Oracle Integration Cloud: Building Integrations That Survive Production · Module 10 · Business events and publish/subscribe
Ordering, and why you cannot rely on it
Lesson 105 of 175 · 2 min
EVENTS ARRIVE OUT OF ORDER. Not occasionally — as a property of how they are delivered, and a design that assumes sequence will corrupt data. The damaging case is concrete: two events about the same record, an update and then a correction, delivered in the wrong order. Your flow applies the correction, then applies the earlier update on top of it, and the record ends up in the older state. Nothing failed. The target is simply wrong, and it will stay wrong until somebody notices. THE DEFENCE IS TO MAKE A LATER UPDATE APPLIED BEFORE AN EARLIER ONE HARMLESS, and there are three ways. ONE: CARRY A VERSION OR TIMESTAMP AND REFUSE TO GO BACKWARDS. Compare what you are about to write against what is there, and ignore anything older. This is the strongest and it needs the target to hold the value — a field, a version number, a…
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