Re: Protocol forced to V2 in low-memory conditions?

On Tue, Sep 10, 2013 at 5:29 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Maciek Sakrejda <m(dot)sakrejda(at)gmail(dot)com> writes:
>> One of our customers seems to be running into exactly the issue
>> hypothesized about by Tom here:
>> http://www.postgresql.org/message-id/8040.1314403175@sss.pgh.pa.us
>> Was the possibility of an inadvertent protocol downgrade addressed as part
>> of that patch? I read through the thread, but it wasn't entirely clear.
>
> No, a quick look at report_fork_failure_to_client shows it still always
> sends V2 protocol. We fixed some of the lesser issues discussed in that
> thread, but I don't think we ever agreed how to deal with this one.
>
> I've been thinking of late that it might be time to retire libpq's
> support for V2 protocol (other than in the specific context of the first
> error message received while trying to make a connection). If we did
> that, we'd remove the code path that thinks it should downgrade to V2
> protocol, and thus fix this problem by removing code not adding more.
>
> However, that doesn't sound like a back-patchable solution, and also
> it remains unclear whether non-libpq clients such as JDBC have an issue
> with this.

It's probably worth polling for that. I believe the jdbc driver at
least has code for it, but I don't know if it's a requirement at this
point.

If it is, that might be a "10.0 release" feature, in how it would
break things :(

--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/