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Subject: RE: [sca-j] NEW ISSUE: "Process" Scope
Hi
Michael,
To me an SCA
runtime should transparently scale each application and be able to run it
into clustered environment.
Introducing such "cluster singletons" via the "DOMAIN" (ex-COMPOSITE) scope is something which has some usecases but opens the door for a lot of problems and bad application architectures. I would prefer not to add new scopes but instead change the semantics of the "COMPOSITE" to the new "PROCESS" you have described. Best
Regards Peter From: Michael Rowley [mailto:mrowley@bea.com] Sent: Monday, 3. March 2008 22:33 To: OASIS Java Subject: [sca-j] NEW ISSUE: "Process" Scope RAISER: Michael
Rowley TARGET: SCA Java Common Annotation
and API specification DESCRIPTION: There are some common scenarios
where neither the STATELESS scope nor the COMPOSITE scope is exactly
appropriate. The scenario is that you have a component that has some
initialization logic that is expensive, but the developer wants calls to this
component to be local as often as possible, in order that they may be
fast. The problem with COMPOSITE scope is
that it must behave as if there were only one instance per domain. Without
some kind of multi-process state sharing mechanism, this typically means that
all requests have to be routed to a single instance in a single process.
Any call to this component from any process other than the one that hosts the
composite-scoped component then becomes expensive. Stateless scope also is not well
suited, since the stateless scope requires that the @Init method be called when
the scope starts – i.e. on every call. There should be a scope that allows
one instance per process. As an aside, the name of the
COMPOSITE scope is confusing, and should possibly be changed to DOMAIN to make
its domain-wide singleton nature more clear. PROPOSAL: Introduce a new PROCESS scope, where
there is at most one instance per JVM. Change the name of COMPOSITE scope
to DOMAIN. |
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