【docker】could not translate host name "db" to address: Name or service not known

$ docker-compose run --rm web rails db:create RAILS_ENV=development
を叩いた時に、以下のようなエラーが発生します。

エラーの内容

Starting hoge-master_db_1 ... done
could not translate host name "db" to address: Name or service not known
Couldn't create 'hoge_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-1.2.2/lib/pg.rb:58:in `initialize'
/usr/local/bundle/gems/pg-1.2.2/lib/pg.rb:58:in `new'
/usr/local/bundle/gems/pg-1.2.2/lib/pg.rb:58:in `connect'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/postgresql_adapter.rb:46:in `postgresql_connection'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:889:in `new_connection'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:933:in `checkout_new_connection'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:912:in `try_to_checkout_new_connection'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:873:in `acquire_connection'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:595:in `checkout'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:439:in `connection'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:1121:in `retrieve_connection'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_handling.rb:238:in `retrieve_connection'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_handling.rb:206:in `connection'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/postgresql_database_tasks.rb:12:in `connection'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/postgresql_database_tasks.rb:21:in `create'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/database_tasks.rb:126:in `create'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/database_tasks.rb:185:in `block in create_current'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/database_tasks.rb:479:in `block (2 levels) in each_current_configuration'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/database_tasks.rb:476:in `each'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/database_tasks.rb:476:in `block in each_current_configuration'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/database_tasks.rb:475:in `each'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/database_tasks.rb:475:in `each_current_configuration'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/database_tasks.rb:184:in `create_current'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/railties/databases.rake:39:in `block (2 levels) in <main>'
/usr/local/bundle/gems/rake-13.0.1/exe/rake:27:in `<top (required)>'
Tasks: TOP => db:create
(See full trace by running task with --trace)

database.yml

default: &default
  adapter: postgresql
  encoding: unicode
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  username: postgres
  password: password
  host: db

development:
  <<: *default
  database: hoge_development

test:
  <<: *default
  database: hoge_test

production:
  <<: *default
  adapter: postgresql
  encoding: unicode
  pool: 5

【補足情報】
docker-compose.yml

version: '3'
services:
  db:
    build:
      context: .
      dockerfile: ./.docker/postgresql/Dockerfile
    volumes:
      - ./.docker/postgresql/volumes:/var/lib/postgresql/data
    environment:
      - DATABASE_USER=postgres
      - DATABASE_PASSWORD=password
  web:
    tty: true
    stdin_open: true
    build:
      context: .
      dockerfile: ./.docker/rails/Dockerfile
    command: bundle exec foreman start -f Procfile.dev
    ports:
      - "3000:3000"
      - "8000:8000"
    volumes:
      - .:/hoge
      - ./.docker/rails/volumes:/usr/local/bundle
    environment:
      - DATABASE_USER=postgres
      - DATABASE_PASSWORD=password
      - BUNDLE_APP_CONFIG="/hoge/.bundle"
    depends_on:
      - db

解決方法をご教授ください。
よろしくお願い致します。

mit0223

2020/05/04 07:24 編集

おそらく、前の質問と同じとは思いますが、念の為、docker-compose.yml を貼ってもらえますでしょうか。

dxo

2020/05/04 07:37

ご返答いただき誠にありがとうございます。 docker-compose.ymlの方、追記させていただきました。ご確認いただけますと幸いです。

行動規範の内容に同意します

回答1件

ベストアンサー

Could not translate host name "db" to address: Name or service not known

docker-compose には、 web と db の2個のコンテナが定義されていますが、 web のコンテナだけを起動しているので、 db のコンテナと通信しようとしても起動しておらず、通信することができません。

最終的には、docker-compose up -d で両方のコンテナを起動できるようにすべきです。そのためには、rails db:create RAILS_ENV=developmentのような初期化コマンドはENTORYPOINT でヘルパースクリプトを作成する必要があるでしょう。

しかし、コマンド単位でデバッグするのであれば、

docker-compose up -d db

で db コンテナを起動しておいて、

docker-compose run --rm web rails db:create RAILS_ENV=development

を実行してみてください。終わった後は、

docker-compose down

でコンテナを落として削除してください。

2020/5/5 コメントを受けて追記
dbコンテナが起動しない問題について

db_1 | Error: Database is uninitialized and superuser password is not specified.

db_1 | You must specify POSTGRES_PASSWORD to a non-empty value for the
db_1 | superuser. For example, "-e POSTGRES_PASSWORD=password" on "docker run".

