Re: Keepalive for max_standby_delay

On Sat, 2010-05-15 at 18:24 +0100, Simon Riggs wrote:

> I will recode using that concept.

There's some behaviours that aren't helpful here:

Startup gets new pointer when it runs out of data to replay. That might
or might not include an updated keepalive timestamp, since there's no
exact relationship between chunks sent and chunks received. Startup
might ask for a new chunk when half a chunk has been received, or when
multiple chunks have been received.

WALSender doesn't chunk up what it sends, though libpq does at a lower
level. So there's no way to make a keepalive happen every X bytes
without doing this from within libpq.

WALSender sleeps even when it might have more WAL to send, it doesn't
check it just unconditionally sleeps. At least WALReceiver loops until
it has no more to receive. I just can't imagine why that's useful
behaviour.

All in all, I think we should be calling this "burst replication" not
streaming replication. That does cause an issue in trying to monitor
what's going on cos there's so much jitter.

--
Simon Riggs www.2ndQuadrant.com