docker-composeでのRuby on Rails環境構築でPostgreSQLが接続されない。

Question

前提・実現したいこと

DockerでRuby on Railsの環境構築をしたいです。
以下のコマンドを打つと以下のようなエラーが出て、データベースに接続されないようです。解決策をお教え下さい。

発生している問題・エラーメッセージ

$ docker-compose run web rake db:create
Starting rails-on-docker_db_1 ... done
could not translate host name "db" to address: Name or service not known
Couldn't create 'myapp_development' database. Please check your configuration.
rake aborted!
PG::ConnectionBad: could not translate host name "db" to address: Name or service not known
/usr/local/bundle/gems/pg-1.1.4/lib/pg.rb:56:in `initialize'
/usr/local/bundle/gems/pg-1.1.4/lib/pg.rb:56:in `new'
/usr/local/bundle/gems/pg-1.1.4/lib/pg.rb:56:in `connect'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/postgresql_adapter.rb:692:in `connect'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/postgresql_adapter.rb:223:in `initialize'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/postgresql_adapter.rb:48:in `new'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/postgresql_adapter.rb:48:in `postgresql_connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/connection_pool.rb:811:in `new_connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/connection_pool.rb:855:in `checkout_new_connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/connection_pool.rb:834:in `try_to_checkout_new_connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/connection_pool.rb:795:in `acquire_connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/connection_pool.rb:523:in `checkout'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/connection_pool.rb:382:in `connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/connection_pool.rb:1014:in `retrieve_connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_handling.rb:118:in `retrieve_connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_handling.rb:90:in `connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/tasks/postgresql_database_tasks.rb:12:in `connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/tasks/postgresql_database_tasks.rb:21:in `create'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/tasks/database_tasks.rb:119:in `create'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/tasks/database_tasks.rb:139:in `block in create_current'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/tasks/database_tasks.rb:316:in `block in each_current_configuration'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/tasks/database_tasks.rb:313:in `each'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/tasks/database_tasks.rb:313:in `each_current_configuration'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/tasks/database_tasks.rb:138:in `create_current'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/railties/databases.rake:29:in `block (2 levels) in <top (required)>'
/usr/local/bundle/gems/rake-12.3.2/exe/rake:27:in `<top (required)>'
Tasks: TOP => db:create
(See full trace by running task with --trace)

該当のソースコード

default: &default
  adapter: postgresql
  encoding: unicode
  database: myapp_developmen
  host: db
  username: postgres
  password:
  pool: 5

development:
  <<: *default
  database: myapp_development

test:
  <<: *default
  database: myapp_test

#  <<: *default
#  database: myapp_production
#  username: myapp
#  password: <%= ENV['MYAPP_DATABASE_PASSWORD'] %>

version: '3'
services:
  db:
    image: postgres:10
    volumes:
      - ./tmp/db:/var/lib/postgresql/data
  web:
    build: .
    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
    volumes:
      - .:/myapp
    ports:
      - "3000:3000"
    depends_on:
      - db

試したこと

参考：公式リファレンス
1.
/tmp/dbの中身を空にした。
2.
docker-compose.ymlで
image:postgres:10に変更した。
他は参考と同じ。
3.
docker-compose run web rails db:create
でも実行したが、変化はなかった。

補足情報（FW/ツールのバージョンなど）

postgresqlで動かしたいです。

Comments

[Orlofsky]

URLは https://teratail.com/help#about-markdown の [リンク] に修正してください。

[退会済みユーザー]

`docker-compose.yml` を書いてください。

Answer 1

こちらが原因かと思われます。
Control startup and shutdown order in Compose | Docker Documentation

Answer 2

調べてみると次のようなやり方を紹介しているものが多かったです。
【ゆるふわ????】Docker ＋ Rails ＋ Heroku ＝「Yay! You’re on Rails!」【本番環境構築】

僕も最近docker+railsでherokuにデプロイを試しています。
上記の方法とは違うのであまりよくない方法かもしれませんが一応紹介します。
＜database.yml＞

  host: <%= ENV.fetch('DATABASE_HOST') %>

heroku側で環境変数（DATABASE_HOST）を設定する
ダッシュボード　->　該当アプリ　->　settings -> Reveal config vars から設定
databaseのアドレスは次のコマンドで確認する。
heroku pg:credentials:url --app ＜herokuアプリ名＞

Answer 3

config/database.ymlのuserをrootにしてみるとどうでしょうか？

Comments

[sawady0920]

$ cat config/database.yml
# PostgreSQL. Versions 9.1 and up are supported.
#
# Install the pg driver:
# gem install pg
# On OS X with Homebrew:
# gem install pg -- --with-pg-config=/usr/local/bin/pg_config
# On OS X with MacPorts:
# gem install pg -- --with-pg-config=/opt/local/lib/postgresql84/bin/pg_config
# On Windows:
# gem install pg
# Choose the win32 build.
# Install PostgreSQL and put its /bin directory on your path.
#
# Configure Using Gemfile
# gem 'pg'
#
default: &default
adapter: postgresql
encoding: unicode
database: myapp_development
# For details on connection pooling, see Rails configuration guide
# http://guides.rubyonrails.org/configuring.html#database-pooling
host: db
username: root
password:
pool: 5

development:
<<: *default
database: myapp_development

# The specified database role being used to connect to postgres.
# To create additional roles in postgres see `$ createuser --help`.
# When left blank, postgres will use the default role. This is
# the same name as the operating system user that initialized the database.
#username: myapp

