Chapter 23 - Internet News The Internet News
Chapter 23 - Internet News The Internet News daemon (INN) is arguably the most popular Netnews server in use today. INN is extremely flexible and is suitable for all but the smallest news sites.135 INN scales well and is suited to large news server configurations. The INN server comprises a number of components, each with their own configuration files that we will discuss in turn. Configuration of INN can be a little involved, but we’ll describe each of the stages in this chapter and arm you with enough information to make sense of the INN manual pages and documentation and build configurations for just about any application. Some INN Internals INN’s core program is the innd daemon. innd’s task is to handle all incoming articles, storing them locally, and to pass them on to any outgoing newsfeeds if required. It is started at boot time and runs continually as a background process. Running as a daemon improves performance because it has to read its status files only once when starting. Depending on the volume of your news feed, certain files such as history (which contain a list of all recently processed articles) may range from a few megabytes to tens of megabytes. Another important feature of INN is that there is always only one instance of innd running at any time. This is also very beneficial to performance, because the daemon can process all articles without having to worry about synchronizing its internal states with other copies of innd rummaging around the news spool at the same time. However, this choice affects the overall design of the news system. Because it is so important that incoming news is processed as quickly as possible, it is unacceptable that the server be tied up with such mundane tasks as serving newsreaders accessing the news spool via NNTP, or decompressing newsbatches arriving via UUCP. Therefore, these tasks have been broken out of the main server and implemented in separate support programs. Figure 23.1 attempts to illustrate the relationships between innd, the other local tasks, and remote news servers and newsreaders. Today, NNTP is the most common means of transporting news articles around, and innd doesn’t directly support anything else. This means that innd listens on a TCP socket (port 119) for connections and accepts news articles using the “ihave” protocol. Articles arriving by transports other than NNTP are supported indirectly by having another process accept the articles and forward them to innd via NNTP. Newsbatches coming in over a UUCP link, for instance, are traditionally handled by the rnews program. INN’s rnews decompresses the batch if necessary, and breaks it up into individual articles; it then offers them to innd one by one. Newsreaders can deliver news when a user posts an article. Since the handling of newsreaders deserves special attention, we will come back to this a little later. 135 Very small news sites should consider a caching NNTP server program like leafnode, which is available at http://wpxx02.toxi.uniwuerzburg. de/~krasel/leafnode.html.