fix: #2700, timeout not enough for writing responses (#2738)

* fix: #2700, timeout not enough for writing responses

* fix: test fail

* chore: add comments

rest/engine.go

@@ -287,10 +287,9 @@ func (ng *engine) withTimeout() internal.StartOption {
 			// without this timeout setting, the server will time out and respond 503 Service Unavailable,
 			// which triggers the circuit breaker.
 			svr.ReadTimeout = 4 * time.Duration(timeout) * time.Millisecond / 5
-			// factor 0.9, to avoid clients not reading the response
+			// factor 1.1, to avoid servers don't have enough time to write responses.
-			// without this timeout setting, the server will time out and respond 503 Service Unavailable,
+			// setting the factor less than 1.0 may lead clients not receiving the responses.
-			// which triggers the circuit breaker.
+			svr.WriteTimeout = 11 * time.Duration(timeout) * time.Millisecond / 10
-			svr.WriteTimeout = 9 * time.Duration(timeout) * time.Millisecond / 10
 		}
 	}
 }

rest/engine_test.go

@@ -323,7 +323,7 @@ func TestEngine_withTimeout(t *testing.T) {
 
 			assert.Equal(t, time.Duration(test.timeout)*time.Millisecond*4/5, svr.ReadTimeout)
 			assert.Equal(t, time.Duration(0), svr.ReadHeaderTimeout)
-			assert.Equal(t, time.Duration(test.timeout)*time.Millisecond*9/10, svr.WriteTimeout)
+			assert.Equal(t, time.Duration(test.timeout)*time.Millisecond*11/10, svr.WriteTimeout)
 			assert.Equal(t, time.Duration(0), svr.IdleTimeout)
 		})
 	}

rest/server.go

@@ -90,6 +90,25 @@ func (s *Server) Routes() []Route {
 	return routes
 }
 
+// ServeHTTP is for test purpose, allow developer to do a unit test with
+// all defined router without starting an HTTP Server.
+//
+// For example:
+//
+//	server := MustNewServer(...)
+//	server.addRoute(...) // router a
+//	server.addRoute(...) // router b
+//	server.addRoute(...) // router c
+//
+//	r, _ := http.NewRequest(...)
+//	w := httptest.NewRecorder(...)
+//	server.ServeHTTP(w, r)
+//	// verify the response
+func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	s.ngin.bindRoutes(s.router)
+	s.router.ServeHTTP(w, r)
+}
+
 // Start starts the Server.
 // Graceful shutdown is enabled by default.
 // Use proc.SetTimeToForceQuit to customize the graceful shutdown period.
@@ -307,8 +326,3 @@ func newCorsRouter(router httpx.Router, headerFn func(http.Header), origins ...s
 func (c *corsRouter) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	c.middleware(c.Router.ServeHTTP)(w, r)
 }
-
-func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-	s.ngin.bindRoutes(s.router)
-	s.router.ServeHTTP(w, r)
-}