How to bring a gRPC defined API to the web browser

Question

We want to build a Javascript/HTML gui for our gRPC-microservices. Since gRPC is not supported on the browser side, we thought of using web-sockets to connect to a node.js serve

Answer 1

An official grpc-web (beta) implementation was released on 3/23/2018. You can find it at

https://github.com/grpc/grpc-web

The following instructions are taken from the README:

Define your gRPC service:

service EchoService {
  rpc Echo(EchoRequest) returns (EchoResponse);

  rpc ServerStreamingEcho(ServerStreamingEchoRequest)
      returns (stream ServerStreamingEchoResponse);
}

Build the server in whatever language you want.

Create your JS client to make calls from the browser:

var echoService = new proto.grpc.gateway.testing.EchoServiceClient(
  'http://localhost:8080');

Make a unary RPC call

var unaryRequest = new proto.grpc.gateway.testing.EchoRequest();
unaryRequest.setMessage(msg);
echoService.echo(unaryRequest, {},
  function(err, response) {
    console.log(response.getMessage());
  });

Streams from the server to the browser are supported:

var stream = echoService.serverStreamingEcho(streamRequest, {});
stream.on('data', function(response) {
  console.log(response.getMessage());
});

Bidirectional streams are NOT supported:

This is a work in progress and on the grpc-web roadmap. While there is an example protobuf showing bidi streaming, this comment make it clear that this example doesn't actually work yet.

Hopefully this will change soon. :)