By default the processor receives items from all inbound edges as they arrive. However, there are important cases where the reception of one edge must be delayed until all other edges are consumed in full. A major example is a join operation. Collating items from several edges by a common key implies buffering the data from all edges except one before emitting any results. Often there is one edge with much more data than the others and this one does not need to be buffered if all the other data is ready.
Edge consumption order is controlled by the priority property. Edges are sorted by their priority number (ascending) and consumed in that order. Edges with the same priority are consumed without particular ordering (as the data arrives).