Google Cloud Datastore Emulator does not use default credentials

Question

Per Google's Cloud Datastore Emulator installation instructions, I was able to install and run the emulator in a bash terminal window without problem with gcloud beta emulators datastore start --project gramm-id.

I also setup the environment variables, per the instructions, in another terminal with $(gcloud beta emulators datastore env-init) and verified they were defined.

However, when I run my python script to add an entity to the local datastore with this code:

from google.cloud import datastore

print(os.environ['DATASTORE_HOST'])          # output: http://localhost:8081
print(os.environ['DATASTORE_EMULATOR_HOST']) # output: localhost:8081


client = datastore.Client('gramm-id')
kind = 'Task'
name = 'simpleTask'

task_key = client.key(kind, name)
task = client.Enity(key=task_key)
task['description'] = 'Buy milk'
client.put(task)

I get the error:

Traceback (most recent call last):
  File "tools.py", line 237, in <module>
    client = datastore.Client('gramm-id')
  File "/home/.../lib/python3.6/site-packages/google/cloud/datastore/client.py", line 205, in __init__
    project=project, credentials=credentials, _http=_http)
... long stack trace ....
  File "/home/.../lib/python3.6/site-packages/google/auth/_default.py", line 306, in default
    raise exceptions.DefaultCredentialsError(_HELP_MESSAGE)
google.auth.exceptions.DefaultCredentialsError: Could not automatically determine credentials. Please set GOOGLE_APPLICATION_CREDENTIALS or explicitly create credentials and re-run the application. For more information, please see https://developers.google.com/accounts/docs/application-default-credentials.

I don't think I need to create a GCP service account and provide access credentials to use the datastore emulator on my machine.

My system:

• Ubuntu 18.04
• Anaconda python 3.6.6
• Google Cloud SDK 215.0.0
• cloud-datastore-emulator 2.0.2.

What am I missing?

Answer 1

gcloud auth application-default login

This will prompt you to login through a browser window and will set your GOOGLE_APPLICATION_CREDENTIALS correctly for you. [1]

Answer 2

In theory you should be able to use mock credentials, e.g.:

class EmulatorCreds(google.auth.credentials.Credentials):

    def __init__(self):
        self.token = b'secret'
        self.expiry = None

    @property
    def valid(self):
        return True

    def refresh(self, _):
        raise RuntimeError('Should never be refreshed.')

client = datastore.Client(
    project='gramm-id',
    credentials=EmulatorCreds() , 
    _http=requests.Session()  # Un-authorized
)

However it seems like this doesn't currently work, so for now you'll need to set GOOGLE_APPLICATION_CREDENTIALS