[Zope] ZASync method calls

[Jonathan]

----- Original Message ----- 
From: "Jan-Ole Esleben" <esleben at gmail.com>
>
> I'm having a really complicated problem that I don't know how to put into
> words properly, because I'm really vague on what's causing it and the
> setup is highly involved; I would be _really_ glad if someone could help 
> me
> out with this:
>
> I have a ZOPE instance (connected to a ZEO server) running a custom
> method call wrapper that decides (based on the method's arguments) to
> run a method asynchronously using zasync (as well as some other stuff that
> I think isn't important in the context of my problem). All this has
> been tested. For various
> reasons, the method call's path is approximately as follows:
>
> 0. Method call using a generic Python method
> 1. Python code - resolves the method's location and name using ZOPE 
> methods
> 2. Method dispatcher (called via ZOPE): dispatches synchronously or
> asynchronously, using zasync, zope_exec and putSessionCall; the method
> called is again a ZOPE method that calls the final method as another
> ZOPE method
>
> The apparent massive indirection cannot be avoided (for rather complicated
> reasons). Everything is supposed to be highly generic.
>
> My problem is this: if I use a test method that dispatches such an 
> asynchronous
> method that is supposed to change an instance variable (the class is
> persistent) and run for ten seconds, then wait for fourteen seconds and 
> see
> if the method has run (check the instance variable) synchronously (while 
> the
> asynchronous method is supposed to work in the background), I find the
> variable unchanged; further checks (using print statements) confirm that 
> the
> asynchronous method indeed doesn't run until my assertion fails, even if I 
> give
> it a lot of time.
>
> If I disconnect both - run the long running method asynchronously, then 
> run
> (via ZOPE directly, not from within the same method call) a synchronous 
> method
> that waits for fourteen seconds and checks the variable, the asynchronous 
> call
> works just fine (even though both run alongsinde for a time).
>
> It isn't the number of threads available to the zserver, I've increased 
> that
> and nothing has changed. Manual tests of asynchronous methods also don't 
> show
> anything wrong with my zasync setup. I can only assume that the 
> asynchronous
> method is _started_ only _after_ the caller has finished. Is there a 
> reason for
> that, and can I circumvent it? Or am I completely wrong and something else
> isn't working?
>
> I'm on Windows XP SP2, ZOPE 2.7.6, Python 2.3.5 with Twisted installed.
>

Is it possible that your asynchronous routine is not committing the 
transaction? ie. If zope considers the async routine to be part of the 
current 'session' then the variable the async routine is updating will not 
be changed until the current session is completed and zope commits the 
transaction (so any checks of the variable during the current session will 
not see any changes to the variable).

To see if this is the case you could add a "get_transaction().commit()" 
statement in your code after you change the variable's contents.

hth

Jonathan