Multi server issue : mail server can't access database server , suddenly

here is the log of dovecot ...

mail1 dovecot[15279]: auth-worker(15288): Error: mysql(localhost): Connect failed to database (dbispconfig): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) - waiting for 5 seconds before retry

 

Does your host have that sock file?
Have you tried rebooting, that should solve issues with some process hanging on to lock file or socket.
Are all services running?

Code:

systemctl --state=failed

I learned the above using Internet Search Engines with your error message. Did you try that before posting?

 

mariadb ... error , the question is why suddendly file system become READ-ONLY ????

Sep 21 08:16:42 mail1 systemd[1]: Starting MariaDB 10.3.23 database server...
Sep 21 08:16:42 mail1 sh[445]: mktemp: failed to create file via template ‘/tmp/wsrep_recovery.XXXXXX’: Read-only file system
Sep 21 08:16:42 mail1 sh[445]: WSREP: mktemp failed
Sep 21 08:16:43 mail1 systemd[494]: mariadb.service: Failed to set up mount namespacing: Read-only file system
Sep 21 08:16:43 mail1 systemd[494]: mariadb.service: Failed at step NAMESPACE spawning /usr/sbin/mysqld: Read-only file system
Sep 21 08:16:43 mail1 systemd[1]: mariadb.service: Main process exited, code=exited, status=226/NAMESPACE
Sep 21 08:16:43 mail1 systemd[1]: mariadb.service: Failed with result 'exit-code'.
Sep 21 08:16:43 mail1 systemd[1]: Failed to start MariaDB 10.3.23 database server.

 

Maybe the disk is full?

Code:

df -hT

 

ok , 500GB space left.
perhaps it's during promox snapshot.
i will monitor thi stonight.

thank youTaleman

 

Reboot solve the issue.
i notice that some services where stop (incron, systemd-timesyncd, dovecot ), i reboot web and mail server.