[
Date Prev][
Date Next][
Thread Prev][
Thread Next][
Date Index][
Thread Index]
[
List Home]
|
RE: [ecf-dev] handling pub-sub providers with RFC 119
|
Hi Scott,
I'm fine with using more than one property to describe the service
location (if it makes sense for certain protocols e.g. JMS).
My main message is that ServicePublication.PROP_KEY_ENDPOINT_LOCATION
property (you called it "endpointID") is the URI describing where to
reach the service or in other words where to connect to and send
invocation messages in order to call the service e.g.
http://myserver.de/myWebService, jms:activemq::B:1099/myServiceTopic or
{tcp://mybroker:1099 + additional property like topicName =
myServiceTopic}.
So this property has actually already the meaning of the new introduced
"connectTargetID" property.
To earth my points to concrete class and methods:
a) org.eclipse.ecf.osgi.services.discovery.IServiceEndpointDescription:
the already existing and inherited method URI getLocation(), which
returns the value of ServicePublication.PROP_KEY_ENDPOINT_LOCATION,
is semantic-wise the same as the new getConnectTargetID() method
returning org.eclipse.ecf.core.identity.ID
If it's just the more convenient return type which is desirable then we
should have at least similar names: e.g. getLocationAsID();
b) org.eclipse.ecf.osgi.services.discovery.IServiceEndpointDescription:
the already existing and inherited method String getEndpointID(), which
returns the value of ServicePublication.PROP_KEY_ENDPOINT_ID,
seems to have a different meaning then the new and similar sounding
getECFEndpointID() method returning an ID.
The first one is just a unique id (#123456) identifying the
stub/endpoint exposing a service. That's I think something similar to
ECF's IServiceID which inherits from ID but gives the ID the meaning to
identify a service instance and not a service container or host. If I
understood correctly the other method getECFEndpointID() is returning
the id of the host machine where the service instance is actually
executed.
To prevent confusion here using another name would make sense e.g.
getServiceHostID().
But maybe I've missed something?! Please let me know.
Regards,
Philipp
> -----Original Message-----
> From: ecf-dev-bounces@xxxxxxxxxxx [mailto:ecf-dev-bounces@xxxxxxxxxxx]
> On Behalf Of Scott Lewis
> Sent: Tuesday, April 28, 2009 6:12 PM
> To: Eclipse Communication Framework (ECF) developer mailing list.
> Subject: Re: [ecf-dev] handling pub-sub providers with RFC 119
>
> Hi Philipp,
>
> Konradi, Philipp wrote:
> > Hi Scott,
> >
> >
> >> Perhaps, but this isn't necessary the endpoint for all clients
> >> participating in the group. That is, what if A (above) publishes a
> >> service? What would its endpoint be in the service publication?
> >>
> > If A would publish a service, then I could think of its service
> endpoint
> > location in the service publication to look like:
> > jms:activemq::B:1099/myServiceTopic
> > B being the hostname of the broker, myServiceTopic being the name of
> the
> > JMS topic on which the ECF JMS provider is listening and the service
> > instance can be invoked.
> > The given URL is probably not 100% correct but hopefully provides an
> > idea of how it might look.
> >
>
> Yes, I agree this is possible (i.e. an endpoint identifier that
> identifies both the pub-sub group *and* the endpoint within that
> group).
>
> But I would say it's sort of clumsy...as such an endpointID can become
> quite complex...and all this is in an opaque String (or an opaque URI
> :). IMHO the ECF ID notion works rather nicely for this...because
>
> a) IDs can have namespaces...so it's possible to use that namespace to
> (e.g.) select a relevant provider (rather than using
> jms:activemq:ecf...etc).
> b) IDs only need to be parsed once (whereas Strings or even opaque
URIs
> potentially many times).
> c) Having two IDs...one to identify the pub sub group to connect to,
> and
> the other to identify the endpoint within the group...seems more
> natural
> to me than to put them into an opaque and complex ID as above.
>
> But in any event, since we (ECF) now have both, we can now accomodate
> providers that such addressing either way.
>
> Scott
>
> > Regards,
> > Philipp
> >
> >
> >> -----Original Message-----
> >> From: ecf-dev-bounces@xxxxxxxxxxx [mailto:ecf-dev-
> bounces@xxxxxxxxxxx]
> >> On Behalf Of Scott Lewis
> >> Sent: Thursday, April 23, 2009 5:09 PM
> >> To: Eclipse Communication Framework (ECF) developer mailing list.
> >> Subject: Re: [ecf-dev] handling pub-sub providers with RFC 119
> >>
> >> Hi Phillip,
> >>
> >>
> >> Konradi, Philipp wrote:
> >>
> >>> Hi Scott,
> >>>
> >>> <stuff deleted>
> >>> [Konradi, Philipp] I'd prefer option two, since option one doesn't
> >>> support the transparency which RFC 119 targeted for OSGi
> application
> >>> (services&clients) bundles.
> >>>
> >>>
> >> Agreed, option 1 doesn't support the intended usage of RFC119
> >> (transparent remoting)...but in fact as I understand it RFC 119 in
> >>
> > it's
> >
> >> current form doesn't actually support this model (pub/sub) of
> >> remoting/remote services (because there is only the notion of
> >> 'endpoint'...and no notion of pubsub group).
> >>
> >> So we (ECF) will/are introducing the API described below to make it
> >> possible to use RFC 119 publication and proxy creation within
pubsub
> >> groups (e.g. JMS). It is, of course, also possible for people to
> use
> >> the ECF remote services API to explicitly access proxies and the
> other
> >> forms of remote communication on IRemoteService as well.
