Long-Running Asynchronous Operations, Displaying Their Events and Progress on Clients

With today's modern applications, we end up with lots of asynchronous operations happening and we somehow have to let the user know what is happening. This, of course, depends on the requirements and business needs.

Let's look at the Amazon case. When you buy something on Amazon, Amazon tells you that your order has been taken. However, it doesn't really mean that you have actually purchased it as the process of taking the payment has not been kicked off yet. The payment process probably goes...