/tmp/mysql.sockの権限エラー

達成したいこと

railsで作成したアプリをAWSでデプロイする過程でunicornを立ち上げたい。

起きている問題

unicornを立ち上げようとすると

master failed to start, check stderr log for details

というエラーが発生。該当するであろう箇所を見にいくと

[unicorn.log]

E, [2021-04-24T03:16:02.619976 #16070] ERROR -- : Can't connect to local MySQL server through socket '/tmp/mysql.sock' (13) (Mysql2::Error::ConnectionError)

というエラーが出ている

環境

ruby 2.6.2
rails 5.2.5
unicorn 5.8
mysql2 0.5.3

その他の状況

/tmpディレクトリでエラー13のpermission errorが出る意味が理解できない。
一応権限見てみる

$ ls -la /tmp/mysql.sock
lrwxrwxrwx 1 root root 25  4月 19 06:06 /tmp/mysql.sock -> /var/lib/mysql/mysql.sock

そもそもリンクファイルなのでリンク元の /tmp/mysql.sockを見にいってみる

$ ls -l /var/lib/mysql/mysql.sock
srwxrwxrwx 1 mysql mysql 0  4月 24 03:15 /var/lib/mysql/mysql.sock

どちらもchmod 777になっている。

my.cnfを見にいってみる

$ vi /etc/my.cnf

[mysqld]
#
# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
innodb_buffer_pool_size = 256M
#
# Remove the leading "# " to disable binary logging
# Binary logging captures changes between backups and is enabled by
# default. It's default setting is log_bin=binlog
# disable_log_bin
#
# Remove leading # to set options mainly useful for reporting servers.
# The server defaults are faster for transactions and fast SELECTs.
# Adjust sizes as needed, experiment to find the optimal values.
# join_buffer_size = 128M
# sort_buffer_size = 2M
# read_rnd_buffer_size = 2M
#
# Remove leading # to revert to previous value for default_authentication_plugin,
# this will increase compatibility with older clients. For background, see:
# https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html#sysvar_default_authentication_plugin
# default-authentication-plugin=mysql_native_password

datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock

log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid

アプリ/config/database.ymlの中身も見てみる。

development:
  <<: *default
  socket: /tmp/mysql.sock
  database: tempo_development
  password:


# 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:
  <<: *default
  socket: /tmp/mysql.sock
  database: tempo_test
  password:


production:
  <<: *default
  socket: /tmp/mysql.sock
  database: tempo_production
  password: <%= Rails.application.credentials.db[:password] %>