Re: (provide 'nnmaildir)

[Russ Allbery <rra@stanford.edu>]

Paul Jarc <prj@po.cwru.edu> writes:

> So an article number for a particluar message must be constant for the
> life of that message... after a message expires, can its article
> number be reused?

No.  From draft-ietf-nntpext-base-09.txt:

    The server MUST ensure that article numbers are issued in order of
    arrival timestamp; that is, articles arriving later MUST have higher
    numbers than those that arrive earlier. The server SHOULD allocate the
    next sequential unused number to each new article.

There is no provision in the NNTP protocol for ever reusing an article
number.

>> Gnus just barf at article numbers > 2^28.

> Ok... but do actual NNTP servers count into infinity?

No.  The article number is required to fit in ten decimal digits, and in
practice is limited to 2^32 - 1.

> They never shift article numbers back to make room; do they ever wrap
> around to 0 (or 1)?  I would have thought that there must be a server
> out there that's been in operation long enough to hit 2^32... or at
> least that the authors of NNTP servers would take it into consideration.

It wasn't taken into consideration in the standard, and there are enough
protocol requirements that the NNTP server authors pretty much have their
hands tied.

So far, there has never been a Usenet newsgroup that's received sufficient
traffic to even come close to wrapping over the entire life of Usenet.
control.cancel is the leading contender, since for a while we were seeing
upwards of ten cancels a second, which would have wrapped the article
number in thirteen years of sustained activity at that level.  Thankfully,
since then spam has dropped off and so have the spam cancels.

At some point, a server might have to have a flag day and reset the
article number somehow, thereby confusing a lot of readers.

-- 
Russ Allbery (rra@stanford.edu)             <http://www.eyrie.org/~eagle/>