SQLSTATE [HY000] [2002] Can not connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (111 "Connection refused")

A few hours ago mysql started to fall on my server. Restarted and hung up after a while. Now I can not even lift it, I get the error:

  

SQLSTATE [HY000] [2002] Can not connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (111 "Connection refused")

Help please !!!

Using CentOS7, it's the first time this happens to me. The server has been online for more than a year. I have about 5 or 6 web portals dropped. Please help :(

I have enough space on the hard drive, more than 20GB available in the OS partition and more than 1TB in the data partition

    ● mariadb.service - MariaDB database server
   Loaded: loaded (/usr/lib/systemd/system/mariadb.service; enabled; vendor preset: disabled)
  Drop-In: /etc/systemd/system/mariadb.service.d
       └─migrated-from-my.cnf-settings.conf
   Active: failed (Result: exit-code) since Wed 2018-07-04 15:10:02 CEST; 36s ago
   Process: 12957 ExecStart=/usr/sbin/mysqld $MYSQLD_OPTS $_WSREP_NEW_CLUSTER $_WSREP_START_POSITION (code=exited, status=1/FAILURE)
   Process: 12945 ExecStartPre=/bin/sh -c [ ! -e /usr/bin/galera_recovery ] && VAR= ||   VAR='/usr/bin/galera_recovery'; [ $? -eq 0 ]   && systemctl set-environment _WSREP_START_POSITION=$VAR || exit 1 (code=exited, status=0/SUCCESS)
   Process: 12943 ExecStartPre=/bin/sh -c systemctl unset-environment _WSREP_START_POSITION (code=exited, status=0/SUCCESS)
   Main PID: 12957 (code=exited, status=1/FAILURE)
   CGroup: /system.slice/mariadb.service

    my_host mysqld[12957]: /usr/sbin/mysqld(+0x414cd6)[0x556d3671ccd6]
    my_host mysqld[12957]: /usr/sbin/mysqld(+0x93a7ce)[0x556d36c427ce]
    my_host mysqld[12957]: /usr/sbin/mysqld(+0x93adf2)[0x556d36c42df2]
    my_host mysqld[12957]: /usr/sbin/mysqld(+0x93e2b8)[0x556d36c462b8]
    my_host mysqld[12957]: /usr/sbin/mysqld(+0x914ce5)[0x556d36c1cce5]
    my_host mysqld[12957]: /lib64/libpthread.so.0(+0x7dc5)[0x7f113e774dc5]
    my_host systemd[1]: mariadb.service: main process exited, code=exited, status=1/FAILURE
    my_host systemd[1]: Failed to start MariaDB database server.
    my_host systemd[1]: Unit mariadb.service entered failed state.
    my_host systemd[1]: mariadb.service failed.