doc: improve configuration documentation

With special attention to setting service commands, and extra special
mention of "pg_ctlcluster" for Debian/Ubuntu users.
This commit is contained in:
Ian Barwick
2018-04-19 16:46:41 +09:00
parent 65c90a2a64
commit 91ca997d40
7 changed files with 270 additions and 132 deletions

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@@ -1,10 +1,10 @@
<sect1 id="configuration-file-settings" xreflabel="configuration file settings"> <sect1 id="configuration-file-settings" xreflabel="configuration file settings">
<indexterm> <indexterm>
<primary>repmgr.conf</primary> <primary>repmgr.conf</primary>
<secondary>settings</secondary> <secondary>basic settings</secondary>
</indexterm> </indexterm>
<title>Configuration file settings</title> <title>Basic configuration file settings</title>
<para> <para>
Each <filename>repmgr.conf</filename> file must contain the following parameters: Each <filename>repmgr.conf</filename> file must contain the following parameters:
</para> </para>
@@ -92,7 +92,10 @@
<para> <para>
For a full list of annotated configuration items, see the file For a full list of annotated configuration items, see the file
<ulink url="https://raw.githubusercontent.com/2ndQuadrant/repmgr/master/repmgr.conf.sample">repmgr.conf.sample</>. <ulink url="https://raw.githubusercontent.com/2ndQuadrant/repmgr/master/repmgr.conf.sample">repmgr.conf.sample</ulink>.
</para>
<para>
For <application>repmgrd</application>-specific settings, see <xref linkend="repmgrd-configuration">.
</para> </para>
<note> <note>

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@@ -0,0 +1,111 @@
<sect1 id="configuration-service-commands" xreflabel="service command settings">
<indexterm>
<primary>repmgr.conf</primary>
<secondary>service command settings</secondary>
</indexterm>
<title>Service command settings</title>
<para>
In some circumstances, &repmgr; (and <application>repmgrd</application>) need to
be able to stop, start or restart PostgreSQL. &repmgr; commands which need to do this
include <link linkend="repmgr-standby-follow"><command>repmgr standby follow</command></link>,
<link linkend="repmgr-standby-switchover"><command>repmgr standby switchover</command></link> and
<link linkend="repmgr-node-rejoin"><command>repmgr node rejoin</command></link>.
</para>
<para>
By default, &repmgr; will use PostgreSQL's <command>pg_ctl</command> to control the PostgreSQL
server. However this can lead to various problems, particularly when PostgreSQL has been
installed from packages, and expecially so if <application>systemd</application> is in use.
</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>
<para>
With this in mind, we recommend to <emphasis>always</emphasis> configure &repmgr; to use the
available system service commands.
</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'
service_reload_command = 'sudo systemctl reload 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 \
/usr/bin/systemctl reload postgresql-9.6</programlisting>
</para>
<important>
<indexterm>
<primary>pg_ctlcluster</primary>
<secondary>service command settings</secondary>
</indexterm>
<para>
Debian/Ubuntu users: instead of calling <command>sudo systemctl</command> directly, use
<command>sudo pg_ctlcluster</command>, e.g.:
<programlisting>
service_start_command = 'sudo pg_ctlcluster 9.6 main start'
service_stop_command = 'sudo pg_ctlcluster 9.6 main stop'
service_restart_command = 'sudo pg_ctlcluster 9.6 main restart'
service_reload_command = 'sudo pg_ctlcluster 9.6 main reload'</programlisting>
and set <filename>/etc/sudoers</filename> accordingly.
</para>
<para>
While <command>pg_ctlcluster</command> should work, it's strongly recommended
to use <command>sudo pg_ctlcluster</command> on <application>systemd</application>
systems, to ensure <application>systemd</application> has a correct picture of
the PostgreSQL application state.
</para>
</important>
</sect1>

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@@ -3,6 +3,7 @@
&configuration-file; &configuration-file;
&configuration-file-settings; &configuration-file-settings;
&configuration-service-commands;
<sect1 id="configuration-permissions" xreflabel="User permissions"> <sect1 id="configuration-permissions" xreflabel="User permissions">
<indexterm> <indexterm>

