b is not a function :b({code:2,message:“Incomplete response”} for grpcwebtext, but ok for grpcweb

[yakovdom]

Hello!

I am trying to create client for my python grpc server.

My server implements server-side streaming methods and unary calls. As follows from library documentation, if I need streaming, i should compile my proto files with mode=grpcwebtext option

But, I also have following unary call method with bytes field in request:

message SaveUserDocumentRequest {
    bytes content = 1;
}

message SaveUserDocumentResponse {
    string url = 1;
}

service MyService {
    rpc SaveUserDocument (SaveUserDocumentRequest) returns (SaveUserDocumentResponse);
}

Client code is:

uploadImage({ content }, callback) {
        try {
            let realRequest = new SaveUserDocumentRequest();
            realRequest.setContent(content)

            this.client.saveUserDocument(realRequest, {}, (err, response) => {
                if(err) {
                    console.log(err)
                    return;
                }
                callback(response)
            })

        } catch(e) {
            console.log(e)
        }
    }

if I compile my protofiles with option mode=grpcweb this rpc method works just fine (but other server-streaming methods don't)

But if I compile my protofiles with option mode=grpcwebtext and trying to use this method, i got following exception:

b is not a function :b({code:2,message:“Incomplete response”}

Please, if you know, what am I doing wrong, let me know Thanks for your help!

[sampajano]

Thanks for question :)

Curious if you are using the Envoy proxy as documented here? https://github.com/grpc/grpc-web#2-run-the-server-and-proxy

[yakovdom]

yes, I use envoy

admin:
  access_log_path: /tmp/admin_access.log
  address:
    socket_address: { address: 0.0.0.0, port_value: 9901 }

static_resources:
  listeners:
    - name: listener_0
      address:
        socket_address: { address: 0.0.0.0, port_value: 8921 }
      filter_chains:
        - filters:
          - name: envoy.filters.network.http_connection_manager
            typed_config:
              "@type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager
              codec_type: auto
              stat_prefix: ingress_http
              route_config:
                name: local_route
                virtual_hosts:
                  - name: local_service
                    domains: ["*"]
                    routes:
                      - match: { prefix: "/" }
                        route:
                          cluster: greeter_service
                          timeout: 0s
                          max_stream_duration:
                            grpc_timeout_header_max: 0s
                    cors:
                      allow_origin_string_match:
                        - prefix: "*"
                      allow_methods: GET, PUT, DELETE, POST, OPTIONS
                      allow_headers: keep-alive,user-agent,cache-control,content-type,content-transfer-encoding,custom-header-1,x-accept-content-transfer-encoding,x-accept-response-streaming,x-user-agent,x-grpc-web,grpc-timeout
                      max_age: "1728000"
                      expose_headers: custom-header-1,grpc-status,grpc-message
              http_filters:
                - name: envoy.filters.http.grpc_web
                  typed_config:
                    "@type": type.googleapis.com/envoy.extensions.filters.http.grpc_web.v3.GrpcWeb
                - name: envoy.filters.http.cors
                  typed_config:
                    "@type": type.googleapis.com/envoy.extensions.filters.http.cors.v3.Cors
                - name: envoy.filters.http.router
                  typed_config:
                    "@type": type.googleapis.com/envoy.extensions.filters.http.router.v3.Router
  clusters:
    - name: greeter_service
      connect_timeout: 10.25s
      type: logical_dns
      http2_protocol_options: {}
      lb_policy: round_robin
      load_assignment:
        cluster_name: cluster_0
        endpoints:
          - lb_endpoints:
            - endpoint:
                address:
                  socket_address:
                    address: 0.0.0.0
                    port_value: 50057

[sampajano]

Ah thanks for the info :)

While i don't know what exactly is not working, i suggest one thing you can do is compare with the echo example (which has streaming mode), and see what client/server responses are different: https://github.com/grpc/grpc-web/tree/master/net/grpc/gateway/examples/echo

hope that helps :)

[yakovdom]

Thanks for your reply! I am afraid, that echo example is not using bytes field and the problem is only with this type of proto fields. Proto messages without fields of bytes type works just fine

And bytes fields works fine in grpcweb mode

Maybe I need to make some changes to client or server, if I want use bytes field in grpcwebtext mode? I've read about some encryption in grpcwebtext, maybe this is the key?

[sampajano]

Ahh i see! Thanks for the info!

Good to know that the issue is ONLY with bytes fields..

It could be bug in proto decoding or grpc-web stack.

Maybe I need to make some changes to client or server, if I want use bytes field in grpcwebtext mode? I've read about some encryption in grpcwebtext, maybe this is the key?

I don't think we specifically "encrypt" the request / response.

Maybe you're referring to this thread? I guess the technique mentioned there could help you check if the response is valid — to narrow down whether it's a server or client issue.

[yakovdom]

Thanks for your help! Somehow, after some iterations of development I can't reproduce this issue any more. The sad thing is that I haven't notice, what have I change to fix it:( But now all works just fine! So thank you very much!

[sampajano]

Oh ok.. 😅 In any case, glad it works for you now! 😃