What i don't understand

I'm building a Rails app production environment on EC2.
unicornAt startupMySQLI get a connection error with, but I can't figure out the cause even after reviewing the settings.

Command executed

ec2-user @ ip ~ $bundle exec unicorn_rails -c config/unicorn.rb -E production -D

error

master failed to start, check stderr log for details

Log contents

Contents of /unicorn.stderr.log
I, [2020-09-14T06: 51: 56.022146 # 21711] INFO-: Refreshing Gem list
I, [2020-09-14T06: 51: 58.226567 # 21711] INFO-: listening on addr = 0.0.0.0:3000 fd = 9
E, [2020-09-14T06: 51: 58.336893 # 21711] ERROR-: Access denied for user'Username' @'localhost' (using password: YES) (Mysql2 :: Error :: ConnectionError)
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ps -aef | grep mysql results

ec2-user 6564 6489 0 03:31 pts/1 00:00:00 grep --color = auto mysql
mysql 28647 1 0 September 14? 00:05:16/usr/sbin/mysqld

databese.yml

default:&default
  adapter: sqlite3
  pool:<% = ENV.fetch ("RAILS_MAX_THREADS") {5}%>
  timeout: 5000
development:
  adapter: mysql2
  encording: utf8
  database: app name_development
  pool: 5
  username: username
  password: Password (set locally)
  host: localhost
#Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test: test:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: app name_test
  pool: 5
  username: username
  password: Password (set locally)
  host: localhost
production:
<<: * default
  database:<% = Rails.application.credentials.db [: database]%>
  username:<% = Rails.application.credentials.db [: username]%>
  password:<% = Rails.application.credentials.db [: password]%>
  socket:<% = Rails.application.credentials.db [: socket]%>

credentials.yml

db:
  database: app name
  username: root
  password: Password (set on the instance)
  socket: /var/lib/mysql/mysql.sock

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master.keyI've reset it, but I don't know what other settings to review.

I would appreciate it if you could teach me just the files that should be checked.
Thanks for your cooperation.

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Work environment

• macOS Catalina
• Amazon Linux2
• EC2
• MySQL
• Ruby on Rails6

Postscript

With the suggestions of yu_1985database.ymlWas rewritten.

default:&default
  adapter: mysql2
  pool:<% = ENV.fetch ("RAILS_MAX_THREADS") {5}%>
  timeout: 5000
  encording: utf8
  database: app name
  pool: 5
  username: root
  password: password
  host: localhost

When I tried to start it in this state, I could see such an error in the log.
(master failed to start, check stderr log for detailsThere is no change in the appearance)

I, [2020-09-16T06: 46: 26.296957 # 8946] INFO-: Refreshing Gem list
bundler: failed to load command: unicorn_rails (/home/ec2-user/.rbenv/versions/2.6.6/bin/unicorn_rails)
NoMethodError: Cannot load database configuration:
undefined method `[]'for nil: NilClass
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We are currently investigating this error.

If i know about this error, please teach me.