How to avoid infinite retry after PerRPCCredentials.GetRequestMetadata returns non-nil error

[jschwinger233]

background:

grpc server already implemented auth token

what I want:

refresh auth token every time a RPC gets called

how I tried to work it out:

make an another grpc call to fetch auth token in PerRPCCredentials.GetRequestMetadata; grpc guarantees PerRPCCredentials.GetRequestMetadata gets called for each RPC

what's the problem

imagine I make a stream grpc call and my client was configured wrong password to fetch auth token, in this case PerRPCCredentials.GetRequestMetadata returns non-nil forever, but what's out of my expectation is I stuck at creating grpc.ClientStream in the infinite retry loop: https://github.com/grpc/grpc-go/blob/master/stream.go#L598-L626

I could make stream fail fast but I don't want, because infinite retry on a stream, like a watch operation, makes sense, but only if the error is transient, and I don't think authentication failure is transient;

I was wondering if grpc.(*clientStream)shouldRetry can do the job to distinguish transient errors from the in-transient ones but the method always returns nil in the first condition: if cs.attempt.s == nil && !cs.callInfo.failFast { return nil }

would please offer some insights for this issue, thanks!

[menghanl]

This issue was fixed by #3677. Please give it a try.