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@@ -39,6 +39,7 @@
<!ENTITY configuration SYSTEM "configuration.sgml"> <!ENTITY configuration SYSTEM "configuration.sgml">
<!ENTITY configuration-file SYSTEM "configuration-file.sgml"> <!ENTITY configuration-file SYSTEM "configuration-file.sgml">
<!ENTITY configuration-file-settings SYSTEM "configuration-file-settings.sgml"> <!ENTITY configuration-file-settings SYSTEM "configuration-file-settings.sgml">
<!ENTITY configuration-service-commands SYSTEM "configuration-service-commands.sgml">
<!ENTITY cloning-standbys SYSTEM "cloning-standbys.sgml"> <!ENTITY cloning-standbys SYSTEM "cloning-standbys.sgml">
<!ENTITY promoting-standby SYSTEM "promoting-standby.sgml"> <!ENTITY promoting-standby SYSTEM "promoting-standby.sgml">
<!ENTITY follow-new-primary SYSTEM "follow-new-primary.sgml"> <!ENTITY follow-new-primary SYSTEM "follow-new-primary.sgml">

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@@ -1,63 +1,145 @@
<chapter id="repmgrd-configuration"> <chapter id="repmgrd-configuration">
<indexterm> <indexterm>
<primary>repmgrd</primary> <primary>repmgrd</primary>
<secondary>configuration</secondary> <secondary>configuration</secondary>
</indexterm> </indexterm>
<title>repmgrd configuration</title> <title>repmgrd configuration</title>
<para>
To use <application>repmgrd</application>, its associated function library must be
included in <filename>postgresql.conf</filename> with:
<programlisting> <para>
shared_preload_libraries = 'repmgr'</programlisting> <application>repmgrd</application> is a daemon which runs on each PostgreSQL node,
</para> monitoring the local node, and (unless it's the primary node) the upstream server
<para> (the primary server or with cascading replication, another standby) which it's
Changing this setting requires a restart of PostgreSQL; for more details see connected to.
the <ulink url="https://www.postgresql.org/docs/current/static/runtime-config-client.html#GUC-SHARED-PRELOAD-LIBRARIES">PostgreSQL documentation</ulink>. </para>
</para> <para>
<para> <application>repmgrd</application> can be configured to provide failover
Additionally the following <application>repmgrd</application> options *must* be set in capability in case the primary upstream node becomes unreachable, and/or
<filename>repmgr.conf</filename> (adjust configuration file locations as appropriate): provide monitoring data to the &repmgr; metadatabase.
<programlisting> </para>
failover=automatic
promote_command='repmgr standby promote -f /etc/repmgr.conf --log-to-file'
follow_command='repmgr standby follow -f /etc/repmgr.conf --log-to-file --upstream-node-id=%n'</programlisting>
</para>
<para>
Note that the <literal>--log-to-file</literal> option will cause
output generated by the &repmgr; command, when executed by <application>repmgrd</application>,
to be logged to the same destination configured to receive log output for <application>repmgrd</application>.
See <filename>repmgr.conf.sample</filename> for further <application>repmgrd</application>-specific settings.
</para>
<para>
When <varname>failover</varname> is set to <literal>automatic</literal>, upon detecting failure
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> <sect1 id="repmgrd-basic-configuration">
The <varname>follow_command</varname> should provide the <literal>--upstream-node-id=%n</literal> <title>repmgrd basic configuration</title>
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; <para>
will attempt to determine the new primary by itself, but if the To use <application>repmgrd</application>, its associated function library <emphasis>must</emphasis> be
original primary comes back online after the new primary is promoted, there is a risk that included in <filename>postgresql.conf</filename> with:
<command>repmgr standby follow</command> will result in the node continuing to follow
the original primary. <programlisting>
</para> shared_preload_libraries = 'repmgr'</programlisting>
</para>
<para>
Changing this setting requires a restart of PostgreSQL; for more details see
the <ulink url="https://www.postgresql.org/docs/current/static/runtime-config-client.html#GUC-SHARED-PRELOAD-LIBRARIES">PostgreSQL documentation</ulink>.
</para>
<sect2 id="repmgrd-automatic-failover-configuration">
<title>automatic failover configuration</title>
<para>
If using automatic failover, the following <application>repmgrd</application> options *must* be set in
<filename>repmgr.conf</filename> :
<programlisting>
failover=automatic
promote_command='/usr/bin/repmgr standby promote -f /etc/repmgr.conf --log-to-file'
follow_command='/usr/bin/repmgr standby follow -f /etc/repmgr.conf --log-to-file --upstream-node-id=%n'</programlisting>
</para>
<para>
Adjust file paths as appropriate; we recomment specifying the full path to the &repmgr; binary.
