Enable MSI authentication for BlockBlobService

[unloadedroe]

Which service(blob, file, queue) does this issue concern?

Blob

Which version of the SDK was used? Please provide the output of pip freeze.

2.1.0

What problem was encountered?

The constructor for the BlockBlobService does not allow the usage of MSI authentication. It was also requested in here.

Have you found a mitigation/solution?

Note: for table service, please post the issue here instead: https://github.com/Azure/azure-cosmosdb-python.

[zezha-msft]

Hi @unloadedroe, thanks for reaching out!

What you are looking for is here.

An OAuth sample is here, you could modify it to use MSI instead.

[jorgecarleitao]

To be explicit about this, use

def get_token():
    # this url is hard-code and only available to services with identity.
    oauth_token = requests.get(
        'http://169.254.169.254/metadata/identity/oauth2/token?api-version=2018-02-01&resource=https%3A%2F%2Fmanagement.azure.com%2F',
        headers={'Metadata': True}
    ).json()

    return oauth_token['access_token']

service = BlockBlobService(account, token_credential=get_token())

this can be integrated to a "AutoUpdatedTokenCredential", like @zezha-msft suggested.