Enhance Postgres connection string handling in ChatService to prioritize LANGGRAPH_PG_URL, derive from DATABASE_URL if available, and fallback to localhost configuration.

th_agenter/services/chat.py

@@ -201,13 +201,22 @@ class ChatService:
         if not ChatService._checkpointer_initialized:
             from langgraph.checkpoint.postgres import PostgresSaver
             import psycopg2
-            # 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",
-            )
+            import re
+            # LangGraph 使用的 Postgres 连接串（psycopg 格式：postgresql://）
+            # 优先级：LANGGRAPH_PG_URL > 从 DATABASE_URL 派生 > 默认 localhost
+            conn_string = os.getenv("LANGGRAPH_PG_URL")
+            if not conn_string:
+                db_url = os.getenv("DATABASE_URL", "")
+                if db_url and "postgresql" in db_url.split("://")[0].lower():
+                    # 将 postgresql+asyncpg:// 转为 postgresql://，供 LangGraph/psycopg 使用
+                    conn_string = re.sub(
+                        r"^postgresql\+[a-zA-Z0-9]+://",
+                        "postgresql://",
+                        db_url,
+                        count=1,
+                    )
+                else:
+                    conn_string = "postgresql://drgraph:yingping@localhost:5433/th_agenter"
             ChatService._conn_string = conn_string
             
             # 检查必要的表是否已存在