Chapter 12. Publish and Subscribe

The trouble with being punctual is that there's nobody there to appreciate it.

�Franklin P. Jones

The traditional guidelines for the use of RSS feeds present a small problem. There is always going to be a balance between the need to be up-to-date and the need to refrain from abusing the feed publisher's server by requesting the feed every few seconds. While the norm is to request the feed a maximum of once an hour, many feeds deserve following much more closely. Conversely, many feeds update only once a day, or less often. Requesting those once an hour is a waste of time and resources and potentially expensive for the publisher. In this chapter, we look at the two systems currently prescribed for RSS feeds to solve these problems.