Flask application in Docker with gunicorn

Question

I have a Flask application which I want to run as a docker container.

I was able to run the container a few times, but out of nowhere, it stopped working.

My requirements are:

requests==2.18.4
gunicorn==19.8.1
connexion==1.4
condu==2.0.0b10
Flask-PyMongo==2.2.0
Flask-JWT-Extended==3.17.0
Flask-Cors==3.0.7

and I'm running the application with the following command:

CMD [ "/usr/local/bin/gunicorn", "-w", "4","-b","0.0.0.0:4001", "--timeout", "120", "application:app"]

The error that I'm getting is:

  File "/usr/local/lib/python3.6/site-packages/gunicorn/arbiter.py", line 583, in spawn_worker
    worker.init_process()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/workers/base.py", line 129, in init_process
    self.load_wsgi()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/workers/base.py", line 138, in load_wsgi
    self.wsgi = self.app.wsgi()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/app/base.py", line 67, in wsgi
    self.callable = self.load()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/app/wsgiapp.py", line 52, in load
    return self.load_wsgiapp()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/app/wsgiapp.py", line 41, in load_wsgiapp
    return util.import_app(self.app_uri)
  File "/usr/local/lib/python3.6/site-packages/gunicorn/util.py", line 350, in import_app
    __import__(module)
  File "/app/application.py", line 5, in <module>
    import connexion as connexion
  File "/usr/local/lib/python3.6/site-packages/connexion/__init__.py", line 3, in <module>
    from .apis import AbstractAPI  # NOQA
  File "/usr/local/lib/python3.6/site-packages/connexion/apis/__init__.py", line 1, in <module>
    from .abstract import AbstractAPI  # NOQA
  File "/usr/local/lib/python3.6/site-packages/connexion/apis/abstract.py", line 14, in <module>
    from ..operation import Operation
  File "/usr/local/lib/python3.6/site-packages/connexion/operation.py", line 7, in <module>
    from .decorators import validation
  File "/usr/local/lib/python3.6/site-packages/connexion/decorators/validation.py", line 9, in <module>
    from werkzeug import FileStorage
ImportError: cannot import name 'FileStorage'
[2020-02-10 10:37:20 +0000] [8] [INFO] Worker exiting (pid: 8)
[2020-02-10 10:37:20 +0000] [9] [ERROR] Exception in worker process
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/gunicorn/arbiter.py", line 583, in spawn_worker
    worker.init_process()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/workers/base.py", line 129, in init_process
    self.load_wsgi()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/workers/base.py", line 138, in load_wsgi
    self.wsgi = self.app.wsgi()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/app/base.py", line 67, in wsgi
    self.callable = self.load()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/app/wsgiapp.py", line 52, in load
    return self.load_wsgiapp()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/app/wsgiapp.py", line 41, in load_wsgiapp
    return util.import_app(self.app_uri)
  File "/usr/local/lib/python3.6/site-packages/gunicorn/util.py", line 350, in import_app
    __import__(module)
  File "/app/application.py", line 5, in <module>
    import connexion as connexion
  File "/usr/local/lib/python3.6/site-packages/connexion/__init__.py", line 3, in <module>
    from .apis import AbstractAPI  # NOQA
  File "/usr/local/lib/python3.6/site-packages/connexion/apis/__init__.py", line 1, in <module>
    from .abstract import AbstractAPI  # NOQA
  File "/usr/local/lib/python3.6/site-packages/connexion/apis/abstract.py", line 14, in <module>
    from ..operation import Operation
  File "/usr/local/lib/python3.6/site-packages/connexion/operation.py", line 7, in <module>
    from .decorators import validation
  File "/usr/local/lib/python3.6/site-packages/connexion/decorators/validation.py", line 9, in <module>
    from werkzeug import FileStorage
ImportError: cannot import name 'FileStorage'
[2020-02-10 10:37:20 +0000] [9] [INFO] Worker exiting (pid: 9)
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/gunicorn/arbiter.py", line 210, in run
    self.sleep()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/arbiter.py", line 360, in sleep
    ready = select.select([self.PIPE[0]], [], [], 1.0)
  File "/usr/local/lib/python3.6/site-packages/gunicorn/arbiter.py", line 245, in handle_chld
    self.reap_workers()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/arbiter.py", line 525, in reap_workers
    raise HaltServer(reason, self.WORKER_BOOT_ERROR)
gunicorn.errors.HaltServer: <HaltServer 'Worker failed to boot.' 3>

