Adds support for registering client dial option handlers (open-teleme…

…try#1)

* Adds RegisterClientDialOptionHandlers api to define DialOptions at the time of connection creation

* Removed unnecessary mutex

config/configgrpc/configgrpc.go

@@ -40,13 +40,19 @@ const (
 	PerRPCAuthTypeBearer = "bearer"
 )
 
+type ClientDialOptionHandler func() grpc.DialOption
+
 var (
 	// Map of opentelemetry compression types to grpc registered compression types
 	grpcCompressionKeyMap = map[string]string{
 		CompressionGzip: gzip.Name,
 	}
 )
 
+var (
+	clientOptionHandlerList = make([]ClientDialOptionHandler, 0)
+)
+
 // Allowed balancer names to be set in grpclb_policy to discover the servers
 var allowedBalancerNames = []string{roundrobin.Name, grpc.PickFirstBalancerName}
 
@@ -98,6 +104,9 @@ type GRPCClientSettings struct {
 	// Sets the balancer in grpclb_policy to discover the servers. Default is pick_first
 	// https://github.com/grpc/grpc-go/blob/master/examples/features/load_balancing/README.md
 	BalancerName string `mapstructure:"balancer_name"`
+
+	// UseGlobalInterceptors defines config if the global client interceptors need to be used
+	SkipGlobalClientOption bool `mapstructure:"skip_global_client_option"`
 }
 
 type KeepaliveServerConfig struct {
@@ -219,6 +228,15 @@ func (gcs *GRPCClientSettings) ToDialOptions() ([]grpc.DialOption, error) {
 		opts = append(opts, grpc.WithDefaultServiceConfig(fmt.Sprintf(`{"loadBalancingPolicy":"%s"}`, gcs.BalancerName)))
 	}
 
+	if !gcs.SkipGlobalClientOption {
+		for _, handler := range clientOptionHandlerList {
+			opt := handler()
+			if opt != nil {
+				opts = append(opts, opt)
+			}
+		}
+	}
+
 	return opts, nil
 }
 
@@ -311,3 +329,9 @@ func GetGRPCCompressionKey(compressionType string) string {
 	}
 	return CompressionUnsupported
 }
+
+func RegisterClientDialOptionHandlers(handlers ...ClientDialOptionHandler) {
+	for _, handler := range handlers {
+		clientOptionHandlerList = append(clientOptionHandlerList, handler)
+	}
+}

config/configgrpc/configgrpc_test.go

@@ -521,3 +521,15 @@ func TestWithPerRPCAuthInvalidAuthType(t *testing.T) {
 	assert.Error(t, err)
 	assert.Nil(t, dialOpts)
 }
+
+func TestRegisterClientDialOptionHandler(t *testing.T) {
+	RegisterClientDialOptionHandlers(func() grpc.DialOption {
+		return grpc.WithUnaryInterceptor(func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
+			return invoker(ctx, method, req, reply, cc, opts...)
+		})
+	})
+	gcs := &GRPCClientSettings{}
+	opts, err := gcs.ToDialOptions()
+	assert.NoError(t, err)
+	assert.Len(t, opts, 2)
+}