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From DBinSD <cdieb...@gmail.com>
Subject Re: EventAdmin Asynchronous/Parallel EventHandler
Date Wed, 18 Jan 2012 16:22:15 GMT

Thanks Holger, this is exactly the info I was looking for.  It sounds like
the Async Unordered Events might get me the performance I was looking for
(though the implications of 'unordered' events might be a problem in some
applications).  I will keep an eye out for an implementation of this
feature.

Thanks again
Chris



Holger Hoffstätte-4 wrote:
> 
> On 18.01.2012 03:35, DBinSD wrote:
>> Does the felix implementation of the EventAdmin service support the
>> delivery
>> of events, asynchronously and in parallel to multiple listeners at once? 
>> It
> 
> This was addressed as part of RFC 157 ("Updates to EventAdmin") sometime
> in 2010 and accepted, though I don't remember offhand what the
> implementation status was/is. IIRC it was part of 4.3.
> 
> The solution added a set of constants that express basic delivery
> behaviour/expectations. Not really enforceable end-to-end QoS constraints
> (which are impossible in Java anyway) but better than nothing.
> 
> --snip--
> 
> 5.2    Asynchronous Unordered Events
> 
> The following constants are added to EventConstants. This allows an Event
> Handler to indicate that it is willing to relax the event ordering
> requirements so that Event Admin can optimize delivery.
> 
> String EVENT_DELIVERY = "event.delivery"
> Service Registration property specifying the delivery qualities requested
> by an Event Handler service.
> 
> Event handlers MAY be registered with this property. Each value of this
> property is a string specifying a delivery quality for the Event handler.
> 
> The value of this property must be of type String, String[], or
> Collection<String>.
> 
> Since:
>         1.3
> See Also:
>         DELIVERY_ASYNC_ORDERED
>         DELIVERY_ASYNC_UNORDERED
> 
> String DELIVERY_ASYNC_ORDERED = "async.ordered"
> Event Handler delivery quality value specifying the Event Handler requires
> asynchronously delivered events be delivered in order. Ordered delivery is
> the default for asynchronously delivered events.
> 
> This delivery quality value is mutually exclusive with
> DELIVERY_ASYNC_UNORDERED. However, if both this value and
> DELIVERY_ASYNC_UNORDERED are specifed for an event handler, this value
> takes precedence.
> 
> Since:
>         1.3
> See Also:
>         EVENT_DELIVERY
> 
> String DELIVERY_ASYNC_UNORDERED = "async.unordered"
> Event Handler delivery quality value specifying the Event Handler does not
> require asynchronously delivered events be delivered in order. This may
> allow an Event Admin implementation to optimize asynchronous event
> delivery by relaxing ordering requirements.
> 
> This delivery quality value is mutually exclusive with
> DELIVERY_ASYNC_ORDERED. However, if both this value and
> DELIVERY_ASYNC_ORDERED are specifed for an event handler,
> DELIVERY_ASYNC_ORDERED takes precedence.
> 
> Since:
>         1.3
> 
> See Also:
>         EVENT_DELIVERY
> 
> --snip--
> 
> Also see
> http://stackoverflow.com/questions/7018762/when-to-use-osgi-eventadmin-and-when-not
> for BJ's official answer.
> 
> hope this helps
> Holger
> 
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> 

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