private static OptionalInt defaultRackAwareNonOverlapCost(final OptionalInt rackAwareNonOverlapCost) {
        if (rackAwareNonOverlapCost == null) {
            return OptionalInt.empty();
        }
        return rackAwareNonOverlapCost;
    }
The rack-aware assignment strategy as configured via
{@link StreamsConfig#RACK_AWARE_ASSIGNMENT_STRATEGY_CONFIG}
streams/src/main/java/org/apache/kafka/streams/processor/assignment/AssignmentConfigs.java