The sqlalchemy cookie cutter uses pyramid_tm to handle the transaction. The docs on that package should answer all your questions:
https://docs.pylonsproject.org/projects/pyramid_tm/en/latest/ Basically what happens is this: * the actual transaction management is provided by zope's transaction package (http://zodb.readthedocs.io/en/latest/transactions.html) * the glue between zope and sqlalchemy is zope.sqlalchemy (https://pypi.python.org/pypi/zope.sqlalchemy) * the template uses pyramid_tm to register a transaction around the request using a pyramid tween. * pyramid_tm manages a "meta transaction" that has different components: one of which is the database "transaction", but there might also be joined transactions for mailing, celery, and other tasks. When the database transaction fails, an exception is raised. You can write a view to catch that exception, as explained in the pyramid_tm docs. In your example, two things can happen based on the The order of access in the race condition and your DB's configuration. 1. One transaction succeeds, the other fails. 2. Both fail (deadlocks or other db errors). SqlAlchemy should trap almost any driver error regarding this, and abstract it into one of it's own core exceptions (http://docs.sqlalchemy.org/en/latest/core/exceptions.html). When one of the joined transactions fails, the transaction manager notifies the rest to issue a rollback-- so the database should rollback, email queues are removed, etc. -- You received this message because you are subscribed to the Google Groups "pylons-discuss" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/pylons-discuss/012c9079-61ed-4462-8d4f-a0a1b8ae4e33%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
