Finite state machines with Akka

Re:Finite state machines with Akka by je42 on Saturday May 14, 2016 @07:49AM (#11695685)

What about Kafka's at-least-once semantics ? Is that being dealt with ?

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Re:Finite state machines with Akka by felipefzdz on Saturday May 14, 2016 @02:34PM (#11697449)

Disclaimer: I'm the author of the post.

In this particular example, both events (item_reported and item_deleted) end up in destructive actions identified by unique id. That idempotency makes safe working with Kafka's at-least-once semantics. You can see that it's safe to execute several times this line of code:

  val newItemsToBeDeleted = items.filterNot(_ == item)

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Re:Finite state machines with Akka by BrandonBradley on Saturday May 14, 2016 @11:01AM (#11696405)

Your question is hard to understand.

https://kafka.apache.org/08/design.html

"So effectively Kafka guarantees at-least-once delivery by default ...."

Edit: Downvote if you want. I was trying to help you.

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Re:Finite state machines with Akka by biot on Saturday May 14, 2016 @02:07PM (#11697327)

GP asked how this system deals with Kafka's at least once semantics. Pointing out that Kafka has at least once semantics is redundant.

What GP was asking: what happens if Kafka delivers the "item added" event twice, but the "item deleted" event only once? Do you end up with an invalid/unrecoverable state?

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