Error message for incorrect endpoint does not provide enough information to debug

[zombiezen]

I recently experienced a rather long debug session where I had misconfigured the endpoint of a gRPC connection to a Google Cloud API. I ultimately ended up having to monkey-patch instrumentation into gRPC to figure out what was going on.

The header-handling code bails at the first error instead of trying to get a larger picture of what's going on.

grpc-go/transport/http_util.go

Lines 237 to 241 in 0ebfac4

	for _, hf := range frame.Fields {
	if err := d.processHeaderField(hf); err != nil {
	return err
	}
	}

What version of gRPC are you using?

v1.11.3

What version of Go are you using (go version)?

go version go1.10.2 linux/amd64

What operating system (Linux, Windows, …) and version?

Linux

What did you do?

Dial a gRPC connection to a non-gRPC endpoint by accident.

What did you expect to see?

The following information would have been helpful in the error:

• HTTP response status code. This helps distinguish an ACL issue from a typo'd endpoint, for instance.
• The requested URL. Without this, I had to trace back through my code to see how the connection was being initialized to see whether this was the issue. If I had this information in the error message, I could have simply seen the problem by a quick inspection of the error message.
• The problematic header's error message (already included).

What did you see instead?

rpc error: code = Internal desc = transport: received the unexpected content-type "text/html; charset=UTF-8"

[utrack]

Also, some (configurable) way to print the body we've received would be cool.

[ayenter]

Bump

[dfawley]

Note per the linked issue that the status code here is supposed to be Unimplemented instead of Internal.

EDIT: for future reference, this can be easily tested via:

$ go run interop/client/client.go --server_host=dsldksd.googleapis.com --server_host_override=dsldksd.googleapis.com --server_port=443 --use_tls=true
FATAL: 2018/12/05 16:33:19 /TestService/UnaryCall RPC failed: rpc error: code = Internal desc = transport: received the unexpected content-type "text/html; charset=UTF-8"
exit status 1

[menghanl]

This should be fixed by #2599.

Closing. Please comment if it is still a problem.