Thanks for the patient review, Arpit Agarwal.
The description for the count metrics and the rate metric is the same e.g. TotalMetadataOperations and MetadataOperationRateNumOps. I am not sure that is correct.
I looked into this, the main difference between MutableCounter and MutableRate is that the value of the former is monotonically increasing and the latter will be reset after some interval time. Others comments have been addressed in the latest patch. New patch attached, please have a review. Thanks.