Methods and apparatus, including computer program products, implementing and using techniques for retrieving events from an event port. A request to retrieve a specified number of events from an event port to which completed events are posted by one or more event sources is received from a computer software application. It is determined whether the specified number of events is available at the event port. If the specified number of events is available at the event port, the specified number of events is retrieved from the event port and the retrieved events are returned to the requesting computer software application. If fewer events than the specified number of events are available at the event port, the request is placed in a request queue with requests to be processed at a later time and the request queue is ordered based on priorities of the requests in the request queue.