The library is asking credentials for running against emulator

[karakanb]

Environment details

• OS type and version: MacOS 11.2.2 (20D80) & Docker 3.2.1
• Python version: Python 3.9.2
• pip version: pip 21.0.1
• google-cloud-pubsub version: 2.2.0

Steps to reproduce

Use the following docker-compose.yml file:

version: "3.7"

services:
  pubsub:
    image: google/cloud-sdk:331.0.0
    command: gcloud beta emulators pubsub start --host-port=0.0.0.0:8085
    ports:
      - "8085:8085"
    restart: unless-stopped

  publisher:
    image: python:3.9.2
    command: sh -c "pip install google-cloud-pubsub~=2.2.0 && python /app/publish.py"
    volumes:
      - .:/app
    environment:
      - PUBSUB_EMULATOR_HOST=pubsub:8085
      - PUBSUB_PROJECT_ID=test-project

and the following content as publish.py in the same directory:

from google.cloud import pubsub_v1

project_id = "test-project"
topic_id = "test-topic"

publisher = pubsub_v1.PublisherClient()
topic_path = publisher.topic_path(project_id, topic_id)
publisher.publish(topic_path, b'My first message!')

When I run the file above, the execution fails with the library failing to run against the local emulator with the error:

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://cloud.google.com/docs/authentication/getting-started

As far as I understand, there should be no credentials involved since the script is running against the emulator, and I'd just expect the request to work as it is.

If I use the 2.1.0 version, the script works just fine. The reason I am running 2.2.0 is because of #325, and since there is no solution to that with 2.4.0 as of today, I needed to downgrade to this version. I am unable to test this due to being unable to run 2.4.0 against the emulator, therefore I wanted to report this in case this is a regression introduced with 2.2.0 that might be there for other versions as well.

Stack trace

$ python publish.py 
Traceback (most recent call last):
  File "/app/publish.py", line 6, in <module>
    publisher = pubsub_v1.PublisherClient()
  File "/usr/local/lib/python3.9/site-packages/google/cloud/pubsub_v1/publisher/client.py", line 141, in __init__
    client_for_mtls_info = publisher_client.PublisherClient(
  File "/usr/local/lib/python3.9/site-packages/google/pubsub_v1/services/publisher/client.py", line 350, in __init__
    self._transport = Transport(
  File "/usr/local/lib/python3.9/site-packages/google/pubsub_v1/services/publisher/transports/grpc.py", line 159, in __init__
    credentials, _ = auth.default(
  File "/usr/local/lib/python3.9/site-packages/google/auth/_default.py", line 483, 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://cloud.google.com/docs/authentication/getting-started

[plamut]

This might be a duplicate of #249, the issue with credentials has been fixed in v2.3.0 (release notes).

@karakanb Can you try upgrading the library and see if it fixes the problem for you?

[karakanb]

As I have mentioned, I cannot upgrade it for now since the v2.3.0 and v2.4.0 have the problem described in #325, so I will wait for future releases, thanks.

[plamut]

Ah, of course, the fix from #297 has not been released yet.

You can use the current development version, if you wish, or indeed wait for the next release, which should happen in the near future.