On Wed, Jan 4, 2017 at 12:22 PM, Thomas Munro <thomas.mu...@enterprisedb.com> wrote: > (replay_lag - (write_lag / 2) may be a cheap proxy > for a lag time that doesn't include the return network leg, and still > doesn't introduce clock difference error)
(Upon reflection it's a terrible proxy for that because of the mix of write/flush work done by WAL receiver today, but would improve dramatically if the WAL writer were doing the flushing. A better yet proxy might involve also tracking receive_lag which doesn't include the write() syscall. My real point is that there are ways to work backwards from the two-way round trip time to get other estimates, but no good ways to undo the damage that would be done to the data if we started using two systems' clocks.) -- Thomas Munro http://www.enterprisedb.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
