Lucas Galfaso wrote > This was my understanding, but reading > > <quote> > 113.7.2 Asynchronous Event Delivery > ... > The Event Admin service can use more than one thread to deliver > events. If it does then it must guarantee that each handler receives > the events in the same order as the events were posted. This ensures > that handlers see events in the expected order. For example, it would > be an error to see a destroyed event before the corresponding created > event. > ... > The Event Admin service ensures that events are delivered in a > well-defined order. For example, if a thread posts events A and B in > the same thread then the handlers should not receive them in the order > B, A. if A and B are posted by different threads at about the same > time then no guarantees about the order of delivery are made. > </quote> > > What is the difference between not sending the events in the order > they are created and using two threads to send the two events with > minimal time difference? At the end of the day, if two threads are > used, then any "reasonable" logic of the second event may have to be > processed before the logic of the first event as nothing warrantees > what thread will be executed first. > Right, therefore the spec defines only the event delivery of a single thread. Events from the same thread have to be delivered in the order they have been sent - regardless of async or sync delivery. So if you have one single thread sending events, your event handler will never be called multi threaded (except your handler sends an event during the event handling of another event maybe).
As soon as more than one thread is sending "everything" can happen which means it depends on the implementation of the event admin. The older event admin implementation 1.0 of Apache Felix for example did queue all events. In this case even in a multi threaded environment events are sent one after the other. The latest Apache Felix Event Admin is faster and sends events in parallel. HTH Carsten -- Carsten Ziegeler [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
