mysql2::error: can't connect to local mysql server through socket '/var/run/mysqld/mysqld.sock' using centos7 code example

Example 1: can't connect to local mysql server through socket '/var/run/mysqld/mysqld.sock'

# Start your mysql server
/etc/init.d/mysql start

Example 2: can't connect to local mysql server through socket '/var/run/mysqld/mysqld.sock'

# this saved my ass
# first  you must perform a graceful shutdown of the server from the command line rather than powering off the server
shutdown -h now

# an additional method for getting it back up again when you run into this problem is to move mysql.sock

# to centos
mv /var/lib/mysql/mysql.sock /var/lib/mysql/mysql.sock.bak

# to ubuntu
mv /var/run/mysqld/mysqld.sock /var/run/mysqld/mysqld.sock.bak

# restart mysql
service mysqld start