Zabbix stopped working after OS upgrade: mysqld.sock issue

[maddy_in65]

I have been running Zabbix server on raspbian since long time. It was updated today to "Buster" but it broken Zabbix mysql connection. The mysqld.sock shows bytes and seems it got brkoen during OS upgrade.

sudo systemctl status zabbix-server
[sudo] password for :
● zabbix-server.service - LSB: Start zabbix-server daemon
Loaded: loaded (/etc/init.d/zabbix-server; generated)
Active: active (exited) since Fri 2021-06-18 12:52:21 IST; 6h ago
Docs: man:systemd-sysv-generator(8)
Process: 622 ExecStart=/etc/init.d/zabbix-server start (code=exited, status=0/SUCCESS)

sudo tail /var/log/zabbix/zabbix_server.log
11267:20210618:121416.405 database is down: reconnecting in 10 seconds
11269:20210618:121416.405 [Z3001] connection to database 'zabbix' failed: [2002] Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2 "No such file or directory")


/var/run/mysqld$ ls -lah
total 4.0K
drwxr-xr-x 2 mysql root 80 Jun 18 12:52 .
drwxr-xr-x 24 root root 680 Jun 18 19:13 ..
-rw-rw---- 1 mysql mysql 4 Jun 18 12:52 mysqld.pid
srwxrwxrwx 1 mysql mysql 0 Jun 18 12:52 mysqld.sock

I have checked mysql service and it is working fine but not sure what is causing zabbix server to connect with DB. Please can someone help.

sudo systemctl status mysql
● mariadb.service - MariaDB 10.3.27 database server
Loaded: loaded (/lib/systemd/system/mariadb.service; enabled; vendor preset: enabled)
Active: active (running) since Fri 2021-06-18 12:52:21 IST; 6h ago

MariaDB [(none)]> SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| zabbix |
+--------------------+
4 rows in set (0.002 sec)