django-fallback-storage

django-fallback-storage allows for the use of multiple storage engines at the same time. It works by iterating through the declared storage backends until one succeeds with the desired storage action.

While usable in a production environment, this tool was primarily designed to help with development of a project.

Consider a production site using the S3BotoStorage backend to store its static assets on Amazon S3 and a development environment that regularly gets database dumps from the production environment. In order to get the media associated with the database dump to work, the development environment could be configured to use the same S3 bucket. This could be problematic, as it would risk making unwanted modifications to the production media.

The FallbackStorage backend provided by django-fallback-storage allows use of the same production production media source in the development environment while delegating all write operations to a different storage backend (such as the filesystem).

This is accomplished by wrapping multiple storage backends, and iterating through them for each request until one of them returns a successful response.

Installation

1. Install the package:

   .. code-block:: bash
   

   $ pip install django-fallback-storage

2. Set fallback_storage.storage.FallbackStorage as your desired storage backend.:

   .. code-block:: python
   

   # settings.py DEFAULT_FILE_STORAGE = "fallback_storage.storage.FallbackStorage"

3. Declare what storage backends fallback storage should use.:

   .. code-block:: python
   

   # All operations will be tried first on FileSystemStorage and then on # S3BotoStorage. FALLBACK_STORAGES = (

   "django.core.files.storage.FileSystemStorage", "storages.backends.s3boto.S3BotoStorage",

   )

API

FallbackStorage implements all of the following backend methods.

• _open()
• _save()
• delete()
• exists()
• listdir()
• size()
• url()
• accessed_time()
• created_time()
• modified_time()
• get_valid_name()
• get_available_name()
• path()

When one of these methods is called, each backend declared in FALLBACK_STORAGES is called. The first successful response is returned.

Any backend which does not implement a given method will be skipped over. If none of the backends implement a called method, then an AttributeError is raised.

Exceptions raised by any backend are reraised if none of the backends returns a successful response.

The following methods behave somewhat specially.

• FallbackStorage.exists(name):

  Will return True if the file exists in any of the storage backends.

• FallbackStorage.listdir(path):

  Will return the set of all directories and files in all of the storage backents.

• FallbackStorage.url(name):

  When computing a url, FallbackStorage first checks if the file exists. If the file exists in none of the storage backends, the last backend is used to compute the file name.

• FallbackStorage.get_available_name(name):

  When django attempts to get an available name for the file, FallbackStorage checks the file name across all storage backends before returning an available name. As such, each file will have a unique name across all storage backends in use.