Thanks for pointing me to that SQLAlchemy cookie cutter, it was very helpful.  
I was able to get something up and working with pyramid_tm and zope.sqlalchemy.

Do you know the motivation for pyramid_tm to be above EXC_VIEW by default?  I 
moved it below EXC_VIEW since I wanted commit errors to be handled by the 
exception views.  Is there any reason why I shouldn’t do this?

— Theron



> On Apr 28, 2017, at 12:12 AM, Bert JW Regeer <[email protected]> wrote:
> 
> Sorry, I fired a little too soon…
> 
> You might want to look at the current state of the art in our sqlalchemy 
> cookie cutter:
> 
> https://github.com/Pylons/pyramid-cookiecutter-alchemy 
> <https://github.com/Pylons/pyramid-cookiecutter-alchemy>
> 
> Request finalized callbacks are explicitly outside of tweens, and outside of 
> any encapsulation.
> 
> You’ll want to look at pyramid_tm or build a tween yourself that handles 
> things in a similar fashion.
> 
>> On Apr 28, 2017, at 00:20, Theron Luhn <[email protected] 
>> <mailto:[email protected]>> wrote:
>> 
>> I have a pretty standard setup of Pyramid and SQLAlchemy, based off 
>> http://docs.pylonsproject.org/projects/pyramid_cookbook/en/latest/database/sqlalchemy.html
>>  
>> <http://docs.pylonsproject.org/projects/pyramid_cookbook/en/latest/database/sqlalchemy.html>
>> 
>> However, this has a problem:  The `cleanup` callback executes *after* the 
>> tween has returned.  I use tweens for both error logging (Rollbar) and 
>> request logging (output via python-fluent-loggerd).  This means that if the 
>> commit and associated flush fail, neither my request logger nor error 
>> logging catch it.
>> 
>> For example, if my tween looked like this:
>> 
>> 
>> class Tween:
>>     def __init__(self, handler, register):
>>         self.handler = handler
>> 
>>     def __call__(self, request):
>>         start = time()
>>         response = self.handler(request)
>>         duration = time() - start
>>         log(duration, response.status_code)  # This shows a success
>>         return response  # session.commit() fails sometime after this
>> 
>> 
>> The log call would report an HTTP 200, even the end result may be a HTTP 500 
>> due to a failure in session.commt()
>> 
>> The obvious solution is to move logging to the WSGI middleware layer, but 
>> then I lose all the Pyramid-specific details, which I am loath to do.  I 
>> could also manually add a try/except to handle errors in the cleanup and 
>> report to Rollbar, but that still means my request logs show a success.
>> 
>> Is there a way I can force SQLAlchemy to commit/rollback (or at least flush) 
>> before the passing the baton back to the tweens?
>> 
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