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/bin/gunicorn", line 8, in <module>
    sys.exit(run())
  File "/usr/local/lib/python3.6/site-packages/gunicorn/app/wsgiapp.py", line 61, in run
    WSGIApplication("%(prog)s [OPTIONS] [APP_MODULE]").run()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/app/base.py", line 223, in run
    super(Application, self).run()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/app/base.py", line 72, in run
    Arbiter(self).run()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/arbiter.py", line 232, in run
    self.halt(reason=inst.reason, exit_status=inst.exit_status)
  File "/usr/local/lib/python3.6/site-packages/gunicorn/arbiter.py", line 345, in halt
    self.stop()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/arbiter.py", line 393, in stop
    time.sleep(0.1)
  File "/usr/local/lib/python3.6/site-packages/gunicorn/arbiter.py", line 245, in handle_chld
    self.reap_workers()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/arbiter.py", line 525, in reap_workers
    raise HaltServer(reason, self.WORKER_BOOT_ERROR)
gunicorn.errors.HaltServer: <HaltServer 'Worker failed to boot.' 3>
[2020-02-10 10:37:20 +0000] [12] [ERROR] Exception in worker process
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/gunicorn/arbiter.py", line 583, in spawn_worker
    worker.init_process()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/workers/base.py", line 129, in init_process
    self.load_wsgi()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/workers/base.py", line 138, in load_wsgi
    self.wsgi = self.app.wsgi()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/app/base.py", line 67, in wsgi
    self.callable = self.load()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/app/wsgiapp.py", line 52, in load
    return self.load_wsgiapp()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/app/wsgiapp.py", line 41, in load_wsgiapp
    return util.import_app(self.app_uri)
  File "/usr/local/lib/python3.6/site-packages/gunicorn/util.py", line 350, in import_app
    __import__(module)
  File "/app/application.py", line 5, in <module>
    import connexion as connexion
  File "/usr/local/lib/python3.6/site-packages/connexion/__init__.py", line 3, in <module>
    from .apis import AbstractAPI  # NOQA
  File "/usr/local/lib/python3.6/site-packages/connexion/apis/__init__.py", line 1, in <module>
    from .abstract import AbstractAPI  # NOQA
  File "/usr/local/lib/python3.6/site-packages/connexion/apis/abstract.py", line 14, in <module>
    from ..operation import Operation
  File "/usr/local/lib/python3.6/site-packages/connexion/operation.py", line 7, in <module>
    from .decorators import validation
  File "/usr/local/lib/python3.6/site-packages/connexion/decorators/validation.py", line 9, in <module>
    from werkzeug import FileStorage
ImportError: cannot import name 'FileStorage'
[2020-02-10 10:37:20 +0000] [12] [INFO] Worker exiting (pid: 12)
[2020-02-10 10:37:20 +0000] [10] [ERROR] Exception in worker process
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/gunicorn/arbiter.py", line 583, in spawn_worker
    worker.init_process()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/workers/base.py", line 129, in init_process
    self.load_wsgi()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/workers/base.py", line 138, in load_wsgi
    self.wsgi = self.app.wsgi()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/app/base.py", line 67, in wsgi
    self.callable = self.load()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/app/wsgiapp.py", line 52, in load
    return self.load_wsgiapp()
  File "/usr/local/lib/python3.6/site-packages/gunicorn/app/wsgiapp.py", line 41, in load_wsgiapp
    return util.import_app(self.app_uri)
  File "/usr/local/lib/python3.6/site-packages/gunicorn/util.py", line 350, in import_app
    __import__(module)
  File "/app/application.py", line 5, in <module>
    import connexion as connexion
  File "/usr/local/lib/python3.6/site-packages/connexion/__init__.py", line 3, in <module>
    from .apis import AbstractAPI  # NOQA
  File "/usr/local/lib/python3.6/site-packages/connexion/apis/__init__.py", line 1, in <module>
    from .abstract import AbstractAPI  # NOQA
  File "/usr/local/lib/python3.6/site-packages/connexion/apis/abstract.py", line 14, in <module>
    from ..operation import Operation
  File "/usr/local/lib/python3.6/site-packages/connexion/operation.py", line 7, in <module>
    from .decorators import validation
  File "/usr/local/lib/python3.6/site-packages/connexion/decorators/validation.py", line 9, in <module>
    from werkzeug import FileStorage
ImportError: cannot import name 'FileStorage'
[2020-02-10 10:37:20 +0000] [10] [INFO] Worker exiting (pid: 10)

I tried to change Python version, gunicorn version, to run the application differently and nothing is working. Can somebody help me, please?

Answer 1

Can't really tell you why it is not working, but a workaround that worked for me was changing the Werkzeug version.

When building with pip 20.0.2, Werkzeug 1.0.0 was installed as a dependency. Version locking it to 0.16.1 in the requirements, which was the version installed during a previous build, solved this issue for me.