我是Docker的新手。我已经对下面的dockerfile进行了编码，以构建我的Flask应用程序：
FROM debian
WORKDIR /code
RUN apt update
RUN apt-get update
RUN apt-get install --yes git python3
RUN apt install --yes python3-pip
COPY requirements.txt requirements.txt
RUN pip3 install -r requirements.txt
RUN apt-get install --yes libcairo2 libpango-1.0-0 libpangocairo-1.0-0 libgdk-pixbuf2.0-0 libffi-dev
COPY app .
RUN python3 /code/config_database.py dev
EXPOSE 5000
ENTRYPOINT ["python3", "/code/app.py", "dev"]
在EXPOSE命令之前的那一行是我尝试连接到另一个容器中的MySQL数据库的地方。使用以下YAML文件构建MySQL映像：
version: "3.7"
services:
bd:
image: "mysql"
command: --default-authentication-plugin=mysql_native_password
environment:
MYSQL_DATABASE: covid3
MYSQL_ROOT_PASSWORD: XXX
MYSQL_USER: root
MYSQL_PASSWORD: XXX
ports:
- "3306:3306"
container_name: bd_mysql
web:
build: .
ports:
- "5000:5000"
depends_on:
- bd
container_name: app_flask
连接网址具有以下值：
DATABASE_URL = 'mysql+pymysql://root:XXX@bd:3306/covid3'
注意 bd 是我正在使用的MySQL计算机。我在其他地方读过我应该使用服务名称作为Docker中的机器数据库地址。我正在使用SQLAlchemy。这是获得与数据库连接的代码：
engine = create_engine(DATABASE_URL, echo=False)
Session = sessionmaker(bind=engine)
当我运行docker时，请使用以下命令：
docker-compose up --build
出现以下错误：
Step 12/14 : RUN python3 /code/config_database.py dev
---> Running in bfb4fd5f831a
Traceback (most recent call last):
File "/usr/local/lib/python3.7/dist-packages/pymysql/connections.py", line 583, in connect
**kwargs)
File "/usr/lib/python3.7/socket.py", line 707, in create_connection
for res in getaddrinfo(host, port, 0, SOCK_STREAM):
File "/usr/lib/python3.7/socket.py", line 748, in getaddrinfo
for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
socket.gaierror: [Errno -2] Name or service not known
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/engine/base.py", line 2285, in _wrap_pool_connect
return fn()
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/base.py", line 363, in connect
return _ConnectionFairy._checkout(self)
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/base.py", line 773, in _checkout
fairy = _ConnectionRecord.checkout(pool)
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/base.py", line 492, in checkout
rec = pool._do_get()
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/impl.py", line 139, in _do_get
self._dec_overflow()
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/util/langhelpers.py", line 69, in __exit__
exc_value, with_traceback=exc_tb,
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/util/compat.py", line 178, in raise_
raise exception
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/impl.py", line 136, in _do_get
return self._create_connection()
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/base.py", line 308, in _create_connection
return _ConnectionRecord(self)
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/base.py", line 437, in __init__
self.__connect(first_connect_check=True)
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/base.py", line 657, in __connect
pool.logger.debug("Error on connect(): %s", e)
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/util/langhelpers.py", line 69, in __exit__
exc_value, with_traceback=exc_tb,
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/util/compat.py", line 178, in raise_
raise exception
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/base.py", line 652, in __connect
connection = pool._invoke_creator(self)
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/engine/strategies.py", line 114, in connect
return dialect.connect(*cargs, **cparams)
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/engine/default.py", line 490, in connect
return self.dbapi.connect(*cargs, **cparams)
File "/usr/local/lib/python3.7/dist-packages/pymysql/__init__.py", line 94, in Connect
return Connection(*args, **kwargs)
File "/usr/local/lib/python3.7/dist-packages/pymysql/connections.py", line 325, in __init__
self.connect()
File "/usr/local/lib/python3.7/dist-packages/pymysql/connections.py", line 630, in connect
raise exc
pymysql.err.OperationalError: (2003, "Can't connect to MySQL server on 'bd' ([Errno -2] Name or service not known)")
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "/code/config_database.py", line 8, in <module>
Base.metadata.create_all(bind=db.engine)
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/sql/schema.py", line 4321, in create_all
ddl.SchemaGenerator, self, checkfirst=checkfirst, tables=tables
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/engine/base.py", line 2057, in _run_visitor
with self._optional_conn_ctx_manager(connection) as conn:
File "/usr/lib/python3.7/contextlib.py", line 112, in __enter__
return next(self.gen)
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/engine/base.py", line 2049, in _optional_conn_ctx_manager
with self._contextual_connect() as conn:
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/engine/base.py", line 2251, in _contextual_connect
self._wrap_pool_connect(self.pool.connect, None),
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/engine/base.py", line 2289, in _wrap_pool_connect
e, dialect, self
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/engine/base.py", line 1555, in _handle_dbapi_exception_noconnection
sqlalchemy_exception, with_traceback=exc_info[2], from_=e
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/util/compat.py", line 178, in raise_
raise exception
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/engine/base.py", line 2285, in _wrap_pool_connect
return fn()
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/base.py", line 363, in connect
return _ConnectionFairy._checkout(self)
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/base.py", line 773, in _checkout
fairy = _ConnectionRecord.checkout(pool)
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/base.py", line 492, in checkout
rec = pool._do_get()
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/impl.py", line 139, in _do_get
self._dec_overflow()
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/util/langhelpers.py", line 69, in __exit__
exc_value, with_traceback=exc_tb,
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/util/compat.py", line 178, in raise_
raise exception
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/impl.py", line 136, in _do_get
return self._create_connection()
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/base.py", line 308, in _create_connection
return _ConnectionRecord(self)
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/base.py", line 437, in __init__
self.__connect(first_connect_check=True)
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/base.py", line 657, in __connect
pool.logger.debug("Error on connect(): %s", e)
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/util/langhelpers.py", line 69, in __exit__
exc_value, with_traceback=exc_tb,
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/util/compat.py", line 178, in raise_
raise exception
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/pool/base.py", line 652, in __connect
connection = pool._invoke_creator(self)
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/engine/strategies.py", line 114, in connect
return dialect.connect(*cargs, **cparams)
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/engine/default.py", line 490, in connect
return self.dbapi.connect(*cargs, **cparams)
File "/usr/local/lib/python3.7/dist-packages/pymysql/__init__.py", line 94, in Connect
return Connection(*args, **kwargs)
File "/usr/local/lib/python3.7/dist-packages/pymysql/connections.py", line 325, in __init__
self.connect()
File "/usr/local/lib/python3.7/dist-packages/pymysql/connections.py", line 630, in connect
raise exc
sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2003, "Can't connect to MySQL server on 'bd' ([Errno -2] Name or service not known)")
(Background on this error at: http://sqlalche.me/e/e3q8)
ERROR: Service 'web' failed to build: The command '/bin/sh -c python3 /code/config_database.py dev' returned a non-zero code: 1
您有什么提示吗？
答案 0 :(得分：0)
从某种意义上说，问题似乎与事件的顺序有关，因为某些步骤是在构建时而不是在docker运行时发生的：
帖子中未共享config_database.py的内容，但是鉴于错误消息，我认为脚本正在尝试连接到DB。
RUN python3 /code/config_database.py dev将尝试在启动之前到达数据库容器。
一个常见的好的做法是在mysql容器本身中初始化数据库，而不是从外部脚本中初始化数据库。这是一个不错的post解释方法。