Ah right, it's not just for requests that go to shared flows. Well, I
think this will all work. My biggest concern is the space requirements
of the CCC, multiplied if this happens in a portal. It's just something
we should look at. Do we know how big the CCC will be?
Daryl Olander wrote:
No, because you have to get access to the "shared flow" lock before you can
enter user code in onCreate, action invocation and JSP rendering. Thus the
statement that we have serialization points for multiple threads within a
session.
On 1/19/06, Rich Feit <[EMAIL PROTECTED]> wrote:
OK... one other thing: is there still a hole here for direct access to
the shared flow through a reference in the page flow?
Daryl Olander wrote:
On 1/19/06, Rich Feit <[EMAIL PROTECTED]> wrote:
I can't tell the difference between this and Daryl's option #2, so I
guess I agree with both of you. :)
Daryl, I have just a few questions:
1) The Lock object is session-scoped, right?
Right...
2) Are you saying that you'd call the CCC's begin/end-context
methods around *every* point that runs user code? So within a given
request, you'd potentially do this around onCreate(), the action
invocation, and JSP rendering?
Exactly...These are the three points where we do this. For the average
request, it would be just the action invocation and JSP rendering.
Eddie O'Neil wrote:
Hm...this is a tricky issue. I'd actually go a different route and
do two things:
1) only create the CCC for each page flow in the presence of @Control
annotations
2) explain how to write code to create a CCC and drive it through its
lifecycle
This is how the JUnit test container works for Controls -- you can use
the ControlsTestCase base class or write code that calls utilities
that provide the CCC and drive it through its lifecycle.
Seems like this provides the best of both worlds -- uses metadata to
decide when controls are used but gives application developers a way
to use controls programmatically without having a Controls-related API
exposed on the Page Flow base class.
Yes, there's a compatibility issue *if* you used JPF from 1.0 and
declared controls programmatically, but that's probably not very
common.
Eddie
On 1/19/06, Daryl Olander <[EMAIL PROTECTED]> wrote:
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 <[EMAIL PROTECTED]> 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
