title: Measure the amount of time a celery message is on the queue
body: <p>Is there a good way to measure the amount of time a celery message spends on the queue? I know I could send a timestamp to the celery task and measure the difference between the beginning of the task and the timestamp sent, but I was hoping there might be a more general way to do it so I don't have to add timestamps to every single one of my celery tasks. </p>