DNS tests are failing deterministically in CI

[ViktorHofer]

https://dev.azure.com/dnceng/public/_build/results?buildId=1011172&view=ms.vss-test-web.build-test-results-tab

System.Net.Internals.SocketExceptionFactory+ExtendedSocketException : Name or service not known
 at System.Net.Dns.GetHostEntryOrAddressesCore(String hostName, Boolean justAddresses, AddressFamily addressFamily) in /_/src/libraries/System.Net.NameResolution/src/System/Net/Dns.cs:line 404
   at System.Net.Dns.GetHostEntryCore(String hostName, AddressFamily addressFamily) in /_/src/libraries/System.Net.NameResolution/src/System/Net/Dns.cs:line 385
   at System.Net.Dns.GetHostByName(String hostName) in /_/src/libraries/System.Net.NameResolution/src/System/Net/Dns.cs:line 272
   at System.Net.NameResolution.Tests.GetHostByNameTest.DnsObsoleteGetHostByName_EmptyString_ReturnsHostName() in /_/src/libraries/System.Net.NameResolution/tests/FunctionalTests/GetHostByNameTest.cs:line 108

We probably need to disable the failing tests right now as apparently something changed in the dns detection which is causing these tests to fail deterministically in CI.

cc @dotnet/ncl

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Issue Details

---

https://dev.azure.com/dnceng/public/_build/results?buildId=1011172&view=ms.vss-test-web.build-test-results-tab

System.Net.Internals.SocketExceptionFactory+ExtendedSocketException : Name or service not known
 at System.Net.Dns.GetHostEntryOrAddressesCore(String hostName, Boolean justAddresses, AddressFamily addressFamily) in /_/src/libraries/System.Net.NameResolution/src/System/Net/Dns.cs:line 404
   at System.Net.Dns.GetHostEntryCore(String hostName, AddressFamily addressFamily) in /_/src/libraries/System.Net.NameResolution/src/System/Net/Dns.cs:line 385
   at System.Net.Dns.GetHostByName(String hostName) in /_/src/libraries/System.Net.NameResolution/src/System/Net/Dns.cs:line 272
   at System.Net.NameResolution.Tests.GetHostByNameTest.DnsObsoleteGetHostByName_EmptyString_ReturnsHostName() in /_/src/libraries/System.Net.NameResolution/tests/FunctionalTests/GetHostByNameTest.cs:line 108

We probably need to disable the failing tests right now as apparently something changed in the dns detection which is causing these tests to fail deterministically in CI.

cc @dotnet/ncl

Author:	ViktorHofer
Assignees:	-
Labels:	area-System.Net, blocking-clean-ci
Milestone:	6.0.0

[wfurt]

Do you know if anything changed with infrastructure @MattGal ? From the logs it seems like the instance cannot resolve it's own name. I'll keep looking as it is not clear why this would happen only on particular distro.

[MattGal]

Do you know if anything changed with infrastructure @MattGal ? From the logs it seems like the instance cannot resolve it's own name. I'll keep looking as it is not clear why this would happen only on particular distro.

Interesting; I know of no intentional changes from this but Weds. is rollout days so if something changed, it would have been yesterday. Taking a look.

[MattGal]

Do you know if anything changed with infrastructure @MattGal ? From the logs it seems like the instance cannot resolve it's own name. I'll keep looking as it is not clear why this would happen only on particular distro.

Interesting; I know of no intentional changes from this but Weds. is rollout days so if something changed, it would have been yesterday. Taking a look.

Ah. SLES 15. Yes, we did update this one yesterday, because SUSE deleted the SLES 15 SP1 image from the gallery, forcing us onto SP2. I'll check it out and see if there's anything we can do and report back. Tracking issue: https://github.com/dotnet/core-eng/issues/12333

[wfurt]

thanks @MattGal. If needed, I can help with the investigation.