Merge pull request #41 from hellofresh/feature/expose-check

EES-3610 Expose method to run health checks w/out HTTP handler

Author: vgarvardt

README.md

@@ -16,6 +16,8 @@
 
 The library exports `Handler` and `HandlerFunc` functions which are fully compatible with `net/http`.
 
+Additionally, library exports `Measure` function that returns summary status for all the registered health checks, so it can be used in non-HTTP environments.
+
 ### Handler
 
 ```go

health.go

@@ -15,11 +15,15 @@ var (
 	checkMap = make(map[string]Config)
 )
 
+// Status type represents health status
+type Status string
+
+// Possible health statuses
 const (
-	statusOK                 = "OK"
-	statusPartiallyAvailable = "Partially Available"
-	statusUnavailable        = "Unavailable"
-	failureTimeout           = "Timeout during health check"
+	StatusOK                 Status = "OK"
+	StatusPartiallyAvailable Status = "Partially Available"
+	StatusUnavailable        Status = "Unavailable"
+	StatusTimeout            Status = "Timeout during health check"
 )
 
 type (
@@ -41,7 +45,7 @@ type (
 	// Check represents the health check response.
 	Check struct {
 		// Status is the check status.
-		Status string `json:"status"`
+		Status Status `json:"status"`
 		// Timestamp is the time in which the check occurred.
 		Timestamp time.Time `json:"timestamp"`
 		// Failures holds the failed checks along with their messages.
@@ -100,10 +104,30 @@ func Handler() http.Handler {
 
 // HandlerFunc is the HTTP handler function.
 func HandlerFunc(w http.ResponseWriter, r *http.Request) {
+	c := Measure()
+
+	w.Header().Set("Content-Type", "application/json")
+	data, err := json.Marshal(c)
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	code := http.StatusOK
+	if c.Status == StatusUnavailable {
+		code = http.StatusServiceUnavailable
+	}
+	w.WriteHeader(code)
+	w.Write(data)
+}
+
+// Measure runs all the registered health checks and returns summary status
+func Measure() Check {
 	mu.Lock()
 	defer mu.Unlock()
 
-	status := statusOK
+	status := StatusOK
 	total := len(checkMap)
 	failures := make(map[string]string)
 	resChan := make(chan checkResponse, total)
@@ -113,12 +137,14 @@ func HandlerFunc(w http.ResponseWriter, r *http.Request) {
 
 	go func() {
 		defer close(resChan)
+
 		wg.Wait()
 	}()
 
 	for _, c := range checkMap {
 		go func(c Config) {
 			defer wg.Done()
+
 			select {
 			case resChan <- checkResponse{c.Name, c.SkipOnErr, c.Check()}:
 			default:
@@ -129,34 +155,20 @@ func HandlerFunc(w http.ResponseWriter, r *http.Request) {
 		for {
 			select {
 			case <-time.After(c.Timeout):
-				failures[c.Name] = failureTimeout
-				setStatus(&status, c.SkipOnErr)
+				failures[c.Name] = string(StatusTimeout)
+				status = getAvailability(status, c.SkipOnErr)
 				break loop
 			case res := <-resChan:
 				if res.err != nil {
 					failures[res.name] = res.err.Error()
-					setStatus(&status, res.skipOnErr)
+					status = getAvailability(status, res.skipOnErr)
 				}
 				break loop
 			}
 		}
 	}
 
-	w.Header().Set("Content-Type", "application/json")
-	c := newCheck(status, failures)
-	data, err := json.Marshal(c)
-	if err != nil {
-		w.WriteHeader(http.StatusInternalServerError)
-		http.Error(w, err.Error(), http.StatusInternalServerError)
-		return
-	}
-
-	code := http.StatusOK
-	if status == statusUnavailable {
-		code = http.StatusServiceUnavailable
