Docker導入後のMysql2::Error::ConnectionError: Unknown MySQL server host 'db' (2)

前提・実現したいこと

Ruby on Railsで作成中のアプリの開発環境をDockerに移行したところ、CapistranoでのEC2へのデプロイの際、エラーが発生しました。

Docker導入前まではデプロイできていました。また、Dockerコンテナ上の開発環境では正常に起動しています。

手が出ない状況です。

恐れ入りますが、開発環境をDockerに移行したあとの、CapistranoでのEC2へのデプロイ方法についてご教示いただけませんでしょうか。

発生している問題・エラーメッセージ

bundle exec cap production deployを実行したところ、deploy:migratingのところでMysql2::Error::ConnectionError: Unknown MySQL server host 'db' (2)というエラーが発生しています。

↓発生したエラーメッセージ

deploy:migrating
      01 $HOME/.rbenv/bin/rbenv exec bundle exec rake db:migrate
      01 rake aborted!
      01 Mysql2::Error::ConnectionError: Unknown MySQL server host 'db' (2)
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/mysql2-0.5.3/lib/mysql2/client.rb:90:in `connect'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/mysql2-0.5.3/lib/mysql2/client.rb:90:in `initialize'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/activerecord-6.0.3.4/lib/active_record/connection_adapters/mysql2_adapter.rb:24:in `new'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/activerecord-6.0.3.4/lib/active_record/connection_adapters/mysql2_adapter.rb:24:in `mysql2_connection'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/activerecord-6.0.3.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:887:in `new_connection'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/activerecord-6.0.3.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:931:in `checkout_new_connection'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/activerecord-6.0.3.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:910:in `try_to_checkout_new_connection'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/activerecord-6.0.3.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:871:in `acquire_connection'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/activerecord-6.0.3.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:593:in `checkout'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/activerecord-6.0.3.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:437:in `connection'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/activerecord-6.0.3.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:1119:in `retrieve_connection'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/activerecord-6.0.3.4/lib/active_record/connection_handling.rb:221:in `retrieve_connection'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/activerecord-6.0.3.4/lib/active_record/connection_handling.rb:189:in `connection'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/activerecord-6.0.3.4/lib/active_record/tasks/database_tasks.rb:238:in `migrate'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/activerecord-6.0.3.4/lib/active_record/railties/databases.rake:86:in `block (3 levels) in <main>'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/activerecord-6.0.3.4/lib/active_record/railties/databases.rake:84:in `each'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/activerecord-6.0.3.4/lib/active_record/railties/databases.rake:84:in `block (2 levels) in <main>'
      01 /var/www/petput/shared/bundle/ruby/2.6.0/gems/rake-13.0.1/exe/rake:27:in `<top (required)>'
      01 /home/ec2-user/.rbenv/versions/2.6.5/bin/bundle:23:in `load'
      01 /home/ec2-user/.rbenv/versions/2.6.5/bin/bundle:23:in `<main>'
      01 Tasks: TOP => db:migrate
      01 (See full trace by running task with --trace)
#<Thread:0x00007f926e224090@/Users/kawashimamitsuhiro/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/sshkit-1.21.2/lib/sshkit/runners/parallel.rb:10 run> terminated with exception (report_on_exception is true):
Traceback (most recent call last):
	13: from /Users/kawashimamitsuhiro/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/sshkit-1.21.2/lib/sshkit/runners/parallel.rb:12:in `block (2 levels) in execute'
	12: from /Users/kawashimamitsuhiro/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/sshkit-1.21.2/lib/sshkit/backends/abstract.rb:31:in `run'
	11: from /Users/kawashimamitsuhiro/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/sshkit-1.21.2/lib/sshkit/backends/abstract.rb:31:in `instance_exec'
	10: from /Users/kawashimamitsuhiro/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/capistrano-rails-1.6.1/lib/capistrano/tasks/migrations.rake:23:in `block (3 levels) in <top (required)>'
	 9: from /Users/kawashimamitsuhiro/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/sshkit-1.21.2/lib/sshkit/backends/abstract.rb:92:in `within'
	 8: from /Users/kawashimamitsuhiro/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/capistrano-rails-1.6.1/lib/capistrano/tasks/migrations.rake:24:in `block (4 levels) in <top (required)>'
	 7: from /Users/kawashimamitsuhiro/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/sshkit-1.21.2/lib/sshkit/backends/abstract.rb:100:in `with'
	 6: from /Users/kawashimamitsuhiro/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/capistrano-rails-1.6.1/lib/capistrano/tasks/migrations.rake:25:in `block (5 levels) in <top (required)>'
	 5: from /Users/kawashimamitsuhiro/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/sshkit-1.21.2/lib/sshkit/backends/abstract.rb:80:in `execute'
	 4: from /Users/kawashimamitsuhiro/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/sshkit-1.21.2/lib/sshkit/backends/abstract.rb:148:in `create_command_and_execute'
	 3: from /Users/kawashimamitsuhiro/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/sshkit-1.21.2/lib/sshkit/backends/abstract.rb:148:in `tap'
	 2: from /Users/kawashimamitsuhiro/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/sshkit-1.21.2/lib/sshkit/backends/abstract.rb:148:in `block in create_command_and_execute'
	 1: from /Users/kawashimamitsuhiro/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/sshkit-1.21.2/lib/sshkit/backends/netssh.rb:170:in `execute_command'
/Users/kawashimamitsuhiro/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/sshkit-1.21.2/lib/sshkit/command.rb:97:in `exit_status=': rake exit status: 1 (SSHKit::Command::Failed)
rake stdout: Nothing written
rake stderr: rake aborted!
Mysql2::Error::ConnectionError: Unknown MySQL server host 'db' (2)

