rails5＋MysqlをDocker-composeにてherokuにデプロイする際のエラー

udemyのこちら
https://www.udemy.com/course/rails-kj/
を学習中

SNS掲示板アプリ
を作らせてもらっている。

Rails 5系
Ruby 2.4.5
mysql2

最後にherokuにデプロイしようとおもって

Rails on DockerをHerokuでDeployするまで
HerokuでMySQLを使おうとして詰まったところ
を参考にして、トライ

流れとしては、
clearDBをアドオンとして追加
configに設定(mysql2に変更)
heroku CLIログイン
heroku containerにログイン
heroku create~~
heroku container:push web
heroku container:release web
heroku run rails db:migrate
heroku open
heroku run rails assets:precompile
heroku config:add RAILS_ENV=production
(アセットパイプライン関連は理解がおいついていない)

しかし、heroku openにてApplication errorとなり、
heroku logs --tailにて

2020-08-31T00:05:17.338031+00:00 app[api]: Deployed web (09d5e5e0baba) by user [e-mail]
2020-08-31T00:05:17.338031+00:00 app[api]: Release v14 created by user [e-mail]
2020-08-31T00:05:17.566831+00:00 heroku[web.1]: State changed from crashed to starting
2020-08-31T00:05:33.102257+00:00 app[api]: Starting process with command `rails db:migrate` by user [e-mail]
2020-08-31T00:05:41.271963+00:00 heroku[web.1]: Starting process with command `irb`
2020-08-31T00:05:44.759411+00:00 app[web.1]: Switch to inspect mode.
2020-08-31T00:05:44.760171+00:00 app[web.1]: 
2020-08-31T00:05:44.815317+00:00 heroku[web.1]: Process exited with status 0
2020-08-31T00:05:44.849695+00:00 heroku[web.1]: State changed from starting to crashed
2020-08-31T00:05:44.852418+00:00 heroku[web.1]: State changed from crashed to starting
2020-08-31T00:05:52.851790+00:00 heroku[run.7980]: State changed from starting to up
2020-08-31T00:05:52.856447+00:00 heroku[run.7980]: Awaiting client
2020-08-31T00:05:52.891424+00:00 heroku[run.7980]: Starting process with command `rails db:migrate`
2020-08-31T00:05:59.894902+00:00 heroku[run.7980]: Process exited with status 0
2020-08-31T00:05:59.927380+00:00 heroku[run.7980]: State changed from up to complete
2020-08-31T00:06:05.419295+00:00 heroku[web.1]: Starting process with command `irb`
2020-08-31T00:06:08.786074+00:00 app[web.1]: Switch to inspect mode.
2020-08-31T00:06:08.786799+00:00 app[web.1]: 
2020-08-31T00:06:08.879555+00:00 heroku[web.1]: Process exited with status 0
2020-08-31T00:06:08.991140+00:00 heroku[web.1]: State changed from starting to crashed
2020-08-31T00:09:58.194158+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=glacial-temple-79557.herokuapp.com request_id=432296e9-7359-4456-bbc2-b885e514a27d fwd="111.97.175.96" dyno= connect= service= status=503 bytes= protocol=https
2020-08-31T00:09:59.223351+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=glacial-temple-79557.herokuapp.com request_id=12c8e692-769d-45a7-9967-ce77256746eb fwd="111.97.175.96" dyno= connect= service= status=503 bytes= protocol=https

と出てしまった。

さらに、
heroku run rails console cすると、

Running via Spring preloader in process 18
WARNING: Spring is running in production. To fix this make sure the spring gem is only present in `development` and `test` groups in your Gemfile and make sure you always use `bundle install --without development test` in production
Loading production environment (Rails 5.0.7.2)

そのため、
Dockerfileでbundle　installを変えて

FROM ruby:2.4.5
RUN apt-get update -qq && apt-get install -y build-essential nodejs
RUN mkdir /app
WORKDIR /app
COPY Gemfile /app/Gemfile
COPY Gemfile.lock /app/Gemfile.lock
RUN bundle install --without development test
COPY . /app

と書き換えたが、治らず。

うーん弱った、、、

以下Docker-compose.yml

Docker-compose.yml

version: '3'
services:
  web:
    build: .
    command: bundle exec rails s -p 3000 -b '0.0.0.0'
    volumes:
      - .:/app
    ports:
      - 3000:3000
    depends_on:
      - db
    tty: true
    stdin_open: true
  db:
    image: mysql:5.7
    volumes:
      - db-volume:/var/lib/mysql
    environment:
      MYSQL_ROOT_PASSWORD: password
volumes:
  db-volume: