Add channel config option

The charm uses a hardcoded channel declared in src/layer.yaml with the
value 1.0/stable, this prevents users from overriding it. This became a
blocker with the release of octavia-diskimage-retrofit 2.0 in the `2.0`
track to support Ubuntu Noble 24.04, the snap migrated to core24[0][1]

This change introduces a new configuration option that defaults to null,
this will allow the charm to use the 1.0/stable channel when running on
Jammy and 2.0/stable when running on Noble. Existing environments
running on Jammy will see no behavior change, and no operator's
intervention is needed when upgrading.

[0] https://github.com/openstack-charmers/octavia-diskimage-retrofit/pull/44
[1] https://github.com/openstack-charmers/octavia-diskimage-retrofit/pull/46

Change-Id: I1ccba9de844f7900c9a8517fff4de2f8c4019871
Signed-off-by: Felipe Reyes <felipe.reyes@canonical.com>

Co-Authored-by: Hemanth Nakkina <hemanth.nakkina@canonical.com>
Change-Id: I1ccba9de844f7900c9a8517fff4de2f8c4019871
Signed-off-by: Hemanth Nakkina <hemanth.nakkina@canonical.com>

src/config.yaml

@@ -1,4 +1,9 @@
 options:
+  channel:
+    type: string
+    default:
+    description: >-
+      The snap channel to install from.
   ubuntu-mirror:
     type: string
     default: ''

src/layer.yaml

@@ -9,10 +9,6 @@ options:
   basic:
     use_venv: True
     include_system_packages: False
-  snap:
-    octavia-diskimage-retrofit:
-      channel: 1.0/stable
-      classic: true
 comment: |
   Using devmode pending resolution of snapd fuse-support issue
   https://github.com/openstack-charmers/octavia-diskimage-retrofit/issues/6

src/reactive/octavia_diskimage_retrofit_handlers.py

@@ -17,6 +17,20 @@ import charms.reactive as reactive
 import charms_openstack.bus
 import charms_openstack.charm as charm
 
+from collections import defaultdict
+from charms.layer import snap
+from charms.reactive.flags import (
+    set_flag,
+    clear_flag,
+)
+from charmhelpers.core.hookenv import (
+    config,
+    log,
+)
+from charmhelpers.core.host import (
+    get_distrib_codename,
+)
+
 charms_openstack.bus.discover()
 
 charm.use_defaults(
@@ -26,6 +40,34 @@ charm.use_defaults(
     'upgrade-charm',
 )
 
+CHANNELS = defaultdict(lambda: 'latest/edge')
+CHANNELS.update({
+    'jammy': '1.0/stable',
+    'noble': '2.0/stable',
+})
+
+
+@reactive.when_not('snap.installed.octavia-diskimage-retrofit')
+def snap_install():
+    channel = config('channel')
+    if not channel:
+        series = get_distrib_codename()
+        channel = CHANNELS[series]
+        log('No snap channel configured, using default '
+            'for series {}: {}'.format(series, channel),
+            level="INFO")
+
+    if validate_snap_risk(channel):
+        clear_flag('snap.channel.invalid')
+        snap.install('core')
+        snap.install('octavia-diskimage-retrofit',
+                     channel=channel,
+                     classic=True)
+    else:
+        log('Invalid snap channel risk level: {}'.format(channel),
+            level="ERROR")
+        set_flag('snap.channel.invalid')
+
 
