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Re: Sync Rep v17

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org, Daniel Farina <daniel(at)heroku(dot)com>
Subject: Re: Sync Rep v17
Date: 2011-02-28 21:12:42
Message-ID: 1298927562.12992.1948.camel@ebony (view raw or flat)
Thread:
Lists: pgsql-hackers
On Sat, 2011-02-19 at 22:52 -0500, Robert Haas wrote:
> On Sat, Feb 19, 2011 at 3:28 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> > First, we should be clear to explain that you are referring to the fact
> > that the request
> >  synchronous_commit = off
> >  synchronous_replication = on
> > makes no sense in the way the replication system is currently designed,
> > even though it is a wish-list item to make it work in 9.2+
> 
> What exactly do you mean by "make it work"?  We can either (1) wait
> for the local commit and the remote commit (synchronous_commit=on,
> synchronous_replication=on), (2) wait for the local commit only
> (synchronous_commit=on, synchronous_replication=off), or (3) wait for
> neither (synchronous_commit=off, synchronous_replication=off).
> There's no fourth possible behavior, AFAICS.

Currently, no, since as we discussed earlier we currently need to fsync
WAL locally before it gets sent to standby.

> The question is whether synchronous_commit=off,
> synchronous_replication=on should behave like (1) or (3)

Yes, that is the right question.

> You have it as #1; I'm arguing
> it should be #3.  I realize it's an arguable point; I'm just arguing
> for what makes most sense to me.

Various comments follow on thread. We can pick this up once we've
committed the main patch.

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


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