[Maria-discuss] Frequently running Event overlapping itself

I have an issue where a fast triggering event, running every 30 seconds, is occasionally running multiple times without each finishing. This is causing duplicate data as things are marked done one at a time. I am trying to figure a solution such that this event can only run singly, but what is the best way? DISABLE at start and ENABLE at end? Do SESSION variables work between event invocations?