[furstenheim]

I liked the article a lot.

I prefer the term retryable to idempotent. If there's a failure in the first call, to be truly idempotent it should fail on the second.

Retryable on the other hand is easier to argue about. Important thing is not the response but the end state of the system.

[lupire]

Idempotent means that repeating the same operation eventually stabilizes, not that Op^2 = Op. It combines retryability of failures with retryability of successes.

Alternatively, idempotency applies to successful operations, orthogonal from error cases.

Retryability doesn't help in the case of the (bad) operation "+1" which is not idempotent.

[wnoise]

Idempotent means exactly Op^2 = Op. If you want a word that means those other things, go find another, this one has long been taken.