fix: Add warning and doc for Windows event loop policy to avoid subpr…

…ocess issues in web surfer and local executor (#5557)

python/packages/autogen-ext/src/autogen_ext/agents/web_surfer/_multimodal_web_surfer.py

@@ -1,12 +1,15 @@
+import asyncio
 import base64
 import hashlib
 import io
 import json
 import logging
 import os
 import re
+import sys
 import time
 import traceback
+import warnings
 from typing import (
     Any,
     AsyncGenerator,
@@ -113,6 +116,18 @@ class MultimodalWebSurfer(BaseChatAgent, Component[MultimodalWebSurferConfig]):
         Be aware that agents may occasionally attempt risky actions, such as recruiting humans for help or accepting cookie agreements without human involvement. Always ensure agents are monitored and operate within a controlled environment to prevent unintended consequences.
         Moreover, be cautious that MultimodalWebSurfer may be susceptible to prompt injection attacks from webpages.
 
+    .. note::
+
+        On Windows, the event loop policy must be set to `WindowsProactorEventLoopPolicy` to avoid issues with subprocesses.
+
+        .. code-block:: python
+
+            import sys
+            import asyncio
+
+            if sys.platform == "win32":
+                asyncio.set_event_loop_policy(asyncio.WindowsProactorEventLoopPolicy())
+
     Args:
         name (str): The name of the agent.
         model_client (ChatCompletionClient): The model client used by the agent. Must be multimodal and support function calling.
@@ -277,6 +292,22 @@ async def _lazy_init(
         """
         On the first call, we initialize the browser and the page.
         """
+
+        # Check the current event loop policy if on windows.
+        if sys.platform == "win32":
+            current_policy = asyncio.get_event_loop_policy()
+            if hasattr(asyncio, "WindowsProactorEventLoopPolicy") and not isinstance(
+                current_policy, asyncio.WindowsProactorEventLoopPolicy
+            ):
+                warnings.warn(
+                    "The current event loop policy is not WindowsProactorEventLoopPolicy. "
+                    "This may cause issues with subprocesses. "
+                    "Try setting the event loop policy to WindowsProactorEventLoopPolicy. "
+                    "For example: `asyncio.set_event_loop_policy(asyncio.WindowsProactorEventLoopPolicy())`. "
+                    "See https://docs.python.org/3/library/asyncio-eventloop.html#asyncio.ProactorEventLoop.",
+                    stacklevel=2,
+                )
+
         self._last_download = None
         self._prior_metadata_hash = None
 

python/packages/autogen-ext/src/autogen_ext/code_executors/local/__init__.py

@@ -59,6 +59,18 @@ class LocalCommandLineCodeExecutor(CodeExecutor, Component[LocalCommandLineCodeE
     For shell scripts, use the language "bash", "shell", or "sh" for the code
     block.
 
+    .. note::
+
+        On Windows, the event loop policy must be set to `WindowsProactorEventLoopPolicy` to avoid issues with subprocesses.
+
+        .. code-block:: python
+
+            import sys
+            import asyncio
+
+            if sys.platform == "win32":
+                asyncio.set_event_loop_policy(asyncio.WindowsProactorEventLoopPolicy())
+
     Args:
         timeout (int): The timeout for the execution of any single code block. Default is 60.
         work_dir (str): The working directory for the code execution. If None,
@@ -165,6 +177,21 @@ def __init__(
 
         self._virtual_env_context: Optional[SimpleNamespace] = virtual_env_context
 
+        # Check the current event loop policy if on windows.
+        if sys.platform == "win32":
+            current_policy = asyncio.get_event_loop_policy()
+            if hasattr(asyncio, "WindowsProactorEventLoopPolicy") and not isinstance(
+                current_policy, asyncio.WindowsProactorEventLoopPolicy
+            ):
+                warnings.warn(
+                    "The current event loop policy is not WindowsProactorEventLoopPolicy. "
+                    "This may cause issues with subprocesses. "
+                    "Try setting the event loop policy to WindowsProactorEventLoopPolicy. "
+                    "For example: `asyncio.set_event_loop_policy(asyncio.WindowsProactorEventLoopPolicy())`. "
+                    "See https://docs.python.org/3/library/asyncio-eventloop.html#asyncio.ProactorEventLoop.",
+                    stacklevel=2,
+                )
+
     def format_functions_for_prompt(self, prompt_template: str = FUNCTION_PROMPT_TEMPLATE) -> str:
         """(Experimental) Format the functions for a prompt.