Fix lint errors in test_fixes.py

- Remove unused logging import (F401)
- Remove duplicate logging import (F811)
- All lint checks now pass locally

Co-Authored-By: João <joao@crewai.com>

src/crewai/utilities/events/crewai_event_bus.py

@@ -1,3 +1,4 @@
+import logging
 import threading
 from contextlib import contextmanager
 from typing import Any, Callable, Dict, List, Type, TypeVar, cast
@@ -12,12 +13,34 @@ EventT = TypeVar("EventT", bound=BaseEvent)
 
 class CrewAIEventsBus:
     """
-    A singleton event bus that uses blinker signals for event handling.
-    Allows both internal (Flow/Crew) and external event handling.
+    Thread-safe singleton event bus for CrewAI events.
+    
+    This class provides a centralized event handling system that allows components
+    to emit and listen for events throughout the CrewAI framework.
+    
+    Thread Safety:
+    - All public methods are thread-safe
+    - Uses a class-level lock to ensure synchronized access to shared resources
+    - Safe for concurrent event emission and handler registration/deregistration
+    - Prevents race conditions that could cause event mixing between sessions
+    
+    Usage:
+        @crewai_event_bus.on(SomeEvent)
+        def handle_event(source, event):
+            # Handle the event
+            pass
+        
+        # Emit an event
+        event = SomeEvent(type="example")
+        crewai_event_bus.emit(source_object, event)
+        
+        # Deregister a handler
+        crewai_event_bus.deregister_handler(SomeEvent, handle_event)
     """
 
     _instance = None
     _lock = threading.Lock()
+    _logger = logging.getLogger(__name__)
 
     def __new__(cls):
         if cls._instance is None:
@@ -67,27 +90,61 @@ class CrewAIEventsBus:
             source: The object emitting the event
             event: The event instance to emit
         """
-        for event_type, handlers in self._handlers.items():
-            if isinstance(event, event_type):
-                for handler in handlers:
-                    try:
-                        handler(source, event)
-                    except Exception as e:
-                        print(
-                            f"[EventBus Error] Handler '{handler.__name__}' failed for event '{event_type.__name__}': {e}"
-                        )
+        with CrewAIEventsBus._lock:
+            for event_type, handlers in self._handlers.items():
+                if isinstance(event, event_type):
+                    for handler in handlers:
+                        try:
+                            handler(source, event)
+                        except Exception as e:
+                            CrewAIEventsBus._logger.error(
+                                "Handler execution failed",
+                                extra={
+                                    "handler": handler.__name__,
+                                    "event_type": event_type.__name__,
+                                    "error": str(e),
+                                    "source": str(source)
+                                },
+                                exc_info=True
+                            )
 
-        self._signal.send(source, event=event)
+            self._signal.send(source, event=event)
 
     def register_handler(
         self, event_type: Type[EventTypes], handler: Callable[[Any, EventTypes], None]
     ) -> None:
         """Register an event handler for a specific event type"""
-        if event_type not in self._handlers:
-            self._handlers[event_type] = []
-        self._handlers[event_type].append(
-            cast(Callable[[Any, EventTypes], None], handler)
-        )
+        with CrewAIEventsBus._lock:
+            if event_type not in self._handlers:
+                self._handlers[event_type] = []
+            self._handlers[event_type].append(
+                cast(Callable[[Any, EventTypes], None], handler)
+            )
+
+    def deregister_handler(
+        self, event_type: Type[EventTypes], handler: Callable[[Any, EventTypes], None]
+    ) -> bool:
+        """
+        Deregister an event handler for a specific event type.
+        
+        Args:
+            event_type: The event type to deregister the handler from
+            handler: The handler function to remove
+            
+        Returns:
+            bool: True if the handler was found and removed, False otherwise
+        """
+        with CrewAIEventsBus._lock:
+            if event_type not in self._handlers:
+                return False
+            
+            try:
+                self._handlers[event_type].remove(handler)
+                if not self._handlers[event_type]:
+                    del self._handlers[event_type]
+                return True
+            except ValueError:
+                return False
 
