CS-438: Test_HW1_Messaging_Broadcast_No_Ack

// Given the following topology
//   A -> B
//     -> C
// If A sends a rumor to B, and B doesn't send back an ack, then A should send a
// rumor to C after the timeout. Here we use a timeout of 0, so the message
// should only be sent to one of the node.

I'm confused by this description. In task 5 we implement a mechanism that keeps attempting to send the rumor to a random neighbour until we receive and ACK from someone.

This seems to agree with the first sentence of the description. So A will send a rumor to B, receive no ACK, and then send the rumor to C.

I don't understand the second sentence. If the timeout is 0, why should we only send the message to one node? This seems illogical.

If we skip sending to B because the timeout is 0, shouldn't we also skip sending to C?

Re: Test_HW1_Messaging_Broadcast_No_Ack

par Yuchen Qian, dimanche, 24 octobre 2021, 01:02

Ack timeout equals to 0 means the node will wait on the ack forever.

The first sentence essentially describes the case where the ack timeout does
not equal to zero (described in task 5): after the timeout occurs on node A,
it will attempt to send the rumor message to another random neighbour.

The second sentence describes the scenario of the test case: A has a timeout
of value 0 so A never times out. After A sends a rumor message to either B or
C, A waits forever until it receives an ack from either B or C. Since B and C
also do not sending back any messages, only one of the node should receive
the rumor.

Hope this answers your question :)

Re: Test_HW1_Messaging_Broadcast_No_Ack

par Emilien Baptiste Baty, dimanche, 24 octobre 2021, 18:37

But if node A waits forever and node B and C doesn't send any messages, then I don't understand how the test is supposed to pass because it will never end. Even if I know that some students managed to pass this test, I don't understand how is that possible

Re: Test_HW1_Messaging_Broadcast_No_Ack

par Tianxiao Shen, dimanche, 24 octobre 2021, 20:59

I had the same question as you. I think it implies that Broadcast() should return and start another goroutine to wait for ack...