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rssCloud design issue

Saturday, July 25, 2009 by Dave Winer.

Bryan Field-Elliot raises an interesting question in the comments on the rssCloud walkthrough.  

"The automatic expiration after 25 hours seems rather arbitrary. If a cloud server is going to have a policy of expiring subscriptions after X hours, I suggest that the value X be published somewhere. Within the <cloud> element perhaps, or, as part of the return value from the pleaseNotify call. That way different implementations of cloud servers can vary this value as they feel appropriate, and different aggregators will have a means to know how often they need to resubscribe." 

I responded as follows (and reposted here because I wanted to make sure it gets proper consideration): 

It's an interesting question. 

On the pro side -- it would add flexibility. 

On the con side -- it would also add complexity. Another thing to test, another thing to break. 

The subscriber should poll anyway, periodically. If it detects a change that it wasn't notified of, it can resub. No harm if already subbed. In my implementation of rssCloud that gives you another 25 hours. 

I'm not sure I shouldn't give you another 25 hours anytime I detect that you're alive, for example, you respond to a notification. 

The point is to give the cloud a rule for when it's okay to clean out garbage. It's really hard to imagine why someone would want a different value.