python - 无法从同一 docker swarm 上运行的其他服务连接到 postgres 服务？

Question

我有这个简单的 flask 应用程序:

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
import time

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI']  = 'postgresql+psycopg2://{user}:{pwd}@{host}:{port}/{db}'.format(
    user = 'postgres',
    pwd = '123456',
    host = 'db',
    port = '5432',
    db = 'test'
)
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app)

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True, nullable=False)
    email = db.Column(db.String(120), unique=True, nullable=False)

    def __repr__(self):
        return '<User %r>' % self.username

if __name__ == "__main__":
    db.create_all()
    app.run(host='0.0.0.0', port=80)

我使用以下 Dockerfile 构建它:

FROM python:3.6

WORKDIR /app

COPY . /app

RUN pip install -r requirements.txt

EXPOSE 80

CMD ["python", "app.py"]

如下:

sudo docker build -t app . 

还有我的docker-compose.yml:

version: "3"
services:
  web:
    image: app:latest
    deploy:
      replicas: 1
      restart_policy:
        condition: on-failure
    ports:
      - "4000:80"
    depends_on:
      - db
    networks:
      - webnet
  db:
    image: postgres
    expose:
      - 5432
    volumes:
      - /var/www/docker-tutorial/data:/var/lib/postgresql/data
    environment:
      POSTGRES_PASSWORD: 123456
      POSTGRES_DB: test
networks:
  webnet:

我的requirements.txt文件:

Flask
Flask-SQLAlchemy
psycopg2

我正在运行:

 docker stack deploy -c docker-compose.yml getstarted

一切正常，但连接数据库时出现以下异常:

sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) could not translate host name "db" to address: Name or service not known

有什么想法导致异常吗？另外，我尝试将 sqlalchemy 的主机参数替换为“getstarted_db”，这是服务的名称，但这也不起作用。

Answer 1

感谢 maxm 评论，我能够解决问题，问题是 web 和 db 服务不在同一网络中。所以我的docker-compose.yml变成如下:

version: "3"
services:
  web:
    image: hello:latest
    deploy:
      replicas: 1
      restart_policy:
        condition: on-failure
    ports:
      - "4000:80"
    depends_on:
      - db
    networks:
      - webnet
  db:
    image: postgres
    expose:
      - 5432
    volumes:
      - /var/www/docker-tutorial/data:/var/lib/postgresql/data
    environment:
      POSTGRES_PASSWORD: 123456
      POSTGRES_DB: test
    networks:
      - webnet

networks:
  webnet: