ktr0731/grpc-web-go-client

gRPC-Web client written in Go

gRPC Web Go client

THE IMPLEMENTATION IS LACKING

gRPC Web client written in Go.

Usage

The server is here.

Send an unary request.

client := grpcweb.NewClient("localhost:50051")

in, out := new(api.SimpleRequest), new(api.SimpleResponse)
in.Name = "ktr"

// You can get the endpoint from grpcweb.ToEndpoint function with descriptors.
// However, I write directly in this example.
req := grpcweb.NewRequest("/api.Example/Unary", in, out)

res, err := client.Unary(context.Background(), req)
if err != nil {
  log.Fatal(err)
}

// hello, ktr
fmt.Println(res.Content.(*api.SimpleResponse).GetMessage())

Send a server-side streaming request.

req := grpcweb.NewRequest("/api.Example/ServerStreaming", in, out)

stream, err := client.ServerStreaming(context.Background(), req)
if err != nil {
  log.Fatal(err)
}

for {
  res, err := stream.Receive()
  if err == io.EOF {
    break
  }
  if err != nil {
    log.Fatal(err)
  }
  fmt.Println(res.Content.(*api.SimpleResponse).GetMessage())
}

Send an client-side streaming request.

stream, err := client.ClientStreaming(context.Background())
if err != nil {
  log.Fatal(err)
}

in, out := new(api.SimpleRequest), new(api.SimpleResponse)
in.Name = "ktr"
req := grpcweb.NewRequest("/api.Example/ClientStreaming", in, out)

for i := 0; i < 10; i++ {
  err := stream.Send(req)
  if err == io.EOF {
    break
  }
  if err != nil {
    log.Fatal(err)
  }
}

res, err := stream.CloseAndReceive()
if err != nil {
  log.Fatal(err)
}

// ktr, you greet 10 times.
fmt.Println(res.Content.(*api.SimpleResponse).GetMessage())

Send a bidirectional streaming request.

in, out := new(api.SimpleRequest), new(api.SimpleResponse)
req := grpcweb.NewRequest("/api.Example/BidiStreaming", in, out)

stream := client.BidiStreaming(context.Background(), req)

go func() {
  for {
    res, err := stream.Receive()
    if err == grpcweb.ErrConnectionClosed {
      return
    }
    if err != nil {
      log.Fatal(err)
    }
    fmt.Println(res.Content.(*api.SimpleResponse).GetMessage())
  }
}()

for i := 0; i < 2; i++ {
  in.Name = fmt.Sprintf("ktr%d", i+1)
  req := grpcweb.NewRequest("/api.Example/BidiStreaming", in, out)

  err := stream.Send(req)
  if err == io.EOF {
    break
  }
  if err != nil {
    log.Fatal(err)
  }
}

// wait a moment to get responses.
time.Sleep(10 * time.Second)

if err := stream.Close(); err != nil {
  log.Fatal(err)
}

grpc-web-go-client's Issues

HTTP2 support

Complete documentation?

Is there any documentation about how can we connect to a grpcweb server ?
There is something in .md file but i think its incomplete?

Trailer parsing requires whitespace after the colon separating key and value

The gRPC-Web protocol specifies the trailer is encoded as "Key-value pairs encoded as a HTTP/1 headers block (without the terminating newline), per https://tools.ietf.org/html/rfc7230#section-3.2" in the last message in the body of the response.

https://tools.ietf.org/html/rfc7230#section-3.2 specifies that the whitespace between the colon and the field value should be optional. However, the code at https://github.com/ktr0731/grpc-web-go-client/blob/master/grpcweb/parser/parser.go#L82 requires that there is exactly one space of whitespace between the colon and the field value.

This causes the following error when using evans (which is really nice by the way, thanks!) with a server that does not leave a space between the colon and the field value:

helloworld.GreeterService@localhost:8081> call SayHello
name (TYPE_STRING) => asdf
command call: failed to send a request: grpc-web: failed to send a request: failed to parse status and trailer: unexpected EOF

helloworld.GreeterService@localhost:8081> 

evans installing fails because of grpc-web-go-client

When I tried to install evans, I got this message.

~ # go get github.com/ktr0731/evans
# github.com/ktr0731/grpc-web-go-client/grpcweb/grpcweb_reflection_v1alpha
/go/src/github.com/ktr0731/grpc-web-go-client/grpcweb/grpcweb_reflection_v1alpha/reflection.go:31:30: multiple-value c.cc.BidiStreaming() in single-value context

You changed client.BidiStreaming couple days ago
46586e1#diff-7e67c0929808c88b228892ce33bcc737R289

But here, still get single return variable.

Don't you forget update this?