in flink-connector-cassandra/src/main/java/org/apache/flink/streaming/connectors/cassandra/CassandraSink.java [459:465]
public CassandraSink<IN> build() throws Exception {
sanityCheck();
if (failureHandler == null) {
failureHandler = new NoOpCassandraFailureHandler();
}
return isWriteAheadLogEnabled ? createWriteAheadSink() : createSink();
}