Installing INN part 2: [Previous]
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2. Feeding a large number of sites
Innd tries to keep as many batchfiles open for as long as possible.
It will normally open as many as it can, using all the available
descriptors minus a fixed number for internal use (log files, etc.).
You can explicitly set the number of files to open by using the "-o"
If you have more outgoing feeds than available descriptors, innd
will recycle the files on a a "least recently used" basis. If most of
your feeds get most articles (or you have vastly more feeds then
available descriptors), this will lead to "file thrashing," closing
and opening all the excess feeds on each article. To reduce this, you
can have innd use an internal buffer for a site by using the "I"
parameter in the newsfeeds file. If a site does not have its batchfile
open, the server will not try to open it until there is more data to be
written then will fit in the buffer. For example, suppose innd was
started with "-o10" and there are 12 sites, all with "I512" in their
newsfeeds entry. If each article generates 50 bytes (a pathname and a
Message-ID), then innd will close and re-assign two descriptors every 10
or so articles.
A better alternative is to use funnels and an exploder. Funnels,
specified in the newsfeeds file, let multiple sites send their output
down a single stream. The advantage of funnels is that this stream can
be a channel; the primary disadvantage is that the funnel specifies what
data is to be written, not the individual sites. (Since most feeds will
want either "Wn" or "Wnm" entries, this is usually not a problem.)
In order for the funnel output to be useful, it usually must be
split into individual, per-site, files. Programs that do this type of
splitting are called "exploders." INN provides two exploders,
filechan and buffchan.
Filechan is the simplest, and most inefficient, exploder. It does
not keep any files open and is very system-call intensive. It can be
used to provide behavior (and performance!) that is similar to B2.11
inews. It can, however, be used as the funnel for an unlimited number
Buffchan keeps all its output files open all the time. It should
not be used for more sites then a single process can have open.
Buffchan also has flags to automatically flush its files, as well as
close and re-open them, every specified number of articles. (The re-
open capability is useful for things like nntplink in its "watch the
batchfile" mode.) Using buffchan with the "-l1\ -c50" flags will
give behavior that is similar to the C News relaynews.
Buffchan can be run as a full exploder ("Tx") in the newsfeeds
file. This means that you can use ctlinnd to send a command line down
buffchan's input stream. (Innd will also send a command whenever
newsgroups are modified.) The only useful message is "flush" which
will close, and re-open, the specified site files. You should also note
that the flow is one-way; full exploders cannot send any acknowledgement
[Source:"Installing InterNetNews 1.5.1"][
File-name:install.ms.2][Revision: 1.19 1996/11/10]
[Copyright: 1991 Rich Salz, 1996 Internet Software Consortium]
Installing INN Part 2 : [Previous]
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