【Rails】circleCIの自動テスト時に発生する「Unknown MySQL server host 'db'」を解消したい

circleCIのjob（bundle exec rake db:create）で発生しているエラーを解消したいのですが、色々とやってみたものの、解決できませんでしたのでどなたかアドバイスをいただきたいです。

＜参考にした記事＞
・https://teratail.com/questions/227081
・https://qiita.com/t-izaki/items/c6ef3239176f9c6697f2 など

解決したい内容

circle CIのbundle exec rake db:createのjobで発生する以下のエラーを解消したい

Unknown MySQL server host 'db' (-2)
Couldn't create 'app_name_development' database. Please check your configuration.

環境

mac os
rails 2.5.3
docker
mysql:5.7

エラー詳細

circle CIのjob
①bundle exec rake db:create

#!/bin/bash -eo pipefail
bundle exec rake db:create
Unknown MySQL server host 'db' (-2)
Couldn't create 'app_name_development' database. Please check your configuration.
rake aborted!
Mysql2::Error::ConnectionError: Unknown MySQL server host 'db' (-2)
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/mysql2-0.5.3/lib/mysql2/client.rb:90:in `connect'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/mysql2-0.5.3/lib/mysql2/client.rb:90:in `initialize'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/mysql2_adapter.rb:22:in `new'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/mysql2_adapter.rb:22:in `mysql2_connection'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:830:in `new_connection'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:874:in `checkout_new_connection'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:853:in `try_to_checkout_new_connection'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:814:in `acquire_connection'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:538:in `checkout'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:382:in `connection'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:1033:in `retrieve_connection'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/connection_handling.rb:118:in `retrieve_connection'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/connection_handling.rb:90:in `connection'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/tasks/mysql_database_tasks.rb:6:in `connection'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/tasks/mysql_database_tasks.rb:14:in `create'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/tasks/database_tasks.rb:119:in `create'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/tasks/database_tasks.rb:139:in `block in create_current'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/tasks/database_tasks.rb:316:in `block in each_current_configuration'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/tasks/database_tasks.rb:313:in `each'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/tasks/database_tasks.rb:313:in `each_current_configuration'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/tasks/database_tasks.rb:138:in `create_current'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.1/lib/active_record/railties/databases.rake:29:in `block (2 levels) in <top (required)>'
/home/circleci/repo/vendor/bundle/ruby/2.5.0/gems/rake-13.0.1/exe/rake:27:in `<top (required)>'
/usr/local/bin/bundle:23:in `load'
/usr/local/bin/bundle:23:in `<main>'
Tasks: TOP => db:create
(See full trace by running task with --trace)

Exited with code exit status 1

※エラーにはなっていないがcircle CI上の以下のjobでcancelが出ている
②Container circleci/mysql:5.7

2020-01-12 12:18:58+00:00 [Note] [Entrypoint]: Database files initialized
2020-01-12 12:18:58+00:00 [Note] [Entrypoint]: Starting temporary server
2020-01-12 12:18:58+00:00 [Note] [Entrypoint]: Waiting for server startup
2020-01-12T12:18:58.310267Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2020-01-12T12:18:58.312135Z 0 [Note] mysqld (mysqld 5.7.28) starting as process 164 ...
2020-01-12T12:18:58.314826Z 0 [Note] InnoDB: PUNCH HOLE support available
2020-01-12T12:18:58.314846Z 0 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2020-01-12T12:18:58.314849Z 0 [Note] InnoDB: Uses event mutexes
2020-01-12T12:18:58.314852Z 0 [Note] InnoDB: GCC builtin __atomic_thread_fence() is used for memory barrier

