Django 无法连接到 mysql

Question

So i put my django app and mysql inside docker container. Here is what i do

Docker file

FROM python:3
ENV PYTHONUNBUFFERED 1
WORKDIR /app
COPY requirements.txt /app/requirements.txt
RUN pip install -r requirements.txt
COPY . /app

and here is my docker-compose-yml

version: '3'
services:
  db:
    container_name: database
    image: mysql:8
    ports:
      - "3306:3306"
    command: --default-authentication-plugin=mysql_native_password

    environment:
      - MYSQL_DATABASE=django_example
      - MYSQL_USER=root
      - MYSQL_PASSWORD=123456
      - MYSQL_ROOT_PASSWORD=123456
      - MYSQL_ROOT_HOST=%
    volumes:
      - "./db:/var/lib/mysql"
  web:
    container_name: app
    build: .
    command: python manage.py runserver 0.0.0.0:8000
    ports:
      - "8000:8000"
    volumes:
      - .:/app
      - /tmp/app/mysqld:/run/mysqld
    depends_on: 
      - db

Then i run it with docker-compose up

I get this error

MySQLdb._exceptions.OperationalError: (2002, "Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)")

Here is my database setting

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'django_example',
        'USER': 'root',
        'PASSWORD': '123456',
        'HOST': 'localhost',
        'PORT': '3306',
    }
}

My docker ps --all

CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS                      PORTS                               NAMES
c61ac60bc037        mysql:latest        "docker-entrypoint.s…"   2 minutes ago       Up 34 seconds               0.0.0.0:3306->3306/tcp, 33060/tcp   py_rest_api_db_1
f00857755a46        py_rest_api_web     "python manage.py ru…"   5 minutes ago       Up 34 seconds               0.0.0.0:8000->8000/tcp              py_rest_api_web_1

So how can i fix it? did i miss something?

