Umlaut Technical Overview
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17:41, 27 December 2007
So there are Services, and they are grouped into Institutions. How do they actually get brought into play to respond to a resolve request? The [[http://umlaut.rubyforge.org/api/classes/Collection.html Collection ]] object. A Collection keeps track of a bunch of services to be used for a given session.
The resolve index action creates a new Collection based on ip address and other session information. The new Collection will discover which Institutions apply to a user, and which Services belong to that Institution, and file them all by priority. Other Services may be found that do not belong to an Institution, for instance Collection is supposed to identify SFX servers for a user's IP addr via the Worldcat Registry, create a Service pointing to that foreign SFX server, and include that in a Collection. Although this functionality may not be working at present.
The Collection is stored in the Session. It is not actually an ActiveRecord, instead it is stored serialized in the Session--along with all it's Services. One catch to this is if you change Service configuration in services.yml, users may still be getting the old configuration from their serialized Collection in their Session. Deleting all Sessions is a good idea to handle this. (Deleting sessions ought not to interfere with anyone's activity in progress, except to uncache certain things).
The stored Collection will not be used if a user's IP address changes--even if they have the same session. For instance, bringing your laptop to a new location will still cause a Collection to be rebuilt.
When the resolve action wants to actually execute services, it goes through each priority level, and asks the Collection for the Services at that priority level.
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