Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hplabs!hplabsz!sartin
From: sartin@hplabsz.HPL.HP.COM (Rob Sartin)
Newsgroups: news.software.b
Subject: Re: Supersedes problems with rapid-fire articles
Summary: batches aren't ordered, cancels should be forwarded
Message-ID: <3919@hplabsz.HPL.HP.COM>
Date: 8 Sep 89 17:03:15 GMT
References: <5200@looking.on.ca> <66812@uunet.UU.NET> <1989Sep7.151826.11816@i88.isc.com>
Reply-To: sartin@hplabs.hp.com (Rob Sartin)
Organization: Hewlett-Packard, Software Technology Lab
Lines: 28

[If you see an earlier version of this article, it's because cancel
doesn't work.  -Rob]

Disclaimer:  it's been a while since I had to administer a news system,
I haven't read the RFC recently.  Despite that, I think I have a valid
argument.

Suppose the following:

1.  Machine A receives article X and batches it for machine B.

2.  Machine A receives cancel for article X, cancels the article and
batches it for machine B.

3.  Machine B (running an old version of B news that doesn't save
cancels), due to the way it processes batches, processes the batch with
the cancel for article X, sees that it hasn't got article X and throws
away the cancel.

4.  Machine B processes the batch with article X and forwards the
article to machines C, D, E, ....

Seems to me this isn't a very robust way to cancel articles.  If you've
watched the way articles propagate, you know that the "due to ..."
clause in 3 is easily met.  It usually happens when a bunch of batches
get queued up and have names whose alphabetical ordering is not the same
as their chronological ordering.  If you've watched the net, you also
know that many sites run old or otherwise unusual software and may not
save a cancel for an article they didn't get.

You don't need dropped articles or alternate paths to spoil the idea
that cancels should only be forwarded if "successful".  If I were
writing news software (which, thankfully, I am not - it would be a
wasted duplication of effort) I would forward cancels.

Rob Sartin			internet: sartin@hplabs.hp.com
Software Technology Lab 	uucp    : hplabs!sartin
Hewlett-Packard			voice	: (415) 857-7592