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Subject: RE: [sca-assembly] RE: [ASSEMBLY-31] Wiring from a reference with nobinding to a service with a binding
There are certianly cases where an optimized binding implementation doesn't
look much different from the full remote implementation. I don't see why
that's a concern. A Web service binding is a case of something between
full local RMI/IIOP that you and I both worked on, versus the JMS case
where there's very little you can do to optimize locally and still maintain
the semantics. In a locally optimized Web service binding, it is often the
case (think security) that a SOAP message has to be created and the ONLY
thing you can avoid is the transport itself.
Dave Booz
STSM, SCA and WebSphere Architecture
Co-Chair OASIS SCA-Policy TC
"Distributed objects first, then world hunger"
Poughkeepsie, NY (845)-435-6093 or 8-295-6093
e-mail:booz@us.ibm.com
http://washome.austin.ibm.com/xwiki/bin/view/SCA2Team/WebHome
Simon Nash
<NASH@uk.ibm.com>
To
12/06/2007 03:59 "Peshev, Peter"
PM <peter.peshev@sap.com>
cc
"OASIS Assembly"
<sca-assembly@lists.oasis-open.org>
Subject
RE: [sca-assembly] RE:
[ASSEMBLY-31] Wiring from a
reference with no binding to a
service with a binding
Peter,
I'll admit that I know very little about JMS (though I intend to learn
much more). I used JMS as an example to make a point, and from your reply
I believe that I have made it reasonably effectively. If these are the
semantics of using "real JMS" to make a call, then any optimization must
preserve the same semantics. This does not look very simple!
I do have some relevant experience, though not for JMS. In a past life, I
implemented local calling optimizations for RMI-IIOP, and there were some
"interesting" wrinkles including very careful attention to cases involving
different classloaders at the source and target ends. In that case,
correct semantics could only be preserved by baking this optimization into
the RMI-IIOP runtime. I think the same is likely to be the case for JMS.
Replacing the JMS invocation by some other kind of "optimized" local call
doesn't seem likely to preserve all of the expected semantics.
Simon
Simon C. Nash, IBM Distinguished Engineer
Member of the IBM Academy of Technology
Tel. +44-1962-815156 Fax +44-1962-818999
"Peshev, Peter" <peter.peshev@sap.com>
06/12/2007 17:36
To
Simon Nash/UK/IBM@IBMGB, "OASIS Assembly"
<sca-assembly@lists.oasis-open.org>
cc
Subject
RE: [sca-assembly] RE: [ASSEMBLY-31] Wiring from a reference with no
binding to a service with a binding
Hi Simon,
can we clarify first the "observable JMS semantics" .
For queues it is guaranteed that there will be exactly once delivery,
there will be no side effect. (Assuming the local call deals with
crashes and provides the quality of service required by the intents)
For JMS topics it is quite different, where as side effect of a call
to a service, a message should be sent, and another service from another
component on the same topic could be invoked. Such usage of topics
coincides pretty much to some pub/sub messaging model that let's say is
in scope of this TC to discuss.
Is this your understanding as well ?
Best Regards
Peter
-----Original Message-----
From: Simon Nash [mailto:NASH@uk.ibm.com]
Sent: Thursday, 6. December 2007 17:55
To: OASIS Assembly
Subject: RE: [sca-assembly] RE: [ASSEMBLY-31] Wiring from a reference
with no binding to a service with a binding
I don't want to spoil the party, but...
It's clearly fine to do this local optimization for <binding.sca>. But
it
is OK to do this for <binding.jms>? To make this safe, it would be
necessary to ensure that all observable JMS semantics are preserved.
Are
we agreed that any local optimization would need to do this?
Simon
Simon C. Nash, IBM Distinguished Engineer
Member of the IBM Academy of Technology
Tel. +44-1962-815156 Fax +44-1962-818999
"Peshev, Peter" <peter.peshev@sap.com>
06/12/2007 14:03
To
Mike Edwards/UK/IBM@IBMGB, "OASIS Assembly"
<sca-assembly@lists.oasis-open.org>
cc
Subject
RE: [sca-assembly] RE: [ASSEMBLY-31] Wiring from a reference with no
binding to a service with a binding
Hi Mike,
At least to me that's very good model and clear description that solves
nicely ASSEMBLY-1 & 31 as long the last paragraph is kept.
