Storage backends

Yubin uses the database to save data about emails: dates, status (queued, sent…) and some fields to easy access, filtering and searching without parsing the email.

In addition, it needs to save full email contents somewhere. Storage backends are responsible of saving and retrieving these emails. You can choose one using the settings.MAILER_STORAGE_BACKEND variable.

DatabaseStorageBackend

django_yubin.storage_backends.DatabaseStorageBackend

By default, Yubin saves emails in the database. This is a simple solution that works well if you send few emails, they are text-only or you don’t attach heavy files.

FileStorageBackend

django_yubin.storage_backends.FileStorageBackend

If that’s not the case, the database can grow a lot with data that is read only a few times, it can increase the size of your backup, etc.

FileStorageBackend uses Django’s default file storage to save emails in the file system and only the path in the database.

With the help of Django Storages you can also save emails in many other file/object storages: AWS S3, MinIO, Azure Storage, Google Cloud Storage, Dropbox, SFTPs, etc.

Custom storage backends

If you have different needs, you can also write your own custom storage backend:

  • Inherit from the base class django_yubin.storage_backends.BaseStorageBackend and implement its abstract methods for getting and settings the email.

  • You can have a look at the other storage backends and the comments in django_yubin.models.Message to have an idea.

  • Set settings.MAILER_STORAGE_BACKEND with the path of your custom storage backend. For example, "my_project.storage_backends.MyCustomStorageBackend".

You can also inherit from other already implemented storage backends. For example, let’s write a custom storage backend that uses an inmutable file system storage:

# my_project.storage_backends.py

from django.core.files.storage import FileSystemStorage
from django_yubin.storage_backends import FileStorageBackend


class _InmutableFileSystemStorage(FileSystemStorage):
    def delete(self, name):
        pass


class InmutableFileStorageBackend(FileStorageBackend):
    storage = _InmutableFileSystemStorage()

# settings.py

MAILER_STORAGE_BACKEND = 'my_project.storage_backends.InmutableFileStorageBackend'

Migrate between storage backends

Yubin versions < 2.0.0 don’t have storage backends and have all the emails saved in the database. When you upgrade Yubin to a version >= 4.0.0, by default it uses the DatabaseStorageBackend so you still have the emails in the database.

In case you want to use the FileStorageBackend, Yubin provides a Django command to do the migration moving emails from the database to the file storage. There is also the opposite command if you want to use again the DatabaseStorageBackend.

Warning: Consider to do a database and/or file storage backup before executing any of these commads.

DB2File

  • Stop any cron, Celery worker, etc. that can send emails.

  • Change settings.MAILER_STORAGE_BACKEND to django_yubin.storage_backends.FileStorageBackend.

  • Execute:

    python manage.py db2file

  • Enable again your Celery workers.

File2DB

  • Stop any cron, Celery worker, etc. that can send emails.

  • Change settings.MAILER_STORAGE_BACKEND to django_yubin.storage_backends.DatabaseStorageBackend.

  • Execute:

    python manage.py file2db

  • Or if you also want to delete the files in the file storage after saving them into the database, execute:

    python manage.py file2db --delete

  • Enable again your Celery workers.

If you use a different or custom storage backend and you want to migrate emails, you should write your own migration commad.