• Package Name: azure-storage-blob
• Package Version: 12.8.1
• Operating System: debian 10
• Python Version: 3.7.3

Describe the bug
When passing a socket (e.g. requests raw response) to BlobClient.upload_blob(), upload_blob incorrectly infers a 0 length and does not read any data out of the socket to upload.

The problem appears to be in request_handlers.py def get_length(data). The function calls fstat(fileno).st_size in a try block, but st_size does not seem to have a valid meaning for socket fds, see https://linux.die.net/man/2/fstat. In my environment this returns zero but does not throw an OSError, so get_length erroneously returns 0.

To Reproduce
This minimal code will upload 0 bytes:

import requests
import os
from azure.storage.blob import BlobClient

blob_client = BlobClient.from_connection_string(
    conn_str=os.environ["BLOB_CONN_STR"],
    container_name="blobtest",
    blob_name="test.iso")

with requests.get('https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/debian-10.10.0-amd64-netinst.iso', stream=True) as resp:
    blob_client.upload_blob(resp.raw, overwrite=True)

Expected behavior
The above code should upload the full iso in chunks.

Additional context
I believe the correct way to handle this is to check if the fd is a regular file or symlink before returning st_size, and if it is not a regular file fall through the rest of the get_length call which ends up returning None which results in the correct behaviour.

I have a pull request I will attach here shortly.