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From Rich Feit <>
Subject Re: Multiple Threads inside a Page Flow instance?
Date Mon, 16 Jan 2006 19:22:21 GMT
Hey Daryl,

We should never allow two threads into user code at the same time, 
although you could potentially get into a situation where you're 
interleaving calls to actions and property getters.  We synchronize the 
page rendering on the controller instance; see PageFlowPageFilter:284.  
Let me know if you see any issues with this, though.


Daryl Olander wrote:

>Rich, I'd love some confirmation of the following if you can,
>I'm in the process of looking at some issue with the BeanContext and Control
>use in NetUI and I have a question about threading.  I believe that we make
>the statement that PageFlow are single threaded.  The issue is that I
>believe we in fact allow more than one thread into a page flow.  Here is an
>example of where I think it can happen.
>If you have a set of frames on a page, all making requests to the same page
>flow, they will serialize access to the actions in the page flow.  When the
>first thread finishes the action and forwards to a JSP, the second thread is
>allowed access to the page flow.  This is the reason we say things are
>single threaded.  The problem is that if the JSP takes a while to run and it
>databinds to properties on the page flow you can have multiple threads
>running through the page flow.  The first thread is calling property getters
>while rendering the JSP and the second thread is running an action.  This is
>actually not uncommon if the property being accessed calls a control that
>accesses an external resource like a database.
>Rich, can you comment on this?  Is there something else that prevents
>multiple threads from entering a page flow?

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