[amluto]

There’s always FIX. </snark>

FIX is, at its core, a message queue, and it’s a free financial industry standard. And, for any serious use in which the message queueing ability is important, FIX is wildly unfit for purpose.

Seriously, a deliver-once [0] message queue between two parties is very simple, and it’s truly remarkable how severely it can be screwed up. I’ve never used IBM’s solution, but I assume it actually works.

[0] Yes, deliver-once is impossible. But arranging for a failure to result in all messages up to a point being delivered, subsequent messages not being delivered, and the fact that a failure occurred being obvious to both parties is straightforward.