Re: [PATCH] V3: Idle in transaction cancellation

On Thursday 16 December 2010 21:41:10 Tom Lane wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> > On Thu, Dec 16, 2010 at 3:18 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> I guess you misunderstood what I said. �What I meant was that we cannot
> >> longjmp *out to the outer level*, ie we cannot take control away from
> >> the input stack. �We could however have a TRY block inside the interrupt
> >> handler that catches and handles (queues) any errors occurring during
> >> transaction abort. �As long as we eventually return control to openssl
> >> I think it should work.
> >
> > Is there any real advantage to that?
>
> Not crashing when something funny happens seems like a real advantage to
> me. (And an unexpected elog(FATAL) will look like a crash to most
> users, even if you want to try to define it as not a crash.)
>
> > How often do we hit an error
> > trying to abort a transaction? And how will we report the error
> > anyway?
>
> Queue it up and report it at the next opportunity, as per upthread.
>
> > I thought the next thing we'd report would be the recovery
> > conflict, not any bizarre can't-abort-the-transaction scenario.
>
> Well, if we discard it because we're too lazy to implement error message
> merging, that's OK. Presumably it'll still get into the postmaster log.
>
> >> (Hm, but I wonder whether there are any hard
> >> timing constraints in the ssl protocol ... although hopefully xact abort
> >> won't ever take long enough that that's a real problem.)
> >
> > That would be incredibly broken.
>
> Think "authentication timeout". I wouldn't be a bit surprised if the
> remote end would drop the connection if certain events didn't come back
> reasonably promptly. There might even be security reasons for that,
> ie, somebody could brute-force a key if you give them long enough.
> (But this is all speculation; I don't actually know SSL innards.)
I will try to read the thread and make a proposal for a more carefull
implementation - just not today... I think the results would be interesting...

Thanks for the input,

Andres