Offloading readers in INN + CNFS

Kjetil Torgrim Homme kjetilho at ifi.uio.no
Sat Oct 23 05:51:45 UTC 1999


[Dan Merillat]

>   I've just described standard load distribution, actually.  It
>   wasn't invented in diablo.

By all means!  But it is _implemented_ in Diablo.

>   > This is "solved" by handtuning the reader boxes to make sure the
>   > overview info is expired before the articles on spool.  Note
>   > that in the general case in the Diablo model the reader box can
>   > never know whether an article exists or not, since it can
>   > contact several spool servers which may specialize in keeping
>   > different types of articles.
>   
>   Not really a "solution", since it invloves guessing when the
>   article is not available.

Yes.  It should be possible to get output from the expire processes on
the spools which can be used to adjust the expire times on the reader
daily.  Or you can just check a couple of times a year.  I'm not
saying it is perfect, but if your spool is large, you can spare room
for some leeway.  Remember ARTICLE will still work, so you can fetch
old articles by References.

>   With CNFS, you know exactly when the article goes away, so the
>   only time a user should see an "Article not found" error is when
>   it got expired since they requested xover.

Well, like I said, this gets hairy quick when the spools expire
articles at different times.  If you have only one spool, or all
spools have identical configuration, you can add special case
communication between spool and reader server.  This setup may well be
so common it is worth doing.  (Matt Dillon is strictly opposed to
adding it to Diablo, he seems to think it spoils the purity of the
design.)

Please don't take this as a criticism of INN, I just wanted to point
out that Diablo has this, and it can be useful to look at its
experiences.


Kjetil T.


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