Leafnode is a USENET software package designed for small sites, with a few tens of readers and only a slow link to the net. Only groups that someone has been reading in the past week are fetched from the upstream NNTP server. When someone stops reading a group, fetchnews will stop reading that group a week later (this is the default which can be configured), and when someone starts reading a group, fetchnews will grab all the articles it can in that group the next time it runs.