[Question]: What happens when service discipline returns None? about ciw HOT 1 CLOSED

Good questions! I did not anticipate this the service disciplines being used like this.

Service discipline functions gives the next customer be be served from the queue.

So any customer that arrives when the server is free always gets served. They are never selected from the queue.

In your case, when customers 1, 2 and 4 arrived there was no one in service, and so they all began service straight away. When customer 3 arrived there was someone in service, they joined the queue, but never left because of the service discipline returning None. When customer 4 arrived, customer 3 was waiting, but not in service, and the server was free, to they began service immediately.

Hope that helps.

from ciw.