Access-Control-Expose-Headers errors in browser when response from server

[scippio]

Hi,

I'm playing with grpc-web and maybe I'm doing something wrong, but I'm geting this:

I'm sucessfully recieved request on server with all data... but response end with this errors in browser (Chrome) :(

My test code:

I create good request from my js client:

import { RegistrationServicePromiseClient, RegistrationServiceClient, Data } from '~/api/registration_grpc_web_pb.js'

...

var data = new Data()
data.setEmail("test@example.com")
data.setPassword("abcd")
var client = new RegistrationServiceClient("https://localhost:8000")
client.newRegistration(data,null,(res) => {
    console.log("res:",res)
})

and on my golang server (in main func):

func main() {
	creds, err := credentials.NewServerTLSFromFile("localhost.pem", "localhost-key.pem")
	if err != nil {
		fmt.Print(err)
	}

	grpcServer := grpc.NewServer(grpc.Creds(creds))
	wrappedGrpc := grpcweb.WrapServer(grpcServer, grpcweb.WithAllowedRequestHeaders([]string{"*"}), grpcweb.WithWebsockets(false))

	srv := TestService{}
	protos.RegisterRegistrationServiceServer(grpcServer, &srv)

	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Access-Control-Allow-Origin", "*")
		w.Header().Set("Access-Control-Allow-Methods", "POST, GET, OPTIONS, PUT, DELETE")
		w.Header().Set("Access-Control-Allow-Headers", "Accept, Content-Type, Content-Length, Accept-Encoding, X-CSRF-Token, Authorization, x-user-agent, x-grpc-web, grpc-status, grpc-message")
		w.Header().Set("Access-Control-Expose-Headers", "grpc-status, grpc-message")
		if r.Method == "OPTIONS" {
			return
		}

		if wrappedGrpc.IsGrpcWebRequest(r) {
			wrappedGrpc.ServeHTTP(w, r)
		} else {
			// Fall back to other servers.
			http.DefaultServeMux.ServeHTTP(w, r)
		}
	})

	httpserver := http.Server{
		Addr:           ":8000",
		Handler:        handler,
		ReadTimeout:    10 * time.Second,
		WriteTimeout:   10 * time.Second,
		MaxHeaderBytes: 1 << 20,
	}
	http2.ConfigureServer(&httpserver, nil)

	err = httpserver.ListenAndServeTLS("localhost.pem", "localhost-key.pem")
	if err != nil {
		panic(err)
	}
}

func (ser *TestService) NewRegistration(ctx context.Context, data *protos.Data) (*protos.Response, error) {

	fmt.Printf("RECIEVED: %v\n", data)

	res := protos.Response{}
	res.Status = 123
	res.Message = "Test"

	return &res, nil
}

Verion grpc-web: 0.9.1

thanks for any help...

[johanbrandhorst]

What does the response from the server look like in the browser? Could you show the output of the network tab in your browser debug tools?

[johanbrandhorst]

You shouldn't have to call http2.ConfigureServer by the way, it will support http/2 automatically.

[scippio]

[johanbrandhorst]

What does the chrome console warning drop down say? I noticed you're serving the UI on HTTP but the grpcwebproxy on HTTPS, it's not a security mismatch?

[scippio]

I don't think so... but good point I'll try unify this...

EDIT: I tried only http and https too everywhere and it's still same...

[jonnyreeves]

Pretty sure this is a CORS issue. Have you configured your proxy to enable CORS preflight requests?

…

On Mon, 22 Apr 2019, 22:29 scippio, ***@***.***> wrote: I don't think so... but good point I'll try unify this... [image: image] <https://user-images.githubusercontent.com/672903/56532642-6fdf2a80-6556-11e9-9376-bcccac8e2539.png> — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#396 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AABQ36IZ3T4E2SXFPH7NZETPRYU5HANCNFSM4HHO2TYQ> .

[scippio]

You can see the OPTIONS request and my server source for pre-flight setup... I don't using any proxy. Only this client and server code.

[scippio]

🤔 When I set this headers manually on server after other headers:

w.Header().Set("grpc-status", "123")
w.Header().Set("grpc-message", "true")

it's recieved ok:

(.. and I don't know why callback is fired five times...)

[scippio]

Ok, I change my client code from "rpcCall" to "unaryCall" (promise version) (functions in generated js files from proto):

So I change exactly this lines:

// var client = new RegistrationServiceClient("https://localhost:8000")
var client = new RegistrationServicePromiseClient("https://localhost:8000")

// client.newRegistration(data,meta,(res) => {
//     console.log("res:",res)
// })

client.newRegistration(data,meta).then((res) => {
     console.log("res:",res)
     console.log("res:",res.toObject())
}).catch((err) => {
     console.log("err: ",err)
})

and it works! But I have still same error messages 😢

[scippio]

I think a found the same problem in the past: grpc/grpc-web#518

EDIT: So I think I will try use Envoy...