1. A method for performing event processing comprising: processing an event stream by an application executed by a computers system, the application comprising a plurality event handlers each receiving an input stream from the event stream, each event handler performing an event handling function and at least one of outputting an output stream to the event stream and updating a state; detecting an overload condition for a particular event handler of the plurality of event handlers; instantiating a plurality of partial handlers corresponding to the particular event handler; distributing events from an input stream corresponding to the particular event handler among the partial handlers; processing the distributed events in the partial handlers to generate partial output streams; aggregating the partial output streams of the partial handlers; and according to the aggregation, at least one of generating an output stream corresponding to the particular event handler and updating a state corresponding to the particular event handler.