</para>
<para>
Note that the <literal>--log-to-file</literal> option will cause
output generated by the &repmgr; command, when executed by <application>repmgrd</application>,
to be logged to the same destination configured to receive log output for <application>repmgrd</application>.
See <filename><ulink url="https://raw.githubusercontent.com/2ndQuadrant/repmgr/master/repmgr.conf.sample">repmgr.conf.sample</ulink></filename>
for further <application>repmgrd</application>-specific settings.
</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:
</para>
<itemizedlist spacing="compact" mark="bullet">
<listitem>
<simpara>
<varname>promote_command</varname> (if the current server is to become the new primary)
</simpara>
</listitem>
<listitem>
<simpara>
<varname>follow_command</varname> (if the current server needs to follow another server which has
become the new primary)
</simpara>
</listitem>
</itemizedlist>
<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.
</para>
</sect2>
<sect2 id="repmgrd-service-configuration">
<indexterm>
<primary>repmgrd</primary>
<secondary>PostgreSQL service configuration</secondary>
</indexterm>
<title>PostgreSQL service configuration</title>
<para>
If using automatic failover, currently <application>repmgrd</application> will need to execute
<link linkend="repmgr-standby-follow"><command>repmgr standby follow</command></link>
to restart PostgreSQL on standbys to have them follow a new primary.
</para>
<para>
To ensure this happens smoothly, it's essential to provide the appropriate system/service restart
command appropriate to your operating system via <varname>service_restart_command</varname>
in <filename>repmgr.conf</filename>. If you don't do this, <application>repmgrd</application>
will default to using <command>pg_ctl</command>, which can result in unexpected problems,
particularly on <application>systemd</application>-based systems.
</para>
<para>
For more details, see <xref linkend="configuration-service-commands">.
</para>
</sect2>
<sect2 id="repmgrd-monitoring-configuration">
<indexterm>
<primary>repmgrd</primary>
<secondary>monitoring configuration</secondary>
</indexterm>
<title>Monitoring configuration</title>
<para>
To enable monitoring, set:
<programlisting>
monitoring_history=yes</programlisting>
in <filename>repmgr.conf</filename>.
</para>
<para>
The default monitoring interval is 2 seconds; this value can be explicitly set using:
<programlisting>
monitor_interval_secs=&lt;seconds&gt;</programlisting>
in <filename>repmgr.conf</filename>.
</para>
<para>
For more details on monitoring, see <xref linkend="repmgrd-monitoring">.
</para>
</sect2>
</sect1>
<sect1 id="repmgrd-connection-settings"> <sect1 id="repmgrd-connection-settings">
<title>repmgrd connection settings</title> <title>repmgrd connection settings</title>
@@ -84,86 +166,19 @@
</sect1> </sect1>
<sect1 id="repmgrd-service-command">
<sect1 id="repmgrd-log-rotation">
<indexterm> <indexterm>
<primary>service commands</primary> <primary>log rotation</primary>
<secondary>repmgrd</secondary> <secondary>repmgrd</secondary>
</indexterm> </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> <title>repmgrd log rotation</title>
<para> <para>
To ensure the current <application>repmgrd</application> logfile does not grow To ensure the current <application>repmgrd</application> logfile
indefinitely, configure your system's <command>logrotate</command> to (specified in <filename>repmgr.conf</filename> with the parameter
regularly rotate it. <option>log_file</option> does not grow indefinitely, configure your
system's <command>logrotate</command> to regularly rotate it.
</para> </para>
<para> <para>
Sample configuration to rotate logfiles weekly with retention for Sample configuration to rotate logfiles weekly with retention for

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@@ -3,6 +3,10 @@
<primary>repmgrd</primary> <primary>repmgrd</primary>
<secondary>monitoring</secondary> <secondary>monitoring</secondary>
</indexterm> </indexterm>
<indexterm>
<primary>monitoring</primary>
<secondary>with repmgrd</secondary>
</indexterm>
<title>Monitoring with repmgrd</title> <title>Monitoring with repmgrd</title>
<para> <para>

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@@ -290,6 +290,9 @@ ssh_options='-q -o ConnectTimeout=10' # Options to append to "ssh"
# /usr/bin/systemctl start postgresql-9.6, \ # /usr/bin/systemctl start postgresql-9.6, \
# /usr/bin/systemctl restart postgresql-9.6 # /usr/bin/systemctl restart postgresql-9.6
# #
# Debian/Ubuntu users: use "sudo pg_ctlcluster" to execute service control commands.
#
# For more details, see: https://repmgr.org/docs/4.0/configuration-service-commands.html
#service_start_command = '' #service_start_command = ''
#service_stop_command = '' #service_stop_command = ''