> >>
> >>
> >>> BTW: in [0]:
> >>>
> >>>
> >>>> Consider the following architecture:
> >>>>
> >>>> A <--> B <--> C
> >>>>
> >>>> In this architecture, we have two clients 'A' and 'C' and a
server
> >>>> 'B'...all participating in the same publish and subscribe group.
> >>>>
> >>>>
> >>> To verify I've understood it correctly: 'server' is in case of JMS
> >>>
> >> the
> >>
> >>> JMS broker?
> >>>
> >>>
> >> Sort of :). In ECF's JMS provider implementation (with TCP anyway)
> >>
> > the
> >
> >> situation looks like this:
> >>
> >> A <--> (JMS Broker) <--> C
> >> |
> >> B
> >>
> >> The JMS Broker can be (and usually will be) run on the same
> >> process/host
> >> as B (the ECF 'group manager'). But this isn't required,
> >>
> > actually...as
> >
> >> the JMS Broker and B can/could be run on a process separate from B.
> >> You
> >> might ask...why have B at all? Well, the answer is that B manages
> the
> >> group membership for the entire group, so that reliable group
> >> membership
> >> changes can be communicated to the others (A and C). It also
> can/does
> >> manage any authentication that occurs for access to the group.
> >>
> >>
> >>>
> >>>> ...By 'these cases'
> >>>> I
> >>>> mean publish and subscribe groups that are used for remote
> services
> >>>> between members of those groups (e.g. JMS groups, etc).
> >>>>
> >>>> Currently, there's no direct support in RFC119 for remote
services
> >>>> within pubsub groups... because although RFC119 has the notion of
> >>>>
> > an
> >
> >>>> 'endpoint ID', this endpoint ID gives the location of the remote
> >>>> service's host...which assumes that the host is a server (i.e.
can
> >>>>
> >> be
> >>
> >>>> reached *directly* from a client), rather than indirectly (i.e.
> via
> >>>>
> >> a
> >>
> >>>> pub/sub group).
> >>>>
> >>>>
> >>> [Konradi, Philipp] That's correct, RFC 119 really does not say a
> >>>
> > word
> >
> >>> about pub-sub... though my thinking was always that pub-sub is
> >>>
> > easily
> >
> >>> possible with RFC 119 as well. But let's see, this discussion
> sounds
> >>> interesting...
> >>> I assume by saying 'endpoint ID' you mean RFC 119
> >>> ServicePublication.PROP_KEY_ENDPOINT_LOCATION property.
> >>> ServicePublication defines also a property called
> >>>
> >> PROP_KEY_ENDPOINT_ID
> >>
> >>> but this is just some unique service endpoint ID (e.g. an UUID)
> >>>
> >> allowing
> >>
> >>> to find out whether service metadata discovered via different
> >>>
> >> discovery
> >>
> >>> providers belongs to the same service instance or not.
> >>> My interpretation of RFC 119 PROP_KEY_ENDPOINT_LOCATION property
is
> >>>
> >> that
> >>
> >>> it's the URL under which the advertised service endpoint can be
> >>>
> >> reached.
> >>
> >> Right this is my understanding.
> >>
> >>
> >>> So in case of an Web service endpoint the url would probably
> contain
> >>> local host and port, in case of JMS (indirect communication) the
> url
> >>> would contain the host name of the JMS broker, port and the queue
> or
> >>> topic name.
> >>>
> >>>
> >> Perhaps, but this isn't necessary the endpoint for all clients
> >> participating in the group. That is, what if A (above) publishes a
> >> service? What would its endpoint be in the service publication?
> >>
> >>
> >>> BTW: Would it make sense to add some (configuration) mechanisms to
> >>> select whether JMS queues or topics (request-response or pub-sub)
> >>>
> >> should
> >>
> >>> be used for exposure of a service?
> >>> I could think of using either intents for this or/and additional
> >>> configuration data with the service.
> >>>
> >>>
> >> Effectively, ECF already now already has this with the
> >> IHostContainerFinder. It would allow the usage of intents (or any
> >> other
> >> service properties) to determine how/what container (and what it's
> >> configuration might be) is made available for usage as the
> >>
> > distribution
> >
> >> provider ...and for JMS can/could determine what JMS queues/topics
> are
> >> used to expose the service (e.g. by creating JMS IContainer
> instances
> >> of
> >> appropriate type).
> >>
> >> A custom IHostContainerFinder can replaced/substituted by creating
> an
> >> implementation of IHostContainerFinder and registering it as a
> service
> >> (whiteboard pattern) via the service registry with a
service.ranking
> >> that is higher than the default one (which is Integer.MIN_VALUE).
> >>
> >> Thanks,
> >>
> >> Scott
> >>
> >>
> >> _______________________________________________
> >> ecf-dev mailing list
> >> ecf-dev@xxxxxxxxxxx
> >> https://dev.eclipse.org/mailman/listinfo/ecf-dev
> >>
> > _______________________________________________
> > ecf-dev mailing list
> > ecf-dev@xxxxxxxxxxx
> > https://dev.eclipse.org/mailman/listinfo/ecf-dev
> >
>
> _______________________________________________
> ecf-dev mailing list
> ecf-dev@xxxxxxxxxxx
> https://dev.eclipse.org/mailman/listinfo/ecf-dev
