Comment by Groxx

>In this post we will show how [exactly once delivery] can be done, plus how simple it is with Atomikos. ...

>The producer should do its processing and send its message as part of a JTA/XA transaction. This ensures a message is sent if and only if the transaction commits. Any failures will result in rollback of the JTA/XA transaction - and no message will be sent. This means that failures can be safely retried until they succeed, without sending the resulting message more than once.

This is at-least-once (retries) with probably-idempotency: a transaction.

As I said: charlatans.

They're selling you "exactly once" in the headline, but clearly state that it is not exactly once in the legalese below. This is less "buyer beware" and more "blatantly false advertising", in exactly the same way as a free energy machine. The abstraction they're offering may indeed be useful, but "exactly once" is literally lying, and I wouldn't trust them to be honest elsewhere eit