というエラーが出ています。dockerhub の postgres の READMEにもあるように postgres のコンテナでは POSTGRES_PASSWORD は必須となっています。また、ユーザIDはPOSTGRES_USER という環境変数で指定することになっています。

docker-compose.yml のdbコンテナの環境変数指定部分を修正してください。
修正前：

Dockerfile
1  db:
2    build:
3      context: .
4      dockerfile: ./.docker/postgresql/Dockerfile
5    volumes:
6      - ./.docker/postgresql/volumes:/var/lib/postgresql/data
7    environment:
8      - DATABASE_USER=postgres
9      - DATABASE_PASSWORD=password

修正後：

Dockerfile
1  db:
2    build:
3      context: .
4      dockerfile: ./.docker/postgresql/Dockerfile
5    volumes:
6      - ./.docker/postgresql/volumes:/var/lib/postgresql/data
7    environment:
8      - POSTGRES_USER=postgres
9      - POSTGRES_PASSWORD=password

投稿2020/05/04 08:03

編集2020/05/05 07:43

mit0223

総合スコア3401

dxo

2020/05/05 03:17 編集

ご返答いただきありがとうございます。今回は、コマンド単位で、試し、 docker-compose run --rm web rails db:create RAILS_ENV=development こちらを叩いたあと、エラーが発生しております。お手数おかけして申し訳ございませんが、ご確認のほどよろしくお願い致します。 Starting hoge-master_db_1 ... done could not translate host name "db" to address: Name or service not known Couldn't create hoge_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-1.2.2/lib/pg.rb:58:in `initialize' /usr/local/bundle/gems/pg-1.2.2/lib/pg.rb:58:in `new' /usr/local/bundle/gems/pg-1.2.2/lib/pg.rb:58:in `connect' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/postgresql_adapter.rb:46:in `postgresql_connection' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:889:in `new_connection' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:933:in `checkout_new_connection' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:912:in `try_to_checkout_new_connection' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:873:in `acquire_connection' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:595:in `checkout' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:439:in `connection' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:1121:in `retrieve_connection' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_handling.rb:238:in `retrieve_connection' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_handling.rb:206:in `connection' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/postgresql_database_tasks.rb:12:in `connection' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/postgresql_database_tasks.rb:21:in `create' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/database_tasks.rb:126:in `create' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/database_tasks.rb:185:in `block in create_current' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/database_tasks.rb:479:in `block (2 levels) in each_current_configuration' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/database_tasks.rb:476:in `each' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/database_tasks.rb:476:in `block in each_current_configuration' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/database_tasks.rb:475:in `each' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/database_tasks.rb:475:in `each_current_configuration' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/database_tasks.rb:184:in `create_current' /usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/railties/databases.rake:39:in `block (2 levels) in <main>' /usr/local/bundle/gems/railties-6.0.2.1/lib/rails/commands/rake/rake_command.rb:23:in `block in perform' /usr/local/bundle/gems/railties-6.0.2.1/lib/rails/commands/rake/rake_command.rb:20:in `perform' /usr/local/bundle/gems/railties-6.0.2.1/lib/rails/command.rb:48:in `invoke' /usr/local/bundle/gems/railties-6.0.2.1/lib/rails/commands.rb:18:in `<main>' /usr/local/bundle/gems/bootsnap-1.4.6/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `require' /usr/local/bundle/gems/bootsnap-1.4.6/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `block in require_with_bootsnap_lfi' /usr/local/bundle/gems/bootsnap-1.4.6/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register' /usr/local/bundle/gems/bootsnap-1.4.6/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require_with_bootsnap_lfi' /usr/local/bundle/gems/bootsnap-1.4.6/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:31:in `require' /usr/local/bundle/gems/activesupport-6.0.2.1/lib/active_support/dependencies.rb:325:in `block in require' /usr/local/bundle/gems/activesupport-6.0.2.1/lib/active_support/dependencies.rb:291:in `load_dependency' /usr/local/bundle/gems/activesupport-6.0.2.1/lib/active_support/dependencies.rb:325:in `require' /hoge/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)>' /hoge/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)

