Refactor Postgres connection string handling in ChatService to use environment variable for better configuration management in Docker and local development.

th_agenter/services/chat.py

@@ -201,14 +201,20 @@ class ChatService:
         if not ChatService._checkpointer_initialized:
             from langgraph.checkpoint.postgres import PostgresSaver
             import psycopg2
-            CONN_STRING = "postgresql://postgres:postgres@localhost:5433/postgres"
-            ChatService._conn_string = CONN_STRING
+            # LangGraph 使用的 Postgres 连接串，优先从环境变量读取，便于在 Docker / 本地区分配置
+            # - Docker 内建议：LANGGRAPH_PG_URL=postgresql://drgraph:yingping@db:5432/th_agenter
+            # - 本地开发可用：  LANGGRAPH_PG_URL=postgresql://drgraph:yingping@localhost:5433/th_agenter
+            conn_string = os.getenv(
+                "LANGGRAPH_PG_URL",
+                "postgresql://drgraph:yingping@localhost:5433/th_agenter",
+            )
+            ChatService._conn_string = conn_string
             
             # 检查必要的表是否已存在
             tables_need_setup = True
             try:
                 # 连接到数据库并检查表是否存在
-                conn = psycopg2.connect(CONN_STRING)
+                conn = psycopg2.connect(conn_string)
                 cursor = conn.cursor()
                 
                 # 检查langgraph需要的表是否存在
@@ -237,7 +243,7 @@ class ChatService:
             if tables_need_setup:
                 self.session.desc = "ChatService初始化 - 正在进行PostgresSaver setup"
                 try:
-                    async with AsyncPostgresSaver.from_conn_string(CONN_STRING) as checkpointer:
+                    async with AsyncPostgresSaver.from_conn_string(conn_string) as checkpointer:
                         await checkpointer.setup()
                     self.session.desc = "ChatService初始化 - PostgresSaver setup完成"
                     logger.info("PostgresSaver setup完成")