Under replicated keys in cassandra?

Question

Can anyone tell me how to check the under replicated keys in cassandra?

I know how to check the replication factor for the keyspace and "nodetool repair" for repairing but I was unable to find which of my keys are under replicated in my cluster.

Thanks.

Answer 1

Cassandra doesn't provide a way to know which keys may have had writes which didn't quite make it to all of the replicas. Even when repair is run it doesn't really provide to the other replicas which exact keys need to be repaired, but ranges where there are inconsistencies.

If you're wondering when to run repair: run it every week (if you have a default gc_grace of 10 days), or after an event where a node is down for more than an hour (or longer than the hint window).