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From Ricardo Rocha <rica...@apache.org>
Subject FOM and stateful components
Date Tue, 03 Jun 2003 14:15:34 GMT
As originally proposed by Stefano, the FOM exposes a getComponent(id)
method but not a corresponding releaseComponent(component), as Sylvain
was quick to point out.

I agree with Sylvain that releaseComponent() is indeed needed for
stateful, pooled components.

Btw, I'm sure when Stefano mentioned stateful components being
questioned he referred to *EJB* stateful session beans that keep
state on behalf of a remote client. In this arena, it's felt that
keeping session state is best done at the webapp layer rather than
inside the EJB container. But that's another matter...

*Avalon* stateful, pooled components, OTH, _require_ to be released
after use.

That said, using try/catch blocks in Javascript to ensure proper
stateful component release looks anti-scripting to me. In an ideal
world, the flow implementation should take care of this aspect for
the flow developer. Of course, I do see such a guarantee is easier
hoped for than implemented.

Because of continuations, automatically releasing components at the
end of request processing is clearly not appropriate.

Things are further complicated by the fact that continuations can be
abandoned. How should we deal with active stateful components in
this case? Even if we hook into continuation expiration, this could
still lead to excesive tying up of pooled heavy-weight components.

Should we reclaim components at the end of sitemap-invoked function
execution? This makes more sense because function completion can span
across requests.

Performing component auto-releasing at the end of sitemap-invoked
function completion (whether because of return or exception) seems a
reasonable thing to do because, typically, such function call will
embody a complete interaction between the user and the application.
If any components were needed during that process it's ok to relase
them at use-case completion.

However, it would preclude keeping components in use across flow
functions. Would this truly limit flow usability?

What about specifying a "retention policy" (session, function) upon
acquiring components? getComponent(id[, scope])


What do you guys think?







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