fix(Core/Database): Gracefully close database workers (#20936)

* Gracefully close database workers

* Change init order. Such a silly compiler flag

* Fix hang if db connection failed to open

src/server/database/Database/DatabaseWorker.cpp

@@ -23,16 +23,11 @@ DatabaseWorker::DatabaseWorker(ProducerConsumerQueue<SQLOperation*>* newQueue, M
 {
     _connection = connection;
     _queue = newQueue;
-    _cancelationToken = false;
     _workerThread = std::thread(&DatabaseWorker::WorkerThread, this);
 }
 
 DatabaseWorker::~DatabaseWorker()
 {
-    _cancelationToken = true;
-
-    _queue->Cancel();
-
     _workerThread.join();
 }
 
@@ -47,7 +42,7 @@ void DatabaseWorker::WorkerThread()
 
         _queue->WaitAndPop(operation);
 
-        if (_cancelationToken || !operation)
+        if (!operation)
             return;
 
         operation->SetConnection(_connection);

src/server/database/Database/DatabaseWorker.h

@@ -41,8 +41,6 @@ private:
     void WorkerThread();
     std::thread _workerThread;
 
-    std::atomic<bool> _cancelationToken;
-
     DatabaseWorker(DatabaseWorker const& right) = delete;
     DatabaseWorker& operator=(DatabaseWorker const& right) = delete;
 };

src/server/database/Database/DatabaseWorkerPool.cpp

@@ -112,7 +112,11 @@ uint32 DatabaseWorkerPool<T>::Open()
 template <class T>
 void DatabaseWorkerPool<T>::Close()
 {
-    LOG_INFO("sql.driver", "Closing down DatabasePool '{}'.", GetDatabaseName());
+    LOG_INFO("sql.driver", "Closing down DatabasePool '{}'. Waiting for {} queries to finish...", GetDatabaseName(), _queue->Size());
+
+    // Gracefully close async query queue, worker threads will block when the destructor
+    // is called from the .clear() functions below until the queue is empty
+    _queue->Shutdown();
 
     //! Closes the actualy MySQL connection.
     _connections[IDX_ASYNC].clear();
@@ -432,6 +436,7 @@ uint32 DatabaseWorkerPool<T>::OpenConnections(InternalIndex type, uint8 numConne
         if (uint32 error = connection->Open())
         {
             // Failed to open a connection or invalid version, abort and cleanup
+            _queue->Cancel();
             _connections[type].clear();
             return error;
         }