fix(server): resolve deadlocks on agent execution failure #609

[lbobinski]

This PR addresses potential deadlocks and resource leaks in the DefaultRequestHandler when agent execution fails, particularly in streaming scenarios.

Fixes #609 🦕

[gemini-code-assist]

Summary of Changes

Hello @lbobinski, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly improves the stability and resilience of the DefaultRequestHandler by addressing potential deadlocks and resource leaks that could occur when agent execution fails, especially in streaming scenarios. The changes ensure that resources are properly released and tasks are gracefully terminated, preventing system hangs and improving overall reliability.

Highlights

• Robust Error Handling: Implemented mechanisms to prevent deadlocks and resource leaks in DefaultRequestHandler by ensuring proper cleanup during agent execution failures, particularly in streaming contexts.
• Producer Task Cancellation: Added logic to explicitly cancel the producer task and immediately close the associated queue upon encountering exceptions during agent execution, unblocking any waiting producers.
• Graceful Cleanup: Enhanced the _cleanup_producer function to tolerate exceptions and asyncio.CancelledError when awaiting the producer task, guaranteeing that subsequent cleanup steps (like closing the queue manager) are always executed.
• Test Adjustment: A redundant assertion mock_agent_executor.execute.assert_called_once() was removed from test_jsonrpc_handler.py to streamline testing logic.

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[gemini-code-assist]

Code Review

This pull request effectively addresses potential deadlocks and resource leaks by ensuring that producer tasks and their associated queues are properly cleaned up when an agent execution fails, especially in streaming and non-blocking scenarios. The changes in on_message_send and on_message_send_stream correctly cancel the producer and close the queue on consumer failure. The modification in _cleanup_producer is also crucial for ensuring cleanup logic runs reliably. I have one suggestion to improve logging in the cleanup path to avoid silently swallowing exceptions.