〜省略〜

2020-01-12T12:19:01.303652Z 0 [Note] InnoDB: Setting file './ibtmp1' size to 12 MB. Physically writing the file full; Please wait ...
2020-01-12T12:19:01.318138Z 0 [Note] InnoDB: File './ibtmp1' size is now 12 MB.
2020-01-12T12:19:01.318732Z 0 [Note] InnoDB: 96 redo rollback segment(s) found. 96 redo rollback segment(s) are active.
2020-01-12T12:19:01.318741Z 0 [Note] InnoDB: 32 non-redo rollback segment(s) are active.
2020-01-12T12:19:01.318999Z 0 [Note] InnoDB: Waiting for purge to start
2020-01-12T12:19:01.369136Z 0 [Note] InnoDB: 5.7.28 started; log sequence number 12440100
2020-01-12T12:19:01.369387Z 0 [Note] InnoDB: Loading buffer pool(s) from /var/lib/mysql/ib_buffer_pool
2020-01-12T12:19:01.369455Z 0 [Note] Plugin 'FEDERATED' is disabled.
2020-01-12T12:19:01.372573Z 0 [Note] InnoDB: Buffer pool(s) load completed at 200112 12:19:01
2020-01-12T12:19:01.375488Z 0 [Note] Found ca.pem, server-cert.pem and server-key.pem in data directory. Trying to enable SSL support using them.
2020-01-12T12:19:01.375504Z 0 [Note] Skipping generation of SSL certificates as certificate files are present in data directory.
2020-01-12T12:19:01.376000Z 0 [Warning] CA certificate ca.pem is self signed.
2020-01-12T12:19:01.376022Z 0 [Note] Skipping generation of RSA key pair as key files are present in data directory.
2020-01-12T12:19:01.376383Z 0 [Note] Server hostname (bind-address): '*'; port: 3306
2020-01-12T12:19:01.376410Z 0 [Note] IPv6 is available.
2020-01-12T12:19:01.376421Z 0 [Note]   - '::' resolves to '::';
2020-01-12T12:19:01.376441Z 0 [Note] Server socket created on IP: '::'.
2020-01-12T12:19:01.376716Z 0 [Warning] Insecure configuration for --pid-file: Location '/var/run/mysqld' in the path is accessible to all OS users. Consider choosing a different directory.
2020-01-12T12:19:01.383112Z 0 [Note] Event Scheduler: Loaded 0 events
2020-01-12T12:19:01.383298Z 0 [Note] mysqld: ready for connections.
Version: '5.7.28'  socket: '/var/run/mysqld/mysqld.sock'  port: 3306  MySQL Community Server (GPL)
2020-01-12T12:19:03.790146Z 2 [Note] Got an error reading communication packets

Job was canceled

関連ファイルの内容

.circleci/config.yml

version: 2
jobs:
  build:
    docker:
      - image: circleci/ruby:2.5.3-node-browsers
        environment:
          BUNDLE_PATH: vendor/bundle
          BUNDLER_VERSION: 2.0.2
          BUNDLE_JOBS: 4
          BUNDLE_RETRY: 3
          
      - image: circleci/mysql:5.7
        environment:
          RAILS_ENV: test
          DB_HOST: 127.0.0.1
          DB_USERNAME: 'root'
          DB_PASSWORD: 'root'
    working_directory: ~/repo
    steps:
      - checkout
      - restore_cache:
          keys:
            - v1-dependencies-{{ checksum "Gemfile.lock" }}
            - v1-dependencies-
      - run:
          name: setup bundler
          command: |
            sudo gem update --system
            sudo gem uninstall bundler
            sudo rm -rf /usr/local/bin/bundle
            sudo rm -rf /usr/local/bin/bundler
            sudo gem install bundler
      - run:
          name: install dependencies
          command: |
            bundle install --jobs=4 --retry=3 --path vendor/bundle
      - run:
          name: install dependencies
          command: yarn
      - save_cache:
          paths:
            - ./vendor/bundle
          key: v1-dependencies-{{ checksum "Gemfile.lock" }}
      - run:
          name: Wait for DB
          command: dockerize -wait tcp://127.0.0.1:3306 -timeout 120s
      - run: bundle exec rake db:create
      - run: bundle exec rake db:schema:load
      - run:
          name: run tests
          command: |
            DISABLE_SPRING=true bundle exec rails test

database.yml

default: &default
  adapter: mysql2
  encoding: utf8
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  username: root
  password: root
  host: db

development:
  <<: *default
  database: app_name_development

test:
  <<: *default
  database: app_name_test