Add /_/health endpoint to of-watchdog

Introduce new endpoint `/_/health` to watchdog for health status of
functions which checks for `/tmp/.lock` file

Added tests for healthHandler

Issues: openfaas/faas#547

Signed-off-by: Vivek Singh <vivekkmr45@yahoo.in>

main.go

@@ -41,6 +41,7 @@ func main() {
 	}
 
 	http.HandleFunc("/", requestHandler)
+	http.HandleFunc("/_/health", makeHealthHandler())
 	log.Fatal(s.ListenAndServe())
 }
 
@@ -227,3 +228,29 @@ func makeHTTPRequestHandler(watchdogConfig config.WatchdogConfig) func(http.Resp
 
 	}
 }
+
+func lockFilePresent() bool {
+	path := filepath.Join(os.TempDir(), ".lock")
+	if _, err := os.Stat(path); os.IsNotExist(err) {
+		return false
+	}
+	return true
+}
+
+func makeHealthHandler() func(w http.ResponseWriter, r *http.Request) {
+	return func(w http.ResponseWriter, r *http.Request) {
+		switch r.Method {
+		case http.MethodGet:
+			if lockFilePresent() == false {
+				w.WriteHeader(http.StatusInternalServerError)
+				return
+			}
+
+			w.WriteHeader(http.StatusOK)
+			w.Write([]byte("OK"))
+			break
+		default:
+			w.WriteHeader(http.StatusMethodNotAllowed)
+		}
+	}
+}

requesthandler_test.go

@@ -0,0 +1,83 @@
+package main
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestHealthHandler_StatusOK_LockFilePresent(t *testing.T) {
+	rr := httptest.NewRecorder()
+
+	present := lockFilePresent()
+
+	if present == false {
+		if err := lock(); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	req, err := http.NewRequest(http.MethodGet, "/_/health", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	handler := makeHealthHandler()
+	handler(rr, req)
+
+	required := http.StatusOK
+	if status := rr.Code; status != required {
+		t.Errorf("handler returned wrong status code - want: %v, got: %v", required, status)
+	}
+
+}
+
+func TestHealthHandler_StatusInternalServerError_LockFileNotPresent(t *testing.T) {
+	rr := httptest.NewRecorder()
+
+	if lockFilePresent() == true {
+		if err := removeLockFile(); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	req, err := http.NewRequest(http.MethodGet, "/_/health", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	handler := makeHealthHandler()
+	handler(rr, req)
+
+	required := http.StatusInternalServerError
+	if status := rr.Code; status != required {
+		t.Errorf("handler returned wrong status code - want: %v, got: %v", required, status)
+	}
+}
+
+func TestHealthHandler_StatusMethodNotAllowed_ForWriteableVerbs(t *testing.T) {
+	rr := httptest.NewRecorder()
+
+	verbs := []string{http.MethodPost, http.MethodPut, http.MethodDelete}
+
+	for _, verb := range verbs {
+		req, err := http.NewRequest(verb, "/_/health", nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		handler := makeHealthHandler()
+		handler(rr, req)
+
+		required := http.StatusMethodNotAllowed
+		if status := rr.Code; status != required {
+			t.Errorf("handler returned wrong status code -  want: %v, got: %v", required, status)
+		}
+	}
+}
+
+func removeLockFile() error {
+	path := filepath.Join(os.TempDir(), ".lock")
+	removeErr := os.Remove(path)
+	return removeErr
+}