Cloud Function & OAuth 2.0 - oauth

Question

I have a issue to use OAuth2.0 on GCP Cloud Function. I use to run this code locally. it works and it open a web browser's page to ask access to my gmail account.
I know that InstalledAppFlow is only use for local application.
SCOPES = ['https://mail.google.com/']
creds = None
if os.path.exists('token.pickle'):
with open('token.pickle', 'rb') as token:
creds = pickle.load(token)
if not creds or not creds.valid:
if creds and creds.expired and creds.refresh_token:
creds.refresh(Request())
else:
flow = InstalledAppFlow.from_client_secrets_file("credentials.json", SCOPES) # <-- Oauth2.0 credential
creds = flow.run_local_server(port=0)
# Save the credentials for the next run
with open('token.pickle', 'wb') as token:
pickle.dump(creds, token)
I then tried to do another way using /tmp repesitory to store the token but still doesn't work and I can't see where is the issue ... Do you have any idea ? thank you so much
SCOPES = ['https://mail.google.com/']
CLIENT_SECRET_FILE = 'credentials.json' #OAuth credentials
APPLICATION_NAME = 'Gmail API Python'
def get_credentials():
store = oauth2client.file.Storage("/tmp/tempcredentials.json")
credentials = store.get()
if not credentials or credentials.invalid:
flow = client.flow_from_clientsecrets(CLIENT_SECRET_FILE, SCOPES)
flow.user_agent = APPLICATION_NAME
credentials = tools.run_flow(flow, store)
return credentials

Answer 1

As stated in the documentation the temporary folder is just for creating temporary files that will be stored in RAM memory and only available for the instance currently executing your code, thus there's no guarantee of persistence between invocations.
You should check this tutorial as it explains how to authenticate from Cloud Functions into Gmail (you will need more than a single function).