mirror of
https://github.com/EnterpriseDB/repmgr.git
synced 2026-03-25 16:16:29 +00:00
2491b8ae52
In some circumstances, e.g. while performing a switchover, it is essential
that repmgrd does not take any kind of failover action, as this will put
the cluster into an incorrect state.
Previously it was necessary to stop repmgrd on all nodes (or at least
those nodes which repmgrd would consider as promotion candidates), however
this is a cumbersome and potentially risk-prone operation, particularly if the
replication cluster contains more than a couple of servers.
To prevent this issue from occurring, this patch introduces the ability
to "pause" repmgrd on all nodes wth a single command ("repmgr daemon pause")
which notifies repmgrd not to take any failover action until the node
is "unpaused" ("repmgr daemon unpause").
"repmgr daemon status" provides an overview of each node and whether repmgrd
is running, and if so whether it is paused.
"repmgr standby switchover" has been modified to automatically pause repmgrd
while carrying out the switchover.
See documentation for further details.
290 lines
10 KiB
Plaintext
290 lines
10 KiB
Plaintext
<refentry id="repmgr-standby-switchover">
|
|
<indexterm>
|
|
<primary>repmgr standby switchover</primary>
|
|
</indexterm>
|
|
|
|
<refmeta>
|
|
<refentrytitle>repmgr standby switchover</refentrytitle>
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>repmgr standby switchover</refname>
|
|
<refpurpose>promote a standby to primary and demote the existing primary to a standby</refpurpose>
|
|
</refnamediv>
|
|
|
|
|
|
<refsect1>
|
|
<title>Description</title>
|
|
|
|
<para>
|
|
Promotes a standby to primary and demotes the existing primary to a standby.
|
|
This command must be run on the standby to be promoted, and requires a
|
|
passwordless SSH connection to the current primary.
|
|
</para>
|
|
<para>
|
|
If other standbys are connected to the demotion candidate, &repmgr; can instruct
|
|
these to follow the new primary if the option <literal>--siblings-follow</literal>
|
|
is specified. This requires a passwordless SSH connection between the promotion
|
|
candidate (new primary) and the standbys attached to the demotion candidate
|
|
(existing primary).
|
|
</para>
|
|
<note>
|
|
<para>
|
|
Performing a switchover is a non-trivial operation. In particular it
|
|
relies on the current primary being able to shut down cleanly and quickly.
|
|
&repmgr; will attempt to check for potential issues but cannot guarantee
|
|
a successful switchover.
|
|
</para>
|
|
<para>
|
|
&repmgr; will refuse to perform the switchover if an exclusive backup is running on
|
|
the current primary.
|
|
</para>
|
|
</note>
|
|
<para>
|
|
For more details on performing a switchover, including preparation and configuration,
|
|
see section <xref linkend="performing-switchover">.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
From <link linkend="release-4.2">repmgr 4.2</link>, &repmgr; will instruct any running
|
|
<application>repmgrd</application> instances to pause operations while the switchover
|
|
is being carried out, to prevent <application>repmgrd</application> from
|
|
unintentionally promoting a node. For more details, see <xref linkend="repmgrd-pausing">.
|
|
</para>
|
|
<para>
|
|
Users of &repmgr; versions prior to 4.2 should ensure that <application>repmgrd</application>
|
|
is not running on any nodes while a switchover is being executed.
|
|
</para>
|
|
</note>
|
|
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Options</title>
|
|
<variablelist>
|
|
|
|
<varlistentry>
|
|
<term><option>--always-promote</option></term>
|
|
<listitem>
|
|
<para>
|
|
Promote standby to primary, even if it is behind or has diverged
|
|
from the original primary. The original primary will be shut down in any case,
|
|
and will need to be manually reintegrated into the replication cluster.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>--dry-run</option></term>
|
|
<listitem>
|
|
<para>
|
|
Check prerequisites but don't actually execute a switchover.
|
|
</para>
|
|
<important>
|
|
<para>
|
|
Success of <option>--dry-run</option> does not imply the switchover will
|
|
complete successfully, only that
|
|
the prerequisites for performing the operation are met.
|
|
</para>
|
|
</important>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>-F</option></term>
|
|
<term><option>--force</option></term>
|
|
<listitem>
|
|
<para>
|
|
Ignore warnings and continue anyway.
|
|
</para>
|
|
<para>
|
|
Specifically, if a problem is encountered when shutting down the current primary,
|
|
using <option>-F/--force</option> will cause &repmgr; to continue by promoting
|
|
the standby to be the new primary, and if <option>--siblings-follow</option> is
|
|
specified, attach any other standbys to the new primary.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>--force-rewind[=/path/to/pg_rewind]</option></term>
|
|
<listitem>
|
|
<para>
|
|
Use <application>pg_rewind</application> to reintegrate the old primary if necessary
|
|
(and the prerequisites for using <application>pg_rewind</application> are met).
