feat: support sse ignore timeout (#2041)

Co-authored-by: Kevin Wan <wanjunfeng@gmail.com>

rest/handler/timeouthandler.go

@@ -24,6 +24,8 @@ const (
 	reason                    = "Request Timeout"
 	headerUpgrade             = "Upgrade"
 	valueWebsocket            = "websocket"
+	headerAccept              = "Accept"
+	valueSSE                  = "text/event-stream"
 )
 
 // TimeoutHandler returns the handler with given timeout.
@@ -56,7 +58,9 @@ func (h *timeoutHandler) errorBody() string {
 }
 
 func (h *timeoutHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-	if r.Header.Get(headerUpgrade) == valueWebsocket {
+	if r.Header.Get(headerUpgrade) == valueWebsocket ||
+		// Server-Sent Event ignore timeout.
+		r.Header.Get(headerAccept) == valueSSE {
 		h.handler.ServeHTTP(w, r)
 		return
 	}
@@ -110,7 +114,7 @@ func (h *timeoutHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 			} else {
 				w.WriteHeader(http.StatusServiceUnavailable)
 			}
-			io.WriteString(w, h.errorBody())
+			_, _ = io.WriteString(w, h.errorBody())
 		})
 		tw.timedOut = true
 	}

rest/handler/timeouthandler_test.go

@@ -156,6 +156,22 @@ func TestTimeoutPanic(t *testing.T) {
 	})
 }
 
+func TestTimeoutSSE(t *testing.T) {
+	timeoutHandler := TimeoutHandler(time.Millisecond)
+	handler := timeoutHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		time.Sleep(time.Millisecond * 10)
+		r.Header.Set("Content-Type", "text/event-stream")
+		r.Header.Set("Cache-Control", "no-cache")
+		r.Header.Set("Connection", "keep-alive")
+		r.Header.Set("Transfer-Encoding", "chunked")
+	}))
+
+	req := httptest.NewRequest(http.MethodGet, "http://localhost", nil)
+	req.Header.Set(headerAccept, valueSSE)
+	resp := httptest.NewRecorder()
+	handler.ServeHTTP(resp, req)
+	assert.Equal(t, http.StatusOK, resp.Code)
+}
 func TestTimeoutWebsocket(t *testing.T) {
 	timeoutHandler := TimeoutHandler(time.Millisecond)
 	handler := timeoutHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {