Can't access public bucket without credentials

On master (ccb779d3e2054310dcff0e4308fe38acfe5784f6) in an environment with no Google credentials (python:3.6.4 Docker image):

# this works
In [2]: gcsfs.GCSFileSystem(token='anon').open('gs://gcp-public-data-landsat/index.csv.gz').read(1)
Out[2]: b'\x1f'

# but this doesn't
In [3]: gcsfs.GCSFileSystem().open('gs://gcp-public-data-landsat/index.csv.gz').read(1)
_call exception: HTTPConnectionPool(host='metadata.google.internal', port=80): Max retries exceeded with url: /computeMetadata/v1/instance/service-accounts/default/?recursive=true (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7fbc9bdd5b00>: Failed to establish a new connection: [Errno -2] Name or service not known',))
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/urllib3/connection.py", line 141, in _new_conn
    (self.host, self.port), self.timeout, **extra_kw)
  File "/usr/local/lib/python3.6/site-packages/urllib3/util/connection.py", line 60, in create_connection
    for res in socket.getaddrinfo(host, port, family, socket.SOCK_STREAM):
  File "/usr/local/lib/python3.6/socket.py", line 745, in getaddrinfo
    for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
socket.gaierror: [Errno -2] Name or service not known
# ... several pages of these logs
# ... then several pages of tracebacks; finally:
RefreshError: HTTPConnectionPool(host='metadata.google.internal', port=80): Max retries exceeded with url: /computeMetadata/v1/instance/service-accounts/default/?recursive=true (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7fbc9b785eb8>: Failed to establish a new connection: [Errno -2] Name or service not known',))

It seems that the default auth should be falling back on anon; I guess this type of exception is not being caught properly? Additionally, if the anon method did eventually succeed, it might be preferable to suppress the logs during the initial failure+retries.

[bnaul]

Makes sense; #100 with one modification (see comments) now works for me:

In [4]: gcsfs.GCSFileSystem().open('gs://gcp-public-data-landsat/index.csv.gz').read(1)
Out[4]: b'\x1f'

[martindurant]

I don’t quite see how that happens, but I have added a line to reset the session if the connection apparently fails. Checking for credentials.valid won’t work because, until the first use of the credentials, they were likely be expired and not (yet) valid. Please correct me if I am wrong.