Re: max_standby_delay considered harmful

Simon Riggs wrote:
> On Mon, 2010-05-03 at 13:13 -0400, Stephen Frost wrote:
> 
> > Perhaps you could speak to the specific user
> > experience difference that you think there would be from this change?
> 
> The difference is really to do with the weight you give to two different
> considerations
> 
> * avoid query cancellations
> * avoid having recovery fall behind, so that failover time is minimised
> 
> Some people recognise the trade-offs and are planning multiple standby
> servers dedicated to different roles/objectives.

I understand Simon's point that the two behaviors have different
benefits.  However, I believe few users will be able to understand when
to use which.

As I remember, 9.0 has two behaviors:
o  master delays vacuum cleanupo  slave delays WAL application

and in 9.1 we will be adding:
o  slave communicates snapshots to master

How would this figure into what we ultimately want in 9.1?

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com