What does this ERROR message mean?

This error means the cassandra-topology.properties file is not a plain text file. Because of this, the file can't be monitored using the ResourceWatcher object. The ResourceWatcher can only monitor plain text files. This is an informational error only. Cassandra/DSE will continue to run but action should be taken.

Why does this ERROR occur?

This error occurs if the cassandra-topology.properties file is contained in a jar file such as a custom snitch library.

How do you fix this ERROR?

The fix is to modify the default cassandra-topology.properties file for your cluster. If a plain text cassandra-topology.properties file is used, you will never see this error message.