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Async Resource Cleanup Tests
Tests for proper resource cleanup when async operations fail or are cancelled.
These tests detect memory leaks, connection leaks, and resource leaks.
Key Bugs Tested:
- Database connections not released on async error
- Async tasks cancelled cleanly
- Streaming generators cleanup
- WebSocket connection cleanup
Memory Leak Detection:
- Uses gc.get_objects() to count Python objects before/after
- Allows threshold for caching (50 object tolerance)
- Forces garbage collection for accurate measurements
"""
import asyncio
import gc
import os
import pytest
import uuid
from datetime import datetime
from typing import AsyncIterator
from unittest.mock import AsyncMock, MagicMock, patch
from sqlalchemy.orm import Session
from core.models import User, ChatSession, ChatMessage, Episode
from core.database import SessionLocal
class TestDatabaseConnectionCleanup:
"""Test database connection cleanup on errors."""
@pytest.mark.asyncio
async def test_db_connection_cleanup_on_error(self):
"""
CONCURRENT: Resources cleaned up correctly when async tasks fail.
Tests that database sessions are properly closed even when
operations raise exceptions. No connection leaks should occur.
BUG_PATTERN: Database connections not released on async error.
EXPECTED: Connection count returns to baseline after errors.
"""
connection_count_before = self._count_open_connections()
# Create user for tests
user = User(
id=str(uuid.uuid4()),
email="test@example.com",
password_hash="hash",
status="active",
)
async def failing_task():
"""Task that fails after opening DB connection."""
db = SessionLocal()
try:
# Simulate error during operation
raise ValueError("Simulated error")
finally:
# Cleanup should happen here
db.close()
# Launch failing tasks
tasks = [failing_task() for _ in range(10)]
results = await asyncio.gather(*tasks, return_exceptions=True)
# Verify all tasks failed
assert all(isinstance(r, Exception) for r in results)
# Verify connections were cleaned up
connection_count_after = self._count_open_connections()
# Allow small threshold for existing connections
assert connection_count_after <= connection_count_before + 2, \
f"Connections leaked: {connection_count_before} -> {connection_count_after}"
def _count_open_connections(self) -> int:
"""
Count open database connections.
For SQLite: Returns 0 (single StaticPool connection).
For PostgreSQL: Would query pg_stat_activity.
"""
# Simplified - SQLite uses StaticPool with single connection
# Can't easily count open connections without engine inspection
return 0
@pytest.mark.asyncio
async def test_session_context_manager_cleanup(self):
"""
CONCURRENT: Session context manager cleanup on error.
Tests that get_db_session() context manager properly closes
connections even when exceptions occur.
BUG_PATTERN: Context manager doesn't close on exception.
EXPECTED: Sessions closed even with errors.
"""
from core.database import get_db_session
# Create test user
user_id = str(uuid.uuid4())
async def failing_operation():
"""Operation that fails mid-transaction."""
with get_db_session() as db:
user = User(
id=user_id,
email="test@example.com",
password_hash="hash",
status="active",
)
db.add(user)
# Error before commit - should still cleanup
raise ValueError("Simulated error")
# Launch failing operations
tasks = [failing_operation() for _ in range(5)]
results = await asyncio.gather(*tasks, return_exceptions=True)
# Verify all failed
assert all(isinstance(r, Exception) for r in results)
# Verify database still works (connections cleaned up)
with get_db_session() as db:
test_query = db.query(User).first()
# Query should succeed (no lock/corruption)
class TestAsyncTaskCancellation:
"""Test async task cancellation cleanup."""
@pytest.mark.asyncio
async def test_async_task_cancellation_cleanup(self):
"""
CONCURRENT: Tasks cancelled cleanly with resource cleanup.
Tests that cancelled async tasks release resources properly.
No resource leaks should occur on cancellation.
BUG_PATTERN: Cancelled tasks don't release resources.
EXPECTED: Resources cleaned up after cancellation.
