I have a service, which publishes data.
It could have many subscribers. 10s not 100s
I want to loosley couple the service from its clients. I.e. I don't want to impliment a client proxy for each client subscriber in the service. I'd like the publishing service to define the contract. Duplex looks good for this scenario.
I've looked at the looked at the publish subscribe example in the SDK and this looks good.
However, the clients may not be always running and I'd like them to get the messages when they reconnect.
Any ideas or thoughts
BenW
Publish Subscribe but with a bit of reliability
Roberto Jucá
BenW,
Loosely coupled Publish/Subscribe notifications pattern is described in the WS-Eventing specification [1]. The current spec supports only a Push Subscription, where a message exchange between the event source and sink(s) is based on the async/fire&forget pattern. The Delivery mode can be extended based on the Event Source implementation such as the Pull, PushWithAck, Batched, Trap, etc., like it is described in the WS-Management specification [2].
Basically, the common part of the loosely coupled notifications is to create a Subscription based on the Event Sink interest (NotifyTo, EndTo, Expires, Filter, etc.) and store it in the Event Storage (memory, Sql, etc.). That’s the job of the Subscription manager service driven by WS-Eventing pattern.
The second service of the Event Source implementation is the Notification manager. This manager will deliver a notification message to the Event Sinks based on their interest (Subscription). Encapsulating a delivery “driver” from the service enables customizing a process delivery mode based on the business needs such as PushWithAck, Pull, etc.
Thanks
Roman
[1] WS-Eventing
[2] WS-Managment (7.0 Eventing)
p.s.
I am going to publish this weekend my article “WS-Eventing for WCF” at www.codeproject.com . This article describes a design and implementation of the WS-Eventing spec (soap stack, subscription and notification managers, Push Subscription, implementation, usage, etc.)
Aussie Dazz
Roman,
Just a short note of thanks for publishing the WS-Eventing for WCF paper. I have found it extremely enlightening and plan to utilise the model in my next up and coming project (Starting next month).
I have had some heart ache in the past trying to bend the Notification approach to my requirements, but, this model is just what the doctor ordered (so to speak).
I am particlularly interested in the ability to persist subscriptions to reliable media - nice :-)
If you know of anyone that has already embodied your model to a "commercial" assembly, I would be interested to know (may cut down my dev time)
Kind regards
NightOwl888