     @contextmanager
     def scoped_handlers(self):

test_fixes.py

@@ -0,0 +1,112 @@
+#!/usr/bin/env python3
+"""
+Simple test script to verify the CI fixes work locally.
+"""
+
+import sys
+import os
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), 'src'))
+
+from crewai.utilities.events.crewai_event_bus import crewai_event_bus
+from crewai.utilities.events.base_events import BaseEvent
+from crewai.utilities.events.llm_events import LLMStreamChunkEvent
+import logging
+
+class TestEvent(BaseEvent):
+    pass
+
+def test_basic_functionality():
+    """Test basic event emission works"""
+    print("Testing basic functionality...")
+    
+    received_events = []
+    
+    @crewai_event_bus.on(LLMStreamChunkEvent)
+    def handler(source, event):
+        received_events.append(f"{source}: {event.chunk}")
+    
+    event = LLMStreamChunkEvent(type='llm_stream_chunk', chunk='test')
+    crewai_event_bus.emit('test_source', event)
+    
+    if len(received_events) == 1 and 'test_source: test' in received_events[0]:
+        print("✅ Basic event emission works")
+        return True
+    else:
+        print("❌ Basic event emission failed")
+        print(f"Received: {received_events}")
+        return False
+
+def test_error_handling():
+    """Test error handling with structured logging"""
+    print("Testing error handling...")
+    
+    logging.basicConfig(level=logging.ERROR)
+    
+    with crewai_event_bus.scoped_handlers():
+        @crewai_event_bus.on(BaseEvent)
+        def broken_handler(source, event):
+            raise ValueError("Simulated handler failure")
+        
+        event = TestEvent(type="test_event")
+        crewai_event_bus.emit("source_object", event)
+        
+        print("✅ Error handling test completed (check logs above)")
+        return True
+
+def test_deregistration():
+    """Test handler deregistration"""
+    print("Testing handler deregistration...")
+    
+    with crewai_event_bus.scoped_handlers():
+        def test_handler(source, event):
+            pass
+        
+        crewai_event_bus.register_handler(TestEvent, test_handler)
+        initial_count = len(crewai_event_bus._handlers.get(TestEvent, []))
+        print(f"Handlers after registration: {initial_count}")
+        
+        result = crewai_event_bus.deregister_handler(TestEvent, test_handler)
+        final_count = len(crewai_event_bus._handlers.get(TestEvent, []))
+        print(f"Handlers after deregistration: {final_count}")
+        print(f"Deregistration result: {result}")
+        
+        if result and final_count == 0:
+            print("✅ Handler deregistration works")
+            return True
+        else:
+            print("❌ Handler deregistration failed")
+            return False
+
+def main():
+    print("Testing CI fixes locally")
+    print("=" * 40)
+    
+    tests = [
+        test_basic_functionality,
+        test_error_handling,
+        test_deregistration
+    ]
+    
+    passed = 0
+    total = len(tests)
+    
+    for test in tests:
+        try:
+            if test():
+                passed += 1
+        except Exception as e:
+            print(f"❌ Test {test.__name__} failed with exception: {e}")
+        print()
+    
+    print(f"Results: {passed}/{total} tests passed")
+    
+    if passed == total:
+        print("🎉 All local tests passed!")
+        return True
+    else:
+        print("💥 Some tests failed!")
+        return False
+
+if __name__ == "__main__":
+    success = main()
+    sys.exit(0 if success else 1)

tests/utilities/events/test_crewai_event_bus.py

@@ -1,7 +1,11 @@
+import threading
+import time
+from concurrent.futures import ThreadPoolExecutor
 from unittest.mock import Mock
 
 from crewai.utilities.events.base_events import BaseEvent
 from crewai.utilities.events.crewai_event_bus import crewai_event_bus
+from crewai.utilities.events.llm_events import LLMStreamChunkEvent
 
 
 class TestEvent(BaseEvent):
@@ -34,14 +38,167 @@ def test_wildcard_event_handler():
     mock_handler.assert_called_once_with("source_object", event)
 
