To be more explicit, and echo Danny's point, I think we have four
options:
1) Mandate that auto-creation of channels works
2) Mandate that auto-creation of channels never works
3) Identify specific situations where #1 or #2 are possible
4) Take no position (this may still imply changes to the spec,
insofar as we highlight the point, while taking no sides)
I raised the issue because #4, it seems to me, leaves the door open
for interoperability failures. ("I deployed X over here with no
problems, but it doesn't work over there.")
Insofar as I've recall the discussion of the concrete use cases for
global domain channels (Oracle's F2F presentation), we explicitly
noted: no filters, no policies, and no bindings on said channels.
Meaning, configuration optional, and it's just a name. If it is just
a name, why can't I auto-create?
Anish notes that some people like the safety net of predefined
names, and I agree that's useful. However, that can be addressed in
a variety of ways that aren't nearly so heavy-handed as to simply
deny the deployment. ("The domain contribution includes references
to global domain channel "foo" that doesn't yet exist.
Continue/Cancel?).
-Eric.
On 2/7/11 9:30 AM, Danny van der Rijn wrote:
Yet all their configuration is optional?
On 2/7/2011 3:39 AM, Mike Edwards wrote:
Eric,
My view is that global channels
- indeed any channels - are more than a name - they have
configuration associated
with them. A system which does
not require them to be declared makes it difficult to provide
required configuration.
Yours, Mike
Dr Mike Edwards
Mail
Point 146, Hursley Park
STSM
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Hants SO21 2JN
SCA & Services Standards
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Co-Chair OASIS SCA Assembly TC
IBM Software Group
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(274097)
e-mail:
From:
Eric Johnson <>
To:
Anish Karmarkar <>
Cc:
Date:
04/02/2011 17:14
Subject:
Re: [sca-assembly]
[Issue 253]: (1.2) Must a global domain channel be
deployed before it can be used?
On 2/4/11 1:37 AM, Anish Karmarkar wrote:
> I don't see this being different than say requiring
that a variable be
> declared before it is used.
<eej>
Which might be a perfect analogy.
If the only point of a global channel is to establish a
name, then
there's actually minimal value to declaring it before it is
used. Many
dynamic languages work this way - Python & Ruby. In the
case of global
domain channels, for many use cases, filters and bindings
don't make
sense, so the channel just becomes a name. At which point,
declaration
before use looks like ceremony over substance.
</eej>
>
> -Anish
> --
>
> On 2/1/2011 10:11 AM, Danny van der Rijn wrote:
>> An interesting argument for tight coupling...
>>
>> On 2/1/2011 6:19 AM, Anish Karmarkar wrote:
>>> I think this is a fine issue to raise, but I
don't quite support the
>>> auto-creation proposal. The only global channel
that is
>>> 'auto-deployed' or always exists is the default
channel.
>>>
>>> I would want the runtime to tell me if I
referenced a channel that has
>>> not been deployed (unless it is the default
channel, which is the
>>> exception). If I want a producer and consumer
(especially if they are
>>> in different composites) to communicate over a
common channel, I would
>>> want the system to catch typos. For example, if
the producer is
>>> connected to the channel "//omg" and the
consumer is connected to
>>> "//zomg", they would be deployed fine but my
application would not
>>> work correctly.
>>>
>>> -Anish
>>> --
>>>
>>> On 1/31/2011 10:19 AM, Eric Johnson wrote:
>>>> Hi Peter,
>>>>
>>>> On 1/31/11 10:02 AM, Peter Niblett wrote:
>>>>> Eric
>>>>>
>>>>> You said..
>>>>>
>>>>> Neither of the above indicate whether
or not the global domain
>>>>> channel
>>>>> can be used before it is referenced.
>>>>
>>>> Ah yes, the joys of a muddled brain on
Monday morning. You're
>>>> correct -
>>>> the question is whether or not the global
domain channel can be used
>>>> before it is *created* via a contribution.
>>>>
>>>> Thanks for catching my circularity.
>>>>
>>>> -Eric.
>>>>>
>>>>> I'm not sure how you can "use" a
channel without referencing it (I
>>>>> assume "reference" means "wire
to/from"), but I think the question
>>>>> you
>>>>> are asking is the one in the title -
"can you reference a channel
>>>>> that
>>>>> hasn't been defined to the SCA
assembly?". I think this is one place
>>>>> where the current spec is clear.. you
can't reference a domain
>>>>> channel
>>>>> that hasn't been defined.
>>>>>
>>>>> So it looks as though your issue is to
say that we should change the
>>>>> spec to say that it permits (in fact
requires) autocreation of domain
>>>>> channels. Presumably these channels
would have to be created with
>>>>> default attributes (though I know you
think they shouldn't have
>>>>> attributes at all).
>>>>>
>>>>> Regards
>>>>>
>>>>> Peter Niblett
>>>>> IBM Senior Technical Staff Member
>>>>> Member of the IBM Academy of Technology
>>>>> +44 1962 815055
>>>>> +44 7825 657662 (mobile)
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> From: Eric Johnson<>
>>>>> To: OASIS SCA Assembly<>
>>>>> Date: 31/01/2011 17:19
>>>>> Subject: [sca-assembly] NEW ISSUE:
(1.2) Must a global domain channel
>>>>> be deployed before it can be used?
>>>>>
------------------------------------------------------------------------
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> Title: Must a global domain channel be
deployed before it can be
>>>>> used?
>>>>>
>>>>> Target: Assembly 1.2 WD 03
>>>>>
>>>>> Description:
>>>>>
>>>>> Via the "@target" and "@source"
attributes defined on a consumer&
>>>>> producer, the assembler can reference
global domain channels.
>>>>>
>>>>> In section 5.8, the presumed to be
normative text reads "SCA runtimes
>>>>> MUST support the use of domain channels
[ASM????]." That is followed
>>>>> by:
>>>>>
>>>>> "To create a Domain Channel, deploy a
composite containing a channel
>>>>> directly to the SCA Domain (i.e., do
not use that composite as the
>>>>> implementation of some component in the
Domain)."
>>>>>
>>>>> Neither of the above indicate whether
or not the global domain
>>>>> channel
>>>>> can be used before it is referenced.
>>>>>
>>>>> Proposal:
>>>>>
>>>>> General theme: do not require the
global domain channel to exist
>>>>> before
>>>>> it can be used.
>>>>>
>>>>> Specific text (needs refinement?):
>>>>>
>>>>> In section 5.8, Paragraph #2, append:
>>>>>
>>>>> When contributing artifacts to a domain
that contain references to
>>>>> global domain channels that have not
been created, the SCA runtime
>>>>> MUST
>>>>> automatically create said global domain
channels, and cannot reject
>>>>> such
>>>>> contributions [ASM????].
>>>>>
>>>>>
>>>>>
>>>>>
---------------------------------------------------------------------
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>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
------------------------------------------------------------------------
>>>>>
>>>>>
>>>>>
>>>>> /
>>>>> /
>>>>>
>>>>> /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
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>>>>>
>>>>>
>>>>>
>>>>>
>>>
>>>
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