ietf-nntp Backfill: not again.

Jack De Winter jack at wildbear.on.ca
Sun Jan 12 09:33:32 PST 1997


At 03:01 PM 1/12/97 +0200, Alan Barrett wrote:
>> If there is a third choice, that of telling servers to do new stuff that
>> is well understood, not too onerous, but not widely implemented, then I
>> would go for the third choice.
>
>Hmm.  I wonder if I have just come up with that third choice.
>
>A few people have suggested things like "If article 14 arrives before
>article 13, just have the slave hide article 14 from the newsreader
>clients until such time as article 13 arrives".  The problem with that
>is that article 13 might never arrive, because it might have been
>canceled or expired.
>
>But what if we had a way for the master to tell the slave "Article 13
>will never arrive"?  It would need a protocol extension and/or a special
>article format (for example, something that looks like an article with
>an Xref line but almost nothing else), and it would need the slave to
>keep track of the difference between {articles that have not yet arrived
>but are expected to arrive later} and {articles that were canceled or
>expired either before or after arrival}.
>
>Given that, the slave could hide article 14 from the users until such
>time as article 13 either arrives or is reported as will-never-arrive.

This sounds like a good start.  My first thought was to approach this
from the point of view of the slave.  You want to be able to scan the
newsgroup in question and figure out if there is any new information
for you to get. (Going through the feed newsgroup by newsgroup was an
assumption, but from the XREF and XREPLIC talking, I assumed it was
okay to assume this for the moment.)  If you are the client, the easiest
thing would be to have a list of all the articles in a given group,
giving article number and message id.  At that point, you can check
in your store to see if you have a mismatch, and request further
information.  The only problem is that if an article is cancelled,
we do not have any current mechanism to get any cancellation information
from the master site.

But then to syncronize, you simply look at the list after you have
finished posting the article to the site.  You have a definitive list
of the messages for that group, and you set the high water mark to
be the highest member of the list, without any gaps save for cancelled
messages, that you currently have.

more comments?

regards,
Jack
-------------------------------------------------
Jack De Winter - Wildbear Consulting, Inc.
(519) 576-3873		http://www.wildbear.on.ca/

Author of SLMail for 95 & NT (http://www.seattlelab.com/)



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