Best Regards
Peter
From: Mike Edwards [mailto:mike_edwards@uk.ibm.com]
Sent: Thursday, 6. December 2007 11:36
To: OASIS Assembly
Subject: RE: [sca-assembly] RE: [ASSEMBLY-31] Wiring from a reference
with
no binding to a service with a binding
Peter,
After some private discussions of the issues with Dave, I now believe
that
Dave's proposal is
the right one. The treatment of services should not be exactly the same
as the treatment of
references.
Creating a proxy object for a reference is a very different process from
the business of
creating an endpoint for a service.
It is reasonable for an SCA runtime to know in advance what endpoints it
has to create for
the services present in the domain - and that the idea that new
endpoints
have to be created
merely to satisfy a new client reference turning up somewhere in the
domain is not reasonable.
So, I think that the principle for a service needs to be that there will
be an endpoint created
for each binding explicitly declared for the service, with the existence
of a binding.sca
endpoint IF no explicit binding is specified.
The point you make in the last paragraph below, I believe DOES apply to
references. So, for
a reference, a "binding.sca" (either implicit or explicit) can be taken
to
mean "give me a connection
to the target service(s), using whatever communication means are
available". In this case,
I think that the proxies given to the component for the reference could
each deal with a separate
protocol and that the protocol used simply "matches" the target
service's
protocol.
I agree - in these cases the protocol used by the proxy is irrelevant to
the implementation code.
IF the reference or the service requires a particular protocol for some
reason, then that need
should be expressed via an intent and the presence of the intent would
then limit the range of
protocols that can be used.
So, I think it gives us a clean model where:
a) For services, you get endpoints for each explicitly declared binding,
with the default of
binding.sca if there is no explicit binding. Multiple bindings imply
multiple endpoints.
b) For references, you get proxies using any of the declared bindings,
with the default of
binding.sca if there is no explicit binding. The binding actually used
for a given wire depends
on the binding(s) attached to the target service, where the principle is
to select compatible
bindings (for the moment, I take that to mean the binding types must be
the same).
In addition, binding.sca is "flexible" for the purposes of wiring and
will
match ANY binding
on the target service(s).
I think that this is the simplest model and avoids the problem
associated
with the model which
you have proposed, that binding.sca may or may not be present depending
on
whether it
can or cannot satisfy the intents attached to the reference.
I think that the model I propose has the merit of simplicity and
encourages the creation of
simple compositions, where most references to targets within the domain
either have no
explicit binding at all (the 80% case) or have binding.sca attached,
while
any service endpoints
which need an explicit binding attached in order to be available outside
the domain don't
have to be concerned about additional endpoints being necessary for
clients within the
domain.
I note that the principle of "optimised communication" between clients
and
providers that
run on the same machine or within the same process, is not affected by
this model. The
runtime is ALWAYS free to optimise communications, as long as the
interfaces to both
client and provider code are honoured.
Yours, Mike.
Strategist - Emerging Technologies, SCA & SDO.
Co Chair OASIS SCA Assembly TC.
IBM Hursley Park, Mail Point 146, Winchester, SO21 2JN, Great Britain.
Phone & FAX: +44-1962-818014 Mobile: +44-7802-467431
Email: mike_edwards@uk.ibm.com
"Peshev, Peter" <peter.peshev@sap.com> wrote on 06/12/2007 08:51:22:
> Hi Mike,
>
> OK, I understand we have different opinion between me and you + Dave
>
> But can you help me understand why ? I guess you are afraid that the
> component may break without binding.xyz in the scenario below. However
> the contract between the SCA assembly and the programming technology
is
> the interface that is on the service. If the SCA runtime can construct
> objects fulfilling the interface, then what is the problem ?
>
> I.e. does it makes a difference for a component with interface.wsdl
> whether its XML-ish data objects in the interface were received via
> HTTP POST operation, via SOAP over JMS, or by direct local call ?
>
> Best Regards
> Peter
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
3AU
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
3AU
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