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doc: add a section about repmgrd and service commands etc.

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Ian Barwick
2018-04-05 11:47:35 +09:00
parent 644a56a645
commit b4dab86c3b
2 changed files with 101 additions and 18 deletions
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116
doc/repmgrd-configuration.sgml
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@@ -33,26 +33,32 @@
</para>
<para>
When <varname>failover</varname> is set to <literal>automatic</literal>, upon detecting failure
of the current primary, <application>repmgrd</application> will execute one of
<varname>promote_command</varname> or <varname>follow_command</varname>,
depending on whether the current server is to become the new primary, or
needs to follow another server which has become the new primary. Note that
these commands can be any valid shell script which results in one of these
two actions happening, but if &repmgr;'s <command>standby follow</command> or
<command>standby promote</command>
commands are not executed (either directly as shown here, or from a script which
performs other actions), the &repmgr; metadata will not be updated and
&repmgr; will no longer function reliably.
of the current primary, <application>repmgrd</application> will execute either
<varname>promote_command</varname> (if the current server is to become the new primary) or
<varname>follow_command</varname> (if the current serverneeds to follow another server which has
become the new primary.
</para>
<note>
<para>
These commands can be any valid shell script which results in one of these
two actions happening, but if &repmgr;'s <command>standby follow</command> or
<command>standby promote</command>
commands are not executed (either directly as shown here, or from a script which
performs other actions), the &repmgr; metadata will not be updated and
&repmgr; will no longer function reliably.
</para>
</note>
<para>
The <varname>follow_command</varname> should provide the <literal>--upstream-node-id=%n</literal>
option to <command>repmgr standby follow</command>; the <literal>%n</literal> will be replaced by
<application>repmgrd</application> with the ID of the new primary node. If this is not provided, &repmgr;
will attempt to determine the new primary by itself, but if the
original primary comes back online after the new primary is promoted, there is a risk that
<command>repmgr standby follow</command> will result in the node continuing to follow
the original primary.
The <varname>follow_command</varname> should provide the <literal>--upstream-node-id=%n</literal>
option to <command>repmgr standby follow</command>; the <literal>%n</literal> will be replaced by
<application>repmgrd</application> with the ID of the new primary node. If this is not provided, &repmgr;
will attempt to determine the new primary by itself, but if the
original primary comes back online after the new primary is promoted, there is a risk that
<command>repmgr standby follow</command> will result in the node continuing to follow
the original primary.
</para>
<sect1 id="repmgrd-connection-settings">
<title>repmgrd connection settings</title>
<para>
@@ -76,6 +82,82 @@
<ulink url="https://www.postgresql.org/docs/current/static/libpq-connect.html#LIBPQ-PARAMKEYWORDS">PostgreSQL documentation</ulink>.
</para>
</sect1>
<sect1 id="repmgrd-service-command">
<indexterm>
<primary>service commands</primary>
<secondary>repmgrd</secondary>
</indexterm>
<title>repmgrd and service commands</title>
<para>
By default, &repmgr; will use <application>pg_ctl</application> to
stop, start, restart, reloadthe PostgreSQL cluster.
However, if installed from a package, particularly under
<application>pg_ctl</application>, it's advisable to specify
the appropriate service commands to perform these options.
</para>
<para>
To do this, specify the appropriate command for each action
in <filename>repmgr.conf</filename> using the following configuration
parameters:
<programlisting>
service_start_command
service_stop_command
service_restart_command
service_reload_command</programlisting>
</para>
<note>
<para>
It's also possible to specify a <varname>service_promote_command</varname>;
this overrides any value contained in the setting <varname>promote_command</varname>.
This is intended for systems which provide a package-level promote command,
such as Debian's <application>pg_ctlcluster</application>.
</para>
</note>
<para>
To confirm which command &repmgr; will execute for each action, use
<command>repmgr node service --list --action=...</command>, e.g.:
<programlisting>
repmgr -f /etc/repmgr.conf node service --list --action=stop
repmgr -f /etc/repmgr.conf node service --list --action=start
repmgr -f /etc/repmgr.conf node service --list --action=restart
repmgr -f /etc/repmgr.conf node service --list --action=reload</programlisting>
</para>
<para>
These commands will be executed by the system user which &repmgr; runs as (usually <literal>postgres</literal>)
and will probably require passwordless sudo access to be able to execute the command.
</para>
<para>
For example, using <application>systemd</application> on CentOS 7, the service commands can be
set as follows:
<programlisting>
service_start_command = 'sudo systemctl start postgresql-9.6'
service_stop_command = 'sudo systemctl stop postgresql-9.6'
service_restart_command = 'sudo systemctl restart postgresql-9.6'</programlisting>
and <filename>/etc/sudoers</filename> should be set as follows:
<programlisting>
Defaults:postgres !requiretty
postgres ALL = NOPASSWD: /usr/bin/systemctl stop postgresql-9.6, \
/usr/bin/systemctl start postgresql-9.6, \
/usr/bin/systemctl restart postgresql-9.6</programlisting>
</para>
<note>
<para>
If using <application>systemd</application>, ensure you have <varname>RemoteIPC</varname> set to <literal>off</literal>.
See the <ulink url="https://wiki.postgresql.org/wiki/Systemd">systemd</ulink>
entry in the <ulink url="https://wiki.postgresql.org/wiki/Main_Page">PostgreSQL wiki</ulink> for details.
</para>
</note>
</sect1>
<sect1 id="repmgrd-log-rotation">
<title>repmgrd log rotation</title>
<para>

3
doc/switchover.sgml
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@@ -76,11 +76,12 @@
<para>
Double-check which commands will be used to stop/start/restart the current
primary; on the primary execute:
primary; on the current primary execute:
<programlisting>
repmgr -f /etc/repmgr.conf node service --list --action=stop
repmgr -f /etc/repmgr.conf node service --list --action=start
repmgr -f /etc/repmgr.conf node service --list --action=restart</programlisting>
</para>
<para>