lazy init mcp session

Signed-off-by: wuhang <wuhang6@huawei.com>

Author: wuhang2014

vllm/entrypoints/context.py

@@ -153,13 +153,15 @@ def __init__(
         messages: list,
         available_tools: list[str],
         tool_server: Optional[ToolServer],
+        request_id: str,
     ):
         self._messages = messages
         self.finish_reason: Optional[str] = None
         self.available_tools = available_tools
         self._tool_sessions: dict[str, Union[ClientSession, Tool]] = {}
         self.called_tools: set[str] = set()
         self._tool_server = tool_server
+        self.request_id = request_id
         self._async_exit_stack: Optional[AsyncExitStack] = None
         self._reference_count = 0
         self._reference_count_lock = asyncio.Lock()
@@ -307,18 +309,6 @@ def need_builtin_tool_call(self) -> bool:
             or recipient.startswith("container.")
         )
 
-    async def _get_tool_session(self, tool_name: str) -> Union["ClientSession", Tool]:
-        if tool_name not in self._tool_sessions and self._tool_server is not None:
-            assert self._async_exit_stack is not None, (
-                "Async exit stack not set. Please report this issue."
-            )
-            self._tool_sessions[
-                tool_name
-            ] = await self._async_exit_stack.enter_async_context(
-                self._tool_server.new_session(tool_name)
-            )
-        return self._tool_sessions[tool_name]
-
     async def call_tool(self) -> list[Message]:
         if not self.messages:
             return []
@@ -342,6 +332,18 @@ async def call_tool(self) -> list[Message]:
     def render_for_completion(self) -> list[int]:
         return render_for_completion(self.messages)
 
+    async def _get_tool_session(self, tool_name: str) -> Union["ClientSession", Tool]:
+        if tool_name not in self._tool_sessions and self._tool_server is not None:
+            assert self._async_exit_stack is not None, (
+                "Async exit stack not set. Please report this issue."
+            )
+            self._tool_sessions[
+                tool_name
+            ] = await self._async_exit_stack.enter_async_context(
+                self._tool_server.new_session(tool_name, self.request_id)
+            )
+        return self._tool_sessions[tool_name]
+
     async def call_search_tool(
         self, tool_session: Union["ClientSession", Tool], last_msg: Message
     ) -> list[Message]:

vllm/entrypoints/openai/serving_responses.py

@@ -364,11 +364,17 @@ async def create_responses(
                 if self.use_harmony:
                     if request.stream:
                         context = StreamingHarmonyContext(
-                            messages, available_tools, self.tool_server
+                            messages,
+                            available_tools,
+                            self.tool_server,
+                            request.request_id,
                         )
                     else:
                         context = HarmonyContext(
-                            messages, available_tools, self.tool_server
+                            messages,
+                            available_tools,
+                            self.tool_server,
+                            request.request_id,
                         )
                 else:
                     context = SimpleContext()