 
-def test_event_bus_error_handling(capfd):
-    @crewai_event_bus.on(BaseEvent)
-    def broken_handler(source, event):
-        raise ValueError("Simulated handler failure")
+def test_event_bus_error_handling(caplog):
+    with crewai_event_bus.scoped_handlers():
+        @crewai_event_bus.on(BaseEvent)
+        def broken_handler(source, event):
+            raise ValueError("Simulated handler failure")
 
-    event = TestEvent(type="test_event")
-    crewai_event_bus.emit("source_object", event)
+        event = TestEvent(type="test_event")
+        crewai_event_bus.emit("source_object", event)
 
-    out, err = capfd.readouterr()
-    assert "Simulated handler failure" in out
-    assert "Handler 'broken_handler' failed" in out
+        assert any("Handler execution failed" in record.message for record in caplog.records)
+        assert any("Simulated handler failure" in str(record.exc_info) if record.exc_info else False for record in caplog.records)
+
+
+def test_concurrent_event_emission_thread_safety():
+    """Test that concurrent event emission is thread-safe"""
+    
+    handler1_events = []
+    handler2_events = []
+    handler_lock = threading.Lock()
+    
+    with crewai_event_bus.scoped_handlers():
+        @crewai_event_bus.on(LLMStreamChunkEvent)
+        def handler1(source, event: LLMStreamChunkEvent):
+            with handler_lock:
+                handler1_events.append(f"Handler1: {event.chunk}")
+        
+        @crewai_event_bus.on(LLMStreamChunkEvent)
+        def handler2(source, event: LLMStreamChunkEvent):
+            with handler_lock:
+                handler2_events.append(f"Handler2: {event.chunk}")
+        
+        def emit_events(thread_id, num_events=20):
+            """Emit events from a specific thread"""
+            for i in range(num_events):
+                event = LLMStreamChunkEvent(
+                    type="llm_stream_chunk",
+                    chunk=f"Thread-{thread_id}-Chunk-{i}"
+                )
+                crewai_event_bus.emit(f"source-{thread_id}", event)
+        
+        num_threads = 5
+        events_per_thread = 20
+        
+        with ThreadPoolExecutor(max_workers=num_threads) as executor:
+            futures = []
+            for thread_id in range(num_threads):
+                future = executor.submit(emit_events, thread_id, events_per_thread)
+                futures.append(future)
+            
+            for future in futures:
+                future.result()
+        
+        expected_total = num_threads * events_per_thread
+        assert len(handler1_events) == expected_total, f"Handler1 received {len(handler1_events)} events, expected {expected_total}"
+        assert len(handler2_events) == expected_total, f"Handler2 received {len(handler2_events)} events, expected {expected_total}"
+
+
+def test_concurrent_handler_registration_thread_safety():
+    """Test that concurrent handler registration is thread-safe"""
+    
+    registered_handlers = []
+    
+    def register_handler(thread_id):
+        """Register a handler from a specific thread"""
+        def handler(source, event):
+            pass
+        
+        handler.__name__ = f"handler_{thread_id}"
+        crewai_event_bus.register_handler(TestEvent, handler)
+        registered_handlers.append(handler)
+    
+    num_threads = 10
+    
+    with ThreadPoolExecutor(max_workers=num_threads) as executor:
+        futures = []
