gRPC - GoLang - Stackdriver tracer - go

Question

I am trying to get the stackdriver tracer to work with gRPC and I need some help. I have been looking at these two links for reference and I still can't get it to work:
https://medium.com/#harlow/tracing-grpc-calls-in-golang-with-google-stackdriver-b22495763a06#.81oa9q21v
https://rakyll.org/grpc-trace/
For simplicity, I am just working with the hello world gRPC example. Here's my client:
func main() {
// Set up a connection to the server.
conn, err := grpc.Dial("localhost:50051", grpc.WithInsecure(), grpc.WithUnaryInterceptor(grpc.UnaryClientInterceptor(clientInterceptor)))
if err != nil {
log.Fatalf("did not connect: %v", err)
}
defer conn.Close()
c := pb.NewGreeterClient(conn)
ctx := context.Background()
tc, err := trace.NewClient(ctx, "{PROJECT-ID}")
if err != nil {
log.Fatal(err)
}
span := tc.NewSpan("/greeter/SayHello")
defer span.Finish()
ctx = trace.NewContext(ctx, span)
r, err := c.SayHello(ctx, &pb.HelloRequest{Name: "world"})
if err != nil {
log.Fatalf("could not greet: %v", err)
}
println("Response:", r.Message)
}
func clientInterceptor(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
// trace current request w/ child span
span := trace.FromContext(ctx).NewChild(method)
defer span.Finish()
// new metadata, or copy of existing
md, ok := metadata.FromContext(ctx)
if !ok {
md = metadata.New(nil)
} else {
md = md.Copy()
}
// append trace header to context metadata
// header specification: https://cloud.google.com/trace/docs/faq
md["X-Cloud-Trace-Context"] = append(
md["X-Cloud-Trace-Context"], fmt.Sprintf("%s/%d;o=1", span.TraceID(), 0),
)
ctx = metadata.NewContext(ctx, md)
return invoker(ctx, method, req, reply, cc, opts...)
}
.. and my gRPC server:
// server is used to implement helloworld.GreeterServer.
type server struct{}
// SayHello implements helloworld.GreeterServer
func (s *server) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
println("HERE")
return &pb.HelloReply{Message: "Hello " + in.Name}, nil
}
func main() {
lis, err := net.Listen("tcp", ":50051")
if err != nil {
log.Fatalf("failed to listen: %v", err)
}
ctx := context.Background()
tc, err := trace.NewClient(ctx, "{PROJECT-ID}")
if err != nil {
log.Fatal(err)
}
s := grpc.NewServer(EnableGRPCTracingServerOption(tc))
pb.RegisterGreeterServer(s, &server{})
println("listening on :50051")
if err := s.Serve(lis); err != nil {
log.Fatalf("failed to serve: %v", err)
}
}
// EnableGRPCTracingServerOption enables parsing google trace header from metadata
// and adds a new child span to the incoming request context.
func EnableGRPCTracingServerOption(traceClient *trace.Client) grpc.ServerOption {
return grpc.UnaryInterceptor(serverInterceptor(traceClient))
}
func serverInterceptor(traceClient *trace.Client) grpc.UnaryServerInterceptor {
return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (resp interface{}, err error) {
// fetch metadata from request context
md, ok := metadata.FromContext(ctx)
if !ok {
md = metadata.New(nil)
}
header := strings.Join(md["X-Cloud-Trace-Context"], "")
// create new child span from google trace header, add to
// current request context
span := traceClient.SpanFromHeader(info.FullMethod, header)
defer span.Finish()
ctx = trace.NewContext(ctx, span)
return handler(ctx, req)
}
}
I when I run the client to initiate the trace, I get the error:
rpc error: code = 13 desc = stream terminated by RST_STREAM with error code: 1
I'm confused because I don't see anything else about authentication; only providing the project ID which can't be enough to initiate tracing for a specific project. What am I missing?

Answer 1

The issue was with:
defer span.Finish()
That call does not block so because I was just doing preliminary testing with one call my program was exiting before the traces could be uploaded. I contacted the author of https://rakyll.org/grpc-trace/ and she actually updated her post with the option of using:
defer span.FinishWait()
which blocks and that fixed it by allowing the traces to be successfully uploaded before the program exited.
Also, with a long running webserver this wouldn't have been an issue because the process wouldn't have been terminated.

Answer 2

I followed those same tutorials and ran into similar problems.
Header keys are converted to lowercase. If you retrieve it on the server side with header := strings.Join(md["x-cloud-trace-context"], "") you should be good.
You can also define your metadata headers with:
span := trace.FromContext(ctx).NewChild(method)
defer span.Finish()
md := metadata.Pairs(
"x-cloud-trace-context", fmt.Sprintf("%s/%d;o=1", span.TraceID(), 0),
)
ctx = metadata.NewContext(ctx, md)