Availability of Cassandra

Question

I am running into an issue "me.prettyprint.hector.api.exceptions.HUnavailableException: : May not be enough replicas present to handle consistency level." when I have RF=1, Read Consistency Level = 1 and one of the nodes in 6 node ring/ cluster is down. All of my reads are failing with this exception. Any idea? Ideally only reads that are looking for data in the node which is down should fail and all other reads should be successful?

Answer 1

There could be a few possibilities:

• You're running a multi-row query (get_range, get_indexed_slices, multiget, or the cql equivalents) that requires multiple nodes to be up
• Your cluster is unbalanced, with the down node owning most of the ring; a bad multi-dc configuration could also produce something similar
• Your cluster wasn't in a good state to begin with, where some nodes don't see others. Make sure nodetool ring shows the same output when run against each node in the cluster

If none of those are the cause, double check that you're specifying the consistency level correctly with Hector and cqlsh.