Re: Notification implementation

[Ignacio Silva-Lepe]

Hi Jean-Sebastien,

Apologies for the tardiness, I was away and without connectivity for a
couple
of days.
Responses in line.


On 6/22/07, Jean-Sebastien Delfino <[EMAIL PROTECTED]> wrote:

Ignacio Silva-Lepe wrote:
> I have been playing with the idea of a notification component
> implementation
> type that would serve as a vehicle to incorporate pub/sub interactions
> into
> SCA/Tuscany. Within a single composite or domain, producers and
consumers
> would be explicitly wired to and from a notification component (ie, a
> component with an implementation.notification). In addition, to enable
> produ-
> cers and consumers to exchange messages across domains or even across
> composites, a binding.notification could be used by composite references
> and services.
> I would like to create a couple of new modules in trunk to host code to
> support
> implementation.notification and binding.notification. If people are ok
> with
> it, I would
> like to do this in the next few days.
> Thoughts?
>

That sounds useful to me. I have a few questions:

Could you describe here how an application developer would program a
notification component? Will the component implement a fixed
notification interface or will this support user defined business
interfaces? Are notification methods just one-way methods?

A notification component would be specified for a given 'space' of messages,
denoted by the interface in a corresponding notification component type,
which in turn is referred to by the notification component's implementation.
This interface is app-specific and defines the makeup of the messages being
exchanged. At least initially, notification methods are intended to be
one-way.

What are you proposing for <implementation> and <binding> element? what

would they look like? How do you declare what you're going to publish
and how does a component declare a subscription? Do you have a sample
composite that you could paste here?

The proposed elements would be <implementation.notification> and
<binding.notification>. A component becomes a publisher or producer by using
a reference to a notification component, and a component declares a
subscription
by defining a service that is wired from a notification component.

Here's a sample composite for a 'local' notification use case, ie, where
producers
and consumers are contained in the same composite (or domain) and explicitly
wired to/from the notification component:


<composite xmlns="http://www.osoa.org/xmlns/sca/1.0";
          name="TrafficAdvisoryNotificationLocalComposite">

   <component name="TrafficAdvisoryProducer">
       <implementation.java class="
org.apache.tuscany.sca.implementation.notification.TrafficAdvisoryProducer
"/>
       <reference name="destination"
target="TrafficAdvisoryNotificationComponent"/>
   </component>

   <component name="TrafficAdvisoryNotificationComponent">
       <implementation.notification name="TrafficAdvisoryNotification"/>
       <!-- Never use > 1 reference elements here !! -->
       <reference name="TrafficAdvisoryNotificationReference"
                  multiplicity="0..n"
                  target="TrafficAdvisoryConsumer1
TrafficAdvisoryConsumer2"/>
   </component>

   <component name="TrafficAdvisoryConsumer1">
       <implementation.java class="
org.apache.tuscany.sca.implementation.notification.TrafficAdvisoryConsumer
"/>
       <property name="name">Consumer1</property>
   </component>

   <component name="TrafficAdvisoryConsumer2">
       <implementation.java class="
org.apache.tuscany.sca.implementation.notification.TrafficAdvisoryConsumer
"/>
       <property name="name">Consumer2</property>
   </component>

</composite>

and here's the corresponding component type:

<componentType xmlns="http://www.osoa.org/xmlns/sca/1.0"; xmlns:xsd="
http://www.w3.org/2001/XMLSchema";>
    <service name="TrafficAdvisoryNotificationService">
          <interface.java interface="
org.apache.tuscany.sca.implementation.notification.TrafficAdvisory"/>
    </service>

    <reference name="TrafficAdvisoryNotificationReference"
               multiplicity="0..n">
          <interface.java interface="
org.apache.tuscany.sca.implementation.notification.TrafficAdvisory"/>
    </reference>
</componentType>

Are you thinking of flowing notifications over various protocols already

supported by Tuscany? or adding a new protocol through this new binding?

I think the simplest case is to flow notifications as literal xml over http,
so that's
what I am working on prototyping.

Thanks

--
Jean-Sebastien


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