Date: Mon, 13 Nov 2023 14:05:23 -0500
From: Bruce Momjian <bruce@momjian.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Yugo NAGATA <nagata@sraoss.co.jp>,
	Alvaro Herrera <alvherre@alvh.no-ip.org>,
	pgsql-hackers@postgresql.org
Subject: Re: Question about non-blocking mode in libpq
Message-ID: <ZVJzc07JRAkx5jwB@momjian.us>
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On Mon, Nov 13, 2023 at 01:01:32PM -0500, Bruce Momjian wrote:
> On Wed, Nov  1, 2023 at 08:47:33AM -0400, Bruce Momjian wrote:
> > On Tue, Oct 31, 2023 at 10:16:07PM -0400, Tom Lane wrote:
> > > Bruce Momjian <bruce@momjian.us> writes:
> > > > On Tue, Oct 31, 2023 at 09:11:06PM -0400, Tom Lane wrote:
> > > >> What I'm objecting to is removal of the bit about "if they need to be
> > > >> called again".  That provides a hint that retry is the appropriate
> > > >> response to a failure.  Admittedly, it's not 100% clear, but your
> > > >> version makes it 0% clear.
> > > 
> > > > I thought the original docs said you had to re-call on failure (it would
> > > > not block but it would fail if it could not be sent), while we are now
> > > > saying that it will be queued in the input buffer.
> > > 
> > > For these functions in nonblock mode, failure means "we didn't queue it".
> > > 
> > > > Is retry really something we need to mention now?  If out of memory is
> > > > our only failure case now ("unable to enlarge the buffer because OOM"),
> > > > is retry really a realistic option?
> > > 
> > > Well, ideally the application would do something to alleviate the
> > > OOM problem before retrying.  I don't know if we want to go so far
> > > as to discuss that.  I do object to giving the impression that
> > > failure is impossible, which I think your proposed wording does.
> > > 
> > > An orthogonal issue with your latest wording is that it's unclear
> > > whether *unsuccessful* calls to these functions will block.
> > 
> > Okay, I see your point now.  Here is an updated patch that addresses
> > both issues.
> 
> Patch applied to master.

My apologies, I forgot this needed to backpatched, so done now.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Only you can decide what is important to you.