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0 pointstaeric9y ago0 comments

I question any amount of guarantees around "one message" anything. There might be this guarantee per actor, but you have no such guarantee per system. And, assuming a real system, this will be a problem.

So, you get to pick, "at most once" or "at least once." And then you need to build your system to act accordingly.

0 comments

hew9y ago

Slightly shooting from the hip here (as I'm still learning).

Low-ish volume- design your system such that data flows [at the relevant crucial points] through a single actor to ensure proper concurrency.

High volume- trickier but I think same idea in principle. First thought that comes to mind here is the new GenStage stuff in Elixir.

taericOP9y ago

I'm not sure what you are suggesting. There is no getting around "at most/at least once." You can shift the posts, some, but at some point that is your choice. This is a good read on the problem: http://bravenewgeek.com/you-cannot-have-exactly-once-deliver...

eweise9y ago

"Exactly once delivery" is not the same as "One message at a time". Akka Actors process one message at a time. Akka does no provide exactly once delivery. It default defaults to "at most once".

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biot9y ago

Correct. Message delivery strategy is separate from message processing once delivered. If you choose at-least-once delivery, you'll need to handle possible duplicates regardless of whether or not you can process a duplicate message in a lock-free manner.

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