Fix internal handlers ServiceBuilder composition

pkg/server/service/internalhandler.go

@@ -8,11 +8,6 @@ import (
 	"strings"
 )
 
-type serviceManager interface {
-	BuildHTTP(rootCtx context.Context, serviceName string) (http.Handler, error)
-	LaunchHealthCheck()
-}
-
 // InternalHandlers is the internal HTTP handlers builder.
 type InternalHandlers struct {
 	api        http.Handler
@@ -21,26 +16,24 @@ type InternalHandlers struct {
 	prometheus http.Handler
 	ping       http.Handler
 	acmeHTTP   http.Handler
-	serviceManager
 }
 
 // NewInternalHandlers creates a new InternalHandlers.
-func NewInternalHandlers(next serviceManager, apiHandler, rest, metricsHandler, pingHandler, dashboard, acmeHTTP http.Handler) *InternalHandlers {
+func NewInternalHandlers(apiHandler, rest, metricsHandler, pingHandler, dashboard, acmeHTTP http.Handler) *InternalHandlers {
 	return &InternalHandlers{
-		api:            apiHandler,
-		dashboard:      dashboard,
-		rest:           rest,
-		prometheus:     metricsHandler,
-		ping:           pingHandler,
-		acmeHTTP:       acmeHTTP,
-		serviceManager: next,
+		api:        apiHandler,
+		dashboard:  dashboard,
+		rest:       rest,
+		prometheus: metricsHandler,
+		ping:       pingHandler,
+		acmeHTTP:   acmeHTTP,
 	}
 }
 
 // BuildHTTP builds an HTTP handler.
 func (m *InternalHandlers) BuildHTTP(rootCtx context.Context, serviceName string) (http.Handler, error) {
 	if !strings.HasSuffix(serviceName, "@internal") {
-		return m.serviceManager.BuildHTTP(rootCtx, serviceName)
+		return nil, nil
 	}
 
 	internalHandler, err := m.get(serviceName)

pkg/server/service/managerfactory.go

@@ -71,13 +71,12 @@ func NewManagerFactory(staticConfiguration static.Configuration, routinesPool *s
 }
 
 // Build creates a service manager.
-func (f *ManagerFactory) Build(configuration *runtime.Configuration) *InternalHandlers {
-	svcManager := NewManager(configuration.Services, f.metricsRegistry, f.routinesPool, f.roundTripperManager)
-
+func (f *ManagerFactory) Build(configuration *runtime.Configuration) *Manager {
 	var apiHandler http.Handler
 	if f.api != nil {
 		apiHandler = f.api(configuration)
 	}
 
-	return NewInternalHandlers(svcManager, apiHandler, f.restHandler, f.metricsHandler, f.pingHandler, f.dashboardHandler, f.acmeHTTPHandler)
+	internalHandlers := NewInternalHandlers(apiHandler, f.restHandler, f.metricsHandler, f.pingHandler, f.dashboardHandler, f.acmeHTTPHandler)
+	return NewManager(configuration.Services, f.metricsRegistry, f.routinesPool, f.roundTripperManager, internalHandlers)
 }

pkg/server/service/service.go

@@ -34,22 +34,28 @@ import (
 const (
 	defaultHealthCheckInterval = 30 * time.Second
 	defaultHealthCheckTimeout  = 5 * time.Second
-)
 
-const defaultMaxBodySize int64 = -1
+	defaultMaxBodySize int64 = -1
+)
 
 // RoundTripperGetter is a roundtripper getter interface.
 type RoundTripperGetter interface {
 	Get(name string) (http.RoundTripper, error)
 }
 
+// ServiceBuilder is a Service builder.
+type ServiceBuilder interface {
+	BuildHTTP(rootCtx context.Context, serviceName string) (http.Handler, error)
+}
+
 // NewManager creates a new Manager.
-func NewManager(configs map[string]*runtime.ServiceInfo, metricsRegistry metrics.Registry, routinePool *safe.Pool, roundTripperManager RoundTripperGetter) *Manager {
+func NewManager(configs map[string]*runtime.ServiceInfo, metricsRegistry metrics.Registry, routinePool *safe.Pool, roundTripperManager RoundTripperGetter, serviceBuilders ...ServiceBuilder) *Manager {
 	return &Manager{
 		routinePool:         routinePool,
 		metricsRegistry:     metricsRegistry,
 		bufferPool:          newBufferPool(),
 		roundTripperManager: roundTripperManager,
+		serviceBuilders:     serviceBuilders,
 		balancers:           make(map[string]healthcheck.Balancers),
 		configs:             configs,
 		rand:                rand.New(rand.NewSource(time.Now().UnixNano())),
@@ -62,6 +68,8 @@ type Manager struct {
 	metricsRegistry     metrics.Registry
 	bufferPool          httputil.BufferPool
 	roundTripperManager RoundTripperGetter
+	serviceBuilders     []ServiceBuilder
+
 	// balancers is the map of all Balancers, keyed by service name.
 	// There is one Balancer per service handler, and there is one service handler per reference to a service
 	// (e.g. if 2 routers refer to the same service name, 2 service handlers are created),
@@ -78,6 +86,17 @@ func (m *Manager) BuildHTTP(rootCtx context.Context, serviceName string) (http.H
 	serviceName = provider.GetQualifiedName(ctx, serviceName)
 	ctx = provider.AddInContext(ctx, serviceName)
 
