I use JMX server to get metrics data for Kafka, but I am confused about some attributes. For example, the object kafka.network:type=RequestMetrics,name=RequestsPerSec,request=FetchFollower
has attributes Count and MeanRate.
The Count attribute seems to be the value of the FetchFollower metric, but I found it ascending, so I guess it is the aggregate value.
What is the MeanRate attribute? Is it the current rate for FetchFollower? And what is the unit here: byte, kbyte, ... ?
As the name RequestsPerSec suggests, the unit measured is the number of requests by FetchFollowers per sec. The MeanRate is the average FetchFollower-requests/sec rate since the broker first went up, so no, it's not current.
You're right about the Count metric--it's the aggregate number of FetchFollower requests, so to get the current rate, you should calculate the Count difference over a window of time.