private static boolean hasValidRackInformation(final ApplicationState applicationState,
                                                   final AssignedTask.Type taskType) {
        for (final KafkaStreamsState state : applicationState.kafkaStreamsStates(false).values()) {
            if (!hasValidRackInformation(state)) {
                return false;
            }
        }

        for (final TaskInfo task : applicationState.allTasks().values()) {
            if (!hasValidRackInformation(task, taskType)) {
                return false;
            }
        }
        return true;
    }
This function returns whether the current application state has the required rack information
to make assignment decisions with.

@param taskType the type of task that we are trying to validate rack information for.

@return whether rack-aware assignment decisions can be made for this application.
streams/src/main/java/org/apache/kafka/streams/processor/assignment/TaskAssignmentUtils.java