+	// Must be before we get configs to handle services without config.
+	for _, builder := range m.serviceBuilders {
+		handler, err := builder.BuildHTTP(rootCtx, serviceName)
+		if err != nil {
+			return nil, err
+		}
+		if handler != nil {
+			return handler, nil
+		}
+	}
+
 	conf, ok := m.configs[serviceName]
 	if !ok {
 		return nil, fmt.Errorf("the service %q does not exist", serviceName)

pkg/server/service/service_test.go

@@ -18,9 +18,9 @@ import (
 	"github.com/traefik/traefik/v2/pkg/testhelpers"
 )
 
-type MockForwarder struct{}
+type mockForwarder struct{}
 
-func (MockForwarder) ServeHTTP(http.ResponseWriter, *http.Request) {
+func (mockForwarder) ServeHTTP(http.ResponseWriter, *http.Request) {
 	panic("implement me")
 }
 
@@ -44,14 +44,14 @@ func TestGetLoadBalancer(t *testing.T) {
 					},
 				},
 			},
-			fwd:         &MockForwarder{},
+			fwd:         &mockForwarder{},
 			expectError: true,
 		},
 		{
 			desc:        "Succeeds when there are no servers",
 			serviceName: "test",
 			service:     &dynamic.ServersLoadBalancer{},
-			fwd:         &MockForwarder{},
+			fwd:         &mockForwarder{},
 			expectError: false,
 		},
 		{
@@ -60,7 +60,7 @@ func TestGetLoadBalancer(t *testing.T) {
 			service: &dynamic.ServersLoadBalancer{
 				Sticky: &dynamic.Sticky{Cookie: &dynamic.Cookie{}},
 			},
-			fwd:         &MockForwarder{},
+			fwd:         &mockForwarder{},
 			expectError: false,
 		},
 	}
@@ -476,6 +476,48 @@ func Test1xxResponses(t *testing.T) {
 	}
 }
 
+type serviceBuilderFunc func(ctx context.Context, serviceName string) (http.Handler, error)
+
+func (s serviceBuilderFunc) BuildHTTP(ctx context.Context, serviceName string) (http.Handler, error) {
+	return s(ctx, serviceName)
+}
+
+type internalHandler struct{}
+
+func (internalHandler) ServeHTTP(_ http.ResponseWriter, _ *http.Request) {}
+
+func TestManager_ServiceBuilders(t *testing.T) {
+	var internalHandler internalHandler
+
+	manager := NewManager(map[string]*runtime.ServiceInfo{
+		"test@test": {
+			Service: &dynamic.Service{
+				LoadBalancer: &dynamic.ServersLoadBalancer{},
+			},
+		},
+	}, nil, nil, &RoundTripperManager{
+		roundTrippers: map[string]http.RoundTripper{
+			"default@internal": http.DefaultTransport,
+		},
+	}, serviceBuilderFunc(func(rootCtx context.Context, serviceName string) (http.Handler, error) {
+		if strings.HasSuffix(serviceName, "@internal") {
+			return internalHandler, nil
+		}
+		return nil, nil
+	}))
+
+	h, err := manager.BuildHTTP(context.Background(), "test@internal")
+	require.NoError(t, err)
+	assert.Equal(t, internalHandler, h)
+
+	h, err = manager.BuildHTTP(context.Background(), "test@test")
+	require.NoError(t, err)
+	assert.NotNil(t, h)
+
+	_, err = manager.BuildHTTP(context.Background(), "wrong@test")
+	assert.Error(t, err)
+}
+
 func TestManager_Build(t *testing.T) {
 	testCases := []struct {
 		desc         string