Mysql max connections and event scheduler
the running events are not part of the connections limit. Then, what is the limit? Is there one?


Connection limit means outer connections, event scheduler is not counted. But there is a lot of another limited resources - limited by some settings or by some physical conditions. And it is too problematic to find what resource limits the server.


  there is no direct limitation of the number of currently running events? 


Yes, such limitation not exists. MySQL treates an event as a trigger which fires on a timer event - and there is no limitation on the number of triggers in the system. 

In general the event procedure must check does its previous instance have already finished its work... by using some flag field/value in a service table, for example, or by some another mark.