Exception at Tried to hard link to file that does not exist

Hi, I'm new to cassandra and told to write a script to backup the cassandra cluster every day, but it throws an exception at one node as below: Exception in thread "main" java.lang.RuntimeException: Tried to hard link to file that does not exist /var/cassandra/data/forseti/activity/forseti-activ

Question: How to monitor the QPS in Cassandra local node or cluster

Hi, everyone, I want to monitor the Cassandra cluster using Zabbix, but I have no idea about hot monitor the QPS on local Cassandra node ? I search the internet but haven't any result about how to get the QPS. anyone had any idea? Thanks!