[LP#2143365] When containerd is installed by resource, don't restart service with apt

src/reactive/containerd.py

@@ -468,7 +468,10 @@ def upgrade_charm():
     if is_state("containerd.resource.installed"):
         # if a resource is currently overriding the deb,
         # upgrade containerd from the apt packages
-        reinstall_containerd()
+        # to make sure we get latest systemd services, latest configs,
+        # and dependencies like runc if needed -- but don't restart into
+        # those services
+        reinstall_containerd(restart=False)
 
     # Re-render config in case the template has changed in the new charm.
     config_changed()
@@ -518,11 +521,35 @@ def install_containerd():
     config_changed()
 
 
-def reinstall_containerd():
+@contextlib.contextmanager
+def _apt_restart_services(restart: bool):
+    """
+    Context manager to conditionally restart services after apt operations.
+
+    Args:
+        restart: whether to restart services after apt operations
+    """
+    original = os.environ.get("NEEDRESTART_SUSPEND")
+    log("Services will {}be restarted after apt operations.".format("" if restart else "not "))
+    if not restart:
+        os.environ.update({"NEEDRESTART_SUSPEND": "1"})
+    else:
+        os.environ.pop("NEEDRESTART_SUSPEND", None)
+    try:
+        yield
+    finally:
+        if original is None:
+            os.environ.pop("NEEDRESTART_SUSPEND", None)
+        else:
+            os.environ["NEEDRESTART_SUSPEND"] = original
+
+
+def reinstall_containerd(restart: bool = True):
     """Install and hold containerd with apt."""
     apt_update(fatal=True)
     apt_unhold(CONTAINERD_PACKAGE)
-    apt_install([CONTAINERD_PACKAGE, "--reinstall"], fatal=True)
+    with _apt_restart_services(restart):
+        apt_install([CONTAINERD_PACKAGE, "--reinstall"], fatal=True)
     apt_hold(CONTAINERD_PACKAGE)
     set_state("containerd.installed")
     remove_state("containerd.resource.evaluated")

tests/integration/test_containerd_integration.py

@@ -14,7 +14,6 @@
 from utils import JujuRun
 import yaml
 
-
 log = logging.getLogger(__name__)
 
 

tests/unit/conftest.py

@@ -1,5 +1,4 @@
 import charms.unit_test
 
-
 charms.unit_test.patch_reactive()
 charms.unit_test.patch_module("requests")

tests/unit/test_containerd_reactive.py

@@ -407,3 +407,43 @@ def test_needs_gpu_reboot_true(check_output, is_state, remove_state, set_state):
     check_output.assert_called_once_with(["nvidia-smi"], stderr=STDOUT)
     set_state.assert_called_once_with("containerd.nvidia.needs_reboot")
     remove_state.assert_not_called()
+
+
+@pytest.mark.parametrize(
+    "restart,initial_env,expected_during,expected_after",
+    [
+        (True, {}, None, None),
+        (False, {}, "1", None),
+        (True, {"NEEDRESTART_SUSPEND": "original"}, None, "original"),
+        (False, {"NEEDRESTART_SUSPEND": "original"}, "1", "original"),
+    ],
+    ids=[
+        "restart=True, no initial env",
+        "restart=False, no initial env",
+        "restart=True, with initial env",
+        "restart=False, with initial env",
+    ],
+)
+@mock.patch.object(containerd, "log")
+@mock.patch.dict(os.environ, {}, clear=True)
+def test_apt_restart_services(mock_log, restart, initial_env, expected_during, expected_after):
+    """Verify _apt_restart_services behavior with various configurations."""
+    # Setup initial environment from parameters
+    os.environ.update(initial_env)
+
+    with containerd._apt_restart_services(restart=restart):
+        # Check value during context
+        if expected_during is None:
+            assert "NEEDRESTART_SUSPEND" not in os.environ
+        else:
+            assert os.environ["NEEDRESTART_SUSPEND"] == expected_during
+
+    # Check value after context
+    if expected_after is None:
+        assert "NEEDRESTART_SUSPEND" not in os.environ
+    else:
+        assert os.environ["NEEDRESTART_SUSPEND"] == expected_after
+
+    # Check log call
+    log_fmt = "" if restart else "not "
+    mock_log.assert_called_once_with(f"Services will {log_fmt}be restarted after apt operations.")