在将Django项目通过Docker部署到生产环境前，需要在本地测试Docker镜像是否可用。
部署的项目用UWSGI作为服务器，生成容器后，访问admin页面报500，于是进入容器内查看Django服务是否开启：
user@starx:~/program/my_project$ docker exec -it 33d729ba5b37 bash
root@33d729ba5b37:/home/my_project# python manage.py runserver
Performing system checks...
System check identified no issues (0 silenced).
Exception in thread django-main-thread:
Traceback (most recent call last):
File "/usr/local/lib/python3.7/site-packages/django/db/backends/base/base.py", line 217, in ensure_connection
self.connect()
File "/usr/local/lib/python3.7/site-packages/django/db/backends/base/base.py", line 195, in connect
self.connection = self.get_new_connection(conn_params)
File "/usr/local/lib/python3.7/site-packages/django/db/backends/mysql/base.py", line 227, in get_new_connection
return Database.connect(**conn_params)
File "/usr/local/lib/python3.7/site-packages/MySQLdb/__init__.py", line 84, in Connect
return Connection(*args, **kwargs)
File "/usr/local/lib/python3.7/site-packages/MySQLdb/connections.py", line 171, in __init__
super(Connection, self).__init__(*args, **kwargs2)
MySQLdb._exceptions.OperationalError: (2002, "Can't connect to MySQL server on '192.168.50.104' (115)")
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "/usr/local/lib/python3.7/threading.py", line 926, in _bootstrap_inner
self.run()
File "/usr/local/lib/python3.7/threading.py", line 870, in run
self._target(*self._args, **self._kwargs)
File "/usr/local/lib/python3.7/site-packages/django/utils/autoreload.py", line 54, in wrapper
fn(*args, **kwargs)
File "/usr/local/lib/python3.7/site-packages/django/core/management/commands/runserver.py", line 120, in inner_run
self.check_migrations()
File "/usr/local/lib/python3.7/site-packages/django/core/management/base.py", line 453, in check_migrations
executor = MigrationExecutor(connections[DEFAULT_DB_ALIAS])
File "/usr/local/lib/python3.7/site-packages/django/db/migrations/executor.py", line 18, in __init__
self.loader = MigrationLoader(self.connection)
File "/usr/local/lib/python3.7/site-packages/django/db/migrations/loader.py", line 49, in __init__
self.build_graph()
File "/usr/local/lib/python3.7/site-packages/django/db/migrations/loader.py", line 212, in build_graph
self.applied_migrations = recorder.applied_migrations()
File "/usr/local/lib/python3.7/site-packages/django/db/migrations/recorder.py", line 73, in applied_migrations
if self.has_table():
File "/usr/local/lib/python3.7/site-packages/django/db/migrations/recorder.py", line 56, in has_table
return self.Migration._meta.db_table in self.connection.introspection.table_names(self.connection.cursor())
File "/usr/local/lib/python3.7/site-packages/django/db/backends/base/base.py", line 256, in cursor
return self._cursor()
File "/usr/local/lib/python3.7/site-packages/django/db/backends/base/base.py", line 233, in _cursor
self.ensure_connection()
File "/usr/local/lib/python3.7/site-packages/django/db/backends/base/base.py", line 217, in ensure_connection
self.connect()
File "/usr/local/lib/python3.7/site-packages/django/db/utils.py", line 89, in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
File "/usr/local/lib/python3.7/site-packages/django/db/backends/base/base.py", line 217, in ensure_connection
self.connect()
File "/usr/local/lib/python3.7/site-packages/django/db/backends/base/base.py", line 195, in connect
self.connection = self.get_new_connection(conn_params)
File "/usr/local/lib/python3.7/site-packages/django/db/backends/mysql/base.py", line 227, in get_new_connection
return Database.connect(**conn_params)
File "/usr/local/lib/python3.7/site-packages/MySQLdb/__init__.py", line 84, in Connect
return Connection(*args, **kwargs)
File "/usr/local/lib/python3.7/site-packages/MySQLdb/connections.py", line 171, in __init__
super(Connection, self).__init__(*args, **kwargs2)
django.db.utils.OperationalError: (2002, "Can't connect to MySQL server on '192.168.50.104' (115)")
错误很简单，连接不到数据库。
查看MySQL监听的IP和端口：
user@starx:~/program/my_project$:~/program/themis$ netstat -anp | grep 3306
(Not all processes could be identified, non-owned process info
will not be shown, you would have to be root to see it all.)
tcp 0 0 127.0.0.1:3306 127.0.0.1:* LISTEN -
tcp 0 0 127.0.0.1:38582 127.0.0.1:3306 ESTABLISHED 10265/python
tcp 0 0 127.0.0.1:3306 127.0.0.1:38582 ESTABLISHED -
...
可以看到本机的MySQL只监听了本地环路接口，所以从Docker容器找不到MySQL的服务，这里修改MySQL配置文件：
sudo vi /etc/mysql/mysql.conf.d/mysqld.cnf
将其中的bing-address改为0.0.0.0，即监听本机所有网络IP：
41 # Instead of skip-networking the default is now to listen only on
42 # localhost which is more compatible and is not less secure.
43 bind-address = 0.0.0.0
修改后可以连接主机的MySQL服务。