MonitoringThreadContainer creates ThreadPoolExecutor at import time, causing pytest to hang

[jaredkeil]

Describe the bug

Similar to the recently fixed issue with SlidingExpirationCacheWithCleanupThread (#1043, #1039), the MonitoringThreadContainer class in host_monitoring_plugin.py creates a ThreadPoolExecutor at class definition time. This causes background threads to be created during module import (such as from aws_advanced_python_wrapper import AwsWrapperConnection), which prevents pytest from terminating cleanly as it waits for these non-daemon threads to finish.

aws-advanced-python-wrapper/aws_advanced_python_wrapper/host_monitoring_plugin.py

Line 568 in 2df8d33

_executor: ClassVar[Executor] = ThreadPoolExecutor(thread_name_prefix="MonitoringThreadContainerExecutor")

Expected Behavior

Importing the aws-advanced-python-wrapper library should not create background threads that prevent process termination. Tests should complete without hanging.

What plugins are used? What other connection properties were set?

iam, aurora-pg

Current Behavior

When running pytest, tests complete successfully, but pytest hangs indefinitely. The process must be killed with Ctrl+C. Stack trace shows threads waiting in concurrent.futures.threads module

 pytest test_reproduction.py
==================================================== test session starts ====================================================
platform darwin -- Python 3.12.3, pytest-9.0.1, pluggy-1.6.0
rootdir: /Users/develop/projects/side/aws_wrapper_bug
configfile: pyproject.toml
collected 1 item

test_reproduction.py .                                                                                                [100%]

===================================================== 1 passed in 4.28s =====================================================
^CException ignored in: <module 'threading' from '/usr/local/Cellar/python@3.12/3.12.3/Frameworks/Python.framework/Versions/3.12/lib/python3.12/threading.py'>
Traceback (most recent call last):
  File "/usr/local/Cellar/python@3.12/3.12.3/Frameworks/Python.framework/Versions/3.12/lib/python3.12/threading.py", line 1592, in _shutdown
    atexit_call()
  File "/usr/local/Cellar/python@3.12/3.12.3/Frameworks/Python.framework/Versions/3.12/lib/python3.12/concurrent/futures/thread.py", line 31, in _python_exit
    t.join()
  File "/usr/local/Cellar/python@3.12/3.12.3/Frameworks/Python.framework/Versions/3.12/lib/python3.12/threading.py", line 1147, in join
    self._wait_for_tstate_lock()
  File "/usr/local/Cellar/python@3.12/3.12.3/Frameworks/Python.framework/Versions/3.12/lib/python3.12/threading.py", line 1167, in _wait_for_tstate_lock
    if lock.acquire(block, timeout):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
KeyboardInterrupt:

Reproduction Steps

test_reproduction.py:

def test_import_causes_hang():
    """This test will pass but pytest will hang after completion"""
    from aws_advanced_python_wrapper import AwsWrapperConnection
    assert True

Run: pytest test_reproduction.py
Result: Tests passes but pytest never exits

Possible Solution

Could apply similar solution used for SlidingExpirationCacheWithCleanupThread - either:

1. Use daemon threads so they don't prevent process termination
2. Use lazy initialization to avoid creating threads at import time

Additional Information/Context

Pytest version: 9.0.1

The AWS Advanced Python Wrapper version used

1.4.0

python version used

3.12.3

Operating System and version

macOS Sequoia 15.7.1 (also reproduced on macOS Monterey 12.7.6)