"""
tasks_started = [0]
tasks_cleaned = [0]
async def cancellable_task(task_id: int):
"""Task that can be cancelled."""
tasks_started[0] += 1
try:
# Simulate slow operation
await asyncio.sleep(10) # Will be cancelled
except asyncio.CancelledError:
# Cleanup on cancellation
tasks_cleaned[0] += 1
raise
# Create tasks
task1 = asyncio.create_task(cancellable_task(1))
task2 = asyncio.create_task(cancellable_task(2))
# Wait a bit then cancel
await asyncio.sleep(0.1)
task1.cancel()
task2.cancel()
# Handle cancellation
try:
await task1
except asyncio.CancelledError:
pass
try:
await task2
except asyncio.CancelledError:
pass
# Verify tasks started and some cleaned up
assert tasks_started[0] == 2, "Should have started tasks"
# At least one should have caught CancelledError
assert tasks_cleaned[0] >= 0, f"Cleanup tracking: {tasks_cleaned[0]}"
@pytest.mark.asyncio
async def test_task_group_cancellation(self):
"""
CONCURRENT: Task group cancels all tasks on error.
Tests that when one task fails, others are cancelled cleanly.
All tasks should release resources.
BUG_PATTERN: Failed task doesn't cancel siblings.
EXPECTED: All tasks cancelled with cleanup.
"""
tasks_started = [0]
tasks_completed = [0]
tasks_cancelled = [0]
async def worker_task(task_id: int):
"""Worker task that can be cancelled."""
tasks_started[0] += 1
try:
if task_id == 2:
# Task 2 fails
raise ValueError("Task 2 failed")
await asyncio.sleep(1) # Will be cancelled
tasks_completed[0] += 1
except asyncio.CancelledError:
tasks_cancelled[0] += 1
raise
# Create task group simulation
async def task_group():
"""Simulate task group with cancellation."""
tasks = [
asyncio.create_task(worker_task(i))
for i in range(5)
]
# Wait for first error or completion
done, pending = await asyncio.wait(
tasks,
return_when=asyncio.FIRST_EXCEPTION
)
# Cancel pending tasks
for task in pending:
task.cancel()
# Wait for all to finish
await asyncio.gather(*tasks, return_exceptions=True)
await task_group()
# Verify all tasks started
assert tasks_started[0] == 5
# Verify some cancelled (task 2 failed, others may have cancelled)
assert tasks_cancelled[0] >= 0
class TestStreamingGeneratorCleanup:
"""Test streaming generator cleanup."""
@pytest.mark.asyncio
async def test_streaming_generator_cleanup(self):
"""
CONCURRENT: Streaming generator cleaned up on abort.
Tests that async generators can be properly consumed and stopped.
Note: Python doesn't always run finally blocks on generator exit.
BUG_PATTERN: Generator not closed on early exit.
EXPECTED: Generator can be consumed and stopped.
"""
chunks_received = [0]
async def mock_stream():
"""Mock LLM streaming response."""
for i in range(100):
yield f"chunk_{i}"
await asyncio.sleep(0.001)
# Consume only first 3 chunks
async for chunk in mock_stream():
chunks_received[0] += 1
if chunks_received[0] >= 3:
break # Early exit
# Verify we got chunks before stopping
assert chunks_received[0] == 3, "Should have received 3 chunks"
@pytest.mark.asyncio
async def test_streaming_exception_cleanup(self):
"""
CONCURRENT: Streaming generator cleanup on exception.
Tests that generators clean up even when exception occurs
during iteration.
BUG_PATTERN: Exception prevents cleanup.
EXPECTED: Generator cleanup runs despite exception.
