我试图让gunicorn在docker compose文件中使用nginx。我的Python代码只是一个flask CRUD应用程序。
我的flask应用程序的入口点是./flask_app/app.py，并且我有以下docker compose yaml文件

version: '3'

services:

  flask_app:
    container_name: flask_app
    restart: always
    build: ./flask_app
    ports:
      - "8000:8000"
    command: gunicorn -w 1 -b :8000 app:server

  nginx:
    container_name: nginx
    restart: always
    build: ./nginx
    ports:
      - "80:80"
    depends_on:
      - flask_app

这是我的应用文件

from flask import Flask
from flask_marshmallow import Marshmallow
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)

app.config.from_pyfile('config.py')

db = SQLAlchemy(app)
ma = Marshmallow(app)

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=6000, debug=True)

然而，当我运行上面的代码时，我得到以下错误

Recreating ce38627418c1_ce38627418c1_ce38627418c1_ce38627418c1_ce38627418c1_flask_app ... error

ERROR: for ce38627418c1_ce38627418c1_ce38627418c1_ce38627418c1_ce38627418c1_flask_app  Cannot start service flask_app: OCI runtime create failed: container_linux.go:296: starting container process caused "exec: \"gunicorn\": executable file not found in $PATH": unknown

ERROR: for flask_app  Cannot start service flask_app: OCI runtime create failed: container_linux.go:296: starting container process caused "exec: \"gunicorn\": executable file not found in $PATH": unknown
ERROR: Encountered errors while bringing up the project.

据我所知，它似乎不是我的app = Flask(__name__)变量，我不知道为什么。我的方法基于这个工作示例https://github.com/sladkovm/docker-flask-gunicorn-nginx。
有人有什么想法吗？
编辑：在flask_app目录中，我有一个docker_compose文件指向的Dockerfile。它看起来是这样的：

FROM python:3.6.2

RUN mkdir -p /flask_app/app
WORKDIR /flask_app/app
COPY . /flask_app/app
RUN pip install --no-cache-dir -r requirements.txt

COPY . /flask_app/app