-	}
-	w.WriteHeader(code)
-	w.Write(data)
+	return newCheck(status, failures)
 }
 
 // Reset unregisters all previously set check configs
@@ -167,9 +179,9 @@ func Reset() {
 	checkMap = make(map[string]Config)
 }
 
-func newCheck(status string, failures map[string]string) Check {
+func newCheck(s Status, failures map[string]string) Check {
 	return Check{
-		Status:    status,
+		Status:    s,
 		Timestamp: time.Now(),
 		Failures:  failures,
 		System:    newSystemMetrics(),
@@ -189,10 +201,10 @@ func newSystemMetrics() System {
 	}
 }
 
-func setStatus(status *string, skipOnErr bool) {
-	if skipOnErr && *status != statusUnavailable {
-		*status = statusPartiallyAvailable
-	} else {
-		*status = statusUnavailable
+func getAvailability(s Status, skipOnErr bool) Status {
+	if skipOnErr && s != StatusUnavailable {
+		return StatusPartiallyAvailable
 	}
+
+	return StatusUnavailable
 }

health_test.go

@@ -23,16 +23,12 @@ func TestRegisterWithNoName(t *testing.T) {
 			return nil
 		},
 	})
-	if err == nil {
-		t.Error("health check registration with empty name should return an error, but did not get one")
-	}
+	require.Error(t, err, "health check registration with empty name should return an error")
 }
 
 func TestDoubleRegister(t *testing.T) {
 	Reset()
-	if len(checkMap) != 0 {
-		t.Errorf("checks lenght differes from zero: got %d", len(checkMap))
-	}
+	assert.Len(t, checkMap, 0)
 
 	healthCheckName := "health-check"
 
@@ -63,22 +59,22 @@ func TestHealthHandler(t *testing.T) {
 
 	res := httptest.NewRecorder()
 	req, err := http.NewRequest("GET", "http://localhost/status", nil)
-	if err != nil {
-		t.Fatal(err)
-	}
+	require.NoError(t, err)
 
-	Register(Config{
+	err = Register(Config{
 		Name:      "rabbitmq",
 		SkipOnErr: true,
 		Check:     func() error { return errors.New(checkErr) },
 	})
+	require.NoError(t, err)
 
-	Register(Config{
+	err = Register(Config{
 		Name:  "mongodb",
 		Check: func() error { return nil },
 	})
+	require.NoError(t, err)
 
-	Register(Config{
+	err = Register(Config{
 		Name:      "snail-service",
 		SkipOnErr: true,
 		Timeout:   time.Second * 1,
@@ -87,8 +83,9 @@ func TestHealthHandler(t *testing.T) {
 			return nil
 		},
 	})
+	require.NoError(t, err)
 
-	h := http.Handler(Handler())
+	h := Handler()
 	h.ServeHTTP(res, req)
 
 	assert.Equal(t, http.StatusOK, res.Code, "status handler returned wrong status code")
@@ -97,7 +94,7 @@ func TestHealthHandler(t *testing.T) {
 	err = json.NewDecoder(res.Body).Decode(&body)
 	require.NoError(t, err)
 
-	assert.Equal(t, statusPartiallyAvailable, body["status"], "body returned wrong status")
+	assert.Equal(t, string(StatusPartiallyAvailable), body["status"], "body returned wrong status")
 
 	failure, ok := body["failures"]
 	assert.True(t, ok, "body returned nil failures field")
@@ -106,8 +103,8 @@ func TestHealthHandler(t *testing.T) {
 	assert.True(t, ok, "body returned nil failures.rabbitmq field")
 
 	assert.Equal(t, checkErr, f["rabbitmq"], "body returned wrong status for rabbitmq")
-	assert.Equal(t, failureTimeout, f["snail-service"], "body returned wrong status for snail-service")
+	assert.Equal(t, string(StatusTimeout), f["snail-service"], "body returned wrong status for snail-service")
 
 	Reset()
-	assert.Len(t, checkMap, 0, "checks length diffres from zero")
+	assert.Len(t, checkMap, 0, "checks length differs from zero")
 }