Session should be rolled back on SQLAlchemyError

[hussaintamboli]

Yesterday, I came across a really painful issue.

I use flask-restless and SQLAlchemy for my API. I got Internal server error due to OperationalError exception in one of my APIs. It was because one of the required column was not passed to the POST request. After that, for all the subsequent requests I started getting another Internal server error due to InvalidRequestError exception.

InvalidRequestError: This Session's transaction has been rolled back due to a previous exception during flush. To begin a new transaction with this Session, first issue Session.rollback() .... 

After a long search I found that a rollback() needs to be issued when an error occurs in commit(). But in this case the commit and rollback is not in my hands but restful's.

So I started looking where and when the rollback is being issued in restless and found these lines in views.py

190 # TODO should `sqlalchemy.exc.InvalidRequestError`s also be caught?
191 except (DataError, IntegrityError, ProgrammingError) as exception:
192   session.rollback()

Note that OperationalError is not handled as a rollback case.

So as a FIX to my issue I modified the views.py and put OperationalError in it. Then I thought, to be on safer side why not issue the rollback on SQLAlchemyError (SQLAlchemy base exception class)

I have created a pull request with my fix.

Please let me know your thoughts on this

[hussaintamboli]

Hi,

Could you please accept my merge request. Because I really want to install flask_restless using pip. And I don't wanna put flask_restless with my fix inside version control.

Without this fix, the randomness issue persists.

[jwg4]

@hussaintamboli Why did you close the issue if your code has not been merged? You should re-open the issue.

[jfinkels]

This should be fixed by 56c8261.

[hussaintamboli]

Great.

Actually the pull request that I had sent before (4bed33f) has the same fix.

Thanks.