Rollback on exception

[marksteward]

SQLAlchemy seems to be committing regardless

[Jonty]

Can we get more info on this? Is this exceptions chucked due to constraint violations? Exceptions due to shit code?

[marksteward]

It seems exceptions thrown before db.session.commit don't stop the changes being saved. This means (for gocardless_start) if payment.bill_url() fails, you've still bought the tickets, but didn't get redirected, so they end up in limbo.

We probably need to add a top-level request exception handler that calls db.session.rollback. Alternatively, it might be sqlalchemy not using transactions correctly with sqlite (haven't tested with psql).

[Jonty]

This sounds like the db connection has autocommit set?

[marksteward]

Probably, I assumed that was Flask's responsibility. So the wrapper also needs to call begin.

[JasperWallace]

i can test this with psql if it would help?

[marksteward]

Heh, I was just about to do the same. Will leave it if you're confident :)

[JasperWallace]

done, what exactly is the test case?

there is a db.session.commit() in buy_prepay_tickets so we are commiting before we generate the bill url...

maybe move the commit to just before we return the redirect?

[JasperWallace]

Looks like this does not happen with postgres so we don't have to worry about it.

Not closeing, but removing from the milestone.

[Jonty]

If this doesn't happen with postgres, why aren't we closing it?

[marksteward]

If the same test been run against sqlite, I'm happy to. Will do this tomorrow.