Following the failure or removal of the replication cluster's existing primary server, repmgr standby follow can be used to make 'orphaned' standbys follow the new primary and catch up to its current state.
To demonstrate this, assuming a replication cluster in the same state as the end of the preceding section (Promoting a standby), execute this:
$ 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
The standby is now replicating from the new primary and repmgr cluster show output reflects this:
$ 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
Note that with cascading replication, repmgr standby follow 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.