Maintenance mechanisms



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Maintenance mechanisms

 

An essential component of the Net News system is the expiration of old articles. Since news articles are created at such a tremendous rate, few if any sites can afford to store more than a small fraction of them for any length of time. The Net News system works around this by expiring or removing all articles older than a certain age as part of a routine task that executes every night. Consequently, vote sources will contain vote information for articles that are no longer available unless steps are taken to expire the vote information as well.

There are two reasonable means for expiring vote information. The first option is to check each vote against some news server, presumably the local one. If the article to which the vote refers is still available from the news server, the vote information about the article is retained, otherwise it is discarded. The second option is to associate a time stamp with the vote information for each article. The vote information can then be expired after it reaches some age just as old news articles are expired. The current implementation of the system allows only one global expiration age to be set, but a trivial extension to the system would allow different groups to be expired at different rates.

Since the vote server is an independent process, it can incorporate expiration as one of its tasks to perform on the vote database. Vote files are harder to work with since there is no process directly associated with them. For this reason, whenever new votes are added to a vote file by the collaborative interface module, the IM arranges for the votes already in the vote file to be examined for validity.



next up previous contents
Next: Comparison of system Up: Design Architecture Previous: Security and privacy



David A. Maltz (dmaltz@cs.cmu.edu)