feat: DB 커넥션 풀 기능 추가

TODO: 동시에 여러 DB 연결 확인해야함. 현재 기능만 확인 완료

include/DatabaseManager.h

@@ -39,18 +39,38 @@ public:
   boost::asio::awaitable<RankingResult> GetRanking(int type,
                                                    std::string nickname);
 
+  //  내부용 객체
+  class PooledConnection {
+  public:
+    PooledConnection(DatabaseManager &manager,
+                     std::unique_ptr<boost::mysql::tcp_ssl_connection> conn);
+    ~PooledConnection();
+
+    boost::mysql::tcp_ssl_connection &Get();
+    boost::mysql::tcp_ssl_connection *operator->();
+
+  private:
+    DatabaseManager &manager_;
+    std::unique_ptr<boost::mysql::tcp_ssl_connection> conn_;
+  };
+
+  boost::asio::awaitable<std::unique_ptr<PooledConnection>> GetConnection();
+
 private:
   DatabaseManager() = default;
+  void ReturnConnection(std::unique_ptr<boost::mysql::tcp_ssl_connection> conn);
 
-  // 비동기 Mutex 역할을 할 함수들
+  // DB 접속 정보 저장용 (새로운 커넥션 생성 시 필요)
-  boost::asio::awaitable<void> Lock();
+  std::string host_, user_, password_, db_;
-  void Unlock();
+  uint16_t port_;
 
-  std::unique_ptr<boost::mysql::tcp_ssl_connection> conn_;
   std::unique_ptr<boost::asio::strand<boost::asio::io_context::executor_type>>
       strand_;
 
-  // 비동기 락 시스템을 위한 상태 변수
+  // 풀 상태 관리
-  bool is_locked_ = false;
+  std::vector<std::unique_ptr<boost::mysql::tcp_ssl_connection>>
+      available_conns_;
   std::queue<std::shared_ptr<boost::asio::steady_timer>> waiting_queue_;
+  const uint16_t max_pool_size_ = 10;
+  int16_t current_total_conns_ = 0;
 };

server/DatabaseManager.cpp

@@ -1,8 +1,27 @@
 #include "DatabaseManager.h"
 #include "Logger.h"
 #include <boost/asio/bind_executor.hpp>
+#include <boost/asio/post.hpp>
 #include <boost/asio/use_awaitable.hpp>
-#include <boost/mysql.hpp>
+
+DatabaseManager::PooledConnection::PooledConnection(
+    DatabaseManager &manager,
+    std::unique_ptr<boost::mysql::tcp_ssl_connection> conn)
+    : manager_(manager), conn_(std::move(conn)) {}
+
+DatabaseManager::PooledConnection::~PooledConnection() {
+  if (conn_)
+    manager_.ReturnConnection(std::move(conn_));
+}
+
+boost::mysql::tcp_ssl_connection &DatabaseManager::PooledConnection::Get() {
+  return *conn_;
+}
+
+boost::mysql::tcp_ssl_connection *
+DatabaseManager::PooledConnection::operator->() {
+  return conn_.get();
+}
 
 DatabaseManager &DatabaseManager::GetInstance() {
   static DatabaseManager instance;
@@ -13,97 +32,112 @@ bool DatabaseManager::Init(boost::asio::io_context &io_context,
                            const std::string &host, uint16_t port,
                            const std::string &user, const std::string &password,
                            const std::string &db) {
-  try {
+  host_ = host;
-    strand_ = std::make_unique<
+  port_ = port;
-        boost::asio::strand<boost::asio::io_context::executor_type>>(
+  user_ = user;
-        io_context.get_executor());
+  password_ = password;
+  db_ = db;
 
-    boost::asio::ip::tcp::resolver resolver(io_context.get_executor());
+  strand_ = std::make_unique<
-    auto endpoints = resolver.resolve(host, std::to_string(port));
+      boost::asio::strand<boost::asio::io_context::executor_type>>(
+      io_context.get_executor());
 
-    boost::mysql::handshake_params params(user, password, db);
+  Logger::Log("DatabaseManager Init 성공 (Connection Pool 준비됨): ", host, ":",
-    static boost::asio::ssl::context ssl_ctx(
+              port);
-        boost::asio::ssl::context::tlsv12_client);
+  return true;
-
-    conn_ = std::make_unique<boost::mysql::tcp_ssl_connection>(
-        io_context.get_executor(), ssl_ctx);
-    conn_->connect(*endpoints.begin(), params);
-
-    Logger::Log("Database 연결 성공 (AsyncLock 적용): ", host, ":", port);
-    return true;
-  } catch (const std::exception &e) {
-    Logger::Log("Database 연결 실패: ", e.what());
-    return false;
-  }
 }
 
