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From Daryl Olander <dolan...@gmail.com>
Subject Re: Page Flow Runtime Control Container Design
Date Thu, 19 Jan 2006 19:02:25 GMT
So it turns out, there is indeed a test that creates a control
programmatically in a page flow.  This seems to leave us with two
alternatives
1) we always create the CCC for every page flow
2) we add an ensureControlContainerContextExists() API (to the base
PageFlowController) to make sure that it is created and initialized.

I lean toward 2 because I think this use case is rare.  It is a backward
compatibility issue with our 1.0 release.

Thoughts?

On 1/18/06, Daryl Olander <dolander@gmail.com> wrote:
>
> This mail summarizes the proposed design for the Control container
> implementation inside of the page flow runtime.  It is a summary of the
> previous threads on this subject.  I'm currently in the process of
> implementing this solution and believe it solves the sets of issues brought
> up in those emails.  I would really like review of this solution and
> comments/questions so we can be sure this works.
>
> There are two basic requirements of the Control container
> 1) All controls have only a single thread in them at a time (Single
> Threaded)
> 2) The resources a control may acquire are only used for a single
> request.  It is ok if the resources are acquired more than once for a single
> request.
>
> In today's implementation, both of these requirements are violated by
> standard page flows and shared flows (and global app).  These issues are
> summarized in the previous threads on this subject.
>
> The proposed solution is this,
>
> For a standard page flow (normal page flow, singleton page flow and nested
> page flow), they have a ControlContainerContext (CCC) for the controls that
> they contain.  The CCC is only allocated if the page flow contains a
> control.  We will have to probably add an API someplace to create this if a
> user wants to create a control programmatically.
>
> For all Shared flows and global app, they will share a single CCC.
>
> During a request, there are three possible synchronization points where
> user code can run and call methods on controls
> 1) during onCreate when a page flow is created
> 2) during the beforeAction/Action/afterAction cycle
> 3) during JSP rendering
>
> During any of these, code may access a shared flow and interact with
> controls. For most page flow requests only 2 and 3 are run.
>
> For a the standard page flows, these synchronization points create a
> single threaded model.  For the standard page flow CCC, we will run the
> beginContext, endContext events which activate the resource lifecycle.  This
> is sufficient to guarantee 1 and 2.
>
> For shared flows, we still have issues if multiple threads are running
> through the session.  To solve this we will do this,
> 1)  We will create a single Lock object that must be obtained in the
> synchronization points before we can proceed.
> 2) Once the lock is obtained, we will run beginContext on the shared flows
> CCC.
> 3) We will run the normal user code
> 4) We will then run the endContext on the shared flows CCC
> 5) We will release the lock
>
> Rich, please verify this will work...
>
> The result of this, is that we will serialize threads within a session
> through these synchronization points.  The result is that shared flows will
> become single threaded (requirement 1 above) and because we run the
> beginContext/endContext that satisfies 2 above.
>
> There is a bit more overhead to this solution because there will typically
> be two CCC objects active at one time.  Deep nesting and singletons will add
> more.  The CCC is only created for page flows that have controls.  The
> benefits is that the CCC objects match the lifetime of the controls that
> they contain.
>
> Please review this and send comments.
>
> Thanks
>
> Daryl
>
>
>

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