Re: Stefan's bug (was: max_standby_delay considered harmful)

On Wed, 2010-05-19 at 08:21 -0400, Tom Lane wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
> > On Wed, May 19, 2010 at 1:47 AM, Fujii Masao <masao.fujii@gmail.com> wrote:
> >> Yes, but I prefer XLogCtl->SharedRecoveryInProgress, which is the almost
> >> same indicator as the boolean you suggested. Thought?
> 
> > It feels cleaner and simpler to me to use the information that the
> > postmaster already collects rather than having it take locks and check
> > shared memory, but I might be wrong.  Why do you prefer doing it that
> > way?
> 
> The postmaster must absolutely not take locks (once there are competing
> processes).  This is non negotiable from a system robustness standpoint.

Masao has not proposed this, in fact his proposal was to deliberately
avoid do so.

I proposed using the state recorded in xlog.c rather than attempting to
duplicate that with a second boolean in postmaster because that seems
likely to be more buggy.

-- Simon Riggs           www.2ndQuadrant.com