-// 비동기 락 획득 (이미 락이 걸려있으면 대기열에 들어감)
+boost::asio::awaitable<std::unique_ptr<DatabaseManager::PooledConnection>>
-boost::asio::awaitable<void> DatabaseManager::Lock() {
+DatabaseManager::GetConnection() {
   auto executor = co_await boost::asio::this_coro::executor;
 
   co_await boost::asio::post(
       boost::asio::bind_executor(*strand_, boost::asio::use_awaitable));
 
-  if (!is_locked_) {
+  std::unique_ptr<boost::mysql::tcp_ssl_connection> conn;
-    is_locked_ = true;
+
-    co_return;
+  if (!available_conns_.empty()) {
+    // 가져오기
+    conn = std::move(available_conns_.back());
+    available_conns_.pop_back();
+  } else if (current_total_conns_ < max_pool_size_) {
+    // 생성
+    current_total_conns_++;
+    try {
+      static boost::asio::ssl::context ssl_ctx(
+          boost::asio::ssl::context::tlsv12_client);
+      conn =
+          std::make_unique<boost::mysql::tcp_ssl_connection>(executor, ssl_ctx);
+
+      boost::asio::ip::tcp::resolver resolver(executor);
+      auto endpoints = resolver.resolve(host_, std::to_string(port_));
+      boost::mysql::handshake_params params(user_, password_, db_);
+
+      co_await conn->async_connect(*endpoints.begin(), params,
+                                   boost::asio::use_awaitable);
+      Logger::Log("새로운 DB 커넥션 생성됨. 현재 총 개수: ",
+                  current_total_conns_);
+    } catch (const std::exception &e) {
+      current_total_conns_--;
+      Logger::Log("커넥션 생성 실패: ", e.what());
+      throw;
+    }
+  } else {
+    // 대기
+    auto timer = std::make_shared<boost::asio::steady_timer>(
+        executor, std::chrono::steady_clock::time_point::max());
+    waiting_queue_.push(timer);
+
+    try {
+      co_await timer->async_wait(boost::asio::use_awaitable);
+    } catch (...) {
+    }
+
+    co_return co_await GetConnection();
   }
 
-  // 이미 잠겨있으면 타이머를 만들어서 대기열에 추가 (비동기 대기)
+  co_return std::make_unique<PooledConnection>(*this, std::move(conn));
-  auto timer = std::make_shared<boost::asio::steady_timer>(
-      executor, std::chrono::steady_clock::time_point::max());
-  waiting_queue_.push(timer);
-
-  try {
-    co_await timer->async_wait(boost::asio::use_awaitable);
-  } catch (...) {
-    // 타이머 취소(Unlock에서 호출함)되면 성공적으로 락을 획득한 것으로 간주
-  }
-  co_return;
 }
 
-// 비동기 락 해제 (대기열에 다음 사람이 있으면 깨워줌)
+void DatabaseManager::ReturnConnection(
-void DatabaseManager::Unlock() {
+    std::unique_ptr<boost::mysql::tcp_ssl_connection> conn) {
-  boost::asio::dispatch(*strand_, [this]() {
+  boost::asio::dispatch(*strand_, [this, conn = std::move(conn)]() mutable {
-    if (waiting_queue_.empty()) {
+    if (!waiting_queue_.empty()) {
-      is_locked_ = false;
+      // 대기 중이면 넣어주기
-    } else {
+      available_conns_.push_back(std::move(conn));
       auto next = waiting_queue_.front();
       waiting_queue_.pop();
       next->cancel();
+    } else {
+      // 없으면 보관
+      available_conns_.push_back(std::move(conn));
     }
   });
 }
 
 boost::asio::awaitable<DatabaseManager::UserData>
 DatabaseManager::LoadUser(std::string nickname) {
-  co_await Lock();
-
   try {
-    if (!conn_) {
+    auto conn_ptr = co_await GetConnection();
-      Unlock();
+    auto &conn = conn_ptr->Get();
-      co_return UserData{nickname, 10000, 0};
-    }
 
     boost::mysql::results result;
-    boost::mysql::statement stmt = co_await conn_->async_prepare_statement(
+    boost::mysql::statement stmt = co_await conn.async_prepare_statement(
         "SELECT username, gold, sword_level, max_sword_level FROM users WHERE "
         "username = ?",
         boost::asio::use_awaitable);
-    co_await conn_->async_execute(stmt.bind(nickname), result,
+    co_await conn.async_execute(stmt.bind(nickname), result,
-                                  boost::asio::use_awaitable);
+                                boost::asio::use_awaitable);
 
