フラスコ、gunicornをパッケージ化する方法

FROM python:3.6
ADD . /app
WORKDIR /app
RUN pip install flask gunicorn
EXPOSE 8000
CMD ["gunicorn", "-b", "0.0.0.0:8000", "app"]

#file:requirements.txt
flask==1.1.4
gunicorn>19

# file: flask_gunicorn_distroless.dockerfile

FROM python:3.6-slim  AS build-env
WORKDIR /app

# First install packages to avoid re-run pip install 
COPY requirements.txt ./
RUN pip install --disable-pip-version-check -r requirements.txt --target /packages

COPY ./versions.py /app
COPY ./app.py /app
COPY ./standalone.py /app

FROM gcr.io/distroless/python3
WORKDIR /app
COPY --from=build-env /app /app
COPY --from=build-env /packages /packages
#instead of COPY --from=build-env /packages /usr/local/lib/python/site-packages

ENV PYTHONPATH=/packages
#instead of ENV PYTHONPATH=/usr/local/lib/python/site-packages

CMD ["standalone.py"]

# file version.py
import sys
import os
import argparse
from pathlib import Path

print("Versions:------------------")
parser = argparse.ArgumentParser()
parser.add_argument('folder', type=str, help='The folder to list.', nargs='?', default=os.getcwd())

#--------------------------
import flask
print("Flask Version:",flask.__version__)

import gunicorn 
print("Gunicorn Version:",gunicorn.__version__)

#--------------------------
print("Getcwd: ",os.getcwd()) 
print("Sys.path count:",str(len(sys.path)))
print('\n'.join(sys.path))


def listFolders(str_path: str):
    dir_path=Path(str_path).expanduser()
    print(" Packages:------------------")
    try:
       for path in dir_path.iterdir():            
         if path.is_dir(): 
            print(path)
    except PermissionError:
       pass

def main(args):
    print('Folder:'+args.folder)
    listFolders(args.folder)


if __name__ == "__main__":
    main(parser.parse_args())
    #listFolders('/packages')

:docker run flask_gunicorn_distroless
Versions:------------------
Flask Version: 1.1.4
Gunicorn Version: 20.1.0
Getcwd:  /app
Sys.path count: 5
/app
/packages
/usr/lib/python39.zip
/usr/lib/python3.9
/usr/lib/python3.9/lib-dynload
Folder:/usr/lib/python3.9
Folders:------------------
/usr/lib/python3.9/multiprocessing
/usr/lib/python3.9/zoneinfo
/usr/lib/python3.9/sqlite3
/usr/lib/python3.9/distutils
/usr/lib/python3.9/venv
/usr/lib/python3.9/http
/usr/lib/python3.9/xml
/usr/lib/python3.9/asyncio
/usr/lib/python3.9/collections
/usr/lib/python3.9/wsgiref
/usr/lib/python3.9/encodings
/usr/lib/python3.9/pydoc_data
/usr/lib/python3.9/ctypes
/usr/lib/python3.9/xmlrpc
/usr/lib/python3.9/test
/usr/lib/python3.9/email
/usr/lib/python3.9/importlib
/usr/lib/python3.9/curses
/usr/lib/python3.9/html
/usr/lib/python3.9/json
/usr/lib/python3.9/logging
/usr/lib/python3.9/dbm
/usr/lib/python3.9/lib-dynload
/usr/lib/python3.9/urllib
/usr/lib/python3.9/concurrent
/usr/lib/python3.9/unittest
/usr/lib/python3.9/__pycache__

#file:app.py
from time import gmtime, strftime   
from flask import Flask

application = Flask(__name__)

@application.route("/")
def index():    
    return {'status':'Available','time':strftime("%H:%M:%S", gmtime())  }    

if __name__ == "__main__":    
    application.run(host="0.0.0.0", port=5000,debug=True)

CMD ["gunicorn", "-b", "0.0.0.0:8000", "app"]

# file:standalone.py
from app import application
import multiprocessing
import gunicorn.app.base

def number_of_workers():
    return  (multiprocessing.cpu_count() * 2) + 1

class StandaloneApplication(gunicorn.app.base.BaseApplication):

    def __init__(self, app, options=None):
        self.options = options or {}
        self.application = app
        super().__init__()

    def load_config(self):
        config = {key: value for key, value in self.options.items()
                  if key in self.cfg.settings and value is not None}
        for key, value in config.items():
            self.cfg.set(key.lower(), value)

    def load(self):
        return self.application

if __name__ == '__main__':
    options = {
        'bind': '%s:%s' % ('0.0.0.0', '8000'),
        'workers': number_of_workers(),
    }
    StandaloneApplication(application, options).run()

docker image ls flask_gunicorn_distroless
REPOSITORY                  TAG       IMAGE ID       CREATED         SIZE
flask_gunicorn_distroless   latest    fa824d3ab0a6   3 minutes ago   70.8MB

docker image ls python:3.9-slim
REPOSITORY   TAG        IMAGE ID       CREATED       SIZE
python       3.9-slim   5e714d33137a   5 days ago    122MB