While moving a node (nodetool move <newtoken>) we noticed that lwt started failing for some (~50%) requests. The java-driver (version 2.0.11) returned com.datastax.driver.core.exceptions.WriteTimeoutException: Cassandra timeout during write query at consistency SERIAL (7 replica were required but only 0 acknowledged the write). The cluster was not under heavy load.
I noticed that the failed lwt requests all took just above 1s. That information and the WriteTimeoutException could indicate that this happens:
I can't explain why though. Why would there be more cas contention just because a node is moving?