ISSUE 30: "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.

sca-j message