     if (result.rows().empty()) {
-      boost::mysql::statement ins_stmt =
+      boost::mysql::statement ins_stmt = co_await conn.async_prepare_statement(
-          co_await conn_->async_prepare_statement(
+          "INSERT INTO users (username, gold, sword_level) VALUES (?, 10000, "
-              "INSERT INTO users (username, gold, sword_level) VALUES (?, "
+          "0)",
-              "10000, 0)",
+          boost::asio::use_awaitable);
-              boost::asio::use_awaitable);
+      co_await conn.async_execute(ins_stmt.bind(nickname), result,
-      co_await conn_->async_execute(ins_stmt.bind(nickname), result,
+                                  boost::asio::use_awaitable);
-                                    boost::asio::use_awaitable);
       Logger::Log("새로운 유저 탄생 (DB): ", nickname);
-      Unlock();
+      co_return UserData{nickname, 10000, 0, 0};
-      co_return UserData{nickname, 10000, 0};
     } else {
       auto row = result.rows().at(0);
       UserData data;
@@ -111,56 +145,44 @@ DatabaseManager::LoadUser(std::string nickname) {
       data.gold = row.at(1).as_uint64();
       data.swordLevel = (uint32_t)row.at(2).as_int64();
       data.maxSwordLevel = (uint32_t)row.at(3).as_int64();
-      Unlock();
       co_return data;
     }
   } catch (const std::exception &e) {
     Logger::Log("LoadUser 에러: ", e.what());
-    Unlock();
+    co_return UserData{nickname, 10000, 0, 0};
-    co_return UserData{nickname, 10000, 0};
   }
 }
 
 boost::asio::awaitable<void> DatabaseManager::SaveUser(std::string nickname,
                                                        uint64_t gold,
                                                        uint32_t swordLevel) {
-  co_await Lock();
-
   try {
-    if (!conn_) {
+    auto conn_ptr = co_await GetConnection();
-      Unlock();
+    auto &conn = conn_ptr->Get();
-      co_return;
-    }
 
     boost::mysql::results result;
-    boost::mysql::statement stmt = co_await conn_->async_prepare_statement(
+    boost::mysql::statement stmt = co_await conn.async_prepare_statement(
         "UPDATE users SET gold = ?, sword_level = ?, max_sword_level = "
         "GREATEST(max_sword_level, ?) WHERE username = ?",
         boost::asio::use_awaitable);
-    co_await conn_->async_execute(
+    co_await conn.async_execute(
         stmt.bind(gold, (int64_t)swordLevel, (int64_t)swordLevel, nickname),
         result, boost::asio::use_awaitable);
   } catch (const std::exception &e) {
     Logger::Log("SaveUser 에러: ", e.what());
   }
-
-  Unlock();
   co_return;
 }
 
 boost::asio::awaitable<DatabaseManager::RankingResult>
 DatabaseManager::GetRanking(int type, std::string nickname) {
-  co_await Lock();
-
   RankingResult res;
   res.myRank = -1;
   res.myValue = 0;
 
   try {
-    if (!conn_) {
+    auto conn_ptr = co_await GetConnection();
-      Unlock();
+    auto &conn = conn_ptr->Get();
-      co_return res;
-    }
 
     std::string columnName = (type == 0) ? "max_sword_level" : "gold";
 
@@ -168,15 +190,14 @@ DatabaseManager::GetRanking(int type, std::string nickname) {
     std::string topQuery = "SELECT username, " + columnName +
                            " FROM users ORDER BY " + columnName +
                            " DESC LIMIT 10";
-    co_await conn_->async_execute(topQuery, topResult,
+    co_await conn.async_execute(topQuery, topResult,
-                                  boost::asio::use_awaitable);
+                                boost::asio::use_awaitable);
 
     uint32_t rank = 1;
     for (auto row : topResult.rows()) {
       RankingResult::Entry entry;
       entry.rank = rank++;
       entry.nickname = row.at(0).as_string();
-      // DB 타입이 달라 분기처리..
       if (type == 0) {
         entry.value = (uint64_t)row.at(1).as_int64();
       } else {
@@ -190,10 +211,10 @@ DatabaseManager::GetRanking(int type, std::string nickname) {
         "SELECT " + columnName + ", (SELECT COUNT(*) + 1 FROM users WHERE " +
         columnName + " > u." + columnName + ") FROM users u WHERE username = ?";
 
-    boost::mysql::statement stmt = co_await conn_->async_prepare_statement(
+    boost::mysql::statement stmt = co_await conn.async_prepare_statement(
         myQuery, boost::asio::use_awaitable);
-    co_await conn_->async_execute(stmt.bind(nickname), myResult,
+    co_await conn.async_execute(stmt.bind(nickname), myResult,
-                                  boost::asio::use_awaitable);
+                                boost::asio::use_awaitable);
 
     if (!myResult.rows().empty()) {
       auto row = myResult.rows().at(0);
@@ -208,6 +229,5 @@ DatabaseManager::GetRanking(int type, std::string nickname) {
     Logger::Log("GetRanking 에러: ", e.what());
   }
 
-  Unlock();
   co_return res;
 }