django-migrate-or-rollback 0.1.0

Management command to attempt Django migrations and rollback on failure

django-migrate-or-rollback

While single migrations in Django are atomic (as long as they have the default atomic=True), a group of migrations are not. Thus, when running migrations, you can have a partial failure where some but not all of your migrations succeed. This library fixes that.

This library provides a new management command migrate_or_rollback. It's a drop-in replacement for the Django builtin management command migrate. Here's how it works:

1. Checks your database and current migration files for the latest migrations run per Django app.
2. Runs migrations as normal.
3. If migrations fail, it rolls back to the migrations identified in step 1.

Instalation

pip install django-migrate-or-rollback

Alternatively, add django-migrate-or-rollback to your requirements.txt file.

Then, add "django_migrate_or_rollback" to your INSTALLED_APPS in settings.py, like so:

# settings.py
INSTALLED_APPS = [
    # ...
    "django_migrate_or_rollback",
]

Usage

Run python manage.py migrate_or_rollback instead of the standard migrate command.

In particular, you should use migrate_or_rollback in place of migrate in your deployment scripts or CI/CD system.

migrate_or_rollback has all of the same options as migrate, such as the --noinput flag.

Warning

This library assumes that your migrations are reversable. Not all migrations are reversible. Additionally, rolling back migrations only reverses schema doesn't rewind the database contents.

In particular:

• Deleted data (such as dropping columns or tables) won't be restored by rolling back the migration that deletes it. To avoid this, you should make fields nullable in one deploy and delete them in the next.
• RunPython statements that are missing a reverse function will error on rollback. At a minimum, add migrations.RunPython.noop as a reverse function. Additionally, RunPython reverse functions can be used to rewind changes to database contents on migration rollback.
• A migration that deletes a non-nullable field will error on rollback. To avoid this, make the field nullable in one deploy and delete it in the next.