Description

Fix the bug that Ctrl+C doesn't returns flow result because the signal handler would raise an exception while asyncio.run cannot handle it correctly.

Note that for py<3.11, there is no default sigint handler when using asyncio.run to run an async function, so we add one for py<3.11 following python's implementation: https://github.com/python/cpython/blob/46c808172fd3148e3397234b23674bf70734fb55/Lib/asyncio/runners.py#L150
Such logic is initialized in this PR: python/cpython#32105

This pull request introduces significant changes to the src/promptflow-core/promptflow/_utils/async_utils.py file, aimed at improving the handling of asynchronous tasks and signal interruption. The changes also include minor modifications to several other files in the src/promptflow-core/promptflow/ directory.

Here are the key changes:

Signal Handling and Asynchronous Task Management:

• src/promptflow-core/promptflow/_utils/async_utils.py: A new class _AsyncTaskSigIntHandler was added to handle SIGINT signals during the execution of asynchronous tasks. This class cancels the current task if a SIGINT signal is received, which is particularly useful for Python versions less than 3.11 where the default cancelling behavior is not supported. The function _invoke_async_with_sigint_handler was also added to invoke asynchronous functions with the SIGINT handler. The function async_run_allowing_running_loop was modified to use this new function. [1] [2] [3]

Minor Changes in Other Files:

• src/promptflow-core/promptflow/_utils/process_utils.py: The signal handler for SIGINT was changed to signal.default_int_handler in the block_terminate_signal_to_parent function.
• src/promptflow-core/promptflow/executor/_async_nodes_scheduler.py: The import of the signal module was removed. In the execute method, the signal handler registration was removed and the exception handling was modified to include asyncio.CancelledError. The signal_handler function was removed and replaced with the cancel method. [1] [2] [3] [4]
• src/promptflow-core/promptflow/executor/flow_executor.py: In the _exec_async method, the exception handling was modified to handle asyncio.CancelledError instead of KeyboardInterrupt.

All Promptflow Contribution checklist:

• The pull request does not introduce [breaking changes].
• CHANGELOG is updated for new features, bug fixes or other significant changes.
• I have read the contribution guidelines.
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• Pull request includes test coverage for the included changes.