You are trying to JOIN 2 unbounded streams (mesEventsChannel , inputPetitionChannel ) which is not allowed. You will need to use a WINDOW over the each Stream for a meaningful JOIN
And how can it be done? I mean, is it neccesary to create two views first and then execute the join query over these two views, or you can execute the query directly over both "windowed" input channels and send both event types through each output channel?
How about creating an event-type with exactly 1 double attribute