I think the best one would be 2 combined with a check if the wal receiver process is running before running that
query with something like:
$ ps aux | egrep ‘wal\sreceiver’
postgres 3858 0.0 0.0 2100112 3312 ? Ss 19:35 0:01 postgres:
wal receiver process streaming 36/900A738
This solution would only be run on the slave and it is pretty easy to setup.
postgres 