 @reactive.when('identity-credentials.connected')
 @reactive.when_not('identity-credentials.available')
@@ -48,3 +90,24 @@ def credentials_available():
 def retrofit_by_cron():
     with charm.provide_charm_instance() as instance:
         instance.handle_auto_retrofit()
+
+
+def validate_snap_risk(channel):
+    """Validate a provided snap channel's risk
+
+    Any prefix is ignored ('0.10' in '0.10/stable' for example).
+
+    :param: channel: string of the snap channel to validate
+    :returns: boolean: whether provided channel is valid
+    """
+    tokens = channel.split('/')
+    if len(tokens) == 1:
+        risk_level = tokens[0]
+    else:
+        # Check if track is a risk level (invalid case like 'stable/edge')
+        track = tokens[0]
+        risk_level = tokens[1]
+        if track in ('stable', 'candidate', 'beta', 'edge'):
+            return False
+
+    return risk_level in ('stable', 'candidate', 'beta', 'edge')

src/tests/bundles/noble-caracal.yaml

@@ -68,7 +68,7 @@ applications:
            path: 'streams/v1/index.sjson',
            max: 1,
            item_filters: [
-               'release~(jammy)',
+               'release~(noble)',
                'arch~(x86_64|amd64)',
                'ftype~(disk1.img|disk.img)'
                ]
@@ -103,8 +103,9 @@ applications:
   octavia-diskimage-retrofit:
     charm: ../../../octavia-diskimage-retrofit.charm
     options:
-      retrofit-uca-pocket: antelope
-      retrofit-series: jammy
+      channel: 2.0/edge
+      retrofit-uca-pocket: caracal
+      retrofit-series: noble
 
 relations:
 

unit_tests/__init__.py

@@ -30,3 +30,11 @@ sys.modules['glanceclient'] = glanceclient
 sys.modules['keystoneauth1'] = keystoneauth1
 sys.modules['keystoneauth1.loading'] = keystoneauth1.loading
 sys.modules['keystoneauth1.session'] = keystoneauth1.session
+
+# Mock out charms.layer modules
+charms_layer = mock.MagicMock()
+charms_layer_snap = mock.MagicMock()
+charms_layer_basic = mock.MagicMock()
+sys.modules['charms.layer'] = charms_layer
+sys.modules['charms.layer.snap'] = charms_layer_snap
+sys.modules['charms.layer.basic'] = charms_layer_basic

unit_tests/test_reactive_octavia_diskimage_retrofit_handlers.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import unittest
 from unittest import mock
 
 import reactive.octavia_diskimage_retrofit_handlers as handlers
@@ -45,6 +46,8 @@ class TestRegisteredHooks(test_utils.TestRegisteredHooks):
             'when_not': {
                 'request_credentials': (
                     'identity-credentials.available',),
+                'snap_install': (
+                    'snap.installed.octavia-diskimage-retrofit',),
             },
         }
         # test that the hooks were registered via the
@@ -76,3 +79,27 @@ class TestOctaviaDiskimageRetrofitHandlers(test_utils.PatchHelper):
     def test_credentials_available(self):
         handlers.credentials_available()
         self.charm_instance.assess_status.assert_called_once_with()
+
+
+class TestValidateSnapRisk(unittest.TestCase):
+
+    def test_valid_risk_only(self):
+        for risk in ('stable', 'candidate', 'beta', 'edge'):
+            with self.subTest(risk=risk):
+                self.assertTrue(handlers.validate_snap_risk(risk))
+
+    def test_valid_channel_with_track(self):
+        self.assertTrue(handlers.validate_snap_risk('0.10/stable'))
+        self.assertTrue(handlers.validate_snap_risk('latest/edge'))
+        self.assertTrue(handlers.validate_snap_risk('1.0/candidate'))
+        self.assertTrue(handlers.validate_snap_risk('2/beta'))
+
+    def test_invalid_risk_only(self):
+        self.assertFalse(handlers.validate_snap_risk('invalid'))
+        self.assertFalse(handlers.validate_snap_risk(''))
+        self.assertFalse(handlers.validate_snap_risk('stable/edge'))
+
+    def test_invalid_risk_with_track(self):
+        self.assertFalse(handlers.validate_snap_risk('0.10/invalid'))
+        self.assertFalse(handlers.validate_snap_risk('latest/'))
+        self.assertFalse(handlers.validate_snap_risk('latest/nightly'))