kubernetes is not routing traffic to grpc service

I am trying to make GRPC work in a digitalocean Kubernetes cluster - but am still to succeed.

> PS: Apologies for the long content

I have found some content regarding this but those revolve around some ingress. For me, these are internal services.

I have a .proto defined as such:

syntax = "proto3";
package imgproto;
option go_package = ".;imgproto";

import "google/protobuf/duration.proto";
import "google/protobuf/timestamp.proto";

service ImaginaryServer {
  rpc Ping(PingPayload) returns (PongPayload) {}
}

message PingPayload {
  google.protobuf.Timestamp ts = 1;
}
message PongPayload {
  google.protobuf.Timestamp ts = 1;
}

After running proto-gen-go, I populate the implementation with:

type ImaginaryServerImpl struct {
	imgproto.UnimplementedImaginaryServer
}


func (s *ImaginaryServerImpl) Ping(_ context.Context, in *imgproto.PingPayload) (*imgproto.PongPayload, error) {
	fmt.Printf("ImaginaryServerImpl.Ping: %v\n", in)
	return &imgproto.PongPayload{
		Ts: timestamppb.New(time.Now()),
	}, nil
}

Create and register it to a GRPC server:

grpcServer := grpc.NewServer()
imgproto.RegisterImaginaryServer(grpcServer, &ImaginaryServerImpl{})

And start the server:

grpcListener, err := net.Listen("tcp", fmt.Sprintf(":%d", constants.PORT_GRPC))
if err != nil {
	return err
}

go func() {
	if err := grpcServer.Serve(grpcListener); err != nil {
		fmt.Println("GRPC Server startup failed with", err)
	}
}()

<-ctx.Done()
grpcServer.GracefulStop()

I wrote up the client as:

grpcConnection, err := grpc.Dial(
	endpoint,
	grpc.WithBlock(),
	grpc.WithTransportCredentials(insecure.NewCredentials()),
	grpc.WithUnaryInterceptor(func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
		fmt.Println("Calling GRPC:", method, req, reply, invoker)
		return nil
	}))
if err != nil {
	return ctx, err
}

client := pmqproto.NewImaginaryClient(grpcConnection)

fmt.Println(" >>>>>>>>>>> PING:")
pong, pingErr := client.Ping(ctx, &imgproto.PingPayload{Ts: timestamppb.Now()}, grpc.WaitForReady(false))
if pingErr != nil {
	fmt.Println(pingErr)
}
fmt.Println(" >>>>>>>>>>> PONG: ", pong.Ts.AsTime().String())

But it looks like the client is returning without actually invoking the RPC.

Log that I am seeing in the client:

>>>>>>>>>>> PING:
Calling GRPC: /imgproto.ImaginaryServer/Ping ts:{seconds:1666113879  nanos:778900352}  0x127aa60
>>>>>>>>>>> PONG:  1970-01-01 00:00:00 +0000 UTC

> There are no logs in the server.

My k8s yaml is as such:

apiVersion: v1
kind: Service
metadata:
  name: reality
  namespace: reality-ns
spec:
  type: ClusterIP
  selector:
    app: reality
  ports:
    - name: grpc
      protocol: TCP
      port: 6772
      targetPort: 6772
---

apiVersion: apps/v1
kind: Deployment
metadata:
  name: reality
  namespace: reality-ns
  labels:
    app: reality
spec:
  selector:
    matchLabels:
      app: reality
  template:
    metadata:
      labels:
        app: reality
    spec:
      containers:
        - name: reality
          image: registry.example.com/binaek/reality
          imagePullPolicy: Always
          command: ["cmd"]
          ports:
            - name: grpc
              containerPort: 6772

I am not able to locate what I am doing wrong. Desperately need help at this point.

> The image uses gcr.io/distroless/base as it's base.

Your interceptor usage is likely preventing execution of the RPC.

// When a unary interceptor(s) is set on a ClientConn, gRPC
// delegates all unary RPC invocations to the interceptor, and it is the
// responsibility of the interceptor to call invoker to complete the processing
// of the RPC.

https://github.com/grpc/grpc-go/blob/9127159caf5a3879dad56b795938fde3bc0a7eaa/interceptor.go#L31-L34

So your interceptor function should instead look like:

grpc.WithUnaryInterceptor(func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
    fmt.Println("Calling GRPC:", method, req, reply, invoker)
    return invoker(ctx, method, req, reply, cc, opts...)
}))