@Override
    public String toString() {
        return "TaskMetadata{" +
                "taskId=" + taskId +
                ", topicPartitions=" + topicPartitions +
                ", committedOffsets=" + committedOffsets +
                ", endOffsets=" + endOffsets +
                ", timeCurrentIdlingStarted=" + timeCurrentIdlingStarted +
                '}';
    }
This function will return the time task idling started, if the task is not currently idling it will return empty
streams/src/main/java/org/apache/kafka/streams/processor/TaskMetadata.java