dreamview: add max update size check.

modules/dreamview/backend/common/dreamview_gflags.cc

@@ -62,3 +62,7 @@ DEFINE_double(sim_map_radius, 300.0,
               "elements around the car.");
 
 DEFINE_int32(dreamview_worker_num, 3, "number of dreamview thread workers");
+DEFINE_bool(enable_update_size_check, true,
+            "True to check if the update byte number is less than threshold");
+DEFINE_uint32(max_update_size, 1000000,
+             "number of max update bytes allowed to push to dreamview FE");

modules/dreamview/backend/common/dreamview_gflags.h

@@ -42,5 +42,7 @@ DECLARE_string(ssl_certificate);
 DECLARE_double(sim_map_radius);
 
 DECLARE_int32(dreamview_worker_num);
+DECLARE_bool(enable_update_size_check);
+DECLARE_uint32(max_update_size);
 
 #endif  // MODULES_DREAMVIEW_BACKEND_COMMON_DREAMVIEW_GFLAGS_H_

modules/dreamview/backend/simulation_world/simulation_world_updater.cc

@@ -119,6 +119,11 @@ SimulationWorldUpdater::SimulationWorldUpdater(WebSocketHandler *websocket,
           to_send = requestPlanning ? simulation_world_with_planning_json_
                                     : simulation_world_json_;
         }
+        if (FLAGS_enable_update_size_check && !requestPlanning &&
+            to_send.size() > FLAGS_max_update_size) {
+          AWARN << "update size is too big:" << to_send.size();
+          return;
+        }
         websocket_->SendData(conn, to_send, true);
       });