fix(db): 重用 DatabaseManager engine pool

database/manager.py

@@ -78,6 +78,9 @@ def sanitize_timestamp(timestamp_str):
     return timestamp_str
 
 class DatabaseManager:
+    _instance_cache = {}
+    _instance_lock = threading.Lock()
+
     def __init__(self, db_path=None):
         """
         初始化資料庫連線。
@@ -86,11 +89,23 @@ class DatabaseManager:
         # V-Fix (2026-01-23): 優先使用 config.py 的資料庫設定
         from config import DATABASE_PATH, DATABASE_TYPE
 
+        effective_db_path = DATABASE_PATH if db_path is None else db_path
+        cache_key = (DATABASE_TYPE, str(effective_db_path))
+
+        # V-Fix (2026-04-30): DatabaseManager 在多 route 內被頻繁直接 new，
+        # 若每次都 create_engine 會不斷新增連線池，最終把 PostgreSQL clients 用光。
+        with self._instance_lock:
+            cached = self._instance_cache.get(cache_key)
+            if cached:
+                self.engine = cached['engine']
+                self.Session = cached['Session']
+                return
+
         if DATABASE_TYPE == 'postgresql':
             # PostgreSQL 模式 - 使用 config.py 的連線字串
             # 連線池配置以提升穩定性
             self.engine = create_engine(
-                DATABASE_PATH,
+                effective_db_path,
                 echo=False,
                 pool_pre_ping=True,      # 自動檢測斷線連線
                 pool_size=5,             # 連線池大小
@@ -104,6 +119,10 @@ class DatabaseManager:
             )
             ensure_metadata_initialized(self.engine, use_postgres_lock=True)
             self.Session = sessionmaker(bind=self.engine)
+            self._instance_cache[cache_key] = {
+                'engine': self.engine,
+                'Session': self.Session,
+            }
             sys_log.info(f"[Database] ✅ 使用 PostgreSQL 資料庫 (連線池已優化)")
             # ADR-013: 確保 AIOps 自動修復表存在並植入種子 PlayBook
             self._init_autoheal_tables()
@@ -111,20 +130,24 @@ class DatabaseManager:
             # SQLite 模式 - 向後相容
             if db_path is None:
                 base_dir = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
-                db_path = os.path.join(base_dir, 'data', 'momo_database.db')
+                effective_db_path = os.path.join(base_dir, 'data', 'momo_database.db')
 
-            if str(db_path).startswith('sqlite://'):
-                sqlite_db_file = make_url(db_path).database
+            if str(effective_db_path).startswith('sqlite://'):
+                sqlite_db_file = make_url(effective_db_path).database
                 if sqlite_db_file:
                     os.makedirs(os.path.dirname(sqlite_db_file), exist_ok=True)
-                self.engine = create_engine(db_path, echo=False)
+                self.engine = create_engine(effective_db_path, echo=False)
             else:
-                os.makedirs(os.path.dirname(db_path), exist_ok=True)
-                self.engine = create_engine(f'sqlite:///{db_path}', echo=False)
+                os.makedirs(os.path.dirname(effective_db_path), exist_ok=True)
+                self.engine = create_engine(f'sqlite:///{effective_db_path}', echo=False)
             Base.metadata.create_all(self.engine)
             self.Session = sessionmaker(bind=self.engine)
+            self._instance_cache[cache_key] = {
+                'engine': self.engine,
+                'Session': self.Session,
+            }
             self._check_and_fix_schema()
-            sys_log.info(f"[Database] 使用 SQLite 資料庫: {db_path}")
+            sys_log.info(f"[Database] 使用 SQLite 資料庫: {effective_db_path}")
 
     def _check_and_fix_schema(self):
         """自動檢查並修復資料庫結構 (僅限 SQLite)"""