What kind of guarantees does tank make?
Suppose one such application is consuming every new event that's publishing ("tailing the log"). As soon as another application successfully publishes 1 or more new messages, the consumer will get them immediately. If the application that attempted to publish failed to do so, or didn't get an ACK for success, then you are guaranteed that no new message(s) were published(i.e no partial message content).
I am not sure if that answers your question, if not, can you please elaborate?
I'd basically like to be able to map messages from one topic to another with a guarantee that none of those messages will be lost; even when some error occurs (either a programming error, system downtime, or network partitions). I'd prefer the application to stop producing messages than lose any of them.
It sounds like that is possible with Tank so I may end up giving it a try.