Manage transaction rollback

[skosh]

When we try to create new active record object into transaction and meet rollback:
database row will not be created but uploader has created file in folder and doesn't remove it.

I changed behavior: now we store file only after commit action. This true and for update action in transaction.

Changes in spec/orm/activerecord_spec.rb:
- Add tests which covers this flows
- replace cleaning folder from 'file_path' to 'public_path'. Cause file_path is 'spec/fixtures'
and we don't create any 'uploads' folders there. We works with 'spec/public/uploads' folder.

[oakypinky]

👍

[sashakovryga]

👍

[mshibuya]

Great work, this will be included in 2.0.0 release!

[fsateler]

I believe this change should be reverted. I'm not saying it doesn't fix the issue it fixes, but it introduces other problems:

• Uploader state is inconsistent between save and commit. For example, reading my_object.file_url.url will return a bogus url if I read before commit.
• A file might not be uploaded after a successful commit. For example, if there is a network failure. This causes the transaction to not be rolled back and invalid records being recorded.
• Even if the upload eventually completes, it can take an arbitrary amount of time, during which the record is invalid.

Thus, this change can introduce data loss and data corruption.

I believe a correct fix for the original issue is to add an after_rollback callback that (tries to) removes the destination files.

[mshibuya]

@fsateler Makes sense, could you open a new issue for that? Or even better if you could work on such an implementation.

[fsateler]

Sure, done at #2545