DataStax Cassandra cassandra.cluster.NoHostAvailable
Please check if your nodes are really listening by opening up a separate connection from say cqlsh terminal, as you say it is running locally so probably a single node. If that connects, you might want to see how many file handles are open, maybe it is running out of those. We had a similar problem couple of years back, that was attributed to available file handles.
I am consistently getting this error under normal conditions. I am using the Python Cassandra driver (v3.11) to connect locally with RPC enabled. The issue presents itself after a period of time. y assumption was that it was related to max number of connections or queries. Any pointers on where to begin troubleshooting would be greatly appreciated.