mirror of
https://github.com/PrefectHQ/fastmcp.git
synced 2026-09-02 04:23:20 +02:00
2954b69274
- Fix race condition in StdioTransport.connect() where concurrent calls would fail - Previously, if connect() was called while another connection was in progress, it would return None immediately instead of waiting for completion - Now concurrent calls wait for the existing connection to complete - Add comprehensive test for concurrent stdio transport connections - Resolves issue where parallel calls resulted in 'Received request before initialization was complete' errors Fixes #1625 Co-authored-by: Jeremiah Lowin <jlowin@users.noreply.github.com>
62 lines
2.2 KiB
Python
62 lines
2.2 KiB
Python
"""Tests for the stdio transport concurrent initialization fix."""
|
|
|
|
import asyncio
|
|
import inspect
|
|
import tempfile
|
|
from pathlib import Path
|
|
|
|
import pytest
|
|
|
|
from fastmcp.client import Client
|
|
from fastmcp.client.transports import PythonStdioTransport
|
|
|
|
|
|
@pytest.mark.asyncio
|
|
async def test_stdio_transport_concurrent_connection():
|
|
"""Test that StdioTransport can handle concurrent connection attempts.
|
|
|
|
This test verifies the fix for issue #1625 where parallel calls to
|
|
stdio MCP servers would fail with "Received request before initialization
|
|
was complete" errors due to a race condition in the connection logic.
|
|
"""
|
|
with tempfile.TemporaryDirectory() as tmp_dir:
|
|
tmp_path = Path(tmp_dir)
|
|
|
|
# Create a simple test server script
|
|
server_script = inspect.cleandoc("""
|
|
from fastmcp import FastMCP
|
|
|
|
mcp = FastMCP()
|
|
|
|
@mcp.tool
|
|
def add(a: int, b: int) -> int:
|
|
return a + b
|
|
|
|
if __name__ == '__main__':
|
|
mcp.run()
|
|
""")
|
|
|
|
script_path = tmp_path / "test_server.py"
|
|
script_path.write_text(server_script)
|
|
|
|
# Test with direct stdio transport - this should work with our fix
|
|
transport = PythonStdioTransport(script_path)
|
|
client = Client(transport)
|
|
|
|
async with client:
|
|
# Test with 50 parallel calls - this would fail before the fix
|
|
tasks = [client.call_tool("add", {"a": i, "b": 1}) for i in range(50)]
|
|
|
|
results = await asyncio.gather(*tasks, return_exceptions=True)
|
|
exceptions = [result for result in results if isinstance(result, Exception)]
|
|
|
|
# Should have no exceptions with our fix
|
|
assert len(exceptions) == 0, (
|
|
f"Found {len(exceptions)} exceptions: {[str(e) for e in exceptions[:5]]}"
|
|
)
|
|
|
|
# All successful results should be correct
|
|
successful_results = [r for r in results if not isinstance(r, Exception)]
|
|
assert len(successful_results) == 50
|
|
for i, result in enumerate(successful_results):
|
|
assert result.data == i + 1 # a=i, b=1, so result should be i+1
|