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Packet loss on local, but not on GitLab

 
Picture of Aaron Joos Lippeveldts
Packet loss on local, but not on GitLab
by Aaron Joos Lippeveldts - Monday, 26 October 2020, 13:08
 

Hi,

I have a rather weird problem I can't figure out.
On my computer (Linux), sometimes the test TestGossiper_Topo1_2Nodes_AntiEntropy fails because 1 of the status packets gets lost.
I don't think it's a problem with my code because I added some logging to confirm the packets get sent, they just do not arrive.
It happens pretty often on my computer, but has not happened at all yet on GitLab.

It can be triggered with the following command:

go test go.dedis.ch/cs438/hw1/gossip -run \^TestGossiper_Topo1_2Nodes_AntiEnt
ropy\$ -count=1000 -failfast -v

Do you have any suggestions of things I could try to investigate this?

Picture of Pasindu Nivanthaka Tennage
Re: Packet loss on local, but not on GitLab
by Pasindu Nivanthaka Tennage - Tuesday, 27 October 2020, 13:23
 

Hi  Lippeveldts,

If I understood correctly, you do not observe packet losses in your laptop, but in GitLab, am I right?

This is a tricky question, because UDP by itself is unreliable and we can't predict when it works well vs when it drops packets. Even on the same machine (localhost) if the number of messages are high, this can lead to dropped packets.

If you believe that this is a problem with out test implementation, please send more information about your problem, and we will check.


Regards


Picture of Aaron Joos Lippeveldts
Re: Packet loss on local, but not on GitLab
by Aaron Joos Lippeveldts - Tuesday, 27 October 2020, 14:42
 

It is the other way around, it seems to happen only on my laptop.
What is especially weird is that it often happens on the first or second anti-entropy round, so not that many packets could have been sent to cause congestion.

Anyway, I have no clue why it happens.
As it's not a problem on GitLab I'm probably just gonna accept it and move on.