django - 'django_1 |运行 docker-compose up 后没有要连接的端口 [s]

Question

我是 docker 新手，已经编写了一个容器化的 django 应用程序和 react 应用程序。当我去运行时docker-compose up我收到一个奇怪的、永久的错误，django 没有要连接的端口。从 react 和 python 端运行服务器都可以。
错误信息

前端 dockerfile:

COPY ./react_app/package.json .
RUN apk add --no-cache --virtual .gyp \
        python \
        make \
        g++ \
    && npm install \
    && apk del .gyp

COPY ./react_app .

ARG API_SERVER
ENV REACT_APP_API_SERVER=${API_SERVER}
RUN REACT_APP_API_SERVER=${API_SERVER} \ 
  npm run build

WORKDIR /usr/src/app
RUN npm install -g serve
COPY --from=builder /usr/src/app/build ./build
Django Python backend Dockerfile

WORKDIR /usr/src/app

ENV PYTHONDONTWRITEBYTECODE 1
ENV PYTHONUNBUFFERED 1

COPY ./requirements.txt .
RUN pip wheel --no-cache-dir --no-deps --wheel-dir /usr/src/app/wheels -r requirements.txt

FROM python:3.7.9-slim-stretch
RUN apt-get update && apt-get install -y --no-install-recommends netcat && \
   apt-get autoremove -y && \
   apt-get clean && \
   rm -rf /var/lib/apt/lists/*

COPY --from=builder /usr/src/app/wheels /wheels
COPY --from=builder /usr/src/app/requirements.txt .
RUN pip install --no-cache /wheels/*
WORKDIR /usr/src/app
COPY ./entrypoint.sh /usr/src/app/entrypoint.sh

COPY ./django_app .

RUN chmod +x /usr/src/app/entrypoint.sh
ENTRYPOINT ["/usr/src/app/entrypoint.sh"]
and the nginx dockerfile

FROM nginx:1.19.0-alpine

RUN rm /etc/nginx/conf.d/default.conf
COPY nginx.conf /etc/nginx/conf.d

WORKDIR /usr/src/app

Django Python 后端 Dockerfile

WORKDIR /usr/src/app

ENV PYTHONDONTWRITEBYTECODE 1
ENV PYTHONUNBUFFERED 1

COPY ./requirements.txt .
RUN pip wheel --no-cache-dir --no-deps --wheel-dir /usr/src/app/wheels -r requirements.txt

FROM python:3.7.9-slim-stretch
RUN apt-get update && apt-get install -y --no-install-recommends netcat && \
   apt-get autoremove -y && \
   apt-get clean && \
   rm -rf /var/lib/apt/lists/*

COPY --from=builder /usr/src/app/wheels /wheels
COPY --from=builder /usr/src/app/requirements.txt .
RUN pip install --no-cache /wheels/*
WORKDIR /usr/src/app
COPY ./entrypoint.sh /usr/src/app/entrypoint.sh

COPY ./django_app .

RUN chmod +x /usr/src/app/entrypoint.sh
ENTRYPOINT ["/usr/src/app/entrypoint.sh"]

和 nginx dockerfile

FROM nginx:1.19.10-alpine

RUN rm /etc/nginx/conf.d/default.conf
COPY nginx.conf /etc/nginx/conf.d

WORKDIR /usr/src/app

我的入口点.sh

#!/bin/sh
if [ "$DATABASE" = "postgres" ]
then
    echo "Waiting for postgres..."
    
    while ! nc -z $DB_HOST $DB_PORT; do
      sleep 0.1
    done
    
    echo "PostgreSQL started"
fi

python manage.py collectstatic --noinput
python manage.py migrate --noinput
echo "from django.contrib.auth.models import User;
User.objects.filter(email='$DJANGO_ADMIN_EMAIL').delete();
User.objects.create_superuser('$DJANGO_ADMIN_USER', '$DJANGO_ADMIN_EMAIL', '$DJANGO_ADMIN_PASSWORD')" | python manage.py shell

exec "$@"

