Actually let me be clear, what i am saying is if user has a pattern where he is send commands from producer to consumer using a queue , in consumer case states are being dequed and processed , after that in consumer loop only we are enqueing next state.
so basically now in queue 2 entry points are there.
suppose consumer has states A, B, C, D in which A is executing right now at the end of its completion it enques another state B.
But at the same time user has pressed a button on the front panel which wants to execute state C.
at this point somtimes order of execution can be A, B, C or A. C, B.
I have not worked on Actor framework till now , so have a very less idea about it.