Bad Gateway 502 Error upgrading app from Python 3.7 to Python 3.8

Question

After successfully porting from Python 2.7 to 3.7 on Google App Engine, I decided to try upgrading to Python 3.8 runtime.

The only changes I made in the configuration from Python 3.7 was to specify the python38 runtime in the app.yaml file and to add google-cloud-datastore to requirements.txt

When I deploy and run the app runtime,I get a Bad Gateway 502 (nginx). Below is the stderr log:

Traceback (most recent call last):
  File "/layers/google.python.webserver/gunicorn/gunicorn/arbiter.py", line 583, in spawn_worker
    worker.init_process()
  File "/layers/google.python.webserver/gunicorn/gunicorn/workers/gthread.py", line 92, in init_process
    super().init_process()
  File "/layers/google.python.webserver/gunicorn/gunicorn/workers/base.py", line 119, in init_process
    self.load_wsgi()
  File "/layers/google.python.webserver/gunicorn/gunicorn/workers/base.py", line 144, in load_wsgi
    self.wsgi = self.app.wsgi()
  File "/layers/google.python.webserver/gunicorn/gunicorn/app/base.py", line 67, in wsgi
    self.callable = self.load()
  File "/layers/google.python.webserver/gunicorn/gunicorn/app/wsgiapp.py", line 49, in load
    return self.load_wsgiapp()
  File "/layers/google.python.webserver/gunicorn/gunicorn/app/wsgiapp.py", line 39, in load_wsgiapp
    return util.import_app(self.app_uri)
  File "/layers/google.python.webserver/gunicorn/gunicorn/util.py", line 358, in import_app
    mod = importlib.import_module(module)
  File "/opt/python3.8/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 783, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/srv/main.py", line 2, in <module>
    from google.cloud import ndb
  File "/layers/google.python.pip/pip/google/cloud/ndb/__init__.py", line 28, in <module>
    from google.cloud.ndb.client import Client
  File "/layers/google.python.pip/pip/google/cloud/ndb/client.py", line 26, in <module>
    from google.cloud.datastore_v1.gapic import datastore_client
ModuleNotFoundError: No module named 'google.cloud.datastore_v1.gapic'

My requirements.txt file has the following:

googleapis_common_protos
google-cloud-ndb
google-cloud-datastore
Flask==0.10.1

I do not specify an entry point in the app.yaml file. Per the docs, there is no requirement to include gunicorn in requirments.txt in that case. Initially I did not have the google-cloud-datastore library included. Python37 runtime did not need it. Seems to make no difference wrt the error with python38 runtime.

As mentioned this works perfectly with the python37 runtime.

Thanks.

SteveGoTex SteveGoTex · Accepted Answer · 2020-11-11T19:44:41

Looks like it was the

Flask==0.10.1 in requirements.txt. Took out the version spec, and removed google-cloud-datastore, as redundant.

All works now.

Sorry to have troubled you with this. But I guess posting the question, helped me see the problem with specifying an old version of flask.

Regards, S

Bad Gateway 502 Error upgrading app from Python 3.7 to Python 3.8

1 Answers