[LP#2047967] Require the upgrade-action when changing the snap channel

charms/kubernetes_snaps.py

@@ -611,11 +611,19 @@ def install(channel, control_plane=False, upgrade=False):
         - upgrade (bool, optional): If True, allows upgrading of snaps. Defaults to
         False.
     """
+    which_snaps = BASIC_SNAPS + CONTROL_PLANE_SNAPS if control_plane else BASIC_SNAPS
 
-    if any(is_upgrade(snap, channel) for snap in BASIC_SNAPS) and not upgrade:
-        status.add(
-            BlockedStatus("Snap channel version has changed. An upgrade is required.")
+    if missing := {s for s in which_snaps if not is_channel_available(s, channel)}:
+        log.warning(
+            "The following snaps do not have a revision on channel=%s: %s",
+            channel,
+            ",".join(sorted(missing)),
         )
+        status.add(BlockedStatus(f"Not all snaps are available on channel={channel}"))
+        return
+
+    if any(is_channel_swap(snap, channel) for snap in which_snaps) and not upgrade:
+        status.add(BlockedStatus("Needs manual upgrade, run the upgrade action."))
         return
 
     # Refresh with ignore_running=True ONLY for non-daemon apps (i.e. kubectl)
@@ -650,15 +658,34 @@ def install_snap(name: str, channel: str, classic=False, ignore_running=False):
     check_call(cmd)
 
 
-def is_snap_installed(name):
+def is_channel_available(snap_name: str, target_channel: str) -> bool:
+    """
+    Check if the target channel exists for a given snap.
+
+    Args:
+    snap_name (str): Then name of the snap package.
+    target_channel (str): The target channel to find.
+
+    Returns:
+    bool: True if snap channel contains a revision, False otherwise.
+    """
+    cmd = ["snap", "info", snap_name]
+    result = check_output(cmd)
+    output = yaml.safe_load(result)
+    channels = output.get("channels") or {}
+    target = channels.get(target_channel) or None
+    return target and target != "--"
+
+
+def is_snap_installed(snap_name) -> bool:
     """Return True if the given snap is installed, otherwise False."""
-    cmd = ["snap", "list", name]
+    cmd = ["snap", "list", snap_name]
     return call(cmd, stdout=DEVNULL, stderr=DEVNULL) == 0
 
 
-def is_upgrade(snap_name: str, target_channel: str):
+def is_channel_swap(snap_name: str, target_channel: str) -> bool:
     """
-    Check if the installed version is less than the target channel version.
+    Check if the installed version is not than the target channel version.
 
     Args:
     snap_name (str): Then name of the snap package.
@@ -671,14 +698,13 @@ def is_upgrade(snap_name: str, target_channel: str):
 
     if is_refresh and (installed_version := get_snap_version(snap_name)):
         channel_version, *_ = target_channel.split("/")
+        current = version.parse(installed_version)
+        target = version.parse(channel_version)
+        return (current.major, current.minor) != (target.major, target.minor)
+    return False
 
-        installed_ver = version.parse(installed_version)
-        target_ver = version.parse(channel_version)
 
-        return (installed_ver.major, installed_ver.minor) < (
-            target_ver.major,
-            target_ver.minor,
-        )
+is_upgrade = is_channel_swap
 
 
 def merge_extra_config(config, extra_config):

tests/unit/test_kubernetes_snaps.py

@@ -5,22 +5,59 @@
 from charms import kubernetes_snaps
 
 
-@pytest.fixture
+@pytest.fixture(autouse=True)
 def subprocess_check_output():
     with mock.patch("charms.kubernetes_snaps.check_output") as mock_run:
         yield mock_run
 
 
-def test_upgrade_action_control_plane(caplog):
+@pytest.fixture(autouse=True)
+def subprocess_call():
+    with mock.patch("charms.kubernetes_snaps.call") as mock_run:
+        yield mock_run
+
+
+@mock.patch.object(kubernetes_snaps, "is_channel_swap", return_value=False)
+@mock.patch.object(kubernetes_snaps, "is_channel_available", return_value=True)
+@mock.patch.object(kubernetes_snaps, "install_snap", mock.MagicMock())
+def test_upgrade_action_control_plane(is_channel_available, is_channel_swap, caplog):
     mock_event = mock.MagicMock()
-    with mock.patch.object(kubernetes_snaps, "is_upgrade", return_value=False):
-        with mock.patch.object(kubernetes_snaps, "install_snap"):
-            kubernetes_snaps.upgrade_snaps("1.28/edge", mock_event, control_plane=True)
+    channel = "1.28/edge"
+    kubernetes_snaps.upgrade_snaps(channel, mock_event, control_plane=True)
+    snaps = kubernetes_snaps.BASIC_SNAPS + kubernetes_snaps.CONTROL_PLANE_SNAPS
+    is_channel_available.assert_has_calls([mock.call(s, channel) for s in snaps])
+    is_channel_swap.assert_has_calls([mock.call(s, channel) for s in snaps])
     assert (
-        "Starting the upgrade of Kubernetes snaps to '1.28/edge' channel."
+        f"Starting the upgrade of Kubernetes snaps to '{channel}' channel."
         in caplog.messages
     )
     assert (
-        "Successfully upgraded Kubernetes snaps to the '1.28/edge' channel."
+        f"Successfully upgraded Kubernetes snaps to the '{channel}' channel."
         in caplog.messages
     )
+
+
+def test_is_snap_available(subprocess_check_output):
+    snap_info = """
+name:      my-snap
+publisher: Canonical✓
+channels:
+  latest/stable:    --
+  1.29/stable:   1.29.0  2024-01-03 (22606) 12MB -
+"""
+    subprocess_check_output.return_value = snap_info.encode()
+    assert not kubernetes_snaps.is_channel_available("my-snap", "latest/stable")
+    assert not kubernetes_snaps.is_channel_available("my-snap", "1.30/stable")
+    assert kubernetes_snaps.is_channel_available("my-snap", "1.29/stable")
+
+
+def test_is_channel_swap(subprocess_call, subprocess_check_output):
+    snap_list = """
+Name     Version       Rev    Tracking       Publisher   Notes
+my-snap  1.29.0        22606  1.29/stable    canonical✓  -
+"""
+    subprocess_call.return_value = 0
+    subprocess_check_output.return_value = snap_list.encode()
+    assert kubernetes_snaps.is_channel_swap("my-snap", "1.28/stable")
+    assert not kubernetes_snaps.is_channel_swap("my-snap", "1.29/stable")
+    assert kubernetes_snaps.is_channel_swap("my-snap", "1.30/stable")