[Python] ServiceUnavailable: 503 DNS resolution failed for service in Windows

[busu...@google.com]

Hi,

I'm posting on behalf of a user who raised this question in the the python library for Google Cloud Firestore. (original issue with example code, stack traces).

They are working in a Windows environment. Calls to the firestore.googleapis.com endpoint through the gRPC client eventually result in this error:

debug_error_string = "{"created":"@1632831473.221000000","description":"Resolver transient failure","file":"src/core/ext/filters/client_channel/client_channel.cc","file_line":1356,"referenced_errors":[{"created":"@1632831473.221000000","description":"DNS resolution failed for service: firestore.googleapis.com","file":"src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc","file_line":202,"grpc_status":14,"referenced_errors":[{"created":"@1632831473.221000000","description":"OS Error","file":"src/core/lib/iomgr/resolve_address_windows.cc","file_line":93,"os_error":"The specified class was not found.\r\n","syscall":"getaddrinfo","wsa_error":10109}]}]}"

Additional Context:

• They are using grpc 1.40.0
• They are able to access the REST API of firestore.googleapis.com through `requests`.
• They tried switching to GRPC_DNS_RESOLVER=native as suggested in  https://github.com/grpc/grpc/issues/18691 without success.
• They can run the same code successfully from their personal (Mac) computer.

Any pointers on what to try next would be much appreciated. Thank you!

[Lidi Zheng]

+Craig Tiller 

The logic around Windows name resolution is stable for years. By searching the socket error 10109, I didn't find any more info: https://docs.microsoft.com/en-us/windows/win32/winsock/windows-sockets-error-codes-2

Craig, since you wrote this module originally, if you have a second, can you help to take a look at what this resolution error could mean?

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[Meredith Slota]

The original issue is still open, but no additional info posted there (yet). Any other folks have any ideas?