Re: Keepalive for max_standby_delay

Simon Riggs wrote:
> On Sat, 2010-05-15 at 11:45 -0400, Tom Lane wrote:
>> I'm also extremely dubious that it's a good idea to set
>> recoveryLastXTime from this.  Using both that and the timestamps from
>> the wal log flies in the face of everything I remember about control
>> theory.  We should be doing only one or only the other, I think.
> 
> I can change it so that the recoveryLastXTime will not be updated if we
> are using the value from the keepalives. So we have one, or the other.
> Remember that replication can switch backwards and forwards between
> modes, so it seems sensible to have a common timing value whichever mode
> we're in.

That means that recoveryLastXTime can jump forwards and backwards.
Doesn't feel right to me either. If you want to expose the
keepalive-time to queries, it should be a separate field, something like
lastMasterKeepaliveTime and a pg_last_master_keepalive() function to
read it.

-- 
  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com