add error handling example

cmd/client/main.go

@@ -19,8 +19,10 @@ import (
 	"gitea.dwysokinski.me/Kichiyaki/grpc-g2a/proto"
 	"github.com/google/uuid"
 	"go.uber.org/zap"
+	"google.golang.org/genproto/googleapis/rpc/errdetails"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/status"
 )
 
 const defaultAddress = "localhost:50001"
@@ -30,6 +32,8 @@ const (
 	exampleServer        = "server"
 	exampleClient        = "client"
 	exampleBidirectional = "bidirectional"
+	exampleJames         = "james"
+	exampleJamesError    = "jameserror"
 )
 
 func main() {
@@ -64,6 +68,10 @@ func main() {
 	switch example {
 	case exampleUnary:
 		sayHello(ctx, client, logger)
+	case exampleJames:
+		sayHelloToJames(ctx, client, logger)
+	case exampleJamesError:
+		sayHelloToJamesError(ctx, client, logger)
 	case exampleServer:
 		sayHelloServerStream(ctx, client, logger)
 	case exampleClient:
@@ -77,12 +85,16 @@ func main() {
 
 func parseExample() string {
 	example := ""
-	flag.StringVar(
-		&example,
-		"example",
+	flag.StringVar(&example, "example", exampleUnary, fmt.Sprintf(
+		"%s, %s, %s, %s, %s or %s (default: %s)",
 		exampleUnary,
-		fmt.Sprintf("%s, %s, %s or %s (default: %s)", exampleUnary, exampleServer, exampleClient, exampleBidirectional, exampleUnary),
-	)
+		exampleJames,
+		exampleJamesError,
+		exampleServer,
+		exampleClient,
+		exampleBidirectional,
+		exampleUnary,
+	))
 	flag.Parse()
 	return example
 }
@@ -133,6 +145,46 @@ func sayHello(ctx context.Context, client proto.GreeterClient, logger *zap.Logge
 	logger.Info("reply received", zap.String("message", reply.GetMessage()))
 }
 
+func sayHelloToJames(ctx context.Context, client proto.GreeterClient, logger *zap.Logger) {
+	name := "James"
+	logger.Info("sending request", zap.String("name", name))
+	reply, err := client.SayHelloToJames(ctx, &proto.HelloRequest{Name: name})
+	if err != nil {
+		logger.Fatal("something went wrong while calling SayHello", zap.Error(err))
+	}
+	logger.Info("reply received", zap.String("message", reply.GetMessage()))
+}
+
+func sayHelloToJamesError(ctx context.Context, client proto.GreeterClient, logger *zap.Logger) {
+	name := "SomeoneElse"
+
+	logger.Info("sending request", zap.String("name", name))
+	reply, err := client.SayHelloToJames(ctx, &proto.HelloRequest{Name: name})
+	if err == nil {
+		logger.Info("unexpected reply received", zap.String("message", reply.GetMessage()))
+		return
+	}
+
+	st, ok := status.FromError(err)
+	if !ok {
+		logger.Fatal("received unexpected error", zap.Error(err))
+	}
+
+	var violations []string
+	for _, detail := range st.Details() {
+		switch d := detail.(type) {
+		case *errdetails.BadRequest:
+			for _, violation := range d.GetFieldViolations() {
+				violations = append(violations, violation.GetField()+": "+violation.GetDescription())
+			}
+		default:
+			logger.Debug("unhandled detail", zap.Any("detail", d))
+		}
+	}
+
+	logger.Info("received error", zap.Error(err), zap.Strings("violations", violations))
+}
+
 const (
 	namesLen = 20
 )

cmd/server/main.go

@@ -19,6 +19,7 @@ import (
 	grpc_recovery "github.com/grpc-ecosystem/go-grpc-middleware/recovery"
 	grpc_ctxtags "github.com/grpc-ecosystem/go-grpc-middleware/tags"
 	"go.uber.org/zap"
+	"google.golang.org/genproto/googleapis/rpc/errdetails"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/credentials"
@@ -156,6 +157,31 @@ func (g *greeterServer) SayHello(_ context.Context, r *proto.HelloRequest) (*pro
 	}, nil
 }
 
+func (g *greeterServer) SayHelloToJames(_ context.Context, r *proto.HelloRequest) (*proto.HelloReply, error) {
+	name := r.GetName()
+
+	if name != "James" {
+		st, err := status.
+			New(codes.InvalidArgument, "invalid name").
+			WithDetails(&errdetails.BadRequest{
+				FieldViolations: []*errdetails.BadRequest_FieldViolation{
+					{
+						Field:       "name",
+						Description: "must be James",
+					},
+				},
+			})
+		if err != nil {
+			return nil, status.New(codes.Internal, "internal server error").Err()
+		}
+		return nil, st.Err()
+	}
+
+	return &proto.HelloReply{
+		Message: buildHelloMsg(name),
+	}, nil
+}
+
 func (g *greeterServer) SayHelloServerStream(r *proto.MultiHelloRequest, stream proto.Greeter_SayHelloServerStreamServer) error {
 	for _, n := range r.GetNames() {
 		if err := stream.Send(&proto.HelloReply{

proto/hello_world.proto

@@ -4,6 +4,7 @@ option go_package = "gitea.dwysokinski.me/Kichiyaki/grpc-g2a/proto";
 
 service Greeter {
   rpc SayHello (HelloRequest) returns (HelloReply) {}
+  rpc SayHelloToJames (HelloRequest) returns (HelloReply) {}
   rpc SayHelloClientStream (stream HelloRequest) returns (MultiHelloReply) {}
   rpc SayHelloServerStream (MultiHelloRequest) returns (stream HelloReply) {}
   rpc SayHelloBidirectionalStream (stream HelloRequest) returns (stream HelloReply) {}