[Standards-JIG] Re: The Ack Hack.

Tony Finch dot at dotat.at
Wed May 10 18:17:43 UTC 2006


On Wed, 10 May 2006, Richard Dobson wrote:
>
> Huh? Im confused, how does what I said indicate I do not want reliable
> delivery? The reliable delivery that we are talking about here is knowing
> whether your stanzas are delivered or not which at the moment we dont, as they
> can just end up dropping into a blackhole, whats wrong with making the client
> session immediately go offline (just as if they had gracefully disconnected)?
> when the connection is detected as dead, and when this happens any non-acked
> stanzas would be bounced back to the sender, rather than being just lost in
> the ether as they are now.

When a connection is lost uncleanly, the stanza can be delivered OK but
the ack can be lost. You can't bounce the stanza if you haven't got the
ack when the connection is lost, because you may bounce a stanza that was
delivered OK. You need to re-connect and work out which stanzas were
handled and which were not.

This re-connection does not have to be "quick" - that's orthogonal to
transactional consistency. I don't think it matters if the user appears to
go offline during the reconnect interval: what we are interested in
finding out is if they need to re-send their last few messages when they
manage to get conected again, and we want to do this automatically instead
of by people saying to each other "did you get my message before i went
offline?"

Tony.
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