We have multi DC Cassandra ring with 2 DCs setup.   We use LOCAL_QUORUM for writes and reads.  The network we have seen between the DC is sometimes flaky lasting few minutes to few 10 of minutes.

I wanted to know what is the best way to measure/monitor either the lag or replication latency between the data centers.  Are there any metrics I can monitor to find the backlog of data that needs to be transferred?

Thanks in advance.