Re: Pause/Resume feature for Hot Standby

On Tue, May 4, 2010 at 4:02 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> In the original patch I had Pause/Resume feature for controlling
> recovery during Hot Standby. It was removed for lack of time.

Well, it's not like we have more time now than we did then. I think
we need to postpone this discussion to 9.1. If we're going to start
accepting patches for new features, then why should we accept only
patches for HS/SR? I have two patches already in the queue that I'd
like to see committed and if I thought that there was a chance of
getting anything further done for 9.0, there'd be several more. Many
other people have patches waiting also, or are holding off development
because we are in feature freeze right now. Hot Standby is a great
feature, but, I don't see any reason to say that we're going to allow
new feature development just for HS but not for anything else.

I also think that worrying about fine-tuning HS at this point is a bit
like complaining that the jump suits of the crew of the Space Shuttle
Challenger were not made of 100% recyclable materials. Just yesterday
we had a report of an HS server getting into a state where it failed
to shut down properly; and I believe that we never fully resolved the
issue of occasional extremely-long spikes in HS response time, either.
Heikki just fixed a bug our btree recovery code which is apparently
new to 9.0 since he did not backpatch it. I think that getting into a
discussion of pausing and resuming recovery, or even the parallel
discussion on max_standby_delay, are fiddling with things that,
granted, are probably not ideal, and yes, we should improve them in a
future release, but they're not what we should be worrying about right
now. What I think we SHOULD be worried about right now - VERY worried
- is stabilizing the existing Hot Standby code to the point where it
won't be an embarrassment to us when we ship it. The rate at which
we're finding new problems even with the small number of people who
test alpha releases and nightly snapshots suggests to me that we're
not there yet.

...Robert