Full Log

Starting database ... done
Starting app      ... done
Attaching to database, app
database | 2020-10-23 06:03:42+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 8.0.22-1debian10 started.
database | 2020-10-23 06:03:42+00:00 [Note] [Entrypoint]: Switching to dedicated user 'mysql'
database | 2020-10-23 06:03:42+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 8.0.22-1debian10 started.
database | 2020-10-23T06:03:43.191491Z 0 [System] [MY-010116] [Server] /usr/sbin/mysqld (mysqld 8.0.22) starting as process 1
database | 2020-10-23T06:03:43.199528Z 0 [Warning] [MY-010159] [Server] Setting lower_case_table_names=2 because file system for /var/lib/mysql/ is case insensitive
database | 2020-10-23T06:03:43.214677Z 1 [System] [MY-013576] [InnoDB] InnoDB initialization has started.
app    | Watching for file changes with StatReloader
app    | Performing system checks...
app    | 
app    | System check identified no issues (0 silenced).
app    | Exception in thread django-main-thread:
app    | Traceback (most recent call last):
app    |   File "/usr/local/lib/python3.9/site-packages/django/db/backends/base/base.py", line 219, in ensure_connection
app    |     self.connect()
app    |   File "/usr/local/lib/python3.9/site-packages/django/utils/asyncio.py", line 26, in inner
app    |     return func(*args, **kwargs)
app    |   File "/usr/local/lib/python3.9/site-packages/django/db/backends/base/base.py", line 200, in connect
app    |     self.connection = self.get_new_connection(conn_params)
app    |   File "/usr/local/lib/python3.9/site-packages/django/utils/asyncio.py", line 26, in inner
app    |     return func(*args, **kwargs)
app    |   File "/usr/local/lib/python3.9/site-packages/django/db/backends/mysql/base.py", line 234, in get_new_connection
app    |     return Database.connect(**conn_params)
app    |   File "/usr/local/lib/python3.9/site-packages/MySQLdb/__init__.py", line 130, in Connect
app    |     return Connection(*args, **kwargs)
app    |   File "/usr/local/lib/python3.9/site-packages/MySQLdb/connections.py", line 185, in __init__
app    |     super().__init__(*args, **kwargs2)
app    | MySQLdb._exceptions.OperationalError: (2002, "Can't connect to MySQL server on 'db' (115)")
app    |
app    | The above exception was the direct cause of the following exception:
app    |
app    | Traceback (most recent call last):
app    |   File "/usr/local/lib/python3.9/threading.py", line 950, in _bootstrap_inner
app    |     self.run()
app    |   File "/usr/local/lib/python3.9/threading.py", line 888, in run
app    |     self._target(*self._args, **self._kwargs)
app    |   File "/usr/local/lib/python3.9/site-packages/django/utils/autoreload.py", line 53, in wrapper
app    |     fn(*args, **kwargs)
app    |   File "/usr/local/lib/python3.9/site-packages/django/core/management/commands/runserver.py", line 121, in inner_run
app    |     self.check_migrations()
app    |   File "/usr/local/lib/python3.9/site-packages/django/core/management/base.py", line 459, in check_migrations
app    |     executor = MigrationExecutor(connections[DEFAULT_DB_ALIAS])
app    |   File "/usr/local/lib/python3.9/site-packages/django/db/migrations/executor.py", line 18, in __init__
app    |     self.loader = MigrationLoader(self.connection)
app    |   File "/usr/local/lib/python3.9/site-packages/django/db/migrations/loader.py", line 53, in __init__
app    |     self.build_graph()
app    |   File "/usr/local/lib/python3.9/site-packages/django/db/migrations/loader.py", line 216, in build_graph
app    |     self.applied_migrations = recorder.applied_migrations()
app    |   File "/usr/local/lib/python3.9/site-packages/django/db/migrations/recorder.py", line 77, in applied_migrations
app    |     if self.has_table():
app    |   File "/usr/local/lib/python3.9/site-packages/django/db/migrations/recorder.py", line 55, in has_table
app    |     with self.connection.cursor() as cursor:
app    |   File "/usr/local/lib/python3.9/site-packages/django/utils/asyncio.py", line 26, in inner
app    |     return func(*args, **kwargs)
app    |   File "/usr/local/lib/python3.9/site-packages/django/db/backends/base/base.py", line 259, in cursor
app    |     return self._cursor()
app    |   File "/usr/local/lib/python3.9/site-packages/django/db/backends/base/base.py", line 235, in _cursor
app    |     self.ensure_connection()
app    |   File "/usr/local/lib/python3.9/site-packages/django/utils/asyncio.py", line 26, in inner
app    |     return func(*args, **kwargs)
app    |   File "/usr/local/lib/python3.9/site-packages/django/db/backends/base/base.py", line 219, in ensure_connection
app    |     self.connect()
app    |   File "/usr/local/lib/python3.9/site-packages/django/db/utils.py", line 90, in __exit__
app    |     raise dj_exc_value.with_traceback(traceback) from exc_value
app    |   File "/usr/local/lib/python3.9/site-packages/django/db/backends/base/base.py", line 219, in ensure_connection
app    |     self.connect()
app    |   File "/usr/local/lib/python3.9/site-packages/django/utils/asyncio.py", line 26, in inner
app    |     return func(*args, **kwargs)
app    |   File "/usr/local/lib/python3.9/site-packages/django/db/backends/base/base.py", line 200, in connect
app    |     self.connection = self.get_new_connection(conn_params)
app    |   File "/usr/local/lib/python3.9/site-packages/django/utils/asyncio.py", line 26, in inner
app    |     return func(*args, **kwargs)
app    |   File "/usr/local/lib/python3.9/site-packages/django/db/backends/mysql/base.py", line 234, in get_new_connection
app    |     return Database.connect(**conn_params)
app    |   File "/usr/local/lib/python3.9/site-packages/MySQLdb/__init__.py", line 130, in Connect
app    |     return Connection(*args, **kwargs)
app    |   File "/usr/local/lib/python3.9/site-packages/MySQLdb/connections.py", line 185, in __init__
app    |     super().__init__(*args, **kwargs2)
app    | django.db.utils.OperationalError: (2002, "Can't connect to MySQL server on 'db' (115)")
database | 2020-10-23T06:03:45.429683Z 1 [System] [MY-013577] [InnoDB] InnoDB initialization has ended.
database | 2020-10-23T06:03:45.557475Z 0 [System] [MY-011323] [Server] X Plugin ready for connections. Bind-address: '::' port: 33060, socket: /var/run/mysqld/mysqlx.sock
database | 2020-10-23T06:03:45.635937Z 0 [System] [MY-010229] [Server] Starting XA crash recovery...
database | 2020-10-23T06:03:45.639397Z 0 [System] [MY-010232] [Server] XA crash recovery finished.
database | 2020-10-23T06:03:45.805023Z 0 [Warning] [MY-010068] [Server] CA certificate ca.pem is self signed.
database | 2020-10-23T06:03:45.805494Z 0 [System] [MY-013602] [Server] Channel mysql_main configured to support TLS. Encrypted connections are now supported for this channel.
database | 2020-10-23T06:03:45.818355Z 0 [Warning] [MY-011810] [Server] Insecure configuration for --pid-file: Location '/var/run/mysqld' in the path is accessible to all OS users. Consider choosing a different directory.
database | 2020-10-23T06:03:45.855862Z 0 [System] [MY-010931] [Server] /usr/sbin/mysqld: ready for connections. Version: '8.0.22'  socket: '/var/run/mysqld/mysqld.sock'  port: 3306  MySQL Community Server - GPL.

Answer 1

Your Database settings has HOST set to localhost . when your django service spins up in container, service will look for mysql on the same container (django) instead of connecting to actual mysql container.

• Change the HOST value to db (db container name).
• Add a depends_on to web in docker compose, to make sure web container waits for db to be up and running.
• You may also need to set MYSQL_ROOT_HOST=% environment variable in mysql container to allow mysql to accept remote connections.

Edit

You can try using below options to wait for db container to be up.

• use wait-for-sh as suggested in docker official docs
• or try the approach here

Answer 2

In your Django settings.py file, change localhost to 127.0.0.1

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'django_example',
        'USER': 'root',
        'PASSWORD': '123456',
        'HOST': '127.0.0.1', # <- Change here
        'PORT': '3306',
    }
}

Also make sure you are running the docker image with -.net=host.

docker run -.net=host [image-name]