At this point, the cluster fails to open. On 11.5 pg_ctl hangs waiting for
the database to open, and eventually times out. On 9.6.15, pg_ctl runs
normally, but tailing the database log shows that it never opens. It loops
at "starting up."
I've found that if you stop the instance and remove the recovery.conf, the
database actually will open normally. But even after that, if you go back
and try to open as a hot standby it will fail to open again. I have so far
not been able to find a way to let this cluster open as a hot standby again.
Affected instances had to be restored from backup.
This is particularly a problem when running postgres in Docker, as Docker
will send SIGKILL if database shutdown takes more than a few seconds.