Use common httpserver across fission (#2409)

* Defining httpserver package to capture httpserver shutdown and
introduces uniform running of http server across codebase.
* Add unit tests for httpserver

Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>

pkg/utils/httpserver/server.go

@@ -0,0 +1,32 @@
+package httpserver
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+
+	"go.uber.org/zap"
+)
+
+func StartServer(ctx context.Context, log *zap.Logger, svc string, port string, handler http.Handler) {
+	server := http.Server{
+		Addr:    fmt.Sprintf(":%s", port),
+		Handler: handler,
+	}
+	l := log.With(zap.String("service", svc), zap.String("addr", server.Addr))
+	l.Info("starting server")
+	go func() {
+		if err := server.ListenAndServe(); err != nil {
+			if err != http.ErrServerClosed {
+				l.Error("server error", zap.Error(err))
+			}
+		}
+	}()
+	<-ctx.Done()
+	l.Info("shutting down server")
+	if err := server.Shutdown(ctx); err != nil {
+		if err != context.Canceled && err != context.DeadlineExceeded {
+			l.Error("server shutdown error", zap.Error(err))
+		}
+	}
+}

pkg/utils/httpserver/server_test.go

@@ -0,0 +1,62 @@
+package httpserver
+
+import (
+	"context"
+	"io/ioutil"
+	"net/http"
+	"testing"
+
+	"github.com/gorilla/mux"
+	"go.uber.org/zap"
+
+	"github.com/fission/fission/pkg/utils/loggerfactory"
+)
+
+func TestStartServer(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	logger := loggerfactory.GetLogger()
+	m := mux.NewRouter()
+	m.Handle("/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		_, err := w.Write([]byte("test handler"))
+		if err != nil {
+			logger.Error("failed to write response", zap.Error(err))
+		}
+	}))
+	go StartServer(ctx, logger, "test", "8999", m)
+
+	tests := []struct {
+		URL        string
+		StatusCode int
+		Body       string
+	}{
+		{
+			URL:        "http://localhost:8999",
+			StatusCode: http.StatusOK,
+			Body:       "test handler",
+		},
+		{
+			URL:        "http://localhost:8999/notfound",
+			StatusCode: http.StatusNotFound,
+			Body:       "404 page not found\n",
+		},
+	}
+	for _, test := range tests {
+		resp, err := http.Get(test.URL)
+		if err != nil {
+			t.Errorf("failed to make get request %v: %v", test.URL, err)
+		}
+		defer resp.Body.Close()
+		if resp.StatusCode != test.StatusCode {
+			t.Errorf("expected status code %v, got %v", test.StatusCode, resp.StatusCode)
+		}
+		body, err := ioutil.ReadAll(resp.Body)
+		if err != nil {
+			t.Errorf("failed to read response body: %v", err)
+		}
+		if string(body) != test.Body {
+			t.Errorf("expected body \"%v\", got \"%v\"", test.Body, string(body))
+		}
+	}
+}