Why do Azure container exposed ports receive connections from the k8s agent pool?

UVProtector 1

Hi, I have a docker image which contains a socket server which listens on port 50000. I created an Azure container instance and configured it to expose port 50000 so that it can listen for connection from am external socket client.

Since the socket server is very specific it only accept one connection but it seem that instead of waiting for a connection from the external client, it gets a connection from k8s-agentpool1-a02aue0l-1.internal.cloudapp.net as soon as the socket server starts which then means that it can no longer listen for the external client app.

My questions are:

why does it do this?
is there a way of stopping it?

prmanhas-MSFT 17,901 Reputation points Microsoft Employee

2020-08-17T13:50:43.307+00:00

@UVProtector Apologies for the delay in response and all the inconvenience caused because of the issue.

I have reached out to our internal team on this and once I have an update will keep you posted on same.

Thanks.
prmanhas-MSFT 17,901 Reputation points Microsoft Employee

2020-08-20T15:26:09.063+00:00

@UVProtector Any update on the issue?

If the suggested response helped you resolve your issue, do click on "Mark as Answer" and "Up-Vote" for the answer that helped you for benefit of the community.

Thanks.

1 answer

prmanhas-MSFT 17,901 Reputation points Microsoft Employee

2020-08-17T17:13:17.88+00:00

@UVProtector Thank you for your patience over the matter .

I had a discussion internally and got to know that there is a possibility that is the liveness probe checking to make sure that the container is up. It seems pretty unusual to have a server that can only accept a single connection.

I would recommend changing the code to handle multiple connections, but if that's not possible you can null out the liveness and readiness probes and I believe that request should stop.

Hope it helps!!!

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UVProtector 1 Reputation point

2020-08-28T07:40:28.61+00:00

Hi @prmanhas-MSFT thank you for your insightful answer, yes you are of course correct that having a server that only accepts one connection is unusual but I have a client that provides no other choice so rewriting the server would not achieve my end goal. As for you suggestion with the liveness and readiness probes I have not found how to disconnect these as yet so I can't confirm the answer. If you could point me in the right direction as to where in the Azure console I might find the configuration for these probes that would be much appreciated.

prmanhas-MSFT 17,901 Reputation points Microsoft Employee

2020-09-02T06:56:48.727+00:00

@UVProtector Apologies for the delay in response. You can find more info here.

You can just use an 'exec' probe that uses the command '/bin/true' and I think that should remove the network call.

Hope it helps!!!

Please 'Accept as answer' if it helped, so that it can help others in the community looking for help on similar topics

UVProtector 1 Reputation point

2020-09-03T14:08:01.89+00:00

Hi @prmanhas-MSFT , I finally managed to add the command to the liveness and readiness probes but I still receive a connection from k8s. In searching on adding the information to the deployment script I noticed that k8s includes an option to specify a specific port for the liveness and readiness but it does not seem to be available in Azure templates so I could not try this option. So I am out of ideas again. Would you have any further suggestions that might point me in the right direction?

Many thanks.

prmanhas-MSFT 17,901 Reputation points Microsoft Employee

2020-09-03T16:06:25.517+00:00

@UVProtector Thank you for your response. I will reach out to our internal team on this and will keep you posted once I have an update.

Thanks
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Why do Azure container exposed ports receive connections from the k8s agent pool?

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