GKE pod not able to access private GCS Bucket (401 unauthorized error)

I am developing an application in Python which will be deployed on Google Kubernetes Engine (GKE) pod. The application involves writing and reading .csv files to Google Cloud Storage (private Google bucket). I am facing an error while trying to read/write files to the Google bucket. The read/write to private google bucket is working when I run the application on my local system.

The operation is failing when the application is deployed to the GKE pod.

The GKE pod in the cluster is not able to access the private GCS bucket even though I am providing credentials the same as local system. Following are some of the details regarding the application and the error which I am facing:

• DockerFile: The docker file contain a reference to the cred.json file which contains credentials of the google cloud service account. The service account has permissions of google cloud storage admin.

FROM python:3.9.10-slim-buster
WORKDIR /pipeline
COPY . .
RUN pip3 install --no-cache-dir -r requirements.txt

EXPOSE 3000

ENV GOOGLE_APPLICATION_CREDENTIALS=/pipeline/cred.json
ENV GIT_PYTHON_REFRESH=quiet

• requirements.txt: Following is the requirements.txt file content (I have included only google cloud related packages as they are relevant related to the error):

google-api-core==2.8.2
google-auth==2.9.0
google-auth-oauthlib==0.5.2
google-cloud-bigquery==3.2.0
google-cloud-bigquery-storage==2.11.0
google-cloud-core==2.3.1
google-cloud-storage==2.4.0
google-crc32c==1.3.0
google-resumable-media==2.3.3
googleapis-common-protos==1.56.3
fsspec==2022.8.2
gcsfs==2022.8.2
gevent==21.12.0

• Error details: Following is the traceback:

Anonymous caller does not have storage.objects.create access to the Google Cloud Storage bucket., 401
ERROR:gcsfs:_request non-retriable exception: Anonymous caller does not have storage.objects.create access to the Google Cloud Storage bucket., 401
Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/gcsfs/retry.py", line 115, in retry_request
    return await func(*args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/gcsfs/core.py", line 384, in _request
    validate_response(status, contents, path, args)
  File "/usr/local/lib/python3.9/site-packages/gcsfs/retry.py", line 102, in validate_response
    raise HttpError(error)
gcsfs.retry.HttpError: Anonymous caller does not have storage.objects.create access to the Google Cloud Storage bucket., 401
Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/local/lib/python3.9/threading.py", line 973, in _bootstrap_inner
    self.run()
  File "/usr/local/lib/python3.9/threading.py", line 910, in run
    self._target(*self._args, **self._kwargs)
  File "/pipeline/training/train.py", line 133, in training
    X.to_csv(file_name, index=False)
  File "/usr/local/lib/python3.9/site-packages/pandas/core/generic.py", line 3563, in to_csv
    return DataFrameRenderer(formatter).to_csv(
  File "/usr/local/lib/python3.9/site-packages/pandas/io/formats/format.py", line 1180, in to_csv
    csv_formatter.save()
  File "/usr/local/lib/python3.9/site-packages/pandas/io/formats/csvs.py", line 261, in save
    self._save()
  File "/usr/local/lib/python3.9/site-packages/pandas/io/formats/csvs.py", line 266, in _save
    self._save_body()
  File "/usr/local/lib/python3.9/site-packages/pandas/io/formats/csvs.py", line 304, in _save_body
    self._save_chunk(start_i, end_i)
  File "/usr/local/lib/python3.9/site-packages/pandas/io/formats/csvs.py", line 315, in _save_chunk
    libwriters.write_csv_rows(
  File "pandas/_libs/writers.pyx", line 72, in pandas._libs.writers.write_csv_rows
  File "/usr/local/lib/python3.9/site-packages/fsspec/spec.py", line 1491, in write
    self.flush()
  File "/usr/local/lib/python3.9/site-packages/fsspec/spec.py", line 1527, in flush
    self._initiate_upload()
  File "/usr/local/lib/python3.9/site-packages/gcsfs/core.py", line 1443, in _initiate_upload
    self.location = sync(
  File "/usr/local/lib/python3.9/site-packages/fsspec/asyn.py", line 96, in sync
    raise return_result
  File "/usr/local/lib/python3.9/site-packages/fsspec/asyn.py", line 53, in _runner
    result[0] = await coro
  File "/usr/local/lib/python3.9/site-packages/gcsfs/core.py", line 1559, in initiate_upload
    headers, _ = await fs._call(
  File "/usr/local/lib/python3.9/site-packages/gcsfs/core.py", line 392, in _call
    status, headers, info, contents = await self._request(
  File "/usr/local/lib/python3.9/site-packages/decorator.py", line 221, in fun
    return await caller(func, *(extras + args), **kw)
  File "/usr/local/lib/python3.9/site-packages/gcsfs/retry.py", line 152, in retry_request
    raise e
  File "/usr/local/lib/python3.9/site-packages/gcsfs/retry.py", line 115, in retry_request
    return await func(*args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/gcsfs/core.py", line 384, in _request
    validate_response(status, contents, path, args)
  File "/usr/local/lib/python3.9/site-packages/gcsfs/retry.py", line 102, in validate_response
    raise HttpError(error)
gcsfs.retry.HttpError: Anonymous caller does not have storage.objects.create access to the Google Cloud Storage bucket., 401

I also tried running the application by making the google cloud bucket public. With this approach, the read and write operations to google cloud bucket are working.

The problem arises when the google cloud bucket is private (which is essential for application deployment).

Any help to resolve this error will be appreciated. Thanks in advance!!