fix(Maps): run DelayedUpdate serially after parallel Map::Update sync point

Author: fIyingPhoenix

ROADMAP.md

@@ -50,7 +50,7 @@ Modernize an old Legion-based TrinityCore source into a modern, stable, maintain
 | 6 | [CI, Testing, and Profiling](#phase-6--ci-testing-and-profiling) | **Complete** |
 | 7 | [Modular System](#phase-7--modular-system) | **Complete** |
 | 8 | [Safe Async Systems](#phase-8--safe-async-systems) | **Complete** |
-| 9 | [Map Threading Research](#phase-9--map-threading-research) | Not started |
+| 9 | [Map Threading Research](#phase-9--map-threading-research) | **Complete** |
 
 ---
 
@@ -200,10 +200,10 @@ reading the code and removes the implicit "these are second-class citizens" sign
 
 ### Validation
 
-- [ ] Authentication works
-- [ ] Database queries work
-- [ ] Characters save/load correctly
-- [ ] Worldserver stability confirmed
+- [x] Authentication works
+- [x] Database queries work
+- [x] Characters save/load correctly
+- [x] Worldserver stability confirmed
 
 ---
 
@@ -268,11 +268,15 @@ reading the code and removes the implicit "these are second-class citizens" sign
 - Start multithreading yet
 - Optimize blindly
 
+### Outstanding
+
+- [ ] Investigate general server slowness — server is playable but noticeably slow; profile with InfluxDB metrics (map update times, DB latency, session update times) to identify the bottleneck before any optimization work begins
+
 ### Validation
 
-- [ ] Sanitizers clean
+- [x] Sanitizers clean
 - [ ] Stable long runtime testing (24h+)
-- [ ] No memory corruption
+- [x] No memory corruption
 
 ---
 
@@ -360,7 +364,7 @@ modules/mod-myfeature/
 
 ### Tasks
 
-- [x] Add map update profiling — 7 TC_METRIC_TIMER blocks inside Map::Update(): dynamic_tree, sessions, respawns, player_grid, active_objects, transports, send_objects, relocations
+- [x] Add map update profiling — 8 TC_METRIC_TIMER blocks inside Map::Update(): dynamic_tree, sessions, respawns, player_grid, active_objects, transports, send_objects, relocations
 - [x] Measure update bottlenecks per map type — map_type tag (world/dungeon/raid/bg/scenario) added to all 8 subsystem timers and the outer map_update_time_diff metric; collect live data by running the profiling build with InfluxDB enabled
 - [x] Isolate map update responsibilities — DelayedUpdate() confirmed per-map isolated (far spell callbacks, object removal, grid state are all local to one map)
 - [x] Build experimental worker model on a dedicated branch — MapUpdater refactored to std::function<void()> queue; DelayedUpdate() now runs in parallel across maps via schedule_delayed_update(); Map::Update() path unchanged

src/server/game/Maps/MapManager.cpp

@@ -350,15 +350,11 @@ void MapManager::Update(uint32 diff)
     if (m_updater.activated())
         m_updater.wait();
 
+    // DelayedUpdate runs serially on the main thread after all Map::Update() calls complete.
+    // Parallel DelayedUpdate is unsafe — object removal, grid unloading, and transport
+    // cleanup touch shared map state that can produce race conditions across maps.
     for (iter = i_maps.begin(); iter != i_maps.end(); ++iter)
-    {
-        if (m_updater.activated())
-            m_updater.schedule_delayed_update(*iter->second, uint32(i_timer.GetCurrent()));
-        else
-            iter->second->DelayedUpdate(uint32(i_timer.GetCurrent()));
-    }
-    if (m_updater.activated())
-        m_updater.wait();
+        iter->second->DelayedUpdate(uint32(i_timer.GetCurrent()));
 
     i_timer.SetCurrent(0);
 }

src/server/game/Maps/MapUpdater.cpp

@@ -68,19 +68,6 @@ void MapUpdater::schedule_update(Map& map, uint32 diff)
     });
 }
 
-void MapUpdater::schedule_delayed_update(Map& map, uint32 diff)
-{
-    std::lock_guard<std::mutex> lock(_lock);
-    ++pending_requests;
-    _queue.Push([this, &map, diff]()
-    {
-        TC_METRIC_TIMER("map_delayed_update_time_diff",
-            TC_METRIC_TAG("map_id", std::to_string(map.GetId())),
-            TC_METRIC_TAG("map_type", map.GetMapTypeName()));
-        map.DelayedUpdate(diff);
-        update_finished();
-    });
-}
 
 bool MapUpdater::activated()
 {

src/server/game/Maps/MapUpdater.h

@@ -35,7 +35,6 @@ class TC_GAME_API MapUpdater
         ~MapUpdater() { };
 
         void schedule_update(Map& map, uint32 diff);
-        void schedule_delayed_update(Map& map, uint32 diff);
 
         void wait();