulink></filename>
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for further <application>repmgrd</application>-specific settings.
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</para>
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<para>
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When <varname>failover</varname> is set to <literal>automatic</literal>, upon detecting failure
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of the current primary, <application>repmgrd</application> will execute one of:
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</para>
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<itemizedlist spacing="compact" mark="bullet">
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<listitem>
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<simpara>
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<varname>promote_command</varname> (if the current server is to become the new primary)
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</simpara>
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</listitem>
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<listitem>
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<simpara>
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<varname>follow_command</varname> (if the current server needs to follow another server which has
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become the new primary)
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</simpara>
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</listitem>
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</itemizedlist>
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<note>
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<para>
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These commands can be any valid shell script which results in one of these
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two actions happening, but if &repmgr;'s <command>standby follow</command> or
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<command>standby promote</command>
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commands are not executed (either directly as shown here, or from a script which
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performs other actions), the &repmgr; metadata will not be updated and
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&repmgr; will no longer function reliably.
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</para>
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</note>
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<para>
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The <varname>follow_command</varname> should provide the <literal>--upstream-node-id=%n</literal>
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option to <command>repmgr standby follow</command>; the <literal>%n</literal> will be replaced by
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<application>repmgrd</application> with the ID of the new primary node. If this is not provided, &repmgr;
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will attempt to determine the new primary by itself, but if the
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original primary comes back online after the new primary is promoted, there is a risk that
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<command>repmgr standby follow</command> will result in the node continuing to follow
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the original primary.
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</para>
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<para>
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<indexterm>
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<primary>connection_check_type</primary>
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</indexterm>
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Additionally, the option <option>connection_check_type</option> to enable selection of the method
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<application>repmgrd</application> uses to determine whether the upstream node is available.
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</para>
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<para>
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Possible values are:
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<itemizedlist spacing="compact" mark="bullet">
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<listitem>
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<simpara>
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<literal>ping</literal> (default) - uses <command>PQping()</command> to
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determine server availability
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</simpara>
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</listitem>
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<listitem>
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<simpara>
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<literal>connection</literal> - determines server availability
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by executing an SQL statement on the node via the existing connection
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</simpara>
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</listitem>
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</itemizedlist>
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</para>
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</sect2>
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@@ -325,10 +325,14 @@ ssh_options='-q -o ConnectTimeout=10' # Options to append to "ssh"
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#standby_disconnect_on_failover=false # If "true", in a failover situation wait for all standbys to
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# disconnect their WAL receivers before electing a new primary
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#sibling_nodes_disconnect_timeout=30 # If "standby_disconnect_on_failover", maximum length of time (in seconds)
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# to wait for other standbys to confirm they have disconnected their
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# WAL receivers
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#primary_visibility_consensus=false # If "true", only continue with failover if no standbys have seen
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# the primary node recently
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# to wait for other standbys to confirm they have disconnected their
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# WAL receivers
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#primary_visibility_consensus=false # If "true", only continue with failover if no standbys have seen
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# the primary node recently
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#failover_validation_command= # Script to execute for an external mechanism to validate the failover
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# decision made by repmgrd. One or both of the following parameter placeholders
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# should be provided, which will be replaced by repmgrd with the appropriate
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# value: %n (node_id), %a (node_name)
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#------------------------------------------------------------------------------
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# service control commands
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