Distinguish between connection and authorization errors

[dfawley]

gRPC users would like to distinguish between connection errors and authorization/other errors so they can programmatically retry RPCs that are more likely to succeed on subsequent attempts. It doesn't seem like there is any way to do this given the current oauth2 API.

My proposal is to make the errors returned by this package (optionally) support a method (like net.Error's Temporary() method) to indicate whether the error was a connection error.

References: https://github.com/grpc/grpc-java/issues/3267 https://github.com/grpc/grpc-go/issues/1704 https://github.com/grpc/grpc/pull/13322

[dfawley]

This issue has come up again as affecting a customer. Is it possible to get a rough estimate for how long such a change would take to implement, and what we would need to do to get it prioritized?