Hello I have 2 Cacti Server with master and slave setup. I am getting error in replication status of mariadb.

Last_SQL_Error: Could not execute Update_rows_v1 event on table microcacti.poller_item; Can't find record in 'poller_item', Error_code: 1032; handler error HA_ERR_KEY_NOT_FOUND; the event's master log master-bin.000015, end_log_pos 520565013

Please help.

I have never setup the replication between two databases in MariaDB/MySQL but looking at the error, this would suggest that your basic table structures are not in sync. When I have done mirroring before with MSSQL that required a backup/restore to ensure the same database was being used for mirroring.

Have you made sure that both sets of tables are in sync? And that the user being used to perform the sync has access to both?

I would suggest galera on a 10.2 or 10.3 instance of MariaDB.