feat: modify mem-reader prompt (#273)

* feat: timeout for nebula query 5s->10s

* feat: exclude heavy feilds when calling memories from nebula db

* test: fix tree-text-mem searcher text

* feat: adjust prompt

* feat: adjust prompt

Author: CaralHsi

src/memos/graph_dbs/nebular.py

@@ -3,6 +3,7 @@
 
 from contextlib import suppress
 from datetime import datetime
+from queue import Empty, Queue
 from threading import Lock
 from typing import TYPE_CHECKING, Any, ClassVar, Literal
 
@@ -86,6 +87,137 @@ def _normalize_datetime(val):
     return str(val)
 
 
+class SessionPoolError(Exception):
+    pass
+
+
+class SessionPool:
+    @require_python_package(
+        import_name="nebulagraph_python",
+        install_command="pip install ... @Tianxing",
+        install_link=".....",
+    )
+    def __init__(
+        self,
+        hosts: list[str],
+        user: str,
+        password: str,
+        minsize: int = 1,
+        maxsize: int = 10000,
+    ):
+        self.hosts = hosts
+        self.user = user
+        self.password = password
+        self.minsize = minsize
+        self.maxsize = maxsize
+        self.pool = Queue(maxsize)
+        self.lock = Lock()
+
+        self.clients = []
+
+        for _ in range(minsize):
+            self._create_and_add_client()
+
+    @timed
+    def _create_and_add_client(self):
+        from nebulagraph_python import NebulaClient
+
+        client = NebulaClient(self.hosts, self.user, self.password)
+        self.pool.put(client)
+        self.clients.append(client)
+
+    @timed
+    def get_client(self, timeout: float = 5.0):
+        try:
+            return self.pool.get(timeout=timeout)
+        except Empty:
+            with self.lock:
+                if len(self.clients) < self.maxsize:
+                    from nebulagraph_python import NebulaClient
+
+                    client = NebulaClient(self.hosts, self.user, self.password)
+                    self.clients.append(client)
+                    return client
+            raise RuntimeError("NebulaClientPool exhausted") from None
+
+    @timed
+    def return_client(self, client):
+        try:
+            client.execute("YIELD 1")
+            self.pool.put(client)
+        except Exception:
+            logger.info("[Pool] Client dead, replacing...")
+            self.replace_client(client)
+
+    @timed
+    def close(self):
+        for client in self.clients:
+            with suppress(Exception):
+                client.close()
+        self.clients.clear()
+
+    @timed
+    def get(self):
+        """
+        Context manager: with pool.get() as client:
+        """
+
+        class _ClientContext:
+            def __init__(self, outer):
+                self.outer = outer
+                self.client = None
+
+            def __enter__(self):
+                self.client = self.outer.get_client()
+                return self.client
+
+            def __exit__(self, exc_type, exc_val, exc_tb):
+                if self.client:
+                    self.outer.return_client(self.client)
+
+        return _ClientContext(self)
+
+    @timed
+    def reset_pool(self):
+        """⚠️ Emergency reset: Close all clients and clear the pool."""
+        logger.warning("[Pool] Resetting all clients. Existing sessions will be lost.")
+        with self.lock:
+            for client in self.clients:
+                try:
+                    client.close()
+                except Exception:
+                    logger.error("Fail to close!!!")
+            self.clients.clear()
+            while not self.pool.empty():
+                try:
+                    self.pool.get_nowait()
+                except Empty:
+                    break
+            for _ in range(self.minsize):
+                self._create_and_add_client()
+        logger.info("[Pool] Pool has been reset successfully.")
+
+    @timed
+    def replace_client(self, client):
+        try:
+            client.close()
+        except Exception:
+            logger.error("Fail to close client")
+
+        if client in self.clients:
+            self.clients.remove(client)
+
+        from nebulagraph_python import NebulaClient
+
+        new_client = NebulaClient(self.hosts, self.user, self.password)
+        self.clients.append(new_client)
+
+        self.pool.put(new_client)
+
+        logger.info("[Pool] Replaced dead client with a new one.")
+        return new_client
+
+
 class NebulaGraphDB(BaseGraphDB):
     """
     NebulaGraph-based implementation of a graph memory store.
@@ -125,19 +257,18 @@ def _get_or_create_shared_pool(cls, cfg: NebulaGraphDBConfig):
         Get a shared NebulaPool from cache or create one if missing.
         Thread-safe with a lock; maintains a simple refcount.
         """
-        from nebulagraph_python.client.pool import NebulaPool, NebulaPoolConfig
-
         key = cls._make_pool_key(cfg)
 
         with cls._POOL_LOCK:
             pool = cls._POOL_CACHE.get(key)
             if pool is None:
                 # Create a new pool and put into cache
-                pool = NebulaPool(
+                pool = SessionPool(
                     hosts=cfg.get("uri"),
-                    username=cfg.get("user"),
+                    user=cfg.get("user"),
                     password=cfg.get("password"),
-                    pool_config=NebulaPoolConfig(max_client_size=cfg.get("max_client", 1000)),
+                    minsize=1,
+                    maxsize=cfg.get("max_client", 1000),
                 )
                 cls._POOL_CACHE[key] = pool
                 cls._POOL_REFCOUNT[key] = 0
@@ -256,17 +387,18 @@ def __init__(self, config: NebulaGraphDBConfig):
 
     @timed
     def execute_query(self, gql: str, timeout: float = 10.0, auto_set_db: bool = True):
-        needs_use_prefix = ("SESSION SET GRAPH" not in gql) and ("USE " not in gql)
-        use_prefix = f"USE `{self.db_name}` " if auto_set_db and needs_use_prefix else ""
-
-        ngql = use_prefix + gql
+        with self.pool.get() as client:
+            try:
+                if auto_set_db and self.db_name:
+                    client.execute(f"SESSION SET GRAPH `{self.db_name}`")
+                return client.execute(gql, timeout=timeout)
 
-        try:
-            with self.pool.borrow() as client:
-                return client.execute(ngql, timeout=timeout)
-        except Exception as e:
-            logger.error(f"[execute_query] Failed: {e}")
-            raise
+            except Exception as e:
+                if "Session not found" in str(e) or "Connection not established" in str(e):
+                    logger.warning(f"[execute_query] {e!s}, replacing client...")
+                    self.pool.replace_client(client)
+                    return self.execute_query(gql, timeout, auto_set_db)
+                raise
 
     @timed
     def close(self):
@@ -940,20 +1072,12 @@ def get_by_metadata(self, filters: list[dict[str, Any]]) -> list[str]:
         """
         where_clauses = []
 
-        def _escape_value(value):
-            if isinstance(value, str):
-                return f'"{value}"'
-            elif isinstance(value, list):
-                return "[" + ", ".join(_escape_value(v) for v in value) + "]"
-            else:
-                return str(value)
-
         for _i, f in enumerate(filters):
             field = f["field"]
             op = f.get("op", "=")
             value = f["value"]
 
-            escaped_value = _escape_value(value)
+            escaped_value = self._format_value(value)
 
             # Build WHERE clause
             if op == "=":