如何在 Rails 应用程序中使用 docker 连接 mysql？

Question

I created a rails app use mysql database. Now want to put them into docker container. I am using docker, docker-machine, docker-compose.

My docker-compose.yml

db:
  image: mysql
  environment:
    MYSQL_ROOT_PASSWORD: <%= ENV['MYSQL_ROOT_PASSWORD'] %>
  ports:
    - "3306:3306"

web:
  build: .
  command: bundle exec rails s -p 3000 -b '0.0.0.0'
  volumes:
    - .:/myapp
  ports:
    - "3000:3000"
  links:
    - db

My config/database.yml

default: &default
  adapter: mysql2
  encoding: utf8
  pool: 5
  username: root
  password: <%= ENV['MYSQL_ROOT_PASSWORD'] %>
  host: <%= ENV['DB_PORT_3306_TCP_ADDR'] %>
  port: <%= ENV['DB_PORT_3306_TCP_PORT'] %>

development:
  <<: *default
  database: myapp_development

test:
  <<: *default
  database: myapp_test

production:
  <<: *default
  database: myapp_production

When boot app

$ docker-compose up
...
sidekiq_1 | Host '172.17.0.5' is not allowed to connect to this MySQL server
...

My web env

$ docker-compose run web env
...
DB_PORT=tcp://172.17.0.3:3306
DB_PORT_3306_TCP=tcp://172.17.0.3:3306
DB_PORT_3306_TCP_ADDR=172.17.0.3
DB_PORT_3306_TCP_PORT=3306
DB_PORT_3306_TCP_PROTO=tcp
WEB_PORT=tcp://172.17.0.6:3000
WEB_PORT_3000_TCP=tcp://172.17.0.6:3000
WEB_PORT_3000_TCP_ADDR=172.17.0.6
WEB_PORT_3000_TCP_PORT=3000
WEB_PORT_3000_TCP_PROTO=tcp
...

My docker-machine ip

$ docker-machine ip myapp
192.168.99.100

Access from browser: http://192.168.99.100:3000 , then saw error:

Mysql2::Error
Host '172.17.0.6' is not allowed to connect to this MySQL server

172.17.0.3 , 172.17.0.5 , 172.17.0.6 , etc. Why they use different ips? Then how to connect mysql? I can't understand the host and port written in the config/database.yml file.

Answer 1

In my case, I'm running Rails in host, and MySQL in docker, the official image.

Adding host: 127.0.0.1 solved the problem.

config/database.yml

default: &default
  adapter: mysql2
  encoding: utf8
  pool: 5
  username: root
  password:
  host: 127.0.0.1

Answer 2

You have to add the container name ( db ) to the host, Example:

config/database.yml

default: &default
  adapter: mysql2
  encoding: utf8
  pool: 5
  username: root
  password: <%= ENV['MYSQL_ROOT_PASSWORD'] %>
  host: db
development:
  <<: *default
  database: myapp_development

test:
  <<: *default
  database: myapp_test

production:
  <<: *default
  database: myapp_production

Look at you this example: docker-to-rails-with-rbenv

Answer 3

IPs are assigned by internal DHCP server. This is why they can changed...

I would recommend reading this post http://blog.carbonfive.com/2015/03/17/docker-rails-docker-compose-together-in-your-development-workflow/ which explains how to configure rails app using host name (and not IPs) to properly connect to a database while using docker-compose.