🐛 Avoid importing and calling close in __del__ during shutdown (#7322)

Two related fixes to prevent 'Exception ignored in __del__' errors
during Python shutdown:

1. Move 'import warnings' to module level in `RabbitmqBroker` and
   `StorageBackend` to avoid `ImportError` when `sys.meta_path` is
   `None` during shutdown.

2. Guard `__del__` with `sys.is_finalizing()` to skip the `close()`
   call during Python shutdown when asyncio/kiwipy event loop
   infrastructure is already torn down, preventing `AttributeError`
   in pytray's `await_` method.

During shutdown:
- `sys.meta_path` becomes `None`, making imports unavailable
- Module globals are set to `None` before garbage collection
- `asyncio.run_coroutine_threadsafe()` fails with `AttributeError`

By deferring the import and skipping close during finalization, we
avoid both issues since the process is exiting anyway.

Fixes #7309

Author: agoscinski

src/aiida/brokers/rabbitmq/broker.py

@@ -3,7 +3,9 @@
 from __future__ import annotations
 
 import functools
+import sys
 import typing as t
+import warnings
 from collections.abc import Iterator
 
 from aiida.brokers.broker import Broker
@@ -49,10 +51,9 @@ def close(self) -> None:
 
     def __del__(self) -> None:
         if self._communicator is not None:
-            import warnings
-
             warnings.warn(f'RabbitmqBroker was not closed explicitly: {self!r}', ResourceWarning, stacklevel=1)
-            self.close()
+            if not sys.is_finalizing():
+                self.close()
 
     def iterate_tasks(self) -> Iterator[t.Any]:
         """Return an iterator over the tasks in the launch queue."""

src/aiida/orm/implementation/storage_backend.py

@@ -11,6 +11,8 @@
 from __future__ import annotations
 
 import abc
+import sys
+import warnings
 from collections.abc import Iterable
 from typing import TYPE_CHECKING, Any, ContextManager, List, Optional, TypeVar, Union
 
@@ -142,10 +144,9 @@ def __del__(self):
             # covers cases where the backend implementation is not yet initialized but object is deleted
             return
         if not closed:
-            import warnings
-
             warnings.warn(f'StorageBackend was not closed explicitly: {self!r}', ResourceWarning, stacklevel=1)
-            self.close()
+            if not sys.is_finalizing():
+                self.close()
 
     @property
     @abc.abstractmethod

tests/brokers/test_rabbitmq.py

@@ -10,13 +10,14 @@
 
 import pathlib
 import uuid
+from unittest.mock import MagicMock
 
 import pytest
 import requests
 from kiwipy.rmq import RmqThreadCommunicator
 from packaging.version import parse
 
-from aiida.brokers.rabbitmq import client, utils
+from aiida.brokers.rabbitmq import RabbitmqBroker, client, utils
 from aiida.engine.processes import ProcessState, control
 from aiida.orm import Int
 
@@ -36,6 +37,33 @@ def raise_connection_error():
     assert 'RabbitMQ @' in str(broker)
 
 
+def test_del_closes_broker_when_not_finalizing(aiida_profile, monkeypatch):
+    """Test `__del__` closes the broker when Python is not finalizing."""
+    broker = RabbitmqBroker(aiida_profile)
+    broker._communicator = MagicMock()
+    close = MagicMock()
+    monkeypatch.setattr(broker, 'close', close)
+
+    with pytest.warns(ResourceWarning, match='RabbitmqBroker was not closed explicitly'):
+        broker.__del__()
+
+    close.assert_called_once_with()
+
+
+def test_del_skips_close_when_finalizing(aiida_profile, monkeypatch):
+    """Test ``__del__`` skips close when Python is finalizing."""
+    broker = RabbitmqBroker(aiida_profile)
+    broker._communicator = MagicMock()
+    close = MagicMock()
+    monkeypatch.setattr(broker, 'close', close)
+    monkeypatch.setattr('sys.is_finalizing', lambda: True)
+
+    with pytest.warns(ResourceWarning, match='RabbitmqBroker was not closed explicitly'):
+        broker.__del__()
+
+    close.assert_not_called()
+
+
 @pytest.mark.parametrize(
     ('version', 'supported'),
     (

tests/orm/implementation/test_backend.py

@@ -13,6 +13,7 @@
 import json
 import pathlib
 import uuid
+from unittest.mock import MagicMock
 
 import pytest
 
@@ -168,6 +169,31 @@ def test_delete_nodes_and_connections(self):
         assert len(group.nodes) == 0
 
 
+def test_del_closes_backend_when_not_finalizing(aiida_profile, monkeypatch):
+    """Test ``__del__`` closes the backend when Python is not finalizing."""
+    backend = aiida_profile.storage_cls(aiida_profile)
+    close = MagicMock()
+    monkeypatch.setattr(backend, 'close', close)
+
+    with pytest.warns(ResourceWarning, match='StorageBackend was not closed explicitly'):
+        backend.__del__()
+
+    close.assert_called_once_with()
+
+
+def test_del_skips_close_when_finalizing(aiida_profile, monkeypatch):
+    """Test ``__del__`` skips close when Python is finalizing."""
+    backend = aiida_profile.storage_cls(aiida_profile)
+    close = MagicMock()
+    monkeypatch.setattr(backend, 'close', close)
+    monkeypatch.setattr('sys.is_finalizing', lambda: True)
+
+    with pytest.warns(ResourceWarning, match='StorageBackend was not closed explicitly'):
+        backend.__del__()
+
+    close.assert_not_called()
+
+
 def test_backup_not_implemented(aiida_config, backend, monkeypatch, tmp_path):
     """Test the backup functionality if the plugin does not implement it."""