feat: mysql connection pool..

in progress

include/DatabaseManager.h

@@ -2,10 +2,13 @@
 
 #include <boost/asio.hpp>
 #include <boost/asio/awaitable.hpp>
+#include <boost/asio/ssl.hpp>
 #include <boost/mysql.hpp>
+#include <deque>
 #include <memory>
 #include <queue>
 #include <string>
+#include <vector>
 
 class DatabaseManager {
 public:
@@ -33,24 +36,60 @@ public:
     uint64_t myValue;
   };
 
+  class ConnectionProxy {
+  public:
+    ConnectionProxy(std::unique_ptr<boost::mysql::tcp_ssl_connection> conn,
+                    DatabaseManager &owner)
+        : conn_(std::move(conn)), owner_(owner) {}
+    ~ConnectionProxy();
+
+    // Move only
+    ConnectionProxy(ConnectionProxy &&other) noexcept
+        : conn_(std::move(other.conn_)), owner_(other.owner_) {}
+    ConnectionProxy &operator=(ConnectionProxy &&other) noexcept {
+      if (this != &other) {
+        conn_ = std::move(other.conn_);
+      }
+      return *this;
+    }
+    ConnectionProxy(const ConnectionProxy &) = delete;
+    ConnectionProxy &operator=(const ConnectionProxy &) = delete;
+
+    boost::mysql::tcp_ssl_connection *operator->() { return conn_.get(); }
+    boost::mysql::tcp_ssl_connection &operator*() { return *conn_; }
+
+  private:
+    std::unique_ptr<boost::mysql::tcp_ssl_connection> conn_;
+    DatabaseManager &owner_;
+  };
+
   boost::asio::awaitable<UserData> LoadUser(std::string nickname);
   boost::asio::awaitable<void> SaveUser(std::string nickname, uint64_t gold,
                                         uint32_t swordLevel);
   boost::asio::awaitable<RankingResult> GetRanking(int type,
                                                    std::string nickname);
 
+  boost::asio::awaitable<ConnectionProxy> GetConnection();
+
 private:
   DatabaseManager() = default;
 
-  // 비동기 Mutex 역할을 할 함수들
-  boost::asio::awaitable<void> Lock();
-  void Unlock();
+  void ReturnConnection(std::unique_ptr<boost::mysql::tcp_ssl_connection> conn);
+  boost::asio::awaitable<std::unique_ptr<boost::mysql::tcp_ssl_connection>>
+  CreateNewConnection();
 
-  std::unique_ptr<boost::mysql::tcp_ssl_connection> conn_;
+  std::deque<std::unique_ptr<boost::mysql::tcp_ssl_connection>> pool_;
+  std::queue<std::shared_ptr<boost::asio::steady_timer>> waiting_queue_;
+
+  boost::asio::io_context *io_context_ = nullptr;
   std::unique_ptr<boost::asio::strand<boost::asio::io_context::executor_type>>
       strand_;
 
-  // 비동기 락 시스템을 위한 상태 변수
-  bool is_locked_ = false;
-  std::queue<std::shared_ptr<boost::asio::steady_timer>> waiting_queue_;
+  boost::asio::ssl::context ssl_ctx_{boost::asio::ssl::context::tlsv12_client};
+
+  std::string host_, user_, password_, db_;
+  uint16_t port_;
+
+  uint32_t max_connections_ = 10;
+  uint32_t current_total_connections_ = 0;
 };