Roughly define database pool interface

CMakeLists.txt

@@ -1840,6 +1840,8 @@ set_src(ENGINE_SERVER GLOB_RECURSE src/engine/server
   authmanager.cpp
   authmanager.h
   databases/connection.h
+  databases/connection_pool.cpp
+  databases/connection_pool.h
   databases/mysql.cpp
   databases/mysql.h
   name_ban.cpp

src/engine/server/databases/connection.h

@@ -25,8 +25,9 @@ public:
 		SUCCESS,
 		ERROR,
 	};
-	// returns true if connection was established
+	// tries to allocate the connection from the pool established
 	virtual Status Connect() = 0;
+	// has to be called to return the connection back to the pool
 	virtual void Disconnect() = 0;
 
 	// get exclusive read/write access to the database

src/engine/server/databases/connection_pool.cpp

@@ -0,0 +1,42 @@
+#include "connection_pool.h"
+
+// helper struct to hold thread data
+struct CSqlExecData
+{
+	CSqlExecData(
+			bool (*pFuncPtr) (IDbConnection *, const ISqlData *),
+			const ISqlData *pSqlRequestData
+	);
+	~CSqlExecData();
+
+	bool (*m_pFuncPtr) (IDbConnection*, const ISqlData *);
+	std::unique_ptr<const ISqlData> m_pSqlRequestData;
+};
+
+CDbConnectionPool::CDbConnectionPool()
+{
+}
+
+CDbConnectionPool::~CDbConnectionPool()
+{
+}
+
+void CDbConnectionPool::RegisterDatabase(std::unique_ptr<IDbConnection> pDatabase, Mode DatabaseMode)
+{
+}
+
+void CDbConnectionPool::Execute(
+		bool (*pFuncPtr) (IDbConnection *, const ISqlData *),
+		std::unique_ptr<ISqlData> pSqlRequestData)
+{
+}
+
+void CDbConnectionPool::ExecuteWrite(
+		bool (*pFuncPtr) (IDbConnection *, const ISqlData *),
+		std::unique_ptr<ISqlData> pSqlRequestData)
+{
+}
+
+void CDbConnectionPool::Shutdown()
+{
+}

src/engine/server/databases/connection_pool.h

@@ -0,0 +1,46 @@
+#ifndef ENGINE_SERVER_DATABASES_CONNECTION_POOL_H
+#define ENGINE_SERVER_DATABASES_CONNECTION_POOL_H
+
+#include "connection.h"
+
+#include <base/tl/threading.h>
+#include <memory>
+#include <vector>
+
+struct ISqlData
+{
+	virtual ~ISqlData();
+};
+
+class CDbConnectionPool
+{
+public:
+	CDbConnectionPool();
+	~CDbConnectionPool();
+
+	enum Mode
+	{
+		READ,
+		WRITE,
+		WRITE_BACKUP,
+		NUM_MODES,
+	};
+
+	void RegisterDatabase(std::unique_ptr<IDbConnection> pDatabase, Mode DatabaseMode);
+
+	void Execute(
+			bool (*pFuncPtr) (IDbConnection *, const ISqlData *),
+			std::unique_ptr<ISqlData> pSqlRequestData);
+	// writes to WRITE_BACKUP server in case of failure
+	void ExecuteWrite(
+			bool (*pFuncPtr) (IDbConnection *, const ISqlData *),
+			std::unique_ptr<ISqlData> pSqlRequestData);
+
+	void Shutdown();
+
+private:
+	std::vector<std::unique_ptr<IDbConnection>> m_aapDbConnections[NUM_MODES];
+	lock m_ConnectionLookupLock[NUM_MODES];
+};
+
+#endif // ENGINE_SERVER_DATABASES_CONNECTION_POOL_H