mit0223

2020/05/04 11:06

db コンテナは正常に起動していますでしょうか？コマンド実行前の docker-compose ps の結果を貼ってもらえますでしょうか。

dxo

2020/05/04 11:18

ご返答並びにご確認いただき誠にありがとうございます。以下、結果を貼らせていただきます。ご確認のほどよろしくお願い致します。 Name Command State Ports ----------------------------------------------------------------------------------------------------------------- hoge-master_db_1 docker-entrypoint.sh postgres Exit 1 hoge-master_web_1 entrypoint.sh bundle exec ... Up 0.0.0.0:3000->3000/tcp, 0.0.0.0:8000->8000/tcp

mit0223

2020/05/04 22:50 編集

> postgres Exit 1 となっているので、コンテナの起動に失敗しています。 docker-compose logs db の結果を貼ってください。できれば、質問を編集して貼ってください。

dxo

2020/05/05 03:19

ご返答ありがとうございます。承知致しました。こちら、結果を貼らせていただきます。どうぞよろしくお願い致します。 Attaching to hoge-master_db_1 db_1 | Error: Database is uninitialized and superuser password is not specified. db_1 | You must specify POSTGRES_PASSWORD to a non-empty value for the db_1 | superuser. For example, "-e POSTGRES_PASSWORD=password" on "docker run". db_1 | db_1 | You may also use "POSTGRES_HOST_AUTH_METHOD=trust" to allow all db_1 | connections without a password. This is *not* recommended. db_1 | db_1 | See PostgreSQL documentation about "trust": db_1 | https://www.postgresql.org/docs/current/auth-trust.html db_1 | Error: Database is uninitialized and superuser password is not specified. db_1 | You must specify POSTGRES_PASSWORD to a non-empty value for the db_1 | superuser. For example, "-e POSTGRES_PASSWORD=password" on "docker run". db_1 | db_1 | You may also use "POSTGRES_HOST_AUTH_METHOD=trust" to allow all db_1 | connections without a password. This is *not* recommended. db_1 | db_1 | See PostgreSQL documentation about "trust": db_1 | https://www.postgresql.org/docs/current/auth-trust.html db_1 | Error: Database is uninitialized and superuser password is not specified. db_1 | You must specify POSTGRES_PASSWORD to a non-empty value for the db_1 | superuser. For example, "-e POSTGRES_PASSWORD=password" on "docker run". db_1 | db_1 | You may also use "POSTGRES_HOST_AUTH_METHOD=trust" to allow all db_1 | connections without a password. This is *not* recommended. db_1 | db_1 | See PostgreSQL documentation about "trust": db_1 | https://www.postgresql.org/docs/current/auth-trust.html db_1 | Error: Database is uninitialized and superuser password is not specified. db_1 | You must specify POSTGRES_PASSWORD to a non-empty value for the db_1 | superuser. For example, "-e POSTGRES_PASSWORD=password" on "docker run". db_1 | db_1 | You may also use "POSTGRES_HOST_AUTH_METHOD=trust" to allow all db_1 | connections without a password. This is *not* recommended. db_1 | db_1 | See PostgreSQL documentation about "trust": db_1 | https://www.postgresql.org/docs/current/auth-trust.html

dxo

2020/05/05 08:19

２度もご回答いただき誠にありがとうございました。大変お手数おかけしました。今回ご指摘いただきました件、参照リンク等を改めて拝見させていただき、しっかり復習しておこうと思いました。ありがとうございました。

行動規範の内容に同意します