Question about concurrency behaviour when consuming raw bytes using the Advanced API about easynetq

[dili91]

I was able to spend more time on this along with other engineers, and we think we finally found an explanation for the above differences:

When using the AdvancedBusExtensions overload that uses the delegate, a Task is declared as return type but there’s nothing really forcing the implementation to be async. You can have a delegate that does no async, and still not have compilation errors (just a self explanatory warning as in the screenshot):

So, in order for the task to be actually returned, all the (blocking) code which is included in your consumer has to execute.
If what you’re doing there is time-consuming, then you’ll face significant issues, due to single messages “blocking” the ones already prefecthed.

The other - very similar - overloaded method that I’ve used in one of my test in the Gist has an Action<ReadOnlyMemory<byte>, MessageProperties, MessageReceivedInfo> parameter that describes the handler, and that gets internally wrapped into a task! This is the reason why, even if the consumer does purely blocking stuff, that is still offloaded to a worker thread and we see concurrent consuming.

Having this behavior clear in mind, I'm happy closing the issue. ✅

With that said, I personally think it would be worth capturing this subtle difference somehow on the extension class, using slightly different signature names and/or improving the documentation.