# 同様のエラーコードが繰り返される

該当のソースコード

Unknown MySQL server host 'db' (2)とあることから、docker-compose.ymlやdatabase.ymlのhostの指定部分が原因だと推定しています。

dockercompose
1version: "3"
2
3services:
4  db:
5    image: mysql:5.6.47
6    environment:
7      MYSQL_USER: root
8      MYSQL_ROOT_PASSWORD: password
9    ports:
10      - "4306:3306"
11    volumes:
12      - ./db/mysql/volumes:/var/lib/mysql
13
14  web:
15    build: .
16    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
17    volumes:
18      - .:/petput
19      - gem_data:/usr/local/bundle
20    ports:
21      - 3000:3000
22    depends_on:
23      - db
24    tty: true
25    stdin_open: true
26
27volumes:
28  gem_data:

database
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: utf8
15  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
16  username: root
17  password: password
18  socket: /tmp/mysql.sock
19  host: db
20
21development:
22  <<: *default
23  database: petput2_development
24
25# Warning: The database defined as "test" will be erased and
26# re-generated from your development database when you run "rake".
27# Do not set this db to the same as development or production.
28test:
29  <<: *default
30  database: petput2_test
31
32# As with config/credentials.yml, you never want to store sensitive information,
33# like your database password, in your source code. If your source code is
34# ever seen by anyone, they now have access to your database.
35#
36# Instead, provide the password as a unix environment variable when you boot
37# the app. Read https://guides.rubyonrails.org/configuring.html#configuring-a-database
38# for a full rundown on how to provide these environment variables in a
39# production deployment.
40#
41# On Heroku and other platform providers, you may have a full connection URL
42# available as an environment variable. For example:
43#
44#   DATABASE_URL="mysql2://myuser:mypass@localhost/somedatabase"
45#
46# You can use this database configuration with:
47#
48#   production:
49#     url: <%= ENV['DATABASE_URL'] %>
50#
51production:
52  <<: *default
53  database: petput2_production
54  username: root
55  password: <%= ENV['DATABASE_PASSWORD'] %>
56  socket: /var/lib/mysql/mysql.sock

試したこと

本番環境のMySQL設定を指定しなおしたら解決できるかと考え、以下のようにhost: localhostとしましたが、解決できませんでした。

database
1production:
2  <<: *default
3  database: petput2_production
4  username: root
5  password: <%= ENV['DATABASE_PASSWORD'] %>
6  socket: /var/lib/mysql/mysql.sock
7  host: localhost

↓この記事に従い
https://qiita.com/mitsu1208g/questions/0659fc82b58cf25fab79

database.ymlのdefaultで、以下の2つをコメントアウトしてみましたが、解決できませんでした。

database
1# password: password
2# host: db

↓こちらの記事も見たのですが、複雑で実行できておりません。
https://teratail.com/questions/321052

開発環境

macOS Big Sur バージョン 11.2.3
Ruby 2.6.5
Rails 6.0.3.4
MySQL 5.6.47

行動規範の内容に同意します

回答1件

自己解決

①↓この記事に従い
https://qiita.com/mitsu1208g/questions/0659fc82b58cf25fab79

database.ymlのdefaultで、以下の2つをコメントアウトした後、ローカルからGitHubにpushし、bundle exec cap production deployを実行したらデプロイできました。

# password: password
# host: db

②本番環境のhost設定を指定しなおしたら解決できるかと考え、database.ymlのproductionでhost: localhostとした後、ローカルからGitHubにpushし、bundle exec cap production deployを実行したらデプロイできました。

database
1production:
2  <<: *default
3  database: petput2_production
4  username: root
5  password: <%= ENV['DATABASE_PASSWORD'] %>
6  socket: /var/lib/mysql/mysql.sock
7  host: localhost

①は一時的な解決策なので、②の方でしばらく様子を見ることとします。

投稿2021/04/04 10:52

Mitsu33

総合スコア0