Re: TCP keepalive support for libpq

On Jun 22, 2010, at 18:43 , Robert Haas wrote:
> What does bother me is the fact that we are engineering a critical
> aspect of our system reliability around vendor-specific implementation
> details of the TCP stack, and that if any version of any operating
> system that we support (or ever wish to support in the future) fails
> to have a reliable implementation of this feature AND configurable
> knobs that we can tune to suit our needs, then we're screwed.  Does
> anyone want to argue that this is NOT a house of cards?


We already depend on TCP keepalives to prevent backends orphaned by client crashes or network outages from lingering
aroundforever. If such a lingering backend is inside a transaction, I'll cause table bloat, prevent clog truncations,
andkeep tables locked forever. 

I'd therefore argue that lingering backends are as least as severe a problem as hung S/R connections are. Since we've
trustedkeepalives to prevent the former for 10 years now, I think we can risk trusting keepalives to prevent the latter
too.

best regards,
Florian Pflug