Grpc-gateway: Support OpenCensus trace propagation

[tmc]

If not direct support we should have clear documentation on how to pass traces across http<>grpc boundaries.

[mattouille]

I was actually just looking at this. I don't quite see an avenue yet but I'll take a deeper look later today.

[Azuka]

Also very interested in this. Has anyone got it working?

[jon-whit]

Does anyone have any examples with this?

[johanbrandhorst]

I haven't used opencensus with the gateway myself but I imagine it's just a matter of creating an interceptor that extracts the trace from the incoming metadata and stuffs it back in the context?

[emcfarlane]

Can be set on the clients grpc options and the http handlers like:

conn, _ := grpc.Dial(addr, grpc.WithStatsHandler(&ocgrpc.ClientHandler{})
mux  := &ochttp.Handler{Handler: runtime.NewServeMux()}

servicepb.RegisterRouteHandler(ctx, mux, conn)

[dharmjit]

@afking
Any example on this. I am facing this issue and seeing different spans(ochttp,ocsql) for the same request.
Thanks

[johanbrandhorst]

If your spans are not contiguous you must not be passing the context along properly. Are you making sure to use the database/sql methods that use context?

[dharmjit]

I might be making some silly mistake. Below is the sample of the code of the server

// RunServer runs HTTP/REST gateway
func RunServer(ctx context.Context, grpcPort, httpPort string) error {
    ctx, cancel := context.WithCancel(ctx)
    defer cancel()
    mux := runtime.NewServeMux()
    opts := []grpc.DialOption{grpc.WithInsecure()}
    if err := v1.RegisterAuthServiceHandlerFromEndpoint(ctx, mux, "localhost:"+grpcPort, opts); err != nil {
        // log.Fatalf("failed to start HTTP gateway: %v", err)
        logger.Log.Fatal("failed to start HTTP gateway", zap.String("reason", err.Error()))
    }
    srv := &http.Server{
        Addr:    ":" + httpPort,
        Handler: &ochttp.Handler{Handler: 
            // middleware.AddLogger(logger.Log, mux)},
            mux},
    }
    // log.Println("starting HTTP/REST gateway...")
    logger.Log.Info("starting HTTP/REST gateway...")
    return srv.ListenAndServe()
}

and below is the implementation of the rpc method

func (s *authServiceServer) Login(ctx context.Context, req *v1.LoginRequest) (*v1.LoginResponse,error){
    // get SQL connection from pool
    c, err := s.connect(ctx)

    if err != nil {
        return nil, err
    }
    defer c.Close()

    // query User by ID and Password
    cCtx, cSpan := trace.StartSpan(ctx, "Select")
    rows, err := c.QueryContext(cCtx, "SELECT count(1) FROM user123")
    if err != nil {
        return nil, status.Error(codes.Unknown, "failed to select from user-> "+err.Error())
    }
    cSpan.End()
    fmt.Printf("number of rows 1:%d",getCount(rows))
    defer rows.Close()
    return &v1.LoginResponse{Username:"1"},nil
}

[johanbrandhorst]

This is not the place for this type of debugging, perhaps join the #opencensus channel on the gophers slack? https://invite.slack.golangbridge.org/

[dharmjit]

Ahh okk I will post it there. This was somewhat related to grpc-gateway so I posted here.