You give general explanations of akka guarantees: least once, at most once and exactly once in chapter 6.5.2. Then you go into examples of the first two, but leave out exactly once. Please show how to implement that. Also you say that unless the business need absolutely requires it, try to use at least once. Please explain why at least once is good enough for most cases and then give examples of real world use cases for each type of guarantee. Like an inventory system where I want to make sure I have enough quantity on hand and not over sell, if at least once is ok, why is it ok and what fail-safes should I use.
In chapter 8.5.6 you start to discuss retry patterns and lightly go over the akka guarantees again. How about just referring to ch 6.5.2 instead here. Maybe you could elaborate a little more on utilizing the durable message systems like kafka and Rabbit MQ. Why would they be a good choice over what akka includes?
|