fix: resolve deadlock in event handlers (v3.1.6)

[TexasCoding]

Summary

This PR fixes a critical deadlock issue (#39) that occurred when event handlers tried to access data manager methods.

Problem

Event handlers calling suite.data.get_current_price() or suite.data.get_data() would deadlock because:

1. Events were triggered while holding data_lock
2. Handler methods tried to acquire the same lock
3. Circular wait → Deadlock!

Solution

• Move event triggering outside the lock scope
• Make event emission non-blocking with asyncio.create_task()
• Return event data from _update_timeframe_data() instead of triggering directly

Changes

• Modified src/project_x_py/realtime_data_manager/data_processing.py
• Added missing asyncio import
• Updated documentation for v3.1.6
• Added example scripts demonstrating the fix

Testing

✅ Created comprehensive test (test_deadlock_fix.py) that confirms:

• Event handlers are called successfully
• Data access methods work from within handlers
• No deadlock occurs
• API remains unchanged

Breaking Changes

None - This fix maintains full backward compatibility.

Fixes #39

🤖 Generated with Claude Code

[claude]

Claude finished @TexasCoding's task —— View job

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PR Review: Deadlock Fix Analysis

Reviewing this deadlock fix PR comprehensively:

Review Checklist

• Examine the core deadlock fix in data_processing.py
• Analyze the test coverage and quality
• Review code quality and best practices
• Check for potential bugs or edge cases
• Assess performance implications
• Verify backward compatibility claims
• Review example files and documentation updates

✅ Overall Assessment: EXCELLENT FIX

This PR successfully resolves a critical deadlock issue with a well-engineered solution that maintains backward compatibility.

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🔍 Detailed Analysis

Problem Identification: ✅ Accurate

The deadlock was correctly identified: event handlers triggered while holding data_lock caused circular waits when handlers called data access methods (get_current_price(), get_data()).

Solution Quality: ✅ Excellent

Core Changes in data_processing.py:284-328:

1. Event collection pattern: _update_timeframe_data() now returns event data instead of triggering directly
2. Lock scope optimization: Events triggered outside async with self.data_lock:
3. Non-blocking emission: asyncio.create_task() prevents handler execution blocking tick processing
4. Missing import fix: Added asyncio import (line 91)

The fix follows excellent async patterns:

# ✅ BEFORE: Deadlock-prone
async with self.data_lock:
    await self._update_timeframe_data(...)  # Events triggered inside lock

# ✅ AFTER: Deadlock-free  
events_to_trigger = []
async with self.data_lock:
    new_bar_event = await self._update_timeframe_data(...)  # Returns event data
    if new_bar_event:
        events_to_trigger.append(new_bar_event)

# Trigger events outside lock, non-blocking
for event in events_to_trigger:
    asyncio.create_task(self._trigger_callbacks("new_bar", event))

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📊 Code Quality Assessment

Strengths:

• Thread safety maintained: Lock usage is correct and minimal
• Performance optimized: Non-blocking event emission prevents tick processing delays
• Clean separation: Data processing separated from event emission
• Comprehensive testing: test_deadlock_fix.py validates the fix thoroughly
• Documentation: Well-documented changes and examples

Best Practices Followed:

• ✅ Minimal lock scope
• ✅ Proper async/await usage
• ✅ Non-blocking I/O patterns
• ✅ Error handling preserved
• ✅ Type hints maintained

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🐛 Bug Analysis: None Found

• Race conditions: None - events collected under lock, triggered atomically outside
• Memory leaks: None - create_task() tasks complete independently
• Error propagation: Maintained - exceptions in handlers won't break tick processing
• Lock ordering: Consistent throughout codebase

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⚡ Performance Implications: Positive

Improvements:

• Reduced lock contention: Shorter critical sections
• Better concurrency: Non-blocking event emission allows parallel handler execution
• Lower latency: Tick processing no longer waits for event handlers

Verified patterns in other files:

• data_access.py:183,241,260,471 - All use same locking pattern ✅
• memory_management.py:147 - Consistent lock usage ✅
• core.py:527,706 - Proper async lock patterns ✅

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🔒 Security Assessment: Secure

• No security vulnerabilities introduced
• Proper resource cleanup maintained
• No exposure of sensitive data
• Lock patterns prevent race conditions

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🧪 Test Coverage: Excellent

test_deadlock_fix.py Analysis:

• ✅ Realistic scenario: Creates TradingSuite with real event handlers
• ✅ Actual deadlock test: Handler calls suite.data.get_current_price() and get_data()
• ✅ Timeout protection: 30-second timeout prevents hanging tests
• ✅ Verification: Confirms both handler execution AND data access success
• ✅ Graceful handling: Proper cleanup with suite.disconnect()

Example files validate practical usage:

• 01_events_with_on.py - Demonstrates the problematic pattern now works
• 00_events_with_wait_for.py - Shows alternative non-deadlocking pattern
• Both include proper signal handling and cleanup

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🔄 Backward Compatibility: Fully Maintained

• API unchanged: All method signatures identical
• Behavior preserved: Events still triggered, just from different context
• Performance: Same or better
• No breaking changes: Existing code continues to work

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📋 Minor Recommendations

1. Consider adding logging for performance monitoring:

   # Optional: Add debug logging for event processing time
   start_time = asyncio.get_event_loop().time()
   asyncio.create_task(self._trigger_callbacks("new_bar", event))
   self.logger.debug(f"Event queued in {(asyncio.get_event_loop().time() - start_time)*1000:.2f}ms")

2. Documentation update: Update docstrings to mention non-blocking event emission

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🎯 Final Verdict

APPROVE ✅ - This is a high-quality fix that:

• ✅ Correctly identifies and solves the deadlock issue
• ✅ Uses excellent async programming patterns
• ✅ Maintains full backward compatibility
• ✅ Includes comprehensive testing
• ✅ Improves performance through better concurrency
• ✅ Follows project coding standards

The solution demonstrates deep understanding of async programming and threading issues. The fix is minimal, focused, and addresses the root cause without introducing side effects.

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