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6a4ed255de
When an MCP server configured as streamableHttp or SSE is unreachable, streamable_http_client's anyio task group cleanup raises RuntimeError / ExceptionGroup that escapes the caller's try/except and crashes the event loop with "Unhandled exception in event loop". Fix: add a lightweight TCP probe (_probe_http_url) before entering the MCP SDK transport. If the port is closed, the server is skipped with a warning instead of crashing. stdio transport is not probed (local process). Closes #3739
107 lines
3.4 KiB
Python
107 lines
3.4 KiB
Python
"""Tests for MCP HTTP probe guard (prevents event-loop crash on unreachable servers)."""
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from __future__ import annotations
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from unittest.mock import AsyncMock, MagicMock, patch
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import pytest
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from nanobot.agent.tools.mcp import _probe_http_url, connect_mcp_servers
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from nanobot.agent.tools.registry import ToolRegistry
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# ---------------------------------------------------------------------------
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# _probe_http_url unit tests
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# ---------------------------------------------------------------------------
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@pytest.mark.asyncio
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async def test_probe_returns_true_for_open_port(tmp_path):
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"""Start a trivial TCP server, probe should return True."""
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server = await asyncio.start_server(
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lambda r, w: None, "127.0.0.1", 0,
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)
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port = server.sockets[0].getsockname()[1]
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try:
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assert await _probe_http_url(f"http://127.0.0.1:{port}/mcp") is True
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finally:
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server.close()
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await server.wait_closed()
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@pytest.mark.asyncio
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async def test_probe_returns_false_for_closed_port():
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"""Port 19999 is almost certainly not listening."""
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assert await _probe_http_url("http://127.0.0.1:19999/mcp") is False
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@pytest.mark.asyncio
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async def test_probe_uses_default_port_for_http():
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"""When no port in URL, should default to 80 (will fail -> False)."""
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assert await _probe_http_url("http://unreachable-host.test/mcp") is False
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# ---------------------------------------------------------------------------
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# connect_mcp_servers skips unreachable HTTP servers
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# ---------------------------------------------------------------------------
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def _make_http_cfg(url: str, transport: str = "streamableHttp"):
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cfg = MagicMock()
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cfg.type = transport
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cfg.url = url
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cfg.command = None
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cfg.args = []
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cfg.env = {}
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cfg.headers = None
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cfg.tool_timeout = 30
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cfg.enabled_tools = ["*"]
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return cfg
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@pytest.mark.asyncio
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async def test_connect_skips_unreachable_streamable_http():
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"""Unreachable streamableHttp server should be skipped with a warning, no crash."""
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registry = ToolRegistry()
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servers = {"dead": _make_http_cfg("http://127.0.0.1:19999/mcp")}
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stacks = await connect_mcp_servers(servers, registry)
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assert stacks == {}
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assert len(registry._tools) == 0
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@pytest.mark.asyncio
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async def test_connect_skips_unreachable_sse():
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"""Unreachable SSE server should be skipped with a warning, no crash."""
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registry = ToolRegistry()
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servers = {"dead": _make_http_cfg("http://127.0.0.1:19999/sse", transport="sse")}
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stacks = await connect_mcp_servers(servers, registry)
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assert stacks == {}
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assert len(registry._tools) == 0
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@pytest.mark.asyncio
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async def test_probe_not_called_for_stdio():
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"""stdio transport should not be probed — it spawns a local process."""
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called = False
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original_probe = _probe_http_url
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async def _spy_probe(url, **kw):
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nonlocal called
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called = True
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return await original_probe(url, **kw)
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with patch("nanobot.agent.tools.mcp._probe_http_url", _spy_probe):
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cfg = MagicMock()
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cfg.type = "stdio"
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cfg.url = None
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cfg.command = "nonexistent-command-xyz"
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cfg.args = []
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cfg.env = None
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cfg.headers = None
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cfg.tool_timeout = 30
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cfg.enabled_tools = ["*"]
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registry = ToolRegistry()
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await connect_mcp_servers({"s": cfg}, registry)
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assert not called, "probe should not be called for stdio transport"
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import asyncio
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