
Questions and Answers on the dynamic feed system:

Q: How do I set feed parameters for a given system as I used to in the
"sys" file or C news batch parameter file?

A: Each system you feed gets a directory in the master feed directory.
In that directory is the system's newsrc file and other associated files.
If you place a file called 'options' there, the first line of that file will
be added to the command line for the 'feed' command.

Thus you can put in things like batch sizes:  "size=60" gives 60K batches.
You can also change the compressing feeding command.  The default is
a combination of compress and uux to make a compressed batch.  You can
put in what you like.   A line like the following:

n=newsrc s=62 "c=compress -b 13|/v/bin/news/batch/bencode|mail bcnews@%s"

Defines the 'newsrc' file as newsrc, a batch size of 62K (before compression)
and an output command that compresses, bencodes and mails to the site.

Q: How about not feeding articles that have come from another site that I
know also talks to the site I am feeding?

A: While loops are not good things in the dynamic feed system, such multiple
feeds can be handled.   Simply add  "path=sitename" options to your options
file.   Articles which contain the listed site name in the Path: line will
not be sent.

Q: Can I change the maximum output size?

A: Right now that is generated from the spacefor command and fed to the
feed program by the dofeeds script.  You can alter the dofeeds script to
change the way this is done.

Q: How often should I send a new subscription list?

A: Depends on what sort of delay you want for new subscriptions.  If you
are an intermediate node, feeding other sites, you should probably do it
fairly often, perhaps a couple of times a day.  That reduces the delays.

Note as well that if you put in patterns to send you new groups in various
hierarchies, they will not get sent to you until your subscription list is
processed again.  So a frequent transmission is good.  (The feeding site can
also arrange to process your subscription request every day if you don't send
a new one.  It doesn't currently run that way.)

Q: What about sending only local articles?  (ie. the feed back from a leaf to
the main site that feeds it.)

A: It would have been possible to do this, but it really isn't very
efficient.  It would involve scanning the whole spool just to see what is
local.  NewsClip (which can replace the 'feed' program with far fancier
feeding programs) can do this if you like.

In general, stick to the old "sys" file method for your back feed, or feeds
of locally generated articles to special sites.o

Q: What about NNTP?

A: If you wish to use dyna-feed with NNTP, you can.  Just set up to use the
feed program in its regular "listing mode" with the "+messageid" option.

This will output a list of filenames and message-ids just like the one
produced from the old "sys" file feeding method.  You can use this file
as input to nntpxmit.  (The modified nntpxmit that takes message ids in the
list of files is best.)

This can be slightly less efficient, because each article is scanned once to
insert it in the list, and again when it is fed to the remote system.

I am sure some NNTP users will put together some fancy uses of this system.
One idea would be to use the arbit program to produce local group lists, and
use that to make a news 'puller' which grabs news from the feed site.
(Rather than nntpxmit, which transmits from the feed to the fed at the feed
site's instigation.)

Q: What about ihave/sendme links?

A: The feed program can be configured to output just a list of message-ids.
You can then use this for an ihave control message.  The rest is up to you.
I haven't developed that area very far yet, because I do not use such links.

Q: How secure is setfeed?

A: Not very.  The channel over which the requests are sent (either uux or
mail or whatever) should be secure because unencrypted passwords are sent.
99% of the time, this will be a direct link between two machines (why else
is there a news feed) so as long as your inter-machine channel is secure,
this will be sort-of-secure.   (Note that some uucp's have a bug whereby
incoming uux files are readable while they sit in the spools, allowing
normal users access to incoming mail and uux transfers.  Beware of this.)

I would be happy for somebody to write a more secure setfeed.  Digital
signature would be the best system.   Note that the use of 'crypt' in
setfeed only protects you against users who get access to the site
password file.  They can't read the passwords there if they are encrypted.
But you should not make that file generally readable anyway.  Short of
digital signature, the plain-password has to come in the feed request.

Q: What about loops in dynamic feeding?

A: If you have truly dynamic feeding, then a loop could be a problem.
You see, once you request a group, the request will travel along the
loop.  Even if everybody unsubscribes, that request will continue to
loop around, and so the group will still get fed.  Not a big problem, I
guess, since the alternative is to use 'sys' files and full feeds, which
give the same result.

Eventually I would like to see a fancy system, that, when asked for a new
group, goes around the local nets (and eventually further) looking for it.
Once it is found, an ACK gets sent back to the desired feeder, and only
that feeder does the work.  That would be a fully dynamic net.
