ECSにログイン後、rails db:createできない　Unknown MySQL server host 'db' (-2)

前提・実現したいこと

こちらの記事を参考にECSにrailsアプリをデプロイをしようとしています。
記事のECSにSSHログインした後、Railsのコンテナに入ってデータベースを作成する際に

rails db:create

を実行したところ以下のエラーが出ました。

発生している問題・エラーメッセージ

Unknown MySQL server host 'db' (-2)
Couldn't create 'app_production' database. Please check your configuration.
rails aborted!
Mysql2::Error::ConnectionError: Unknown MySQL server host 'db' (-2)
/usr/local/bundle/gems/mysql2-0.5.3/lib/mysql2/client.rb:90:in `connect'
/usr/local/bundle/gems/mysql2-0.5.3/lib/mysql2/client.rb:90:in `initialize'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/mysql2_adapter.rb:24:in `new'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/connection_adapters/mysql2_adapter.rb:24:in `mysql2_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/mysql_database_tasks.rb:8:in `connection'
/usr/local/bundle/gems/activerecord-6.0.2.1/lib/active_record/tasks/mysql_database_tasks.rb:16: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-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require'
/usr/local/bundle/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `block in require_with_bootsnap_lfi'
/usr/local/bundle/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register'
/usr/local/bundle/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:21:in `require_with_bootsnap_lfi'
/usr/local/bundle/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:30: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'
/app/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)>'
/app/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)

該当のソースコード

docker
1version: "2"
2services:
3  app:
4    build:
5      context: .
6      dockerfile: ./docker/rails/Dockerfile
7    command: bundle exec puma -C config/puma.rb
8    ports:
9      - "3000:3000"
10    volumes:
11      - .:/app
12      - /var/tmp
13      - sockets:/app/tmp/sockets
14    tty: true
15    depends_on:
16      - db
17    extends:
18      file: ./docker/mysql/password.yml
19      service: password
20  db:
21    build:
22      context: .
23      dockerfile: ./docker/mysql/Dockerfile
24    ports:
25      - "3306:3306"
26    volumes:
27      - db_data:/var/lib/mysql
28    extends:
29      file: ./docker/mysql/password.yml
30      service: password
31  nginx:
32    build:
33      context: .
34      dockerfile: ./docker/nginx/Dockerfile
35    ports:
36      - "80:80"
37    volumes:
38      - sockets:/app/tmp/sockets
39    depends_on:
40      - app
41
42volumes:
43  db_data:
44  sockets:
45

database.yml
1# MySQL. Versions 5.5.8 and up are supported.
2#
3# Install the MySQL driver
4#   gem install mysql2
5#
6# Ensure the MySQL gem is defined in your Gemfile
7#   gem 'mysql2'
8#
9# And be sure to use new-style password hashing:
10#   https://dev.mysql.com/doc/refman/5.7/en/password-hashing.html
11#
12default: &default
13  adapter: mysql2
14  encoding: utf8mb4
15  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
16  username: root
17  password: password
18  host: db
19
20development:
21  <<: *default
22  database: app_development
23
24# Warning: The database defined as "test" will be erased and
25# re-generated from your development database when you run "rake".
26# Do not set this db to the same as development or production.
27test:
28  <<: *default
29  database: app_test
30
31# As with config/credentials.yml, you never want to store sensitive information,
32# like your database password, in your source code. If your source code is
33# ever seen by anyone, they now have access to your database.
34#
35# Instead, provide the password as a unix environment variable when you boot
36# the app. Read https://guides.rubyonrails.org/configuring.html#configuring-a-database
37# for a full rundown on how to provide these environment variables in a
38# production deployment.
39#
40# On Heroku and other platform providers, you may have a full connection URL
41# available as an environment variable. For example:
42#
43#   DATABASE_URL="mysql2://myuser:mypass@localhost/somedatabase"
44#
45# You can use this database configuration with:
46#
47#   production:
48#     url: <%= ENV['DATABASE_URL'] %>
49#
50production:
51  <<: *default
52  database: app_production
53  username: app
54  password: <%= ENV['APP_DATABASE_PASSWORD'] %>
55

試したこと

Dockerボリュームを一度削除してもう一度行ってみましたが同じエラーになりました。
解決法を教えていただけたら幸いです。よろしくお願いします。

yu_1985

2021/02/06 10:25

参考記事においてdocker-composeは最初ローカルで構成を確認するのにしか使っていないと思うのですが、EC2にSSHログインしてからの操作を具体的に記載してもらってもいいですか？言葉だけではなくちゃんとどこでどのコマンドを打ったか、まであるとわかりやすいです。あと、環境変数を確認するところでちゃんとECSのタスク定義で定義した環境変数が参照できてましたか？

sus

2021/02/07 01:37

EC2インスタンスにSSHログインの項目で$ ssh -i [キーペアのpath] ec2-user@[パブリック IP]を用いてEC2にログインし、$ docker psでコンテナの起動を確認後、$ docker exec -it [RailsコンテナのID] /bin/bashでrailsコンテナに入ってrails db:createを実行したところ上記のエラーになりました環境変数は設定した値がきちんと表示されています

行動規範の内容に同意します

回答1件

ベストアンサー

よく読んだらdatabase.ymlの設定ミスですね。

記載していただいたdatabase.ymlではdafaultのところでしかhostの設定を記載していません。

yaml
1default: &default
2  adapter: mysql2
3  encoding: utf8mb4
4  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
5  username: root
6  password: password
7  host: db

development、test,productionではこのdefaultの設定を引っ張って来て、それにプラスして環境固有の値を設定する、という記載の仕方をしています。
※細かい挙動については要確認ですが、各環境で設定した値はdefaultの値に上書きされるはず

しかしながら、各環境ではhostの設定を記載していないので、どの環境でもhost: dbが適用されます。
つまり環境変数を設定したはいいものの、その環境変数を使っていないということです。
記事ではそうなっていないはずなので、参考にして修正してみてください。
下準備

yaml
1default: &default
2  adapter: mysql2
3  encoding: utf8mb4
4  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
5  username: root
6  password: password #編集
7  host: db #編集
8# ...省略
9production:
10  <<: *default
11  database: <%= ENV['DB_DATABASE'] %>
12  adapter: mysql2
13  encoding: utf8mb4
14  charset: utf8mb4
15  collation: utf8mb4_general_ci
16  host: <%= ENV['DB_HOST'] %>
17  username: <%= ENV['DB_USERNAME'] %>
18  password: <%= ENV['DB_PASSWORD'] %>