# The password associated with the postgres role (username).
#password:

# Connect on a TCP socket. Omitted by default since the client uses a
# domain socket that doesn't need configuration. Windows does not have
# domain sockets, so uncomment these lines.
#host: localhost

# The TCP port the server listens on. Defaults to 5432.
# If your server runs on a different port number, change accordingly.
#port: 5432

# Schema search path. The server defaults to $user,public
#schema_search_path: myapp,sharedapp,public

# Minimum log levels, in increasing order:
# debug5, debug4, debug3, debug2, debug1,
# log, notice, warning, error, fatal, and panic
# Defaults to warning.
#min_messages: notice

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
<<: *default
database: myapp_test

# As with config/secrets.yml, you never want to store sensitive information,
# like your database password, in your source code. If your source code is
# ever seen by anyone, they now have access to your database.
#
# Instead, provide the password as a unix environment variable when you boot
# the app. Read http://guides.rubyonrails.org/configuring.html#configuring-a-database
# for a full rundown on how to provide these environment variables in a
# production deployment.
#
# On Heroku and other platform providers, you may have a full connection URL
# available as an environment variable. For example:
#
# DATABASE_URL="postgres://myuser:mypass@localhost/somedatabase"
#
# You can use this database configuration with:
#
# production:
# url: <%= ENV['DATABASE_URL'] %>
#
#production:
# <<: *default
# database: myapp_production
# username: myapp
# password: <%= ENV['MYAPP_DATABASE_PASSWORD'] %>

docker-compose.ymlを以上の内容に変更いたしました。

以下のコマンドを改めて実行したところ、実行結果に変化はないように思われます。
$ docker-compose run web rails db:create
Starting rails-on-docker_db_1 ... done
could not translate host name "db" to address: Name or service not known
Couldn't create 'myapp_development' database. Please check your configuration.
rails aborted!
PG::ConnectionBad: could not translate host name "db" to address: Name or service not known
/usr/local/bundle/gems/pg-1.1.4/lib/pg.rb:56:in `initialize'
/usr/local/bundle/gems/pg-1.1.4/lib/pg.rb:56:in `new'
/usr/local/bundle/gems/pg-1.1.4/lib/pg.rb:56:in `connect'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/postgresql_adapter.rb:692:in `connect'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/postgresql_adapter.rb:223:in `initialize'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/postgresql_adapter.rb:48:in `new'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/postgresql_adapter.rb:48:in `postgresql_connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/connection_pool.rb:811:in `new_connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/connection_pool.rb:855:in `checkout_new_connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/connection_pool.rb:834:in `try_to_checkout_new_connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/connection_pool.rb:795:in `acquire_connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/connection_pool.rb:523:in `checkout'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/connection_pool.rb:382:in `connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/connection_pool.rb:1014:in `retrieve_connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_handling.rb:118:in `retrieve_connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/connection_handling.rb:90:in `connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/tasks/postgresql_database_tasks.rb:12:in `connection'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/tasks/postgresql_database_tasks.rb:21:in `create'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/tasks/database_tasks.rb:119:in `create'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/tasks/database_tasks.rb:139:in `block in create_current'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/tasks/database_tasks.rb:316:in `block in each_current_configuration'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/tasks/database_tasks.rb:313:in `each'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/tasks/database_tasks.rb:313:in `each_current_configuration'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/tasks/database_tasks.rb:138:in `create_current'
/usr/local/bundle/gems/activerecord-5.2.3/lib/active_record/railties/databases.rake:29:in `block (2 levels) in <top (required)>'
/usr/local/bundle/gems/railties-5.2.3/lib/rails/commands/rake/rake_command.rb:23:in `block in perform'
/usr/local/bundle/gems/railties-5.2.3/lib/rails/commands/rake/rake_command.rb:20:in `perform'
/usr/local/bundle/gems/railties-5.2.3/lib/rails/command.rb:48:in `invoke'
/usr/local/bundle/gems/railties-5.2.3/lib/rails/commands.rb:18:in `<top (required)>'
/usr/local/bundle/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require'
/usr/local/bundle/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `block in require_with_bootsnap_lfi'
/usr/local/bundle/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register'
/usr/local/bundle/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:21:in `require_with_bootsnap_lfi'
/usr/local/bundle/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:30:in `require'
/usr/local/bundle/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:291:in `block in require'
/usr/local/bundle/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:257:in `load_dependency'
/usr/local/bundle/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:291:in `require'
/myapp/bin/rails:9:in `<top (required)>'
/usr/local/bundle/gems/spring-2.1.0/lib/spring/client/rails.rb:28:in `load'
/usr/local/bundle/gems/spring-2.1.0/lib/spring/client/rails.rb:28:in `call'
/usr/local/bundle/gems/spring-2.1.0/lib/spring/client/command.rb:7:in `call'
/usr/local/bundle/gems/spring-2.1.0/lib/spring/client.rb:30:in `run'
/usr/local/bundle/gems/spring-2.1.0/bin/spring:49:in `<top (required)>'
/usr/local/bundle/gems/spring-2.1.0/lib/spring/binstub.rb:11:in `load'
/usr/local/bundle/gems/spring-2.1.0/lib/spring/binstub.rb:11:in `<top (required)>'
/myapp/bin/spring:15:in `<top (required)>'
bin/rails:3:in `load'
bin/rails:3:in `<main>'
Tasks: TOP => db:create
(See full trace by running task with --trace)