|
|
If using PostgreSQL 9.3 or 9.4, and the <application>pg_rewind</application>
|
|
binary is not installed in the PostgreSQL <filename>bin</filename> directory,
|
|
provide its full path. For more details see also <xref linkend="switchover-pg-rewind">.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>-R</option></term>
|
|
<term><option>--remote-user</option></term>
|
|
<listitem>
|
|
<para>
|
|
System username for remote SSH operations (defaults to local system user).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>--repmgrd-no-pause</option></term>
|
|
<listitem>
|
|
<para>
|
|
Don't pause <application>repmgrd</application> while executing a switchover.
|
|
</para>
|
|
<para>
|
|
This option should not be used unless you take steps by other means
|
|
to ensure <application>repmgrd</application> is paused or not
|
|
running on all nodes.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
|
|
<varlistentry>
|
|
<term><option>--siblings-follow</option></term>
|
|
<listitem>
|
|
<para>
|
|
Have standbys attached to the old primary follow the new primary.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Configuration file settings</title>
|
|
|
|
<para>
|
|
Note that following parameters in <filename>repmgr.conf</filename> are relevant to the
|
|
switchover operation:
|
|
<itemizedlist spacing="compact" mark="bullet">
|
|
|
|
<listitem>
|
|
<simpara>
|
|
<literal>replication_lag_critical</literal>:
|
|
if replication lag (in seconds) on the standby exceeds this value, the
|
|
switchover will be aborted (unless the <literal>-F/--force</literal> option
|
|
is provided)
|
|
</simpara>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<simpara>
|
|
<literal>shutdown_check_timeout</literal>: maximum number of seconds to wait for the
|
|
demotion candidate (current primary) to shut down, before aborting the switchover.
|
|
</simpara>
|
|
<simpara>
|
|
Note that this parameter is set on the node where <command>repmgr standby switchover</command>
|
|
is executed (promotion candidate); setting it on the demotion candidate (former primary) will
|
|
have no effect.
|
|
</simpara>
|
|
<note>
|
|
<para>
|
|
In versions prior to <link linkend="release-4.2">&repmgr; 4.2</link>, <command>repmgr standby switchover</command> would
|
|
use the values defined in <literal>reconnect_attempts</literal> and <literal>reconnect_interval</literal>
|
|
to determine the timeout for demotion candidate shutdown.
|
|
</para>
|
|
</note>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<simpara>
|
|
<literal>standby_reconnect_timeout</literal>:
|
|
maximum number of seconds to attempt to wait for the demotion candidate (former primary)
|
|
to reconnect to the promoted primary (default: 60 seconds)
|
|
</simpara>
|
|
</listitem>
|
|
|
|
</itemizedlist>
|
|
</para>
|
|
</refsect1>
|
|
|
|
|
|
<refsect1>
|
|
<title>Execution</title>
|
|
|
|
<para>
|
|
Execute with the <literal>--dry-run</literal> option to test the switchover as far as
|
|
possible without actually changing the status of either node.
|
|
</para>
|
|
<important>
|
|
<para>
|
|
<application>repmgrd</application> must be shut down on all nodes while a switchover is being
|
|
executed. This restriction will be removed in a future &repmgr; version.
|
|
</para>
|
|
</important>
|
|
<para>
|
|
External database connections, e.g. from an application, should not be permitted while
|
|
the switchover is taking place. In particular, active transactions on the primary
|
|
can potentially disrupt the shutdown process.
|
|
</para>
|
|
</refsect1>
|
|
|
|
<refsect1 id="repmgr-standby-switchover-events">
|
|
<title>Event notifications</title>
|
|
<para>
|
|
<literal>standby_switchover</literal> and <literal>standby_promote</literal>
|
|
<link linkend="event-notifications">event notifications</link> will be generated for the new primary,
|
|
and a <literal>node_rejoin</literal> event notification for the former primary (new standby).
|
|
</para>
|
|
<para>
|
|
If using an event notification script, <literal>standby_switchover</literal>
|
|
will populate the placeholder parameter <literal>%p</literal> with the node ID of
|
|
the former primary.
|
|
</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Exit codes</title>
|
|
<para>
|
|
Following exit codes can be emitted by <command>repmgr standby switchover</command>:
|
|
</para>
|
|
<variablelist>
|
|
|
|
<varlistentry>
|
|
<term><option>SUCCESS (0)</option></term>
|
|
<listitem>
|
|
<para>
|
|
The switchover completed successfully.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>ERR_SWITCHOVER_FAIL (18)</option></term>
|
|
<listitem>
|
|
<para>
|
|
The switchover could not be executed.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>ERR_SWITCHOVER_INCOMPLETE (22)</option></term>
|
|
<listitem>
|
|
<para>
|
|
The switchover was executed but a problem was encountered.
|
|
Typically this means the former primary could not be reattached
|
|
as a standby. Check preceding log messages for more information.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>See also</title>
|
|
<para>
|
|
For more details see the section <xref linkend="performing-switchover">.
|
|
</para>
|
|
</refsect1>
|
|
|
|
</refentry>
|