3 ms·

It still annoys me that a company/product that impresses me so much (Confluent/Kafka) has doubled down so hard and so many times on their "Exactly Once" ridicul

It still annoys me that a company/product that impresses me so much (Confluent/Kafka) has doubled down so hard and so many times on their "Exactly Once" ridiculousness. Admit your mistake and clarify you really mean "idempotency" or "effectively once," and only if you say completely within the bounds of Kafka, and move on. It's becoming a bit of a joke having to combat their fairy dust in my profession.

clhodapp 9y ago
"Effectively once" is a great way to describe how it actually works!
nl 9y ago
In the article this claims to debunk, it says: Another objection I’ve heard to this is that it isn’t really “exactly once” but actually “effectively once”. I don’t disagree that that phase is better (though less commonly understood) but I’d point out that we’re still debating the definitions of undefined terms! I have to say I agree with this.
doug1001 9y ago
until this thread, i had not actually heard the term "effectively once"; what's more, i've always believed that "indempotent" means "at most once." how do the two guarantees, "effectively once" and "at most once" differ?
- LgWoodenBadger 9y ago
  "At most once" has the implication of "you may never get it" (if the one and only attempt failed anywhere along the way) "Effectively once" implies "you got the same thing 1000 times but ignored 999 of them because you already got it." With an "exactly once" guarantee, I could send you a stream of integers (1,2,3,4,5) and you could blindly/naively/simplistically add them with no special concern and be confident that your answer of 15 was correct. With "effectively once," you'd have to keep track of what you've seen before so you know not to add 4 an extra 6 times and come up with the wrong sum of 39. With "at most once" you may be sitting around with a sum of 0 and think that's correct.

clhodapp 9y ago

"Effectively once" is a great way to describe how it actually works!

nl 9y ago

In the article this claims to debunk, it says: Another objection I’ve heard to this is that it isn’t really “exactly once” but actually “effectively once”. I don’t disagree that that phase is better (though less commonly understood) but I’d point out that we’re still debating the definitions of undefined terms! I have to say I agree with this.

doug1001 9y ago

until this thread, i had not actually heard the term "effectively once"; what's more, i've always believed that "indempotent" means "at most once." how do the two guarantees, "effectively once" and "at most once" differ?

LgWoodenBadger 9y ago
"At most once" has the implication of "you may never get it" (if the one and only attempt failed anywhere along the way) "Effectively once" implies "you got the same thing 1000 times but ignored 999 of them because you already got it." With an "exactly once" guarantee, I could send you a stream of integers (1,2,3,4,5) and you could blindly/naively/simplistically add them with no special concern and be confident that your answer of 15 was correct. With "effectively once," you'd have to keep track of what you've seen before so you know not to add 4 an extra 6 times and come up with the wrong sum of 39. With "at most once" you may be sitting around with a sum of 0 and think that's correct.