Docker-compose.yml

version: "3.7"

services:
  django:
    build:
      context: ./backend
      dockerfile: Dockerfile
    volumes:
      - django_static_volume:/usr/src/app/static
    expose:
      - 8000
    env_file:
      - ./backend/.env
    command: gunicorn candle.wsgi:application --bind 0.0.0.0:8000
    depends_on:
      - db
  db:
    image: postgres:12.0-alpine
    volumes:
      - postgres_data:/var/lib/postgresql/data/
    env_file:
      - ./postgres/.env
  react:
    build:
      context: ./frontend
      dockerfile: Dockerfile
      args:
        - API_SERVER=${ENV_API_SERVER}
    volumes:
      - react_static_volume:/usr/src/app/build/static
    expose:
      - 3000
    env_file:
      - .env
    command: serve -s build -l 3000
    depends_on:
      - django

  nginx:
    restart: always
    build: ./nginx
    volumes:
      - django_static_volume:/usr/src/app/django_files/static
      - react_static_volume:/usr/src/app/react_files/static
    ports:
      - 80:80
    depends_on:
      - react

volumes:
  postgres_data:
  django_static_volume:
  react_static_volume:

Nginx 配置

upstream django_backend {
    server django:8000;
}

upstream react_frontend {
    server react:3000;
}

server {

    listen 80;

    ###########
    # URL ROUTING #
    ###########

    location /admin {
        proxy_pass http://django_backend;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host;
        proxy_redirect off;
    }

    location /api {
        proxy_pass http://django_backend;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host;
        proxy_redirect off;
    }

    ###########
    # STATIC FOLDER ROUTING #
    ###########

    location /static/admin/ {
        alias /usr/src/app/django_files/static/admin/;
    }

    location /static/rest_framework/ {
        alias /usr/src/app/django_files/static/rest_framework/;
    }

    location /static/ {
        alias /usr/src/app/react_files/static/;
    }

    location /media/ {
        alias /usr/src/app/media/;
    }

    ###########
    # URL ROUTING #
    ###########

    location / {
        proxy_pass http://react_frontend;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host;
        proxy_redirect off;
    }


}

我找不到与此相关的任何内容，而且我也是 Docker 的新手。

Answer 1

这是一个网络猫错误。具体来说，当您在运行 nc 时提供主机名而不是端口时会发生这种情况。 .
例子:

# nc -z 8.8.8.8
no port[s] to connect to

然后，您的入口点脚本看到 netcat 退出并出现错误，并重新运行它直到成功，但它永远不会成功。
调试过程
我怀疑这是一个 netcat 问题，因为入口点脚本打印“Waiting for postgres...”而不是“PostgreSQL started”。但是，我无法让 netcat 产生“无端口”错误。
所以我运行了一个基础镜像的副本，并手动安装了 netcat。

docker run -it python:3.7.9-slim-stretch bash
# in container
apt-get update
apt-get install netcat

我仍然无法让 netcat 产生错误。于是我下载了netcat的源代码:

# still in container
apt-get source netcat

然后，带着 source code of netcat 的副本，我找到了这个代码:

  if (argv[optind] == NULL)
    bail ("no port[s] to connect to");

翻译:如果刚刚完成解析主机值的参数解析代码用完参数，则发出“没有要连接的端口[s]”错误。
我们可以通过在容器内运行 nc 来检查这一点:

root@cc139fd40237:/source/netcat-1.10# nc -z localhost
no port[s] to connect to

有趣的是，Ubuntu 有不同版本的 netcat，有不同的错误信息。

$ nc -z localhost
nc: missing port number

...所以这就是我无法在容器外重现 netcat 错误的原因!
健壮的 shell 脚本
在这一行中，未设置 DB_HOST 或 DB_PORT:

while ! nc -z $DB_HOST $DB_PORT; do

除了解决问题之外，这是使您的脚本更加健壮的好机会。如果您添加 set -u到你的 shell 脚本的顶部，你会得到一个更有帮助的错误消息:

Waiting for postgres...
entrypoint.sh: 7: DB_PORT: parameter not set

您也可以使用 shellcheck tool - 在您的脚本中，它建议您引用参数:

In entrypoint.sh line 6:
    while ! nc -z $DB_HOST $DB_PORT; do
                  ^------^ SC2086: Double quote to prevent globbing and word splitting.
                           ^------^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
    while ! nc -z "$DB_HOST" "$DB_PORT"; do

这也是一个绝妙的主意。