+        for thread_id in range(num_threads):
+            future = executor.submit(register_handler, thread_id)
+            futures.append(future)
+        
+        for future in futures:
+            future.result()
+    
+    assert len(registered_handlers) == num_threads
+    assert len(crewai_event_bus._handlers[TestEvent]) >= num_threads
+
+
+def test_thread_safety_with_mixed_operations():
+    """Test thread safety when mixing event emission and handler registration"""
+    
+    received_events = []
+    event_lock = threading.Lock()
+    
+    with crewai_event_bus.scoped_handlers():
+        def emit_events(thread_id):
+            for i in range(10):
+                event = TestEvent(type="test_event")
+                crewai_event_bus.emit(f"source-{thread_id}", event)
+                time.sleep(0.001)
+        
+        def register_handlers(thread_id):
+            for i in range(5):
+                def handler(source, event):
+                    with event_lock:
+                        received_events.append(f"Handler-{thread_id}-{i}: {event.type}")
+                
+                handler.__name__ = f"handler_{thread_id}_{i}"
+                crewai_event_bus.register_handler(TestEvent, handler)
+                time.sleep(0.001)
+        
+        with ThreadPoolExecutor(max_workers=6) as executor:
+            futures = []
+            
+            for thread_id in range(3):
+                futures.append(executor.submit(emit_events, thread_id))
+            
+            for thread_id in range(3):
+                futures.append(executor.submit(register_handlers, thread_id))
+            
+            for future in futures:
+                future.result()
+        
+        assert len(received_events) >= 0
+
+
+def test_handler_deregistration_thread_safety():
+    """Test that concurrent handler deregistration is thread-safe"""
+    
+    with crewai_event_bus.scoped_handlers():
+        handlers_to_remove = []
+        
+        for i in range(10):
+            def handler(source, event):
+                pass
+            handler.__name__ = f"handler_{i}"
+            crewai_event_bus.register_handler(TestEvent, handler)
+            handlers_to_remove.append(handler)
+        
+        def deregister_handler(handler):
+            """Deregister a handler from a specific thread"""
+            return crewai_event_bus.deregister_handler(TestEvent, handler)
+        
+        with ThreadPoolExecutor(max_workers=5) as executor:
+            futures = []
+            for handler in handlers_to_remove:
+                future = executor.submit(deregister_handler, handler)
+                futures.append(future)
+            
+            results = [future.result() for future in futures]
+        
+        assert all(results), "All handlers should be successfully deregistered"
+        
+        remaining_count = len(crewai_event_bus._handlers.get(TestEvent, []))
+        assert remaining_count == 0, f"Expected 0 handlers remaining, got {remaining_count}"
+
+
+def test_deregister_nonexistent_handler():
+    """Test deregistering a handler that doesn't exist"""
+    
+    with crewai_event_bus.scoped_handlers():
+        def dummy_handler(source, event):
+            pass
+        
+        result = crewai_event_bus.deregister_handler(TestEvent, dummy_handler)
+        assert result is False, "Deregistering non-existent handler should return False"

