Hi,

I'm interested in using your exporter to monitor a streaming replication cluster. However it looks like it's missing a few metrics, specifically these would be interesting:

pg_is_in_recovery()
pg_last_xact_replay_timestamp()
pg_last_xlog_replay_location()
pg_last_xlog_receive_location()
pg_current_xlog_location()
pg_is_in_backup()

from http://www.postgresql.org/docs/9.4/static/functions-admin.html