Re: Keepalive for max_standby_delay

Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> On Wed, 2010-06-02 at 13:14 -0400, Tom Lane wrote:
>> This patch seems to me to be going in fundamentally the wrong direction.
>> It's adding complexity and overhead (far more than is needed), and it's
>> failing utterly to resolve the objections that I raised to start with.

> Having read your proposal, it seems changing from time-on-sender to
> time-on-receiver is a one line change to the patch.

> What else are you thinking of removing, if anything?

Basically, we need to get rid of everything that feeds timestamps from
the WAL content into the kill-delay logic.

>> In particular, Simon seems to be basically refusing to do anything about
>> the complaint that the code fails unless master and standby clocks are
>> in close sync. I do not believe that this is acceptable, and since he
>> won't fix it, I guess I'll have to.

> Syncing two servers in replication is common practice, as has been
> explained here; I'm still surprised people think otherwise.

Doesn't affect the complaint in the least: I do not find it acceptable
to have that be *mandated* in order for our code to work sensibly.
I would be OK with having something approaching what you want as a
non-default optional behavior (with a clearly-documented dependency
on having synchronized clocks). But in any case the current behavior is
still quite broken as regards reading stale timestamps from WAL.

regards, tom lane