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cedf734f15Fix context manager ordering in FastMCPTransport so the task group (server run + subscriptions) is cancelled before the lifespan (Docket Worker) tears down. Also break subscription loop on terminal task states. Closes #3498
56 lines
2 KiB
Python
56 lines
2 KiB
Python
"""Tests for the in-memory FastMCPTransport.
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These tests verify transport-level behavior that affects all tests using
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Client(server) with an in-process FastMCP server.
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"""
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import time
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import pytest
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from fastmcp import Client, FastMCP
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@pytest.mark.timeout(10)
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async def test_task_teardown_does_not_hang():
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"""In-memory transport must tear down in under 2 seconds after a task call.
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This is a regression test for a teardown ordering bug where the Docket
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Worker shutdown would hang for 5 seconds on every test that used
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task=True. The root cause was the server lifespan (which owns the Docket
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Worker) being torn down BEFORE the task group (which owns the server's
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run() and all its pub/sub subscriptions). Fakeredis blocking operations
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held by those subscriptions prevented the Worker's internal TaskGroup
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from cancelling its children, causing a 5-second stall until the
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Client's move_on_after(5) timeout fired.
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The fix is to nest the task group INSIDE the lifespan context so that
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all server tasks (and their fakeredis resources) are cancelled and
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drained before Docket teardown begins.
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If this test takes ~5 seconds, the context manager nesting in
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FastMCPTransport.connect_session() has been reversed — the lifespan
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must be the OUTER context and the task group must be the INNER context.
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"""
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mcp = FastMCP("teardown-test")
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@mcp.tool(task=True)
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async def fast_tool(x: int) -> int:
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return x * 2
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t0 = time.monotonic()
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async with Client(mcp) as client:
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task = await client.call_tool("fast_tool", {"x": 21}, task=True)
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result = await task.result()
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assert result.data == 42
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elapsed = time.monotonic() - t0
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assert elapsed < 2.0, (
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f"Client teardown took {elapsed:.1f}s — expected <2s. "
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f"This usually means the context manager nesting in "
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f"FastMCPTransport.connect_session() is wrong: the lifespan "
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f"must be the OUTER context and the task group the INNER context. "
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f"See the comment in memory.py for details."
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)
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