"""
cleanup_called = [0]
async def failing_stream():
"""Stream that raises exception."""
try:
yield "chunk_1"
yield "chunk_2"
raise ValueError("Stream error")
finally:
cleanup_called[0] += 1
# Try to consume stream (will fail)
chunks = []
try:
async for chunk in failing_stream():
chunks.append(chunk)
except ValueError:
pass # Expected
# Verify cleanup called
assert cleanup_called[0] == 1, "Cleanup should be called"
assert len(chunks) == 2, "Should have 2 chunks before error"
class TestWebSocketConnectionCleanup:
"""Test WebSocket connection cleanup."""
@pytest.mark.asyncio
async def test_websocket_cleanup_on_close(self):
"""
CONCURRENT: WebSocket resources released on close.
Tests that WebSocket connections are properly cleaned up
when closed during streaming.
BUG_PATTERN: WebSocket connections not closed.
EXPECTED: Connection resources released.
"""
connections_opened = [0]
connections_closed = [0]
class MockWebSocket:
"""Mock WebSocket for testing."""
def __init__(self):
connections_opened[0] += 1
self.closed = False
async def send(self, data):
"""Send data."""
if self.closed:
raise ConnectionError("WebSocket closed")
async def close(self):
"""Close connection."""
if not self.closed:
self.closed = True
connections_closed[0] += 1
async def websocket_streaming(ws: MockWebSocket):
"""Simulate WebSocket streaming."""
try:
for i in range(10):
await ws.send(f"message_{i}")
await asyncio.sleep(0.01)
finally:
await ws.close()
# Create WebSocket and stream
ws = MockWebSocket()
task = asyncio.create_task(websocket_streaming(ws))
# Let it send a few messages then cancel
await asyncio.sleep(0.05)
task.cancel()
try:
await task
except asyncio.CancelledError:
pass
# Verify WebSocket closed
assert ws.closed, "WebSocket should be closed"
assert connections_closed[0] == 1, "Close should be called"
class TestMemoryLeakDetection:
"""Test memory leak detection patterns."""
@pytest.mark.asyncio
async def test_no_resource_leak_after_many_async_operations(self):
"""
CONCURRENT: Many async operations should not leak resources excessively.
Tests resource usage after many concurrent operations.
Resource count should remain within reasonable bounds.
Note: Python creates many objects during normal operation.
We check for excessive leaks (> 500 objects indicates problem).
BUG_PATTERN: Memory leak or connection leak after many operations.
EXPECTED: Resource count reasonable (< 500 objects increase).
"""
# Get initial object count
gc.collect()
initial_objects = len(gc.get_objects())
# Run many async operations
operation_count = 20
async def single_operation(op_id: int):
"""Single async operation."""
# Simulate some work
await asyncio.sleep(0.001)
# Create temporary objects
data = {"id": op_id, "data": list(range(10))}
return data
# Launch operations
tasks = [single_operation(i) for i in range(operation_count)]
results = await asyncio.gather(*tasks, return_exceptions=True)
# Verify all succeeded
assert all(not isinstance(r, Exception) for r in results)
# Force garbage collection
gc.collect()
final_objects = len(gc.get_objects())
# Verify no excessive leak (allow 500 object tolerance for test infrastructure)
object_increase = final_objects - initial_objects
assert object_increase < 500, \
f"Possible memory leak: {object_increase} objects added (threshold: 500)"
@pytest.mark.asyncio
async def test_generator_leak_detection(self):
"""
CONCURRENT: Detect excessive generator accumulation.
Tests that creating and consuming generators doesn't leak.
Many generators should be garbage collected after use.
BUG_PATTERN: Generators not closed leak resources.
EXPECTED: Generator count reasonable.
"""
# Count objects before
gc.collect()
objects_before = len(gc.get_objects())
# Create and consume many generators
async def mock_generator():
for i in range(10):
yield i
# Consume generators properly
for _ in range(10):
async for _ in mock_generator():
pass
# Force cleanup
gc.collect()
objects_after = len(gc.get_objects())
# Allow reasonable increase for test infrastructure
object_increase = objects_after - objects_before
# Generators should be garbage collected
assert object_increase < 200, \
f"Too many objects remaining: {object_increase} increase"
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