Azure Storage

A custom storage system for Django using Microsoft Azure Storage backend.

Notes

Be aware Azure file names have some extra restrictions. They can’t:

• end with a dot (.) or slash (/)
• contain more than 256 slashes (/)
• be longer than 1024 characters

This is usually not an issue, since some file-systems won’t allow this anyway. There’s default_storage.get_name_max_len() method to get the max_length allowed. This is useful for form inputs. It usually returns 1024 - len(azure_location_setting). There’s default_storage.get_valid_name(...) method to clean up file names when migrating to Azure.

Gzipping for static files must be done through Azure CDN.

Install

Install Azure SDK:

pip install django-storages[azure]

Private VS Public Access

The AzureStorage allows a single container. The container may have either public access or private access. When dealing with a private container, the AZURE_URL_EXPIRATION_SECS must be set to get temporary URLs.

A common setup is having private media files and public static files, since public files allow for better caching (i.e: no query-string within the URL).

One way to support this is having two backends, a regular AzureStorage with the private container and expiration setting set, and a custom backend (i.e: a subclass of AzureStorage) for the public container.

Custom backend:

# file: ./custom_storage/custom_azure.py
class PublicAzureStorage(AzureStorage):
    account_name = 'myaccount'
    account_key = 'mykey'
    azure_container = 'mypublic_container'
    expiration_secs = None

Then on settings set:

# django < 4.2
DEFAULT_FILE_STORAGE = 'storages.backends.azure_storage.AzureStorage'
STATICFILES_STORAGE = 'custom_storage.custom_azure.PublicAzureStorage'

# django >= 4.2
STORAGES = {
    "default": "storages.backends.azure_storage.AzureStorage",
    "staticfiles": "custom_storage.custom_azure.PublicAzureStorage",
}

Private VS Public URL

The difference between public and private URLs is that private includes the SAS token. With private URLs you can override certain properties stored for the blob by specifying query parameters as part of the shared access signature. These properties include the cache-control, content-type, content-encoding, content-language, and content-disposition. See https://docs.microsoft.com/en-us/rest/api/storageservices/set-blob-properties#remarks

You can specify these parameters by:

az_storage = AzureStorage()
az_url = az_storage.url(blob_name, parameters={'content_type': 'text/html;'})

Settings

The following settings should be set within the standard Django configuration file, usually settings.py.

Set the default storage (i.e: for media files) and the static storage (i.e: fo static files) to use the azure backend:

DEFAULT_FILE_STORAGE = 'storages.backends.azure_storage.AzureStorage'
STATICFILES_STORAGE = 'storages.backends.azure_storage.AzureStorage'

The following settings are available:

AZURE_ACCOUNT_NAME

This setting is the Windows Azure Storage Account name, which in many cases is also the first part of the url for instance: http://azure_account_name.blob.core.windows.net/ would mean:

AZURE_ACCOUNT_NAME = "azure_account_name"

AZURE_ACCOUNT_KEY

This is the private key that gives Django access to the Windows Azure Account.

AZURE_CONTAINER

This is where the files uploaded through Django will be uploaded. The container must be already created, since the storage system will not attempt to create it.

AZURE_SSL

Set a secure connection (HTTPS), otherwise it makes an insecure connection (HTTP). Default is True

AZURE_UPLOAD_MAX_CONN

Number of connections to make when uploading a single file. Default is 2

AZURE_CONNECTION_TIMEOUT_SECS

Global connection timeout in seconds. Default is 20

AZURE_BLOB_MAX_MEMORY_SIZE

Maximum memory used by a downloaded file before dumping it to disk. Unit is in bytes. Default is 2MB

AZURE_URL_EXPIRATION_SECS

Seconds before a URL expires, set to None to never expire it. Be aware the container must have public read permissions in order to access a URL without expiration date. Default is None

AZURE_OVERWRITE_FILES

Overwrite an existing file when it has the same name as the file being uploaded. Otherwise, rename it. Default is False

AZURE_LOCATION

Default location for the uploaded files. This is a path that gets prepended to every file name.

AZURE_ENDPOINT_SUFFIX

Defaults to core.windows.net. Use core.chinacloudapi.cn for Azure.cn accounts.

AZURE_CUSTOM_DOMAIN

The custom domain to use for generating URLs for files. For example, www.mydomain.com or mycdn.azureedge.net.

AZURE_CONNECTION_STRING

If specified, this will override all other parameters. See http://azure.microsoft.com/en-us/documentation/articles/storage-configure-connection-string/ for the connection string format.

AZURE_TOKEN_CREDENTIAL

A token credential used to authenticate HTTPS requests. The token value should be updated before its expiration.

AZURE_CACHE_CONTROL

A variable to set the Cache-Control HTTP response header. E.g. AZURE_CACHE_CONTROL = "public,max-age=31536000,immutable"

AZURE_OBJECT_PARAMETERS

Use this to set content settings on all objects. To set these on a per-object basis, subclass the backend and override AzureStorage.get_object_parameters.

This is a Python dict and the possible parameters are: content_type, content_encoding, content_language, content_disposition, cache_control, and content_md5.

AZURE_API_VERSION

The api version to use. The default value is None.