如何从docker容器中的python脚本连接本地主机上的mysql数据库

Question

我有一个mysql数据库运行在本地主机上(ubuntu16.04)。在同一台主机上，我有一个用于运行python脚本的docker容器。此脚本必须连接到本地主机上的mysqldb。正如在这些帖子(post1，post2)中所描述的，我为本地数据库设置了bind=0.0.0.0，并找到了本地主机的ip地址，并在我的python中使用它连接到数据库，但是它没有工作。下面我展示了我的设置和如何运行码头集装箱。我的python脚本(analysis.py)如下所示：

import pandas as pd
import sqlalchemy as db

def find_max_age():
   cnx = db.create_engine('mysql+mysqlconnector://root:password@172.17.0.1:3306/datasets')
   cnx_res = db.create_engine('mysql+mysqlconnector://root:password@172.17.0.1:3306/results')
   df = pd.read_sql("select * from test_table", cnx)
   idx = df['age'].idxmax() == df.index
   df_res = df[idx]

   df_res.to_sql('max_age4', con=cnx_res, index=False)


if __name__ == '__main__':
   find_max_age()

我的Dockerfile看起来像follwos：

FROM python:2.7-slim
EXPOSE 80 3306
WORKDIR /app
COPY requirements.txt /app
RUN pip install -r requirements.txt
COPY analysis.py /app
CMD python analysis.py

最后，requirements.txt看起来就像

mysql-connector-python
sqlalchemy
pandas

我构建了码头形象如下：

docker build -t max_age_app .

然后，我使用以下映像启动容器：

docker run -d max_age_app:latest

容器以退出代码1退出，当我查看容器的相应日志时，会在其中发现以下错误：

> Traceback (most recent call last):
  File "analysis.py", line 24, in <module>
    find_max_age()
  File "analysis.py", line 11, in find_max_age
    df = pd.read_sql("select * from test_table", cnx)
  File "/usr/local/lib/python2.7/site-packages/pandas/io/sql.py", line 397, in read_sql
    chunksize=chunksize)
  File "/usr/local/lib/python2.7/site-packages/pandas/io/sql.py", line 1063, in read_query
    result = self.execute(*args)
  File "/usr/local/lib/python2.7/site-packages/pandas/io/sql.py", line 954, in execute
    return self.connectable.execute(*args, **kwargs)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 2074, in execute
    connection = self.contextual_connect(close_with_result=True)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 2123, in contextual_connect
    self._wrap_pool_connect(self.pool.connect, None),
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 2162, in _wrap_pool_connect
    e, dialect, self)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1476, in _handle_dbapi_exception_noconnection
    exc_info
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/util/compat.py", line 265, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb, cause=cause)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 2158, in _wrap_pool_connect
    return fn()
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line 400, in connect
    return _ConnectionFairy._checkout(self)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line 788, in _checkout
    fairy = _ConnectionRecord.checkout(pool)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line 529, in checkout
    rec = pool._do_get()
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line 1193, in _do_get
    self._dec_overflow()
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/util/langhelpers.py", line 66, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line 1190, in _do_get
    return self._create_connection()
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line 347, in _create_connection
    return _ConnectionRecord(self)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line 474, in __init__
    self.__connect(first_connect_check=True)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line 671, in __connect
    connection = pool._invoke_creator(self)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/strategies.py", line 106, in connect
    return dialect.connect(*cargs, **cparams)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/default.py", line 412, in connect
    return self.dbapi.connect(*cargs, **cparams)
  File "/usr/local/lib/python2.7/site-packages/mysql/connector/__init__.py", line 172, in connect
    return CMySQLConnection(*args, **kwargs)
  File "/usr/local/lib/python2.7/site-packages/mysql/connector/connection_cext.py", line 78, in __init__
    self.connect(**kwargs)
  File "/usr/local/lib/python2.7/site-packages/mysql/connector/abstracts.py", line 731, in connect
    self._open_connection()
  File "/usr/local/lib/python2.7/site-packages/mysql/connector/connection_cext.py", line 179, in _open_connection
    sqlstate=exc.sqlstate)
sqlalchemy.exc.DatabaseError: (mysql.connector.errors.DatabaseError) 2003 (HY000): Can't connect to MySQL server on '172.17.0.1' (111) (Background on this error at: http://sqlalche.me/e/4xp6)

为了确定本地主机的ip，我使用了ifconfig命令，得到如下结果：

docker0   Link encap:Ethernet  HWaddr 02:42:a2:a6:d7:ff  
          inet addr:172.17.0.1 

enp0s3    Link encap:Ethernet  HWaddr 08:00:27:bb:7e:b5  
          inet addr:10.0.2.15 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1 

因此，为了从容器中连接本地数据库，我尝试了172.17.0.1，但是它没有工作。

启动容器时，是否必须通过-p选项匹配容器和本地主机之间的任何端口？

我很感谢你的帮助。

Answer 1

为了解决这个问题，必须在本地主机上正确配置mysql数据库。除上文讨论的内容外，还必须采取以下步骤：

• 使用python应用程序查找您的停靠容器的IP地址。您可以使用docker inspect <container_name>。
• 在本地mysql数据库中为该IP地址创建一个新用户(以及相应的密码)。有关如何做到这一点的信息，你可以在这个post中找到。介绍了如何在mysql中设置密码策略。

之后，使用命令docker run -d max_age_app启动容器就足以让python将数据写入本地主机上的数据库中。

Answer 2

您不应该在容器上EXPOSE端口3306，因为MySQL服务器正在侦听它外部的本地主机。我怀疑这是一个网络问题，所以试着看看本地主机是否有与地址172.17.0.1的接口，以及您是否可以从容器内(例如)到达这个地址。尝试docker exec -ti _your_container_name /bin/sh，然后尝试ping 172.17.0.1)。您还应该检查mysql日志，看看那里是否报告了一些错误。