feat(gameplay): add task ID to chunk requests to discard stale responses

src/dev_panel.cpp

@@ -573,6 +573,7 @@ void DevPanel::show_client_world_table_bar() {
     if (ImGui::Button("Spawn Point")) {
         m_player->set_player_pos({0.0f, 255.0f, 0.0f});
     }
+    ImGui::Text("Chunk Task Id %d", m_app.client_world().get_chunk_task_id());
 }
 
 void DevPanel::show_player_tab_item() {

src/gameplay/client_world.cpp

@@ -416,8 +416,10 @@ void ClientWorld::request_chunk() {
     }
     auto uuid = m_player.get_uuid();
     Arena arena;
+    ++m_chunk_task_id;
     auto* req = Arena::Create<ChunkDataReq>(&arena);
     for (const auto& pos : need_send_pos) {
+        req->set_task_id(m_chunk_task_id.load());
         req->set_uuid(uuid);
         auto* p = req->mutable_pos();
         p->set_x(pos.x);
@@ -429,6 +431,9 @@ void ClientWorld::request_chunk() {
 }
 
 void ClientWorld::receive_chunk(ChunkDataRsp data) {
+    if (data.task_id() < m_chunk_task_id) {
+        return;
+    }
 
     {
         std::lock_guard lock(m_chunks_mutex);
@@ -573,6 +578,9 @@ void ClientWorld::rendering_distance(int rendering_distance) {
                  m_rendering_distance.load());
     request_chunk();
 }
+
+int ClientWorld::get_chunk_task_id() const { return m_chunk_task_id.load(); }
+
 const std::vector<ChunkRenderSnapshot>& ClientWorld::render_snapshots() const {
     return m_render_snapshots;
 };

src/gameplay/server_player.cpp

@@ -31,4 +31,7 @@ bool ServerPlayer::is_disconnect(TickType current_gametick) const {
     return false;
 }
 
+int ServerPlayer::task_id() const { return m_chunk_task_id.load(); }
+void ServerPlayer::task_id(int id) { m_chunk_task_id = id; }
+
 } // namespace Cubed

src/gameplay/server_world.cpp

@@ -524,10 +524,32 @@ glm::vec3 ServerWorld::get_player_pos(const std::string& uuid) const {
     return it->second.get_pos();
 }
 
-void ServerWorld::handle_chunk_req(const std::string& uuid, ChunkPos pos) {
-
+void ServerWorld::handle_chunk_req(int task_id, const std::string& uuid,
+                                   ChunkPos pos) {
+    {
+        std::shared_lock lock(m_player_mutex);
+        auto it = m_players.find(uuid);
+        if (it == m_players.end()) {
+            return;
+        }
+        if (it->second.task_id() < task_id) {
+            // task_id is an atomic variable, can be operated on directly
+            it->second.task_id(task_id);
+        }
+    }
     auto pool = m_gen_thread_pool.load();
-    pool->enqueue([uuid, pos, this]() {
+    pool->enqueue([task_id, uuid, pos, this]() {
+        {
+            std::shared_lock lock(m_player_mutex);
+            auto it = m_players.find(uuid);
+            if (it == m_players.end()) {
+                return;
+            }
+            if (task_id < it->second.task_id()) {
+                // Old chunk requests are simply discarded
+                return;
+            }
+        }
         Arena arean;
         ChunkDataRsp* rsp = Arena::Create<ChunkDataRsp>(&arean);
         auto* rsq_pos = rsp->mutable_pos();
@@ -578,7 +600,7 @@ void ServerWorld::handle_chunk_req(const std::string& uuid, ChunkPos pos) {
             Logger::error("Player {} session not exist", uuid);
             return;
         }
-
+        rsp->set_task_id(task_id);
         s->send(make_packet(*rsp));
     });
 }

src/gameplay/session.cpp

@@ -77,7 +77,8 @@ asio::awaitable<void> Session::read_loop() {
                 // Logger::info("Session: Receive Chunk Data req");
                 if (decode_packet(*req, body_data, header)) {
                     m_server_world.handle_chunk_req(
-                        req->uuid(), ChunkPos(req->pos().x(), req->pos().z()));
+                        req->task_id(), req->uuid(),
+                        ChunkPos(req->pos().x(), req->pos().z()));
                 }
             }
             if (cmd_id == to_num(PacketEnum::BLOCK_CHANGE_REQ)) {

src/proto/world/chunk_data.proto

@@ -3,19 +3,21 @@ syntax = "proto3";
 import "common/chunk_pos.proto";
 
 message ChunkDataReq {
-    string uuid = 1;
-    ChunkPosNet pos = 2;
+    int32 task_id = 1;
+    string uuid = 2;
+    ChunkPosNet pos = 3;
 }
 
 message ChunkDataRsp {
-    ChunkPosNet pos = 1;
-    uint32 chunk_seed = 2;
-    int32 biome_type = 3;
-    repeated uint32 chunk_blocks = 4 [packed=true];
-    repeated uint32 neighbor_blocks_1 = 5 [packed=true];
-    repeated uint32 neighbor_blocks_2 = 6 [packed=true];
-    repeated uint32 neighbor_blocks_3 = 7 [packed=true];
-    repeated uint32 neighbor_blocks_4 = 8 [packed=true];
+    int32 task_id = 1;
+    ChunkPosNet pos = 2;
+    uint32 chunk_seed = 3;
+    int32 biome_type = 4;
+    repeated uint32 chunk_blocks = 5 [packed=true];
+    repeated uint32 neighbor_blocks_1 = 6 [packed=true];
+    repeated uint32 neighbor_blocks_2 = 7 [packed=true];
+    repeated uint32 neighbor_blocks_3 = 8 [packed=true];
+    repeated uint32 neighbor_blocks_4 = 9 [packed=true];
 }
 
 message S2C_ClearAllChunks {