Mike Edwards wrote:
On 08/02/2011 10:08, ant elder wrote:
On Tue, Feb 8, 2011 at 9:56 AM, Simon Laws<simonsl...@googlemail.com>
wrote:
I can see that relaxing the current spec restrictiveness would be
difficult as things would break in some circumstances, but it does
seem like there will be situations when the assembler really knows it
would be fine but even so they can't get the PBR optimization because
the impls aren't coded with the @AllowsPassByReference annotation.
Isn't that a similar situation to where the remotable annotation was
added to the interface SCDL element, and there could be a similar
allowsPassByReference attribute added to the service and reference
SCDL elements?
...ant
Hi Ant.
Can you say a bit more about the "situations when the assembler really
knows it would be fine"? Reading previous posts to this thread doesn't
convince me that that is the case.
Simon
We'll have to wait for Raymond to see if thats anything like his
situation, but there are lots of ways the assembler could know, he may
well have full access to the source but still be limited in making any
updates due to production lifecycle or control issues. This seems like
a similar situation as Java EE appservers have and I believe many
appservers have mechanisims for overriding and enabling PBR support in
their ORB or EJB modules to gain performance benefits.
...ant
Folks,
One possibility to start with would be to add a Tuscany extension
attribute which could be used by an Assembler to mark a particular
service and/or reference as "AllowsPassByReference".
This would cope with the situation where the Java components are not
marked, but the assembler knows enough about them to know that the
marking is correct.
Yours, Mike.
I'm very dubious about the wisdom of this. I bear the scars from a
previous life of a situation where a flag was added to an enterprise
application server (which shall remain nameless) to override the PBV
semantics required by the architecture in the interests of performance
optimization when the user of the product "knew" that using PBR would
be safe. Needless to say, on a number of occasions this flag was set
incorrectly and this resulted in accusations of runtime bugs that were
eventually shown after laborious debugging to have been caused by the
PBR "optimization" being enabled incorrectly.
IMO it's the implementation's responsibility to make the correct
assertions about whether it's PBR-safe. Implementations that don't
assert @AllowsPassByReference will have worse performance than those
that do support it. If a component developer cares about performance,
they need to code their implementation to play by the APBR rules and
turn on the flag to say they have done that. If the flag isn't turned
on by the implementer, I can't imagine that an assembler will have a
detailed enough knowledge of the implementation to be able to safely
provide the APBR assertion that the component developer couldn't/
wouldn't/didn't provide.
(Deep breath) Now I feel better after getting that off my chest :-)
Simon
