I think you're on the right way. The key problem you're facing is instantiation.
DS components can made in such a way that the require a configuration
(configurationPolicy=require). By using managed service factory Configurations
you can configure each instance. This allows you to use Configuration Admin to
control instances of DS components, including specifying the filters of the
references.
So I would translate your processes to DS component that register services and
depend on services. You have to choose if a service is an input or an output.
This is the eternal sink/source problem. In a push model the DS component
registers a service that is accepting input (i.e. void methods with
parameters). In the pull model the service is a source and is called (i.e. no
parameter methods with a return value).
public Push {
void out(Object o);
}
public Pull {
Object in();
}
With the push model you need a source that can generate initial values and with
the pull model you need to ask for a result that then ripples back.
You can then put your nets in a bundle in a standard location like
OSGI-INF/nets/*.xml
An extender bundle then detects a net bundle and reads the XML. It then
translates the XML to Configuration Admin Configurations, making sure the
components are wired up as defined in the XML. You probably need a unique
identifier for the net and then make sure each service that is registered uses
that unique id and make sure any references are also link to other services of
this unique id.
If the bundle is uninstalled, the extender removes the Configurations.
Hope this helps. Kind regards,
Peter Kriens
> a) How can these processes be instantiated from a XML file as DS components?
You could translate
> b) Is is feasible to model typed ports as services? How would then the
> "channel" over which the communication happens look like?
> c) The whole net of processes as one bundle?
> d) Perhaps you would model this in a totally different way?
On 2 mrt. 2012, at 06:26, Michael Köndling wrote:
> Hello,
>
> since I'm new to OSGi I would like to ask the experts a few questions on a
> design question.
>
> We have a Java-based data-flow system which consists of processes
> (technically threads) which have typed input and output ports. There are
> various types of these processses, like read-, write-, compound-, and
> filter-processes. The type of the input port determins which data structure
> the process can handle.
> There is a XML file which describes a configuration - a net - of these
> processes. Some "Configurator" reads the XML file, instantiates and starts
> these processes.
>
> Except some reader which is reading from a data-source immediately, the other
> threads are blocked until they receive data through a channel (connection of
> input and output port). Processes block if the channel is empty while reading
> or the channel is full while writing. Since a process could receive from any
> other process on its input-port this adds nondeterminism to the whole system.
>
> The runtime environment should be able to handle many nets of these processes.
> Now, we have the task to "port this to osgi".
>
> Using DS I would map in this way:
>
> Net -> Bundle
> Process -> DS Service Component
> Port of Process -> Service provided/required by DS Service Component
>
> The questions for me then are
> a) How can these processes be instantiated from a XML file as DS components?
> b) Is is feasible to model typed ports as services? How would then the
> "channel" over which the communication happens look like?
> c) The whole net of processes as one bundle?
> d) Perhaps you would model this in a totally different way?
>
> Would appreciate any help on this.
> Thank you in advance!
> Michael
>
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