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If replay is paused, we can't be really sure that more WAL will be received between the check and the promote operation, which would risk the promote operation not taking place during the switchover (it would happen as soon as WAL replay is resumed and pending WAL is replayed). Therefore we simply quit with an informative slew of messages and leave the user to sort it out. GitHub #540.
357 lines
12 KiB
Plaintext
357 lines
12 KiB
Plaintext
<refentry id="repmgr-standby-switchover">
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<indexterm>
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<primary>repmgr standby switchover</primary>
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</indexterm>
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<refmeta>
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<refentrytitle>repmgr standby switchover</refentrytitle>
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</refmeta>
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<refnamediv>
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<refname>repmgr standby switchover</refname>
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<refpurpose>promote a standby to primary and demote the existing primary to a standby</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<para>
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Promotes a standby to primary and demotes the existing primary to a standby.
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This command must be run on the standby to be promoted, and requires a
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passwordless SSH connection to the current primary.
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</para>
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<para>
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If other standbys are connected to the demotion candidate, &repmgr; can instruct
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these to follow the new primary if the option <literal>--siblings-follow</literal>
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is specified. This requires a passwordless SSH connection between the promotion
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candidate (new primary) and the standbys attached to the demotion candidate
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(existing primary).
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</para>
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<note>
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<para>
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Performing a switchover is a non-trivial operation. In particular it
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relies on the current primary being able to shut down cleanly and quickly.
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&repmgr; will attempt to check for potential issues but cannot guarantee
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a successful switchover.
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</para>
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<para>
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&repmgr; will refuse to perform the switchover if an exclusive backup is running on
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the current primary, or if WAL replay is paused on the standby.
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</para>
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</note>
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<para>
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For more details on performing a switchover, including preparation and configuration,
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see section <xref linkend="performing-switchover">.
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</para>
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<note>
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<para>
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From <link linkend="release-4.2">repmgr 4.2</link>, &repmgr; will instruct any running
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<application>repmgrd</application> instances to pause operations while the switchover
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is being carried out, to prevent <application>repmgrd</application> from
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unintentionally promoting a node. For more details, see <xref linkend="repmgrd-pausing">.
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</para>
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<para>
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Users of &repmgr; versions prior to 4.2 should ensure that <application>repmgrd</application>
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is not running on any nodes while a switchover is being executed.
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</para>
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</note>
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</refsect1>
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<refsect1>
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<title>Options</title>
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<variablelist>
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<varlistentry>
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<term><option>--always-promote</option></term>
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<listitem>
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<para>
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Promote standby to primary, even if it is behind or has diverged
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from the original primary. The original primary will be shut down in any case,
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and will need to be manually reintegrated into the replication cluster.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--dry-run</option></term>
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<listitem>
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<para>
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Check prerequisites but don't actually execute a switchover.
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</para>
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<important>
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<para>
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Success of <option>--dry-run</option> does not imply the switchover will
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complete successfully, only that
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the prerequisites for performing the operation are met.
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</para>
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</important>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-F</option></term>
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<term><option>--force</option></term>
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<listitem>
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<para>
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Ignore warnings and continue anyway.
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</para>
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<para>
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Specifically, if a problem is encountered when shutting down the current primary,
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using <option>-F/--force</option> will cause &repmgr; to continue by promoting
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the standby to be the new primary, and if <option>--siblings-follow</option> is
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specified, attach any other standbys to the new primary.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--force-rewind[=/path/to/pg_rewind]</option></term>
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<listitem>
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<para>
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Use <application>pg_rewind</application> to reintegrate the old primary if necessary
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(and the prerequisites for using <application>pg_rewind</application> are met).
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If using PostgreSQL 9.3 or 9.4, and the <application>pg_rewind</application>
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binary is not installed in the PostgreSQL <filename>bin</filename> directory,
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provide its full path. For more details see also <xref linkend="switchover-pg-rewind">.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-R</option></term>
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<term><option>--remote-user</option></term>
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<listitem>
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<para>
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System username for remote SSH operations (defaults to local system user).
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--repmgrd-no-pause</option></term>
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<listitem>
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<para>
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Don't pause <application>repmgrd</application> while executing a switchover.
