Today i have an error mariadb server when my friend try dumping, the error log is

1. systemctl status mariadb.service
   ● mariadb.service - MariaDB database server
   Loaded: loaded (/lib/systemd/system/mariadb.service; enabled; vendor preset: enabled)
   Drop-In: /etc/systemd/system/mariadb.service.d
   └─migrated-from-my.cnf-settings.conf
   Active: failed (Result: timeout) since Thu 2017-12-21 11:46:03 WIB; 26s ago
   Process: 6069 ExecStartPre=/bin/sh -c [ ! -e /usr/bin/galera_recovery ] && VAR= || VAR=`/usr/bin/galera_recovery`; [ $? -eq 0 ] && systemctl set-environment _WSRE
   Process: 6064 ExecStartPre=/bin/sh -c systemctl unset-environment _WSREP_START_POSITION (code=exited, status=0/SUCCESS)
   Process: 6060 ExecStartPre=/usr/bin/install -m 755 -o mysql -g root -d /var/run/mysqld (code=exited, status=0/SUCCESS)
   Main PID: 6195
   CGroup: /system.slice/mariadb.service
   └─6195 /usr/sbin/mysqld

Dec 21 11:44:56 ubuntu mysqld[6195]: 2017-12-21 11:44:56 139809002477824 [Note] InnoDB: Processed 10934 .ibd/.isl files
Dec 21 11:45:12 ubuntu mysqld[6195]: 2017-12-21 11:45:12 139809002477824 [Note] InnoDB: Processed 12243 .ibd/.isl files
Dec 21 11:45:28 ubuntu mysqld[6195]: 2017-12-21 11:45:28 139809002477824 [Note] InnoDB: Processed 13387 .ibd/.isl files
Dec 21 11:45:44 ubuntu mysqld[6195]: 2017-12-21 11:45:44 139809002477824 [Note] InnoDB: Processed 14872 .ibd/.isl files
Dec 21 11:46:00 ubuntu mysqld[6195]: 2017-12-21 11:46:00 139809002477824 [Note] InnoDB: Processed 16137 .ibd/.isl files
Dec 21 11:46:03 ubuntu systemd[1]: mariadb.service: State 'stop-final-sigterm' timed out. Skipping SIGKILL. Entering failed mode.
Dec 21 11:46:03 ubuntu systemd[1]: Failed to start MariaDB database server.
Dec 21 11:46:03 ubuntu systemd[1]: mariadb.service: Unit entered failed state.
Dec 21 11:46:03 ubuntu systemd[1]: mariadb.service: Failed with result 'timeout'.
Dec 21 11:46:16 ubuntu mysqld[6195]: 2017-12-21 11:46:16 139809002477824 [Note] InnoDB: Processed 17842 .ibd/.isl files

journalctl -xe
Dec 21 11:44:40 ubuntu mysqld[6195]: 2017-12-21 11:44:40 139809002477824 [Note] InnoDB: Processed 9548 .ibd/.isl files
Dec 21 11:44:49 ubuntu sshd[6778]: Connection closed by 192.168.8.2 port 28196 [preauth]
Dec 21 11:44:56 ubuntu mysqld[6195]: 2017-12-21 11:44:56 139809002477824 [Note] InnoDB: Processed 10934 .ibd/.isl files
Dec 21 11:45:12 ubuntu mysqld[6195]: 2017-12-21 11:45:12 139809002477824 [Note] InnoDB: Processed 12243 .ibd/.isl files
Dec 21 11:45:28 ubuntu mysqld[6195]: 2017-12-21 11:45:28 139809002477824 [Note] InnoDB: Processed 13387 .ibd/.isl files
Dec 21 11:45:44 ubuntu mysqld[6195]: 2017-12-21 11:45:44 139809002477824 [Note] InnoDB: Processed 14872 .ibd/.isl files
Dec 21 11:45:50 ubuntu sshd[6780]: Connection closed by 192.168.8.2 port 29348 [preauth]
Dec 21 11:46:00 ubuntu mysqld[6195]: 2017-12-21 11:46:00 139809002477824 [Note] InnoDB: Processed 16137 .ibd/.isl files
Dec 21 11:46:03 ubuntu systemd[1]: mariadb.service: State 'stop-final-sigterm' timed out. Skipping SIGKILL. Entering failed mode.
Dec 21 11:46:03 ubuntu systemd[1]: Failed to start MariaDB database server.
– Subject: Unit mariadb.service has failed
– Defined-By: systemd
– Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
–
– Unit mariadb.service has failed.
–
– The result is failed.
Dec 21 11:46:03 ubuntu systemd[1]: mariadb.service: Unit entered failed state.
Dec 21 11:46:03 ubuntu systemd[1]: mariadb.service: Failed with result 'timeout'.
Dec 21 11:46:16 ubuntu mysqld[6195]: 2017-12-21 11:46:16 139809002477824 [Note] InnoDB: Processed 17842 .ibd/.isl files
Dec 21 11:46:32 ubuntu mysqld[6195]: 2017-12-21 11:46:32 139809002477824 [Note] InnoDB: Processed 19459 .ibd/.isl files