> 2019-05-23 04:17:02 EDT 23593 DETAIL: The database cluster was initialized with PG_CONTROL_VERSION 960, but the server was compiled with PG_CONTROL_VERSION 1100.
It appears that you have not upgraded the standby server, so either use "rsync" or simply destroy and rebuild it from scratch "repmgr standby clone..."
https://www.postgresql.org/docs/11/pgupgrade.html
Upgrade Streaming Replication and Log-Shipping standby servers
If you used link mode and have Streaming Replication (see Section 26.2.5) or Log-Shipping (see Section 26.2) standby servers, you can follow these steps to quickly upgrade them. You will not be running pg_upgrade on the standby servers, but rather rsync on the primary. Do not start any servers yet.
If you did not use link mode, do not have or do not want to use rsync, or want an easier solution, skip the instructions in this section and simply recreate the standby servers once pg_upgrade completes and the new primary is running.
Greg.
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