rpc: add explicit 200 response for empty HTTP GET (#20952)

rpc/http.go

@@ -208,6 +208,7 @@ func (t *httpServerConn) SetWriteDeadline(time.Time) error { return nil }
 func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	// Permit dumb empty requests for remote health-checks (AWS)
 	if r.Method == http.MethodGet && r.ContentLength == 0 && r.URL.RawQuery == "" {
+		w.WriteHeader(http.StatusOK)
 		return
 	}
 	if code, err := validateRequest(r); err != nil {

rpc/http_test.go

@@ -23,32 +23,78 @@ import (
 	"testing"
 )
 
+func confirmStatusCode(t *testing.T, got, want int) {
+	t.Helper()
+	if got == want {
+		return
+	}
+	if gotName := http.StatusText(got); len(gotName) > 0 {
+		if wantName := http.StatusText(want); len(wantName) > 0 {
+			t.Fatalf("response status code: got %d (%s), want %d (%s)", got, gotName, want, wantName)
+		}
+	}
+	t.Fatalf("response status code: got %d, want %d", got, want)
+}
+
+func confirmRequestValidationCode(t *testing.T, method, contentType, body string, expectedStatusCode int) {
+	t.Helper()
+	request := httptest.NewRequest(method, "http://url.com", strings.NewReader(body))
+	if len(contentType) > 0 {
+		request.Header.Set("Content-Type", contentType)
+	}
+	code, err := validateRequest(request)
+	if code == 0 {
+		if err != nil {
+			t.Errorf("validation: got error %v, expected nil", err)
+		}
+	} else if err == nil {
+		t.Errorf("validation: code %d: got nil, expected error", code)
+	}
+	confirmStatusCode(t, code, expectedStatusCode)
+}
+
 func TestHTTPErrorResponseWithDelete(t *testing.T) {
-	testHTTPErrorResponse(t, http.MethodDelete, contentType, "", http.StatusMethodNotAllowed)
+	confirmRequestValidationCode(t, http.MethodDelete, contentType, "", http.StatusMethodNotAllowed)
 }
 
 func TestHTTPErrorResponseWithPut(t *testing.T) {
-	testHTTPErrorResponse(t, http.MethodPut, contentType, "", http.StatusMethodNotAllowed)
+	confirmRequestValidationCode(t, http.MethodPut, contentType, "", http.StatusMethodNotAllowed)
 }
 
 func TestHTTPErrorResponseWithMaxContentLength(t *testing.T) {
 	body := make([]rune, maxRequestContentLength+1)
-	testHTTPErrorResponse(t,
+	confirmRequestValidationCode(t,
 		http.MethodPost, contentType, string(body), http.StatusRequestEntityTooLarge)
 }
 
 func TestHTTPErrorResponseWithEmptyContentType(t *testing.T) {
-	testHTTPErrorResponse(t, http.MethodPost, "", "", http.StatusUnsupportedMediaType)
+	confirmRequestValidationCode(t, http.MethodPost, "", "", http.StatusUnsupportedMediaType)
 }
 
 func TestHTTPErrorResponseWithValidRequest(t *testing.T) {
-	testHTTPErrorResponse(t, http.MethodPost, contentType, "", 0)
+	confirmRequestValidationCode(t, http.MethodPost, contentType, "", 0)
 }
 
-func testHTTPErrorResponse(t *testing.T, method, contentType, body string, expected int) {
-	request := httptest.NewRequest(method, "http://url.com", strings.NewReader(body))
-	request.Header.Set("content-type", contentType)
-	if code, _ := validateRequest(request); code != expected {
-		t.Fatalf("response code should be %d not %d", expected, code)
+func confirmHTTPRequestYieldsStatusCode(t *testing.T, method, contentType, body string, expectedStatusCode int) {
+	t.Helper()
+	s := Server{}
+	ts := httptest.NewServer(&s)
+	defer ts.Close()
+
+	request, err := http.NewRequest(method, ts.URL, strings.NewReader(body))
+	if err != nil {
+		t.Fatalf("failed to create a valid HTTP request: %v", err)
 	}
+	if len(contentType) > 0 {
+		request.Header.Set("Content-Type", contentType)
+	}
+	resp, err := http.DefaultClient.Do(request)
+	if err != nil {
+		t.Fatalf("request failed: %v", err)
+	}
+	confirmStatusCode(t, resp.StatusCode, expectedStatusCode)
+}
+
+func TestHTTPResponseWithEmptyGet(t *testing.T) {
+	confirmHTTPRequestYieldsStatusCode(t, http.MethodGet, "", "", http.StatusOK)
 }