feat(server): Adding way to register pingers (#25)

pkg/httputils/httputils.go

@@ -21,9 +21,12 @@ var (
 	_ swagger.Provider = (&app{}).Swagger
 )
 
+// Pinger describes a function to check liveness of app
+type Pinger = func() error
+
 // App of package
 type App interface {
-	Health(http.Handler) App
+	Health(Pinger) App
 	Middleware(model.Middleware) App
 	ListenAndServe(http.Handler) (*http.Server, <-chan error)
 	ListenServeWait(http.Handler)
@@ -49,7 +52,7 @@ type app struct {
 
 	shutdown    bool
 	middlewares []model.Middleware
-	health      http.Handler
+	pingers     []Pinger
 }
 
 // Flags adds flags for configuring package
@@ -79,8 +82,8 @@ func New(config Config) App {
 		okStatus:      *config.okStatus,
 		graceDuration: graceDuration,
 
-		health:      HealthHandler(*config.okStatus),
 		middlewares: make([]model.Middleware, 0),
+		pingers:     make([]Pinger, 0),
 	}
 }
 
@@ -102,15 +105,29 @@ func versionHandler() http.Handler {
 	})
 }
 
-// HealthHandler for dealing with state of app
-func HealthHandler(okStatus int) http.Handler {
+// Health set health http handler
+func (a *app) healthHandler() http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != http.MethodGet {
 			w.WriteHeader(http.StatusMethodNotAllowed)
 			return
 		}
 
-		w.WriteHeader(okStatus)
+		if a.shutdown {
+			w.WriteHeader(http.StatusServiceUnavailable)
+			return
+		}
+
+		for _, pinger := range a.pingers {
+			if err := pinger(); err != nil {
+				logger.Error("unable to ping: %s", err)
+
+				w.WriteHeader(http.StatusServiceUnavailable)
+				return
+			}
+		}
+
+		w.WriteHeader(a.okStatus)
 	})
 }
 
@@ -125,16 +142,16 @@ func ChainMiddlewares(handler http.Handler, middlewares ...model.Middleware) htt
 	return result
 }
 
-// Health set health http handler
-func (a *app) Health(health http.Handler) App {
-	a.health = health
+// Middleware add given middleware to list
+func (a *app) Middleware(middleware model.Middleware) App {
+	a.middlewares = append(a.middlewares, middleware)
 
 	return a
 }
 
-// Middleware add given middleware to list
-func (a *app) Middleware(middleware model.Middleware) App {
-	a.middlewares = append(a.middlewares, middleware)
+// Health add given pinger to list
+func (a *app) Health(pinger Pinger) App {
+	a.pingers = append(a.pingers, pinger)
 
 	return a
 }
@@ -173,18 +190,15 @@ func (a *app) Swagger() (swagger.Configuration, error) {
 // ListenAndServe starts server
 func (a *app) ListenAndServe(handler http.Handler) (*http.Server, <-chan error) {
 	versionHandler := versionHandler()
+	healthHandler := a.healthHandler()
 	defaultHandler := ChainMiddlewares(handler, a.middlewares...)
 
 	httpServer := &http.Server{
 		Addr: a.listenAddress,
 		Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			switch r.URL.Path {
 			case "/health":
-				if a.shutdown {
-					w.WriteHeader(http.StatusServiceUnavailable)
-					return
-				}
-				a.health.ServeHTTP(w, r)
+				healthHandler.ServeHTTP(w, r)
 
 			case "/version":
 				versionHandler.ServeHTTP(w, r)

pkg/httputils/httputils_test.go

@@ -89,43 +89,6 @@ func TestVersionHandler(t *testing.T) {
 	}
 }
 
-func TestHealthHandler(t *testing.T) {
-	var cases = []struct {
-		intention  string
-		request    *http.Request
-		want       string
-		wantStatus int
-	}{
-		{
-			"simple",
-			httptest.NewRequest(http.MethodGet, "/", nil),
-			"",
-			http.StatusNoContent,
-		},
-		{
-			"invalid method",
-			httptest.NewRequest(http.MethodOptions, "/", nil),
-			"",
-			http.StatusMethodNotAllowed,
-		},
-	}
-
-	for _, testCase := range cases {
-		t.Run(testCase.intention, func(t *testing.T) {
-			writer := httptest.NewRecorder()
-			HealthHandler(http.StatusNoContent).ServeHTTP(writer, testCase.request)
-
-			if result := writer.Code; result != testCase.wantStatus {
-				t.Errorf("HealthHandler = %d, want %d", result, testCase.wantStatus)
-			}
-
-			if result, _ := request.ReadBodyResponse(writer.Result()); string(result) != testCase.want {
-				t.Errorf("HealthHandler = `%s`, want `%s`", string(result), testCase.want)
-			}
-		})
-	}
-}
-
 func TestChainMiddlewares(t *testing.T) {
 	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Write([]byte("handler"))