Subscription watch lists for event handling

A computer program product for watch list oriented processing of events in a multi-object event data processing system, the computer program product comprising:

• a non-transitory computer readable storage medium comprising a device having computer readable program code embodied therewith, the computer readable program code comprising:
• computer readable program code for executing an event loop in a host computing system and receiving events in the event loop;
• computer readable program code for producing an occurrence of resource consumption resulting from an application of subscription rules prior to processing the received events in the event loop and permitting sequential processing of the received events in the event loop without concurrent corresponding additional resource consumption by:
• computer readable program code for pre-processing prior to a receipt of events occurring in connection with different objects, a set of subscriptions against a pool of objects monitored for events in the data processing system by applying a set of subscription rules for different ones of the subscriptions to the objects in the pool before processing the received events, the application of the rules producing a watch list of objects and corresponding subscribers based upon subscription criteria for subscriptions to the received events;
• computer readable program code for persisting the watch list produced by the application of the rules into a database;
• computer readable program code for periodically according to a schedule accounting for changes in composition of the pool by repeating the pre-processing of the set of subscriptions to produce a new version of the watch list that is reflective of a contemporaneous state of the object pool while re-designated the watch list produced by the application of the rules in the database as a watch list for an old state of the pool that existed prior to the contemporaneous state of the object pool;
• computer readable program code for receiving events in the data processing system corresponding to different ones of the objects in the pool of objects;
• computer readable program code for determining for each of the received events, a corresponding object for a corresponding one of the received events, and looking up in the old watch list an identifier of the corresponding object to both the watch list for the old state, and if the identifier is not found in the old watch list, looking up in the new watch list the identifier so as to determine if the corresponding one of the received events pertains to an object referenced in either the old watch list or the new watch list;
• and,
• computer readable program code for forwarding for each one of the received events, a notification to one or more subscribers corresponding to an object in either of the watch lists matching an object implicated by the one of the received events so as to produce an occurrence of resource consumption resulting from the application of the subscription rules prior to the processing of the received events thereby permitting sequential processing of the received events without concurrent corresponding resource consumption.