verify_thread_safety.py

@@ -0,0 +1,156 @@
+#!/usr/bin/env python3
+"""
+Simple verification script for thread safety fix without pytest dependencies.
+"""
+
+import sys
+import os
+import threading
+from concurrent.futures import ThreadPoolExecutor
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), 'src'))
+
+def test_basic_functionality():
+    """Test basic event emission works"""
+    print("Testing basic functionality...")
+    
+    from crewai.utilities.events.crewai_event_bus import crewai_event_bus
+    from crewai.utilities.events.llm_events import LLMStreamChunkEvent
+    
+    received_events = []
+    
+    @crewai_event_bus.on(LLMStreamChunkEvent)
+    def handler(source, event):
+        received_events.append(f"{source}: {event.chunk}")
+    
+    event = LLMStreamChunkEvent(type='llm_stream_chunk', chunk='test')
+    crewai_event_bus.emit('test_source', event)
+    
+    if len(received_events) == 1 and 'test_source: test' in received_events[0]:
+        print("✅ Basic event emission works")
+        return True
+    else:
+        print("❌ Basic event emission failed")
+        print(f"Received: {received_events}")
+        return False
+
+def test_thread_safety():
+    """Test thread safety of concurrent event emission"""
+    print("Testing thread safety...")
+    
+    from crewai.utilities.events.crewai_event_bus import crewai_event_bus
+    from crewai.utilities.events.llm_events import LLMStreamChunkEvent
+    
+    handler1_events = []
+    handler2_events = []
+    handler_lock = threading.Lock()
+    
+    with crewai_event_bus.scoped_handlers():
+        @crewai_event_bus.on(LLMStreamChunkEvent)
+        def handler1(source, event: LLMStreamChunkEvent):
+            with handler_lock:
+                handler1_events.append(f"Handler1: {event.chunk}")
+        
+        @crewai_event_bus.on(LLMStreamChunkEvent)
+        def handler2(source, event: LLMStreamChunkEvent):
+            with handler_lock:
+                handler2_events.append(f"Handler2: {event.chunk}")
+        
+        def emit_events(thread_id, num_events=10):
+            """Emit events from a specific thread"""
+            for i in range(num_events):
+                event = LLMStreamChunkEvent(
+                    type="llm_stream_chunk",
+                    chunk=f"Thread-{thread_id}-Chunk-{i}"
+                )
+                crewai_event_bus.emit(f"source-{thread_id}", event)
+        
+        num_threads = 3
+        events_per_thread = 10
+        
+        with ThreadPoolExecutor(max_workers=num_threads) as executor:
+            futures = []
+            for thread_id in range(num_threads):
+                future = executor.submit(emit_events, thread_id, events_per_thread)
+                futures.append(future)
+            
+            for future in futures:
+                future.result()
+        
+        expected_total = num_threads * events_per_thread
+        success = (len(handler1_events) == expected_total and 
+                  len(handler2_events) == expected_total)
+        
+        if success:
+            print(f"✅ Thread safety test passed - each handler received {expected_total} events")
+            return True
+        else:
+            print("❌ Thread safety test failed")
+            print(f"Handler1 received {len(handler1_events)} events, expected {expected_total}")
+            print(f"Handler2 received {len(handler2_events)} events, expected {expected_total}")
+            return False
+
+def test_deregistration():
+    """Test handler deregistration"""
+    print("Testing handler deregistration...")
+    
+    from crewai.utilities.events.crewai_event_bus import crewai_event_bus
+    from crewai.utilities.events.base_events import BaseEvent
+    
+    class TestEvent(BaseEvent):
+        pass
+    
+    with crewai_event_bus.scoped_handlers():
+        def test_handler(source, event):
+            pass
+        
+        crewai_event_bus.register_handler(TestEvent, test_handler)
+        initial_count = len(crewai_event_bus._handlers.get(TestEvent, []))
+        
+        result = crewai_event_bus.deregister_handler(TestEvent, test_handler)
+        final_count = len(crewai_event_bus._handlers.get(TestEvent, []))
+        
+        if result and final_count == 0 and initial_count == 1:
+            print("✅ Handler deregistration works")
+            return True
+        else:
+            print("❌ Handler deregistration failed")
+            print(f"Initial count: {initial_count}, Final count: {final_count}, Result: {result}")
+            return False
+
+def main():
+    print("Verifying thread safety fix for Issue #2991")
+    print("=" * 50)
+    
+    tests = [
+        test_basic_functionality,
+        test_thread_safety,
+        test_deregistration
+    ]
+    
+    passed = 0
+    total = len(tests)
+    
+    for test in tests:
+        try:
+            if test():
+                passed += 1
+        except Exception as e:
+            print(f"❌ Test {test.__name__} failed with exception: {e}")
+            import traceback
+            traceback.print_exc()
+        print()
+    
+    print(f"Results: {passed}/{total} tests passed")
+    
+    if passed == total:
+        print("🎉 All thread safety tests passed!")
+        print("The fix for Issue #2991 is working correctly.")
+        return True
+    else:
+        print("💥 Some tests failed!")
+        return False
+
+if __name__ == "__main__":
+    success = main()
+    sys.exit(0 if success else 1)