On Tue, Jun 5, 2012 at 9:53 PM, Magnus Hagander <mag...@hagander.net> wrote: > Right now, pg_receivexlog sets: > replymsg->write = InvalidXLogRecPtr; > replymsg->flush = InvalidXLogRecPtr; > replymsg->apply = InvalidXLogRecPtr; > > when it sends it's status updates. > > I'm thinking it sohuld set replymsg->write = blockpos instad. > > Why? That way you can see in pg_stat_replication what has actually > been received by pg_receivexlog - not just what we last sent. This can > be useful in combination with an archive_command that can block WAL > recycling until it has been saved to the standby. And it would be > useful as a general monitoring thing as well. > > I think the original reason was that it shouldn't interefer with > synchronous replication - but it does take away a fairly useful > usecase...
I think that not only replaymsg->write but also ->flush should be set to blockpos in pg_receivexlog. Which allows pg_receivexlog to behave as synchronous standby, so we can write WAL to both local and remote synchronously. I believe there are some use cases for synchronous pg_receivexlog. OTOH, neither replaymsg->write nor ->flush should be set to InvalidXLogRecPtr, to prevent pg_basebackup from behaving as synchronous standby. Regards, -- Fujii Masao -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
