116 lines
4.0 KiB
Python
116 lines
4.0 KiB
Python
"""Regression tests for issue #66092.
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Streamable-HTTP / SSE MCP transports run their stream pump inside an anyio
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TaskGroup. A transient stream drop (idle timeout, brief backend blip) surfaces
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as a ``BaseExceptionGroup`` escaping the transport context manager. Before the
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fix that group reached ``run()``'s error path, which applied exponential
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backoff and eventually parked the server for 300s and deregistered its tools —
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a multi-minute tool outage for a sub-second glitch.
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``_run_http`` now converts such a transport TaskGroup failure into a clean
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``"reconnect"`` (immediate rebuild, no backoff/park), while still propagating
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real shutdown/cancellation and genuine connect/handshake failures.
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"""
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from __future__ import annotations
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import asyncio
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import pytest
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from tools.mcp_tool import MCPServerTask
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def _group(*excs) -> BaseExceptionGroup:
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return BaseExceptionGroup("transport drop", list(excs))
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# ── Unit coverage for the decision helper ────────────────────────────────────
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class TestReconnectOrReraiseGroup:
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def test_live_session_transient_drop_reconnects(self):
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task = MCPServerTask("t")
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task._ready.set() # a live session was established this attempt
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assert task._reconnect_or_reraise_group(
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_group(ConnectionError("sse stream dropped"))
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) == "reconnect"
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def test_no_live_session_reraises_for_backoff(self):
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task = MCPServerTask("t")
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# _ready NOT set: a connect/handshake failure, not a transient drop —
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# let run()'s backoff handle it instead of hot-looping.
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with pytest.raises(BaseExceptionGroup):
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task._reconnect_or_reraise_group(_group(ConnectionError("handshake")))
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# ── Integration coverage: real _run_http new-HTTP branch ─────────────────────
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class _RaisingTransportCM:
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"""Fake streamable-HTTP transport whose __aexit__ raises a group, mimicking
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the SDK's anyio TaskGroup tearing down on a stream drop."""
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def __init__(self, exc):
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self._exc = exc
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async def __aenter__(self):
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return (object(), object(), lambda: "session-id")
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async def __aexit__(self, *exc_info):
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raise self._exc
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class _FakeSession:
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async def initialize(self):
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return object()
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class _FakeSessionCM:
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async def __aenter__(self):
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return _FakeSession()
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async def __aexit__(self, *exc_info):
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return False
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def _make_http_task(monkeypatch, transport_exc):
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task = MCPServerTask("http-drop")
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monkeypatch.setattr("tools.mcp_tool._MCP_HTTP_AVAILABLE", True, raising=False)
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monkeypatch.setattr("tools.mcp_tool._MCP_NEW_HTTP", True, raising=False)
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monkeypatch.setattr(
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"tools.mcp_tool.streamable_http_client",
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lambda url, http_client=None: _RaisingTransportCM(transport_exc),
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raising=False,
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)
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monkeypatch.setattr(
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"tools.mcp_tool.ClientSession",
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lambda *a, **k: _FakeSessionCM(),
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raising=False,
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)
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async def _no_discover(self):
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return None
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async def _reconnect_lifecycle(self):
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return "reconnect"
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monkeypatch.setattr(MCPServerTask, "_discover_tools", _no_discover)
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monkeypatch.setattr(MCPServerTask, "_wait_for_lifecycle_event", _reconnect_lifecycle)
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return task
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def test_run_http_transport_group_returns_reconnect(monkeypatch):
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task = _make_http_task(monkeypatch, _group(ConnectionError("stream dropped")))
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reason = asyncio.run(task._run_http({"url": "http://127.0.0.1:9/mcp"}))
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assert reason == "reconnect"
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# We had a live session; readiness stays set for run() to clear on re-entry.
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assert task._ready.is_set()
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def test_run_http_transport_group_reraises_on_shutdown(monkeypatch):
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task = _make_http_task(monkeypatch, _group(ConnectionError("stream dropped")))
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task._shutdown_event.set()
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with pytest.raises(BaseExceptionGroup):
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asyncio.run(task._run_http({"url": "http://127.0.0.1:9/mcp"}))
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