Re: max_standby_delay considered harmful

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Greg Smith <greg(at)2ndquadrant(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: max_standby_delay considered harmful
Date: 2010-05-08 23:34:18
Message-ID: 201005082334.o48NYIA28405@momjian.us
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Greg Smith wrote:
> Bruce Momjian wrote:
> > I think the big question is whether this issue is significant enough
> > that we should ignore our policy of no feature design during beta
>
> The idea that you're considering removal of a feature that we already
> have people using in beta and making plans around is a policy violation
> too you know. A freeze should include not cutting things just because
> their UI or implementation is not ideal yet. And you've been using the
> word "consensus" here when there is no such thing. At best there's
> barely a majority here among people who have stated an opinion, and
> consensus means something much stronger even than that; that means
> something closer to unanimity. I thought the summary of where the
> project is at Josh wrote at
> http://archives.postgresql.org/message-id/4BE31279.7040002@agliodbs.com
> was excellent, both from a technical and a process commentary
> standpoint. I'd be completely happy to follow that plan, and then we'd
> be at a consensus--with no one left arguing.

I can't argue with anything you have said in your email. The big
question is whether designing during beta is worth it in this case, and
whether we can get something that is useful and gives us useful feedback
for 9.1, and is it worth spending the time to figure this out during
beta? If we can, great, let's do it, but I have not seen that yet, and
I am unclear how long we should keep trying to find it.

I think everyone agrees the current code is unusable, per Heikki's
comment about a WAL file arriving after a period of no WAL activity, and
look how long it took our group to even understand why that fails so
badly. I thought Tom's idea had problems, and there were ideas of how
to improve it. It just seems like we are drifting around on something
that has no easy solution, and not something that we are likely to hit
during beta where we should be focusing on the release. Saying we have
three months to fix this during beta seems like a recipe for delaying
the final release, and this feature is not worth that.

What we could do is to convert max_standby_delay to a boolean, 'ifdef'
out the code that was handling non-boolean cases, and then if someone
wants to work on a patch in a corner and propose something in a month
that improves this, we can judge the patch on its own merits, and apply
it if it is a great benefit, because basically that is what we are doing
now if we fix this --- adding a new patch/feature during beta.
(Frankly, because we are not requiring an initdb during beta, I am
unclear how we are going to rename max_standby_delay to behave as a
boolean.)

It is great if we can get a working max_standby_delay, but I fear
drifting/distraction at this stage.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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