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Add standby promotion documentation

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Ian Barwick
2017-09-22 17:31:09 +09:00
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<chapter id="follow-new-primary" xreflabel="Following a new primary">
<title>Following a new primary</title>
<para>
Following the failure or removal of the replication cluster's existing primary
server, <xref linkend="repmgr-standby-follow"> can be used to make 'orphaned' standbys
follow the new primary and catch up to its current state.
</para>
<para>
To demonstrate this, assuming a replication cluster in the same state as the
end of the preceding section (<xref linkend="promoting-standby">),
execute this:
<programlisting>
$ repmgr -f /etc/repmgr.conf repmgr standby follow
INFO: changing node 3's primary to node 2
NOTICE: restarting server using "pg_ctl -l /var/log/postgresql/startup.log -w -D '/var/lib/postgresql/data' restart"
waiting for server to shut down......... done
server stopped
waiting for server to start.... done
server started
NOTICE: STANDBY FOLLOW successful
DETAIL: node 3 is now attached to node 2
</programlisting>
</para>
<para>
The standby is now replicating from the new primary and `repmgr cluster show`
output reflects this:
<programlisting>
$ repmgr -f /etc/repmgr.conf cluster show
ID | Name | Role | Status | Upstream | Location | Connection string
----+-------+---------+-----------+----------+----------+--------------------------------------
1 | node1 | primary | - failed | | default | host=node1 dbname=repmgr user=repmgr
2 | node2 | primary | * running | | default | host=node2 dbname=repmgr user=repmgr
3 | node3 | standby | running | node2 | default | host=node3 dbname=repmgr user=repmgr</programlisting>
</para>
<para>
Note that with cascading replication, <command>repmgr standby follow</command> can also be
used to detach a standby from its current upstream server and follow the
primary. However it's currently not possible to have it follow another standby;
we hope to improve this in a future release.
</para>
</chapter>