feat: 🎸 add --single-threaded flag to fetch azure

[sunny0826]

Add same flag --single-threaded for the Azure fetching script.

--single-threaded: Run in single-threaded mode. This is useful when multiple processes don't work well with the azure client due to ssl issues.

[iojw]

@sunny0826 What exactly is the error that occurs with SSL? Can you share more details?

[sunny0826]

Requesting too much data from api/retail/prices will most likely result in the following error:

...
Done fetching pricing germanywestcentral
Getting pricing for norwayeast
Done fetching pricing italynorth
Done fetching pricing norwayeast
multiprocessing.pool.RemoteTraceback: 
"""
Traceback (most recent call last):
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/site-packages/urllib3/connectionpool.py", line 711, in urlopen
    self._prepare_proxy(conn)
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/site-packages/urllib3/connectionpool.py", line 1007, in _prepare_proxy
    conn.connect()
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/site-packages/urllib3/connection.py", line 419, in connect
    self.sock = ssl_wrap_socket(
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/site-packages/urllib3/util/ssl_.py", line 449, in ssl_wrap_socket
    ssl_sock = _ssl_wrap_socket_impl(
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/site-packages/urllib3/util/ssl_.py", line 493, in _ssl_wrap_socket_impl
    return ssl_context.wrap_socket(sock, server_hostname=server_hostname)
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/ssl.py", line 500, in wrap_socket
    return self.sslsocket_class._create(
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/ssl.py", line 1073, in _create
    self.do_handshake()
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/ssl.py", line 1342, in do_handshake
    self._sslobj.do_handshake()
ssl.SSLZeroReturnError: TLS/SSL connection has been closed (EOF) (_ssl.c:1131)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/site-packages/requests/adapters.py", line 486, in send
    resp = conn.urlopen(
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/site-packages/urllib3/connectionpool.py", line 798, in urlopen
    retries = retries.increment(
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/site-packages/urllib3/util/retry.py", line 592, in increment
    raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPSConnectionPool(host='prices.azure.com', port=443): Max retries exceeded with url: /api/retail/prices?$filter=serviceName%20eq%20%27Virtual%20Machines%27%20and%20priceType%20eq%20%27Consumption%27%20and%20armRegionName%20eq%20%27brazilsouth%27&$skip=1000 (Caused by SSLError(SSLZeroReturnError(6, 'TLS/SSL connection has been closed (EOF) (_ssl.c:1131)')))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/multiprocessing/pool.py", line 125, in worker
    result = (True, func(*args, **kwds))
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/multiprocessing/pool.py", line 48, in mapstar
    return list(map(*args))
  File "/Users/guoxudong_1/ai/skypilot/sky/clouds/service_catalog/data_fetchers/fetch_azure.py", line 85, in get_pricing_df
    r = requests.get(url)
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/site-packages/requests/api.py", line 73, in get
    return request("get", url, params=params, **kwargs)
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/site-packages/requests/api.py", line 59, in request
    return session.request(method=method, url=url, **kwargs)
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/site-packages/requests/sessions.py", line 589, in request
    resp = self.send(prep, **send_kwargs)
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/site-packages/requests/sessions.py", line 703, in send
    r = adapter.send(request, **kwargs)
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/site-packages/requests/adapters.py", line 517, in send
    raise SSLError(e, request=request)
requests.exceptions.SSLError: HTTPSConnectionPool(host='prices.azure.com', port=443): Max retries exceeded with url: /api/retail/prices?$filter=serviceName%20eq%20%27Virtual%20Machines%27%20and%20priceType%20eq%20%27Consumption%27%20and%20armRegionName%20eq%20%27brazilsouth%27&$skip=1000 (Caused by SSLError(SSLZeroReturnError(6, 'TLS/SSL connection has been closed (EOF) (_ssl.c:1131)')))
"""

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/guoxudong_1/ai/skypilot/sky/clouds/service_catalog/data_fetchers/fetch_azure.py", line 155, in get_all_regions_instance_types_df
    dfs = dfs.get()
  File "/Users/guoxudong_1/anaconda3/envs/sky-dev/lib/python3.8/multiprocessing/pool.py", line 771, in get
    raise self._value
requests.exceptions.SSLError: None: Max retries exceeded with url: /api/retail/prices?$filter=serviceName%20eq%20%27Virtual%20Machines%27%20and%20priceType%20eq%20%27Consumption%27%20and%20armRegionName%20eq%20%27brazilsouth%27&$skip=1000 (Caused by None)

[iojw]

Thank you @sunny0826! LGTM, just some minor copy fixes.