On Mon, Jun 15, 2015 at 9:04 AM, Anton Bushmelev <djeday84@xxxxxxxxx> wrote: > Hello, thank t for response, measure in bytes may bemore correct, but to > bring it to the customer? :) I think it is easier to say that the standby > database lags behind master no more than 15 minutes, than the fact that it > differs for 1 megabyte. > ps: sorry for my English > > > On 06/15/2015 02:57 AM, Michael Paquier wrote: >> >> Isn't your mistake the fact that you rely on the assumption that >> replication lag measured in terms of timestamp is a good thing while >> it should be estimated in terms of byte difference by comparing WAL >> positions between the master and its standbys? Comparing pg_last_xact_replay_timestamp() with now() to measure replication lag makes little sense: this function shows the timestamp of the *last transaction replayed* during recovery (see here: http://www.postgresql.org/docs/devel/static/functions-admin.html#FUNCTIONS-RECOVERY-CONTROL ). Hence if your master server has no activity for a certain amount of time, meaning that no transactions could be replayed on the standby, this will continuously increase. -- Michael -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