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</para>
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<para>
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This option should not be used unless you take steps by other means
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to ensure <application>repmgrd</application> is paused or not
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running on all nodes.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--siblings-follow</option></term>
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<listitem>
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<para>
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Have standbys attached to the old primary follow the new primary.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Configuration file settings</title>
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<para>
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The following parameters in <filename>repmgr.conf</filename> are relevant to the
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switchover operation:
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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>replication_lag_critical</primary>
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<secondary>with "repmgr standby switchover "</secondary>
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</indexterm>
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<term><option>replication_lag_critical</option></term>
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<listitem>
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<para>
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If replication lag (in seconds) on the standby exceeds this value, the
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switchover will be aborted (unless the <literal>-F/--force</literal> option
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is provided)
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</para>
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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>shutdown_check_timeout</primary>
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<secondary>with "repmgr standby switchover "</secondary>
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</indexterm>
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<term><option>shutdown_check_timeout</option></term>
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<listitem>
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<para>
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The maximum number of seconds to wait for the
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demotion candidate (current primary) to shut down, before aborting the switchover.
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</para>
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<para>
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Note that this parameter is set on the node where <command>repmgr standby switchover</command>
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is executed (promotion candidate); setting it on the demotion candidate (former primary) will
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have no effect.
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</para>
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<note>
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<para>
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In versions prior to <link linkend="release-4.2">&repmgr; 4.2</link>, <command>repmgr standby switchover</command> would
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use the values defined in <literal>reconnect_attempts</literal> and <literal>reconnect_interval</literal>
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to determine the timeout for demotion candidate shutdown.
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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>wal_receive_check_timeout</primary>
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<secondary>with "repmgr standby switchover "</secondary>
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</indexterm>
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<term><option>wal_receive_check_timeout</option></term>
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<listitem>
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<para>
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After the primary has shut down, the maximum number of seconds to wait for the
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walreceiver on the standby to flush WAL to disk before comparing WAL receive location
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with the primary's shut down location.
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</para>
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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>standby_reconnect_timeout</primary>
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<secondary>with "repmgr standby switchover "</secondary>
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</indexterm>
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<term><option>standby_reconnect_timeout</option></term>
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<listitem>
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<para>
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The maximum number of seconds to attempt to wait for the demotion candidate (former primary)
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to reconnect to the promoted primary (default: 60 seconds)
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</para>
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<para>
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Note that this parameter is set on the node where <command>repmgr standby switchover</command>
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is executed (promotion candidate); setting it on the demotion candidate (former primary) will
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have no effect.
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</para>
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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>node_rejoin_timeout</primary>
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<secondary>with "repmgr standby switchover "</secondary>
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</indexterm>
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<term><option>node_rejoin_timeout</option></term>
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<listitem>
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<para>
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maximum number of seconds to attempt to wait for the demotion candidate (former primary)
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to reconnect to the promoted primary (default: 60 seconds)
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</para>
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<para>
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Note that this parameter is set on the the demotion candidate (former primary);
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setting it on the node where <command>repmgr standby switchover</command> is
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executed will have no effect.
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</para>
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<para>
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However, this value <emphasis>must</emphasis> be less than <option>standby_reconnect_timeout</option> on the
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promotion candidate (the node where <command>repmgr standby switchover</command> is executed).
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Execution</title>
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<para>
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Execute with the <literal>--dry-run</literal> option to test the switchover as far as
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possible without actually changing the status of either node.
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</para>
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<para>
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External database connections, e.g. from an application, should not be permitted while
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the switchover is taking place. In particular, active transactions on the primary
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can potentially disrupt the shutdown process.
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</para>
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</refsect1>
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<refsect1 id="repmgr-standby-switchover-events">
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<title>Event notifications</title>
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<para>
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<literal>standby_switchover</literal> and <literal>standby_promote</literal>
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<link linkend="event-notifications">event notifications</link> will be generated for the new primary,
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and a <literal>node_rejoin</literal> event notification for the former primary (new standby).
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</para>
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<para>
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If using an event notification script, <literal>standby_switchover</literal>
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will populate the placeholder parameter <literal>%p</literal> with the node ID of
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the former primary.
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</para>
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</refsect1>
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<refsect1>
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<title>Exit codes</title>
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<para>
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One of the following exit codes will be emitted by <command>repmgr standby switchover</command>:
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</para>
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<variablelist>
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<varlistentry>
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<term><option>SUCCESS (0)</option></term>
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<listitem>
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<para>
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The switchover completed successfully.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>ERR_SWITCHOVER_FAIL (18)</option></term>
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<listitem>
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<para>
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The switchover could not be executed.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>ERR_SWITCHOVER_INCOMPLETE (22)</option></term>
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<listitem>
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<para>
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The switchover was executed but a problem was encountered.
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Typically this means the former primary could not be reattached
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as a standby. Check preceding log messages for more information.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>See also</title>
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<para>
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For more details see the section <xref linkend="performing-switchover">.
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</para>
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</refsect1>
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</refentry>
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