Add snapped version of LXD support to nova-lxd

If LXD is installed via a snap, then the location of the console log
changes from the package version.  This patchset detects whether LXD is
snapped, and if so, provides a slightly different path for the console.


(cherry picked from commit e2aab580bd)

Change-Id: Id5c0ca2fd4b70f06b683c75ce5162b3f1a709187

nova/tests/unit/virt/lxd/test_common.py

@@ -36,31 +36,49 @@ class InstanceAttributesTest(test.NoDBTestCase):
         super(InstanceAttributesTest, self).tearDown()
         self.CONF_patcher.stop()
 
-    def test_instance_dir(self):
+    def test_is_snap_lxd(self):
+        with mock.patch('os.path.isfile') as isfile:
+            isfile.return_value = False
+            self.assertFalse(common.is_snap_lxd())
+            isfile.return_value = True
+            self.assertTrue(common.is_snap_lxd())
+
+    @mock.patch.object(common, 'is_snap_lxd')
+    def test_instance_dir(self, is_snap_lxd):
         ctx = context.get_admin_context()
         instance = fake_instance.fake_instance_obj(
             ctx, name='test', memory_mb=0)
+        is_snap_lxd.return_value = False
 
         attributes = common.InstanceAttributes(instance)
 
         self.assertEqual(
             '/i/instance-00000001', attributes.instance_dir)
 
-    def test_console_path(self):
+    @mock.patch.object(common, 'is_snap_lxd')
+    def test_console_path(self, is_snap_lxd):
         ctx = context.get_admin_context()
         instance = fake_instance.fake_instance_obj(
             ctx, name='test', memory_mb=0)
+        is_snap_lxd.return_value = False
 
         attributes = common.InstanceAttributes(instance)
-
         self.assertEqual(
             '/var/log/lxd/instance-00000001/console.log',
             attributes.console_path)
 
-    def test_storage_path(self):
+        is_snap_lxd.return_value = True
+        attributes = common.InstanceAttributes(instance)
+        self.assertEqual(
+            '/var/snap/lxd/common/lxd/logs/instance-00000001/console.log',
+            attributes.console_path)
+
+    @mock.patch.object(common, 'is_snap_lxd')
+    def test_storage_path(self, is_snap_lxd):
         ctx = context.get_admin_context()
         instance = fake_instance.fake_instance_obj(
             ctx, name='test', memory_mb=0)
+        is_snap_lxd.return_value = False
 
         attributes = common.InstanceAttributes(instance)
 

nova/virt/lxd/common.py

@@ -24,10 +24,25 @@ _InstanceAttributes = collections.namedtuple('InstanceAttributes', [
 
 def InstanceAttributes(instance):
     """An instance adapter for nova-lxd specific attributes."""
+    if is_snap_lxd():
+        prefix = '/var/snap/lxd/common/lxd/logs'
+    else:
+        prefix = '/var/log/lxd'
     instance_dir = os.path.join(conf.CONF.instances_path, instance.name)
-    console_path = os.path.join('/var/log/lxd/', instance.name, 'console.log')
+    console_path = os.path.join(prefix, instance.name, 'console.log')
     storage_path = os.path.join(instance_dir, 'storage')
     container_path = os.path.join(
         conf.CONF.lxd.root_dir, 'containers', instance.name)
     return _InstanceAttributes(
         instance_dir, console_path, storage_path, container_path)
+
+
+def is_snap_lxd():
+    """Determine whether it's a snap installed lxd or a package installed lxd
+
+    This is easily done by checking if the bin file is /snap/bin/lxc
+
+    :returns: True if snap installed, otherwise False
+    :rtype: bool
+    """
+    return os.path.isfile('/snap/bin/lxc')