private static ConstrainedPrioritySet standbyTaskPriorityListByLoad(final Map<ProcessId, KafkaStreamsState> clientStates,
                                                                        final Map<ProcessId, KafkaStreamsAssignment> assignments) {
        return new ConstrainedPrioritySet(
            (processId, taskId) -> !assignments.get(processId).tasks().containsKey(taskId),
            processId -> {
                final double capacity = clientStates.get(processId).numProcessingThreads();
                final double numTasks = assignments.get(processId).tasks().size();
                return numTasks / capacity;
            }
        );
    }
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