无法运行rake db:使用docker-compose在Dockerfile中创建

Question

除了我从一个现有的应用程序开始,我在教程中有一个Dockerfile并且docker-compose.yml喜欢.

我docker-compose.yml看起来像:

db:
  image: postgres
  ports:
    - "5432"
web:
  build: .
  command: bundle exec rails s -p 3000 -b '0.0.0.0'
  volumes:
    - .:/myapp
  ports:
    - "3030:3030"
  links:
    - db

并且Dockerfile:

FROM ruby:2.1.4
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev nodejs
RUN mkdir /myapp
WORKDIR /myapp
ADD Gemfile /myapp/Gemfile
RUN bundle install
ADD . /myapp
# RUN bundle exec rake db:create
# RUN bundle exec rake db:migrate
# RUN bundle exec rake db:seed

和 database.yml

development:
  adapter: postgresql
  encoding: utf8
  database: myapp_development
  host: db
  pool: 5
  username: postgres
  password:

如你所见,我评论RUN bundle exec rake db:create是因为我收到了一个错误:

could not translate host name "db" to address: Name or service not known
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/postgresql_adapter.rb:1222:in `initialize'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/postgresql_adapter.rb:1222:in `new'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/postgresql_adapter.rb:1222:in `connect'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/postgresql_adapter.rb:324:in `initialize'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/postgresql_adapter.rb:28:in `new'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/postgresql_adapter.rb:28:in `postgresql_connection'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/abstract/connection_pool.rb:315:in `new_connection'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/abstract/connection_pool.rb:325:in `checkout_new_connection'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/abstract/connection_pool.rb:247:in `block (2 levels) in checkout'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/abstract/connection_pool.rb:242:in `loop'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/abstract/connection_pool.rb:242:in `block in checkout'
/usr/local/lib/ruby/2.1.0/monitor.rb:211:in `mon_synchronize'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/abstract/connection_pool.rb:239:in `checkout'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/abstract/connection_pool.rb:102:in `block in connection'
/usr/local/lib/ruby/2.1.0/monitor.rb:211:in `mon_synchronize'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/abstract/connection_pool.rb:101:in `connection'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/abstract/connection_pool.rb:410:in `retrieve_connection'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/abstract/connection_specification.rb:171:in `retrieve_connection'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/connection_adapters/abstract/connection_specification.rb:145:in `connection'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/railties/databases.rake:144:in `rescue in create_database'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/railties/databases.rake:85:in `create_database'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/railties/databases.rake:62:in `block (3 levels) in <top (required)>'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/railties/databases.rake:62:in `each'
/usr/local/bundle/gems/activerecord-3.2.21/lib/active_record/railties/databases.rake:62:in `block (2 levels) in <top (required)>'
/usr/local/bundle/gems/rake-10.4.2/lib/rake/task.rb:240:in `call'
/usr/local/bundle/gems/rake-10.4.2/lib/rake/task.rb:240:in `block in execute'
/usr/local/bundle/gems/rake-10.4.2/lib/rake/task.rb:235:in `each'
/usr/local/bundle/gems/rake-10.4.2/lib/rake/task.rb:235:in `execute'
/usr/local/bundle/gems/rake-10.4.2/lib/rake/task.rb:179:in `block in invoke_with_call_chain'
/usr/local/lib/ruby/2.1.0/monitor.rb:211:in `mon_synchronize'
/usr/local/bundle/gems/rake-10.4.2/lib/rake/task.rb:172:in `invoke_with_call_chain'
/usr/local/bundle/gems/rake-10.4.2/lib/rake/task.rb:165:in `invoke'
/usr/local/bundle/gems/rake-10.4.2/lib/rake/application.rb:150:in `invoke_task'
/usr/local/bundle/gems/rake-10.4.2/lib/rake/application.rb:106:in `block (2 levels) in top_level'
/usr/local/bundle/gems/rake-10.4.2/lib/rake/application.rb:106:in `each'
/usr/local/bundle/gems/rake-10.4.2/lib/rake/application.rb:106:in `block in top_level'
/usr/local/bundle/gems/rake-10.4.2/lib/rake/application.rb:115:in `run_with_threads'
/usr/local/bundle/gems/rake-10.4.2/lib/rake/application.rb:100:in `top_level'
/usr/local/bundle/gems/rake-10.4.2/lib/rake/application.rb:78:in `block in run'
/usr/local/bundle/gems/rake-10.4.2/lib/rake/application.rb:176:in `standard_exception_handling'
/usr/local/bundle/gems/rake-10.4.2/lib/rake/application.rb:75:in `run'
/usr/local/bundle/gems/rake-10.4.2/bin/rake:33:in `<top (required)>'
/usr/local/bundle/bin/rake:16:in `load'
/usr/local/bundle/bin/rake:16:in `<main>'
Couldn't create database for {"adapter"=>"postgresql", "encoding"=>"utf8", "database"=>"myapp_development", "host"=>"db", "pool"=>5, "username"=>"postgres", "password"=>nil}

相反,我只好docker-compose build 再 docker-compose run web rake db:create等.

为什么我不能在Dockerfile中进行db-creation/migration.它会非常清楚.我能做到吗？

Answer 1

当你的web形象是建立(下面的说明Dockerfile),它没有到连接db容器.

Web服务器和数据库映像是独立的,并且在启动它们时链接容器(遵循docker-compose.yml文件的定义).

在映像构建期间无法链接到容器,因为它会破坏映像构建必须可重现的原则.同样,在映像构建期间也无法从主机安装卷.

docker-compose run web rake db:create您使用的命令是初始化数据库的正确方法.

或者,您可以docker-compose使用默认启动容器,然后使用该docker exec命令rake db:create在web容器中执行.