John H Meyers <jhmeyers@xxxxxxx> wrote:
Since news servers generally receive the spool in time sequence,
and drop messages older than some specified age, one might
be able to ascertain that if any message in any one group
is now no longer on the server, then it is pretty safe to assume
that all older messages in that group have expired,
and this could be used in a simple way for knowing
when to manually purge expired messages from M2.
There are many reasons why this might not always be true (and I've
probably forgotten some reasons):
* Cancelled messages (though this is often disabled)
* Messages with explicit expiration dates (this is honored more often)
* Some servers use different expiration dates for different "types" of
messages, even in one group (single article messages saved for months
or even years, multipart articles expired pretty soon, days to weeks).
On the other hand, IF all earlier messages are indeed deleted the low
watermark from the group command should have been adjusted, and in
practice it is almost always keept very close to the real value, so
there should be no need for this crude and fallible heurestic.
The client ought to send group commands now and then to update both
low and high watermark anyway, so that it knows what's happening with
the group and can grab new headers...
The most likely cause for large swaths for "unavailable" articles
inside the "active" area is there are indeed one or more articles with
low article numbers left, that the client isn't updating the low
watermark or a a very broken server, get a new one... :-).
However, I can not get my Opera 8.01 (or any earlier version)
to even tell me whether or not any given message remains
on the news server when I try to display it -- all I can get
is "Message body not downloaded" in the message window,
and if I wait and wait and wait and wait some more,
and if nothing further ever happens, then I begin to
*suspect* that perhaps the news server responded that
it didn't still have that message, although Opera
never passes such a response back to me in any visible form.
I should mention that in my news account Properties > Incoming
I have no options checked, which means in particular that
I do not wish to retain newsgroup message bodies at all,
so every time I display a message, I presume that Opera
will be going back to the news server for it
and that Opera ought then to be able to know
when a news server says "I can't retrieve that message"
although I can never really get Opera to tell me that for sure.
Yep, Opera should know. The news server should get an error back,
probably 423 (that's what INN sends, it also uses "Bad article number"
in the optional comment field).
Of course if the server is really bad all bets are of... There have
been cases where servers just drops the connection when one attempts
to retreiving certain articles, but that's usually a sign of a
corrupted newsserver (disk crash or something has corrupted the
internal newsserver indexes).