We can know the LSN of last committed WAL record on primary by using
pg_current_xlog_location(). It seems there's no API to know the time
when the WAL record was created. I would like to know standby delay by
using pg_last_xact_replay_timestamp() and such that API.
If there's no such a API, it would be useful to invent usch an API IMO.
Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp