Natterings about history files

[Russ Allbery]

Forrest J Cavalier <mibsoft at epix.net> writes:

> I estimate, but have not measuered, that most of the requests by message
> ID come from the referrer header.  That means it is likely that the
> message is in the current newsgroup.

> Does nnrpd check the current newsgroup before doing a history lookup?  I
> thought it used to, but I don't recall.

I don't *think* so... let me check.  Nope, it goes directly to a history
lookup.

> That is what I meant by looking up the message ID in overview.  Even a
> linear probe of 1000 messages (probably already in memory) is going to
> be way faster than an open of 2 day-history files.)

Hm.  You think so?  That's somewhat counterintuitive to me.  On one hand
you've got a linear walk of all the overview data in the newsgroup and on
the other hand you've got 2x (open/seek/read) per history file.
Admittedly, open is really expensive as system calls go....

Anyway, I think the majority of message ID lookups are probably coming
from NEWNEWS clients on those servers that have enabled NEWNEWS.  But I
haven't measured either.  :)

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