Add regression test for issue #1027 #1069
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The stdio cleanup was hanging indefinitely when processes ignored termination signals or took too long to exit. This caused the MCP client to freeze during shutdown, especially with servers that don't handle SIGTERM properly. The fix introduces a 2-second timeout for process termination. If a process doesn't exit gracefully within this window, it's forcefully killed. This ensures the client always completes cleanup in bounded time while still giving well-behaved servers a chance to exit cleanly. This resolves hanging issues reported when MCP servers ignore standard termination signals or perform lengthy cleanup operations. Also adds regression tests for #559. resolves #555 Co-authored-by: Cristian Pufu <[email protected]>
The MCP specification recommends closing stdin first to allow servers to exit gracefully before resorting to signals. This approach gives well-behaved servers the opportunity to detect stdin closure and perform clean shutdown without forceful termination. The shutdown sequence now follows a graceful escalation path: first closing stdin and waiting 2 seconds for voluntary exit, then sending SIGTERM if needed, and finally using SIGKILL as a last resort. This minimizes the risk of data loss or corruption while ensuring cleanup always completes. This unified approach works consistently across all platforms and improves compatibility with MCP servers that monitor stdin for lifecycle management. resolves #765 Co-authored-by: davenpi <[email protected]>
When terminating MCP servers, child processes were being orphaned because only the parent process was killed. This caused resource leaks and prevented proper cleanup, especially with tools like npx that spawn child processes for the actual server implementation. This was happening on both POSIX and Windows systems - however because of implementation details, resolving this is non-trivial and requires introducing psutil to introduce cross-platform utilities for dealing with children and process trees. This addresses critical issues where MCP servers using process spawning tools would leave zombie processes running after client shutdown. resolves #850 resolves #729 Co-authored-by: jingx8885 <[email protected]> Co-authored-by: Surya Prakash Susarla <[email protected]>
Refactor the MCP spec-compliant stdio shutdown sequence into a separate _shutdown_process function to document that this is an MCP specific shutdown sequence. Logic remains unchanged. Co-authored-by: davenpi <[email protected]>
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This test shows that MCP server cleanup code in lifespan doesn't run when the process is terminated, but does run when stdin is closed first (as implemented in PR #1044). The test includes: - Demonstration of current broken behavior (cleanup doesn't run) - Verification that stdin closure allows graceful shutdown - Windows-specific ResourceWarning handling - Detailed documentation of the issue and solution Github-Issue:#1027
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Motivation and Context
Issue #1027 reports that MCP server cleanup code (after yield in lifespan) is unreachable when the process is terminated. This PR adds tests that:
How Has This Been Tested?
Added two tests in
test_1027_win_unreachable_cleanup.py:test_lifespan_cleanup_executed- Shows cleanup doesn't run with current termination (xfails)test_stdin_close_triggers_cleanup- Shows cleanup works when stdin is closed first (passes)Tested on both macOS and Windows.
When run with PR #1044's changes, both tests pass.
Breaking Changes
None. Tests only.
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Additional context