[NNTP] Large article numbers extension

[Thomas Gschwind]

Hi all!


On Wed, Jul 27, 2005 at 10:04:09AM +0000, Charles Lindsey wrote:
> In <20050726145938.GA20716 at finch-staff-1.thus.net> "Clive D.W. Feather" <clive at demon.net> writes:
> 2. Have a flag day.
> 
> Has anyone actually looked into how a flag day would be organized?

Sounds like a good option, if done right.

> Presumably the server goes off line for a few hours while it renumbers all
> the articles in the affected group, starting from 1 (or perhaps from
> some large constant).
> 
> What does the client see when it comes back? Presumably its .newsrc file
> is all wrong. Somehow it has to reset that line of its .newsrc file, at
> which point it will be offered all the already-read articles in the group
> as it they were new. Tedious, but manageable, and no articles are lost.
> And with a bit of assistance from the server (for example, a list mapping
> old numbers to new ones, or making the new numbers differ by a large
> constant from the old ones, or keeping the old group around in a renamed
> form, with Xref headers of old articles pointing to both groups) things
> could be made almost tolerable.

It is necessary to provide an explicit renumbering table or to keep the
old newsgroup around.  As you say if the numbers differ by a large
constant, the implementation should be fairly simple.  As soon as the
low and high watermark exceed 2^30, simply subtract 2^30 from all the
articles (or 2^31 in case of unsigned article numbers).  Note the
constant SHOULD be highest possible watermark divided by 2.

New clients would see that there was a wrap-around and would do the same
thing.

Old clients would automatically see that the newsgroup was "reset" and
would display many of the read articles again.  That could be solved
with a dirty hack.  If one has a client that uses a .newsrc file, use a
script that copies the .newsrc file away before, starts the news client,
and after termination of the client compares the .newsrc, and "fixes"
the .newsrc file.  Sure one has to restart the client to get see the
articles one has read but that should be OK.

Only problem, if the news server administrator has to reset a newsgroup
and resets the low watermark to one, when the server is close to a
wrap-around.  In this case, new clients would think a wrap-around has
occurred.  But I guess any wrap-around implementation might have this
problem.

Regards,
Thomas
-- 
Thomas Gschwind                      Email: thomasg at ieee.org
IBM Zurich Research Lab
Saeumerstrasse 4                     Tel: +41-1-724-8990
CH-8803 Rueschlikon, Switzerland     Fax: +41-1-724-8953