What does this error mean?

This error means a process that is running in an infinite loop thread encountered an exception but is still running.

Why does this error occur?

Cassandra uses an InfiniteLoopExecutor to run specific tasks in a continuous loop. If the loop encounters an Interrupted Exception (e.g. Thread.sleep) while the loop is not shutdown, the message is logged.

How do you fix this error?

Since the thread is only interrupted, and not shut down, there is really no need to fix anything. The loop is still continuing to execute.