How to run a script after Pyramid's transaction manager has returned

Question

How can I run myscript.py after the transaction manager has returned. Additionally, I would prefer if the script was not blocking.

In my view, I am receiving a file from a POST. Since I'm creating the file with repoze.filesafe's create_file(), it keeps the file in a temporary location until the transaction manager returns. The file only exists on the harddisk in its correct path after transaction manager has returned without an error.

Therefore, I need to run my script after the transaction manager has returned.

Answer 1

You can register a hook to be run after commit via the transaction package. Register one in your view:

import transaction


def your_after_commit(success, arg1, arg2, kwarg1=None, kwarg2=None):
    if success:
        print "Transaction commit succeeded"
    else:
        print "Transaction commit failed"


def someview(request):
    current_transaction = transaction.get()
    current_transaction.addAfterCommitHook(your_after_commit, args=(1, 2), kws={kwarg1='foo', kwargs2='bar'})

This still runs your script in the context of the current request (e.g. the request does not complete until your script returns). If you need a full asynchronous setup, you'll need to move to a proper asynchronous solution such as Celery. You would not use that with a transaction hook; just register a task to be run with Celery instead.