Re: checkpoints are duplicated even while the system is idle

On Thu, Oct 6, 2011 at 6:56 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
>> Do we want this backpatched? If so, suggest just 9.1 and 9.0?
>
> -1 for backpatching; it's more an improvement than a bug fix.

OK, works for me.

> In any case, I think we still need to respond to the point Kevin made
> about how to tell an idle master from broken replication.  Right now,
> you will get at least a few bytes of data every checkpoint_timeout
> seconds.  If we change this, you won't.

> I'm inclined to think that the way to deal with that is not to force out
> useless WAL data, but to add some sort of explicit "I'm alive" heartbeat
> signal to the walsender/walreceiver protocol.  The hard part of that is
> to figure out how to expose it where you can see it on the slave side
> --- or do we have a status view that could handle that?

Different but related issue and yes, am on it, and yes, the way you just said.

I foresee a function that tells you the delay based on a protocol
message of 'k' for keepalive.

--
 Simon Riggs                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services